Method that Promotes or Preserves the Desirable Color of Meat

Articles, films and packaging methods that promote or preserve the desirable color of meat

Field of the Invention

By the present invention there is provided an article for packaging food comprising an agent that forms a red color, food packaging and methods of packaging food comprising said article.

Background

The color of the meat is an important quality feature that affects its commercialization. Consumers often use color as an indication of the quality and freshness of meat. The color of the meat is related to the quantity and chemical state of the myoglobin present in the meat. Myoglobin is present in the muscle tissue of all animals and works by storing and providing oxygen by reversible binding with molecular oxygen, thus creating an intracellular source of oxygen for mitochondria. Pork and poultry typically contain smaller amounts of myoglobin than that of cattle and, therefore, is lighter in color.

Myoglobin includes an open binding site called heme that can bind to certain molecules, such as molecular oxygen ("oxygen" or O2) or water. Myoglobin without a molecule attached to the heme group is a purple molecule called deoximioglobin. The presence and type of ligand bound at the myoglobin binding site can alter the color of myoglobin. The color of the meat may vary based on the amount of myoglobin present and amount and type (s) of the molecule (s) bound to the heme group. Molecular oxygen easily acts as a ligand that binds to the heme group allowing the biological transport of oxygen from the blood stream to the mitochondria of the cells. When oxygen binds to the heme group, deoximioglobin becomes oxythioglobin, characterized by a red color. When a water molecule joins the heme group, the myoglobin molecule takes a brown color and is called methioglobin. The carbon monoxide (CO) bond can cause a color similar to that produced by the oxygen bond. It has been described that nitric oxide (NO) forms a stable pink color in cured meats.

Historically, fresh meat products available to consumers have been prepared and packaged substantially for final use at the final sales site. A product packaging that retains the desirable color of fresh meat can favor marketing and make meat attractive to consumers. Current meat packaging technology may improperly preserve the favorable color of meat for various reasons. The conventional packaging format used by retailers of fresh meat is to spread a thin plastic film around a foam tray that supports the product. The film is permeable to oxygen so the color of the meat quickly changes to a bright red. However, the duration of the bright red color is only about three days. Therefore, this packaging format is not desirable because the color is often unacceptable before the meat can be exposed or sold, even if it is nutritious and suitable for consumption. As a result, for a long time, in centralized packaging operations a packaging format that maintains the color of fresh meat has been sought for a longer period of time. Alternatively, the meat has been packaged in vacuum, oxygen barrier bags, which are vacuum sealed and avoid oxygen contact with the meat until the package is opened. Vacuum packed red meat products are nutritious, healthy and long lasting. However, they can cause an undesirable purple color of packaged meat that does not change to the desirable red color until the meat is exposed to the air. Consumer acceptance of meat that has a purple color is less than that of meat that has a red color. To provide meat with the red color preferred by consumers, the meat has also been packaged in modified atmosphere ("MAP") containers, in which the meat is kept in a sealed bag containing an atmosphere other than ambient air. For example, one of said commercially acceptable MAPs contains an oxygen-enriched atmosphere (with an oxygen content of up to 80% by volume) to better maintain a preferred red color. A case of available MAP maintains meat in carbon dioxide, with a very low oxygen content, until just before the meat is exposed to oxygen to cause the change to the desired red color. Alternatively, the meat may be in contact with a MAP that has an atmosphere containing a small concentration of carbon monoxide (CO) (for example, 0.4% by volume) to maintain a preferred red color of the meat. However, although MAPs containing CO can maintain a duration comparable to that of vacuum-packed meat, the red color induced by the presence of CO can be perceived as "unnatural" bright red. In addition, the red color developed by CO tends to extend to a significant portion of the meat product causing a permanent "flushing" of the inside of the meat that can be preserved even after the meat has been fully cooked. The bright red CO-myoglobin complex is called "carboximioglobin." The presence of carbon monoxide also adversely affects the sale of MAP packages containing CO among consumers.

MAPs also require a larger space for contact of the modified atmosphere with the surface of the meat that, over time, affects the desired color. This requirement of a higher space causes a greater volume of the container, higher transport costs and storage requirements and also limits the appearance of presentation making the product less visible due to the high side walls of the receptacle and the space between the film and the surface of meat

What is needed are items for packaging that maintain a favorable color of the meat and provide adequate or longer shelf life and freshness of the meat.

In curing meat, nitrites or nitrates, such as sodium nitrite, are frequently used, which can also affect the color of the meat. Nitrites and nitrates are additives generally accepted as suitable for use in foods and are preservatives commonly used in the curing process of products such as hams, meat for meals, Bolognese and hot dogs. Nitrites and nitrates are used to cure and disinfect meats in the meat industry, often producing a stable pink to red color in the process. For example, GB 2187081A discloses immersing meat in an aqueous solution of sodium chloride, polyphosphate ions and nitrite ions to preserve meat. See also McGee, "Meat," On Food and Cooking, Rev. Ed., 2004, Chapter 3, pages 118178 (Scribner, New York, NY), which is incorporated herein by reference. The presence of oxygen can oxidize free nitric oxide to nitrite ion thus reducing its availability to associate with the myoglobin molecule. Packaging films comprising nitrites or nitrates have been described as desiccants, food preservatives and volatile corrosion inhibitors for packaging metal products. Antifungal agents, including food preservatives, such as sodium nitrite, can be applied to various types of containers to preserve biodegradable containers from premature fungal attack, as described in JP7-258467A. The oxygen barrier films used for food packaging can contain a nitrate as a moisture absorbing agent in a barrier material made of EVOH or in another layer of a multilayer films, as described in JP5-140344A and U.S. Patent Nos. 4,407,897 (Farell et al.), 4,425,410 (Farell et al.), 4,792,484 (Moritani), 4,929,482 (Moritani et al.), 4,960,639 (Oda et al. .) and 5,153,038 (Koyama et al.). It has also been described to include nitrates or nitrites in films for packaging to absorb moisture, for example, to inhibit corrosion of metal products, as described in US Pat. Nos. 2,895,270 (Blaess), 5,715,945 (Chandler) , 5,894,040 (Foley et al.), 5,937,618 (Chandler), 6,465,109 (Ohtsuka) and 6,942,909 (Shirrell et al.), In published U.S. patent application number 2005/0019537 (Nakaishi et al.), in the British patent number

1,048,770 (Canadian Technical Tape Ltd.) and in European patents numbers EP 0 202 771 B1 (Aicello Chemical Co. Ltd.), EP 0 662 527 B1 (Cirtec Corp.) and EP 1 139 478 A2 (Aicello Chemical Co . Ltd.). None of these barrier films described contain a meat contact portion comprising a nitrite or nitrate intended to maintain the desirable coloration of a meat product.

In many packaging applications, such as vacuum packaging, heat sealable films are desired for food packaging. Packaging can be made of heat sealable films. A typical bag for food packaging can include one, two or three sides heat sealed by the manufacturer of the bag, which originate one or two open sides that allow the introduction of the product to be packaged. A typical food receptacle may include a shaped tray, with a heat sealable lid film sealed to the tray. See, for example, U.S. Patent Nos. 5,058,761 (Williams), 5,558,891 (Lawless et al.) And 7,017,774 (Haedt).

Contractile films, bags and wrappers have also been used to package fresh, frozen and processed meats for wholesale or retail sales and as processing films for cooking applications and pasteurization processes after cooking. Meats cured with nitrites and / or nitrates have been packaged in contractile films. See, for example, US Patents Nos. 6,815,023 (Tatarka et al.), 6,777,046 (Tatarka et al.), 6,749,648 (Idlas), 5,472,722 (Burger), 5,047,253 (Juhl et al.) and 4,391,862 (Bornstein et al.).

Patent application WO 2005/097486 describes an uncooked meat product vacuum packed in a multilayer polymeric film, said polymeric film having a first oxygen barrier layer and a second layer containing a selected nitrogen oxide from the group consisting of sodium nitrite, sodium nitrate, potassium nitrite, potassium nitrate and mixtures of these compounds. In addition, this document more generally describes films for packaging food used to create and stabilize a desirable color on the surface that is seen of a food containing myoglobin, without negatively affecting the color below the surface of the food, said citation comprising. film (a) a layer of food contact, capable of contacting the food contained in the container formed with the film, and (b) an effective amount of a compound containing a nitrogen oxide applied to the food contact layer and capable of interacting with the food containing myoglobin to produce the desirable color.

What is needed are products for packaging, such as films for packaging food, that include a portion of food contact and that comprise a material intended to maintain or promote the desirable coloration of a food containing myoglobin, especially fresh meat.

Summary

In a first embodiment, an article for food packaging is provided. The food packaging article comprises a food contact layer comprising a myoglobin-red producing agent and an oxygen barrier layer. The myoglobin red producing agent is selected from a list of compounds according to claim 1.

In a second embodiment, a food container is provided. The food package has a food containing myoglobin and a water content of at least 5% by weight and a receptacle comprising an article for packaging food according to claim 1 in the form of a polymeric film. The receptacle contains the food in a medium with a reduced oxygen content and the contact layer with the food has a contact surface with it of which at least a portion is in contact with at least a portion of the surface of a food that contains myoglobin. The myoglobin red producing agent is selected from a list of compounds according to claim 1.

In a third embodiment, a method of promoting a desirable color on the surface of a fresh meat product containing myoglobin is provided. The method comprises supplying a receptacle comprising a polymeric film having an oxygen barrier layer and a food contact layer, provide a fresh meat product containing myoglobin and having a water content of at least 5% by weight and contacting the fresh meat product containing myoglobin with a myoglobin-red producing agent to produce a product of fresh meat that contains myoglobin and that has less than 0.5% by weight of sodium chloride. The myoglobin red producing agent is selected from a list of compounds according to claim 1. In some aspects, the method further comprises removing oxygen from the environment surrounding the fresh meat product and storing the fresh meat product in a medium substantially free of oxygen for a time sufficient to allow the appearance of the desirable color. In other aspects, the polymeric film comprises the myoglobin red producing agent and the method further comprises packaging the fresh meat product in contact with the contact layer with said product.

The articles, compositions, films, packages and methods provided by the present invention are useful for providing packaged products of fresh, frozen, thawed, processed and / or cured meat having a desirable surface color, such as red in the case of fresh meat of cattle.

Brief description of several views of the drawings

Figure 1 shows a schematic cross-sectional view of a first example of multilayer film.

Figure 2 shows a schematic cross-sectional view of a second example of multilayer film.

Figure 3 shows a schematic cross-sectional view of a third example of multilayer film.

Figure 4 shows a schematic cross-sectional view of a fourth example of multilayer film.

Figure 5 shows a schematic cross-sectional view of a tray containing meat, with a top wrap of the barrier film type.

Figure 6 shows a top view of a vacuum packed meat cut with a thin film.

Figure 7 shows a schematic cross-sectional view of a meat in a preformed receptacle.

Detailed description of preferred embodiments

Definitions

According to the present invention, "article for packaging" refers to a manufactured object that can be in the form of a continuous band, for example, single-layer or multi-layer films, single-layer or multi-layer sheets, receptacles, for example, bags, shrink bags, bags, wrappers, trays, trays with a lid, trays with a wrap, shrink packaging, vacuum packaging of thin films, thermoforming containers, Packaging inserts or combinations thereof. Those skilled in the art should appreciate that, in accordance with the present invention, the items for packaging can include flexible, rigid or semi-rigid materials and can be heat shrinkable or not and oriented or non-oriented.

When describing plastic film containers, various polymer acronyms are used in the present invention, which are listed below. Also, to refer to polymer blends, two points will be used (:) to indicate that the components to the left and right of the two points are mixed. When referring to the structure of a film, an inclined bar (/) will be used to indicate that the components to the left and right of the inclined bar are in different layers and the relative position of components in the layers can also be indicated using the inclined bar to indicate limits of the layers of a film. Acronyms commonly used herein include:

EAA copolymer of ethylene and acrylic acid

EAO copolymer of ethylene and at least one α-olefin

EBA copolymer of ethylene and butyl acrylate

EEA ethylene and ethyl acrylate copolymer

EMA copolymer of ethylene and methyl acrylate

EMAA copolymer of ethylene and methacrylic acid

EVA ethylene vinyl acetate copolymer

EVOH a saponified or hydrolyzed copolymer of ethylene and vinyl acetate

PB poly (butylene-1) (a homopolymer of butylene and / or a copolymer of a main portion of ethylene and a

or more α-olefins)

PE polyethylene (a homopolymer of ethylene and / or a copolymer of a main portion of ethylene and one or more α-olefins)

PP homopolymer or polypropylene copolymer

PET poly (ethylene terephthalate)

PETG poly (ethylene terephthalate) modified with glycol

PLA poly (lactic acid)

PVDC poly (vinylidene chloride) [also includes copolymers of vinylidene chloride, especially with vinyl chloride and / or methyl acrylate (MA)], also called sarán

Here, "core layer" refers to a layer located between and in contact with at least two other layers.

Here, "outer layer" is a relative term and is not necessarily a surface layer.

The term "outermost layer" refers to a layer that comprises the outermost surface of a film or product. For example, an outer layer can form the outer surface of a container that contacts the outer layer of another container during the two-pack overlapping heat sealing.

The term "inner layer" refers to a layer that comprises the innermost surface of a film or product. For example, an inner layer forms the inner surface of a closed container. The inner layer may be the contact layer with the food and / or the sealing layer.

Here, the terms "barrier" and "barrier layer", applied to films and / or film layers, are used with reference to the ability of a film or film layer to serve as a moisture barrier and against one or more gases.

Here, the term "cellulose" includes any natural or synthetic material comprising paper fibers, wood fibers, pulp or wood dust, etc., preferably cellulosic fibers (such as rayon, lyophilized cellulose, cellulose acetate, carbamate cellulose and deacetylated cellulose acetate) and regenerated cellulose (eg cellophane). Here, the term "nonwoven" refers to nonwoven paper, fabrics and textiles and includes continuous bands made of filaments fused together, continuous bands formed dry and continuous bands formed wet. Nonwoven products are made of natural or synthetic fibers bonded together forming a continuous band.

The term "nanocomposite" means a mixture that includes a polymer or copolymer that disperses a plurality of individual lamellae that can be obtained from exfoliated modified clay and that have oxygen barrier properties.

The term "adhesive layer" or "bonding layer" refers to a layer or material placed on one or more layers to promote adhesion of that layer to another surface. Preferably, the adhesive layers are located between two layers of a multilayer film to keep the two layers in relative position with each other and avoid undesirable de-stratification. Unless otherwise indicated, an adhesive layer may have any suitable composition that provides a desired level of adhesion with one or more surfaces in contact with the material of the adhesive layer. Optionally, an adhesive layer placed between a first layer and a second layer of a multilayer film may comprise components of the first layer and the second layer to promote simultaneous adhesion of the adhesive layer to the first layer and the second sided layer. opposite of the adhesive layer.

Here, the terms "sealing layer" and "heat sealing layer" refer to a layer or layers of the outer film involved in the sealing of the film: itself, another layer of the same film or another film and / or another article that is not a movie, for example, a tray. In general, the sealing layer is an inner layer of any suitable thickness and provides the sealing of the film to itself or to another layer. With respect to packages that have only sealed the fin type, as opposed to sealed the wrap type, the term "sealing layer" refers to the inner surface layer of the film of a package. The inner layer can also act as a contact layer with food in food containers.

"Food contact layer", "food contact portion" or "food contact surface" refers to the portion of a packaging material that contacts a packaged meat product. Preferably, the food packaging film includes a food contact layer and comprising a red producing agent in an amount effective to promote or preserve the desirable appearance or color of the meat product.

The term "polyolefin" is generally used herein to include polymers such as polyethylene, copolymers of ethylene and α-olefins (EAO), polypropylene, polybutene and copolymers of ethylene having a major amount by weight of ethylene polymerized with an amount less than a comonomer such as vinyl acetate, and other polymeric resins that fall within the classification of the "olefin" family. Polyolefins can be prepared by a variety of processes well known in the art, including continuous and discontinuous processes using individual reactors, in stages or sequential, suspended processes, solution and fluidized bed and one or more catalysts, including, for example, homogeneous and heterogeneous systems and catalysts Ziegler, Phillips, metallocenes, single site and forced geometry, to produce polymers that have different combinations of properties. These polymers can be substantially linear or highly branched and the degree of branching, dispersion and average molecular weight may vary depending on the parameters and processes chosen for their manufacture in accordance with what is described in the polymer manufacturing techniques.

"Polyethylene" is the name of a polymer whose basic structure is characterized by the chain - (CH2 – CH2–) n. A polyethylene homopolymer is generally described as a solid having a partially amorphous phase and a partially crystalline phase and a density of 0.915 to 0.970 g / cm 3. It is known that the relative crystallinity of a polyethylene affects its physical properties. The amorphous phase imparts flexibility and high impact resistance while the crystalline phase imparts stiffness and a high softening temperature.

"Unsubstituted polyethylene" generally refers to a high density homopolymer having a crystallinity of 70 to 90 percent and a density of 0.96 to 0.97 g / cm 3. The most commercially used polyethylenes are not unsubstituted polymers but have C2-C8 alkyl groups attached to the basic chain. These substituted polyethylenes are also known as branched chain polyethylenes. Also, commercially available polyethylenes often include other substituted groups produced by copolymerization. Branching with alkyl groups generally reduces crystallinity, density and melting point. It is admitted that the density of a polyethylene is closely related to its crystallinity. The physical properties of commercially available polyethylenes are also affected by the average molecular weight and molecular weight distribution, branch length and type of substituents.

Those skilled in the art consider various broad categories of polymers and copolymers as "polyethylene." The inclusion of a particular polymer in one of these "polyethylene" categories is often based on the density of the "polyethylene" and the process by which it has been manufactured since the process frequently determines the degree of branching, crystallinity and density. In general, the nomenclature used is not specific to a compound but refers to a range of compositions. This range frequently includes homopolymers and copolymers.

For example, "high density polyethylene" (HDPE) is commonly used in the art to refer to: (a) homopolymers of densities between about 0.960 and 0.970 g / cm3 and (b) copolymers of ethylene and an α olefin (usually 1-butene or 1-hexene) with densities between 0.940 and 0.958 g / cm3. The HDPE includes polymers made with Ziegler or Phillips type catalysts and also includes high molecular weight polyethylenes. Unlike HDPE, whose chains have some branching, there are "very high molecular weight polyethylenes" which are special, essentially unbranched polymers, which have a much greater molecular weight than HDPE.

Hereinafter, the term "polyethylene" (unless otherwise indicated) will be used to refer to ethylene homopolymers as well as copolymers of ethylene and α-olefins and this term will be used regardless of the presence or absence of groups branched substituents.

Another broad group of polyethylenes are "high pressure and low density polyethylenes" (LDPE). The term LDPE designates branched homopolymers having densities between 0.915 and 0.930 g / cm3. LDPEs typically contain long branches outside the main chain (often referred to as "main structure") formed by alkyl substituents of 2 to 8 or more carbon atoms.

"Linear Low Density Polyethylene" (LLDPE) are copolymers of ethylene and olefins having

α densities 0.915 to 0.940 g / cm3. The α-olefin used is usually 1-butene, 1-hexene or 1-octene and usually Ziegler catalysts are used (although Phillips catalysts are also used to produce LLDPE having densities at the greater end of the cited range, and also they use metallocenes and other types of catalysts to produce well-known variations of LLDPE).

The copolymers of ethylene and α-olefins (EAO) are copolymers having ethylene as the main component, copolymerized with one or more α-olefins such as 1-octene, 1-hexene or 1-butene, as the minor component. EAOs include copolymers known as LLDPE, VLDPE, ULDPE and elastomers and can be manufactured using a variety of processes and catalysts, including metallocene, single site and forced geometry catalysts as well as Ziegler-Natta and Phillips catalysts.

"Very low density polyethylene" (VLDPE), also called "ultra low density polyethylene" (ULDPE), comprises copolymers of ethylene and α-olefins, usually 1-butene, 1-hexene or 1-octene, and is admitted by Experts in the art who have a high degree of linearity in their structure, with short ramifications instead of the long lateral chains characteristic of LDPE. However, VLDPEs have lower densities than LLDPEs. Those skilled in the art admit that the densities of VLDPE vary between 0.860 and 0.915 g / cm3. In the publication of European patent document number 120,503, whose text and drawings are incorporated by reference in the present invention, a process for manufacturing VLDPE is described. Sometimes VLDPEs that have a density less than 0.900 g / cm3 are called "plastomers."

Polyethylenes can be used alone or mixed with each other and / or with copolymers, forming single-layer or multi-layer films, for food packaging applications, such as poultry meat, fresh red meat and processed meat.

Here, the term "modified" refers to a chemical derivative, for example, one that has any form of anhydride functionality, such as maleic acid anhydride, crotonic acid, citrazonic acid, itaconic acid, fumaric acid, etc. , grafted into a polymer or copolymerized with a polymer, or any other functionality associated with one or more polymers, and also includes derivatives of said functionalities, such as acids, esters and metal salts derived from them. Other examples of common modifications are acrylate modified polyolefins.

Here, the terms identifying polymers, such as "polyamide" or "polypropylene," include not only polymers comprising repeating units derived from monomers that polymerize to form a polymer of the aforementioned type, but also include comonomers thus as modified and unmodified polymers manufactured, for example, by derivatization of a polymer after polymerization by adding functional groups or moieties along the polymer chain. In addition, the terms identifying polymers also include "mixtures" of said polymers. Therefore, the terms "polyamide polymer" and "nylon polymer" may refer to a homopolymer containing polyamide, a copolymer containing polyamide or mixtures thereof.

The term "polyamide" means a high molecular weight polymer that has amido bonds (-CONH-) n that are along the molecular chain and includes "nylon" resins that are well known polymers that have a multitude of uses, including its usefulness as films, bags and wrappers for packaging products. See, for example, Modern Plastics Encyclopedia, 88, volume 64, number 10A, pages 34-37 and 554-555 (McGraw-Hill Inc., 1987), which is incorporated herein by reference. Polyamides are preferably selected from nylon compounds approved for use in producing articles intended for food processing, handling and packaging.

The term "nylon" used herein refers more specifically to aliphatic or aromatic synthetic polyamides, in crystalline, semi-crystalline or amorphous form, characterized by the presence of the amido group -CONH. This term refers to polyamides and copolyamides.

Therefore, the terms "polyamide" or "nylon" encompass polymers comprising repetitive units derived from monomers, such as caprolactam, which polymerize forming a polyamide, as well as copolymers derived from copolymerization of caprolactam with a comonomer which, when polymerized alone, it does not cause the formation of a polyamide. Preferably, the polymers are selected from compositions approved as suitable for producing articles intended for use in food processing, handling and packaging, such as nylon resins approved by the US Food and Drug Administration by document 21 CFR § 177.1500 ("resins of nylon ”), which is incorporated herein by reference. Examples of these polymeric nylon resins for use in food processing and packaging include nylon 66, nylon 610, nylon 66/610, nylon 6/66, nylon 11, nylon 6, nylon 66T, nylon 612, nylon 12, nylon 6/12, nylon 6/69, nylon 46, nylon 6-3-T, nylon MXD-6, nylon MXDI, nylon 12T and nylon 6I / 6T, all described in document 21 CFR § 177.1500. Examples of such polyamides include homopolymers and copolymers of nylon, such as those selected from the group consisting of nylon 4.6 [poly (tetramethylene adipamide)], nylon 6.6 [poly (hexamethylene adipamide)], nylon 6.9 [poly (hexamethylene) nonanodiamide)], nylon 6,10 [poly (hexamethylensebacamide)], nylon 6,12 [poly (hexamethylene diadenediamide)], nylon 6/12 [poly (caprolactam-co-dodecanediamide), nylon 6,6 / 6 [poly (hexamethylene adipamide) -co-caprolactam], nylon 66/610 (manufactured, for example, by condensation of mixtures of salts of nylon 66 and salts of nylon 610), nylon 6/69 (manufactured for example, by condensation of

ε

caprolactam, hexamethylenediamine and azelaic acid), nylon 11 [poly (undecanolactam)], nylon 12 [poly (laurillactam)] and copolymers or mixtures thereof.

The term "amorphous" used in the term "amorphous nylon copolymer" indicates the absence of a regular three-dimensional arrangement of molecules or subunits of molecules that extend over distances that are large with respect to atomic dimensions. However, there may be regularity in the structure at the local level. See "Amorphous Polymers," Encyclopedia of Polymer Science and Engineering, 2nd edition, pages 789-842 (J. Wiley & Sons Inc., 1985). In particular, the term "amorphous nylon copolymer" refers to a material that those skilled in the art of differential scanning calorimetry (DSC) recognize that it does not have a measurable melting point (less than 0.5 cal / g) or a heat of fusion measured by DSC using ASTM 3417-83. The amorphous nylon copolymer can be manufactured by condensation of hexamethylenediamine, terephthalic acid and isophthalic acid according to known processes. Amorphous nylon also includes amorphous nylon prepared by condensation polymerization reactions of diamines with dicarboxylic acids. For example, an aliphatic diamine is combined with an aromatic dicarboxylic acid or an aromatic diamine is combined with an aliphatic dicarboxylic acid giving suitable amorphous nylon.

Here, "EVOH" refers to a copolymer of ethylene and vinyl acetate. Apart from that, EVOH is known as a saponified or hydrolyzed copolymer of ethylene and vinyl acetate and refers to a copolymer of vinyl alcohol having an ethylene comonomer. EVOH is prepared by hydrolysis (or saponification) of a copolymer of ethylene and vinyl acetate. Preferably the degree of hydrolysis is about 50 to 100 mole percent, more preferably about 85 to 100 mole percent and most preferably at least 97%. It is well known that in order to be a very effective barrier against oxygen, hydrolysis-saponification must be almost complete, that is, to a degree of at least 97%. EVOH is commercially available in resin form with various percentages of ethylene and there is a direct relationship between ethylene content and melting point. For example, a melting point of about 175 ° C or less is characteristic of EVOH materials having an ethylene content of about 38 mol% or more. An EVOH having an ethylene content of 38 mol% has a melting point of approximately 175 ° C. When the ethylene content increases, the melting point decreases. Also, EVOH polymers that have higher percentages of ethylene have higher gas permeabilities. A melting point of approximately 158 ° C corresponds to an ethylene content of 48 mol%. EVOH copolymers having higher or lower ethylene contents can also be used. It is assumed that processing ability and orientation are facilitated with larger content. However, gas permeability, in particular to oxygen, may become undesirably high for certain packaging applications that are sensitive to microbial development in the presence of oxygen. On the contrary, smaller contents may have lower gas permeabilities but the processing ability and orientation may be more difficult.

Here, the term "polyester" refers to synthetic homopolymers and copolymers that have ester bonds between monomer units and that can be formed by condensation polymerization methods. Polymers of this type are preferably aromatic polyesters and more preferably homopolymers and copolymers of poly (ethylene terephthalate), poly (ethylene isophthalate), poly (butylene terephthalate), poly (ethylene naphthalate) and mixtures of these polymers. Suitable aromatic polyesters may have an intrinsic viscosity between 0.60 and 1.0, preferably between 0.60 and 0.80.

"Reduced oxygen atmosphere" when referring to a packaged meat product refers to a reduction in the partial pressure of oxygen in contact with the packaged meat product, compared to the partial pressure of oxygen in Earth's atmosphere at temperature and standard pressure at sea level. The reduced oxygen atmosphere containers may include modified atmosphere containers in which the partial pressure of oxygen is lower than that of the Earth's atmosphere at standard temperature and pressure at sea level, or vacuum containers, which contain gas pressure minimum in contact with packaged meat. Modified atmosphere containers can create a substantially reduced oxygen atmosphere in which an oxygen content of less than 3.0% oxygen (volume / volume) (v / v) and preferably less than 1.0% oxygen is desirable (v / v). For processed meat, an oxygen content of less than 0.5% (v / v) is desirable.

"Vacuum packaging" refers to actively removing atmospheric gases, more specifically oxygen, from the inside of the container and sealing the container so that virtually no gas is able to penetrate the container from the outside. The result is a container with a minimum amount of oxygen gas in contact with the meat contained in the container. The removal of oxygen from the immediate environment of the product slows down processes of bacterial and oxidative deterioration, thus maintaining the quality of fresh meat for a longer period of time.

"MAP" is the abbreviation for "modified atmosphere container." This is a package format in which a gas has been actively introduced into the upper space of the container before sealing. In general, the gas is modified to be different from what is normally found in Earth's atmosphere. The result is a container with a considerable volume of gas that surrounds the surface that is seen of the product present in the container. A MAP of fresh meat can use an oxygen-enriched atmosphere or an oxygen-free atmosphere to effectively increase its duration.

"RAP" is the abbreviation for "reduced atmosphere container". This can be a form of MAP in which the atmospheric gases are minimal, so that the material of the container physically contacts its interior content. RAP can also be a form of vacuum packaging in which the atmosphere inside the package has not been completely removed. Examples include conventional fresh meat containers, such as a "tray with a PVC top wrap" and the conventional case of a poultry meat container in which a shrink film or bag is sealed tightly around a meat tray. In general, the fresh meat contained in a RAP has a larger profile than the tray used to contain the meat so that the film of the container surrounding the product makes considerable physical contact with the surface of the meat.

"Container for consumption" refers to any receptacle that contains a meat product for the purpose of its exposure and sale to domestic consumers.

“Prepared packaged” meat refers to a container of fresh meat for consumption that has been pre-packaged and / or labeled at a centralized point and supplied for retail sale in a format, so it is ready for immediate exposure and sale . The ready-to-eat container actively lengthens the duration of a fresh meat product so it allows the extra time it needs to be packaged in a central facility, distributed to the retail seller and exposed to light for selection and purchase by consumers.

"Myoglobin-red-producing agent" refers to any agent (or precursor) that binds or interacts with a non-denatured structure that contains myoglobin (including, but not limited to, deoxythioglobin, oximioglobin, methioglobin, carboximioglobin and myoglobin- nitric oxide) present in a fresh meat product to produce or preserve a desired color, such as a red color indicative of fresh meat. The myoglobin red-producing agent can also interact or cause an interaction with the hemoglobin present in a meat product to produce, maintain or increase, that is, to "fix" a desired color. Therefore, the myoglobin red color producing agent is not a colored additive but acts as a color fixer. Examples of red producing agents include gases, such as oxygen and carbon monoxide.

"Deoximioglobin" refers to myoglobin in which oxygen is not present in the heme group. The iron atom of the heme group is in a reduced ferrous state. Deoximioglobin is associated with the non-flushed purple pigment of fresh meat.

"Oxythioglobin" refers to the oxygenated form of deoxyximoglobin in which the heme group ligand is an oxygen gas molecule. Oxythioglobin is associated with the bright red pigment of fresh meat.

"Metmioglobin" refers to an oxidized form of myoglobin in which the iron of the heme group is in a ferric oxidized state. Methioglobin causes an oxidized brown pigment characteristic of fresh meat.

"Carboximioglobin" refers to the reduced, non-denatured form of the carboxylated deoxythioglobin pigment in which the heme group ligand is carbon monoxide. The color of carboximioglobin is red.

"Nitroximioglobin" is the reduced, non-denatured form of the nitrosilated deoxythioglobin pigment. The heme group ligand is a molecule of nitrogen monoxide (NO). Nitrogen monoxide is also called nitric oxide. Nitroximioglobin is also called myoglobin-nitric oxide, nitrosohemochromogen

or nitrosomyoglobin, among other names. Nitroximioglobin has the same red color as oximioglobin and carboximioglobin.

"Methioglobin-nitric oxide" is the non-denatured oxidized form of deoxythioglobin when nitrite ion is present. It is used to describe the brown color of meat that typically occurs when nitrite is added during the curing process.

"Nitrosohemochrome" refers to the nitrosylated protoporphyrin (heme complex) that separates from the globin protein of the myoglobin molecule. Nitrosohemochrome provides the stable pink to brown color of cooked cured processed meat in which the heme group iron is in a reduced state.

"Meat" or "meat product" refers to any tissue that contains myoglobin or hemoglobin from an animal, such as ox, pig, veal, lamb, chicken or turkey; game meat, such as deer, quail and duck; fish and seafood. Meat may be in a variety of forms, including primary or subprimary cuts and cuts for retail sale, as well as minced or mixed meat. The meat or meat product is preferably fresh, raw, uncooked meat, although it can also be frozen, chilled or thawed meat. It is also believed that meat can be subjected to other radiation, biological, chemical or physical treatments. The suitability of any particular treatment can be determined without undue experimentation in view of the present description. As long as the myoglobin red color producing agent is effective in promoting, developing, increasing or maintaining a desirable color, it can be advantageously used for that purpose. Preferably the meat is less than 20 days post mortem. More preferably, the meat is less than 12 days or even less than 6 days or less post mortem.

Primary cuts of meat are also called cuts for wholesale sales and these two terms refer to large sections of an open carcass that are usually sold and / or transported to butchers who further subdivide the primary cuts into subprimary cuts and cuts Individuals for retail sales to consumers. Examples of primary cuts of cattle are: round, hindquarters, sirloin, side, rib, skirt, leg and shoulder. Examples of primary cuts of pork are: loin, leg, shoulder and belly.

Subprimary cuts are of intermediate size and can be further divided into cuts for retail sales or sometimes sold as retail cuts. Subprimary cuts of beef include: front leg, shoulder, ribs, steaks, round, ribs and sirloin. Subprimary pork cuts include: back, center cut, sirloin, leg end and rib.

The cuts for retail sale are cuts for consumers made by dividing the cuts for wholesale into smaller pieces. Examples of beef cuts for retail sale include: frying pieces, such as round, top round, dice, sirloin, steak, rib, skirt, side and tip; roasting pieces, such as shoulder, salted skirt, fresh skirt, stew meat, short ribs, round eye, rolled back quarter, leg cross sections, meat rollers, minced meat and dumplings. Examples of pork cuts for retail sale include: bacon, salted pork, ham, ham steaks, ham slices, pork steaks, pork chops, fatty loin, sausages and minced pork.

"Fresh meat" means uncooked, uncured, non-smoked and unmarinated meat. Fresh meat includes post mortem meat that has been physically divided, for example, by cutting, crushing or mixing. There is no salt added in fresh meat that has not been improved. The sodium present by nature is less than 50 mg / 100 g of meat, which corresponds to a salt content of less than about 0.15% by weight, preferably less than 0.128% by weight. Sodium values ​​are in a database of the nutritional composition of meat called “National Nutrient Data Bank”, and the data is published in Agriculture Handbook No. 8, “Composition of Foods-Raw Processed, Prepared”, denominated in the industry "Handbook 8", both incorporated herein by reference.

"Enhanced meat" means meat to which water and other ingredients have been added, such as sodium chloride, phosphates, antioxidants and flavorings, for example, to make the meat moist and more tender and to help increase its duration. Fresh beef, pork or poultry, after being "improved," may typically contain 0.3-0.6% by weight of salt (sodium chloride).

"Processed meat" means meat that has been altered by heating and chemical processes, for example, cooking and curing. Cooked ham, hot dogs and meat to eat are examples of processed cured meat.

"Processed uncured meats" are processed meats that do not contain nitrites or nitrates. Processed uncured meats typically contain more than 1.0% by weight, typically 1.2-2.0% by weight of sodium chloride (salt). Roasted meat and sauce are examples of uncured processed meat.

"Cured meat" means meat preserved by direct addition of nitrite (or nitrate, which is converted into nitrite) and which has, for example, at least 50 ppm of sodium nitrite and at least 1% by weight of added salt, this it is, sodium chloride, in order to preserve it by delaying bacterial development. In the curing compositions, nitrites, nitrates or mixtures of both are commonly present, together with sodium chloride. "Uncured meat" does not contain nitrites or added nitrates. Wet cured meats are soaked in brine. Dry cured meats have salt applied to the surface. Injection-cured meats have the curing salts applied by injection into the meat by needle.

Processed cured meats frequently have 2-3.5% by weight of salt. In processed meats, a content of 3.5-4.0% by weight (2.6-3.0% based on dry weight in treated meat) is required as the level of sodium chloride (sodium chloride can be substituted totally or partially by potassium chloride) to slow bacterial development and allow a duration of 60-90 days, although other means of preservation can also be used to maintain the duration with reduced salt levels. According to RB Pegg and F. Shahidi, Nitrite Curing of Meat, 2000, Food & amp; Nutrition Pres Inc., Trumbull, CT, cured meats typically have salt levels of 1.2-1.8% by weight in bacon, 2-3% by weight in ham, 1-2% by weight in sausages and 2 -4% in jerky. It is believed that fresh meat, such as beef, pork and poultry, has no nitrites or natural or added nitrates. The United States Department of Agriculture (USDA) allows nitrites and nitrates added in cured and processed meat to a maximum level of 625 ppm of sodium nitrite or 2,187 ppm of sodium nitrate in dried cured products. In other applications these levels have different limits; for example, in typical products of fully cooked meat the limit (such as sodium nitrite) is 156 ppm and in minced meats 200 ppm. The maximum nitrite level in hot dogs or Bolognese is typically 156 ppm while in bacon it is 120 ppm. In these cured meats, sodium ascorbate (or similar compounds) may be present.

In Europe it is believed that the maximum level of salt and nitrite required by law for curing is 1.0% by weight and 50 ppm, respectively. The USDA has established that: “for safety, the Agency requires a minimum of 120 ppm of added nitrite in all cured products“ kept refrigerated ”, unless the establishment can demonstrate that safety is ensured through other conservation processes, such as processes thermal and humidity and pH control. This limit of 120 ppm of added nitrite is based on revised safety data when the standard for the bacon was developed. ” (See “Processing Inspectors' Calculations Handbook, chapter 3, page 12, 1995 edition). The Handbook also specifies: “Although there is no regulated minimum of the level of added nitrite, however 40 ppm of nitrite is useful because it has a preservative effect. This amount has also proved sufficient to fix the color and achieve the desired appearance of cured meat or poultry. ”

The meat product can be any meat suitable for human consumption that contains a molecule similar to myoglobin. References to total myoglobin in a meat product refer to the amount of myoglobin-like molecules that are physiologically present in meat tissue before being collected for human consumption. Specific meat products contain a level of myoglobin sufficient to provide their characteristic color. Examples of suitable fresh meats include beef, veal, poultry and lamb. The concentration of myoglobin varies in these different types of meat products. For example, cattle typically contain about 3-20 mg of myoglobin per gram of meat, pork contains about 1-5 mg of myoglobin per gram of meat, and chicken contains less than about 1 mg of myoglobin per gram of meat. Therefore, the total concentration of myoglobin compounds in the meat products described above is typically between about 0.5 mg and 25 mg of myoglobin compounds per gram of meat product.

In fresh meat (post mortem muscle tissue) oxygen can be continuously associated and dissociated from the heme complex of the non-denatured myoglobin molecule. It is the relative abundance of three forms of the non-denatured myoglobin pigment that determines the visual color of fresh meat. These forms include purple deoximioglobin (reduced myoglobin), red oxythioglobin (oxygenated myoglobin) and brown methioglobin (oxidized myoglobin). The form of desoximioglobin typically predominates immediately after slaughtering the animal. Therefore, freshly cut meat has a purple color. This purple color can persist for a long time if the pigment is not exposed to the action of oxygen. Cutting or crushing exposes the pigment to the action of oxygen in the atmosphere and the purple color can quickly turn bright red (oxythioglobin) or brown (methioglobin). Therefore, although deoximioglobin is technically indicative of fresher meat, it is the red color of the meat that consumers use as the first criteria to perceive the freshness of a meat. It is believed, without wishing to be bound by any theory, that the preferred red color of fresh meat occurs when at least 50% of the deoxymyoglobin molecules are oxygenated to the oxythioglobin state. It may happen that the percentage changes in each of these forms continue when fresh meat is exposed to the action of oxygen for longer periods of time. The immediate conversion of the purple color to the desirable red color or the undesirable brown color depends on the partial pressure of oxygen on the surface. The purple color is favored by a very low level of oxygen and may predominate at oxygen levels of 0-0.2% by volume. The brown color is promoted by a slightly higher level of oxygen (0.2 to 5.0%). The discrimination on the part of the consumers is evident to 40% of methioglobina, that typically makes the meat not salable even though it continues being nutritious and apt for the consumption.

Certain biochemical reactions that occur in muscle tissue after death can also affect the color of fresh meat, such as the presence of active glycolytic enzymes that convert oxygen to carbon dioxide. Reducing coenzymes called methioglobin reductases, present in meat, convert methioglobin into deoxymeglobin and its activity is called "MRA", which is an abbreviation for "metmyoglobin reducing activity". MRA can be described as the ability of the muscle to reduce methioglobin to its natural state of deoximioglobin. MRA is lost when oxidizable substrates are depleted or when heat or acids denature enzymes. When enzymes lose their activity or become denatured, the heme pigment iron automatically oxidizes to the form of methioglobin and the brown color stabilizes and predominates. MRA persists for a period of time after death, depending on the amount of exposure of meat tissue to oxygen. During this time, oxygen is continuously consumed by the tissue of the meat. The oxygen consumption rate is called "OCR" ("oxygen consumption rate"). When meat that has a high OCR is exposed to the action of oxygen, the oxygen tension is reduced so rapidly that methioglobin is favored below the surface that is seen. If it is close to the surface that is seen, it affects the perceived color of the meat. MRA is important to minimize this layer of methioglobin that forms between the red surface and the purple interior. When the MRA is lost, the brown methioglobin layer becomes thicker and migrates to the surface, thus ending its exposure time. When the MRA is high, the methioglobin layer is thin and sometimes not visible to the naked eye.

The MRA and OCR serve to determine the most suitable types of retail packaging to prolong the desirable appearance of the meat as much as possible. Hermetically sealed containers with films that are a barrier against oxygen will cause a low oxygen tension on the surface of the meat. Therefore, methioglobin formation occurs and the surface that is seen changes to an undesirable brown color. However, if the OCR is high enough to keep the migrating oxygen active through the film of the container and the MRA is good enough to reduce the methioglobin that forms on the surface, then the natural deoxymyoglobin displaces the methioglobin . After a certain period of time, the perceived color changes from brown to purple. These two colors are not acceptable to consumers. For this reason, vacuum packaging has historically been an unacceptable format for fresh prepared packaged meat although it is used for the transport of subprimary cuts and other large cuts of meat from the slaughterhouse to the butcher shops for processing and repackaging. On the other hand, vacuum containers are the format chosen for processed cured and cooked meats in which the myoglobin pigment has been denatured by heat. The heat of cooking causes the globin portion of the nitrosilated myoglobin molecule to become denatured and separated from the heme portion. It is the dissociated nitrosylated heme complex that gives processed and cured meats their characteristic color. When oxygen is removed from a package of cured processed meat, the color and taste of the product may deteriorate more slowly than when oxygen is present. In the present invention, oxygen must be removed from the environment of fresh raw meat before the preferred color develops. A certain amount of oxygen penetrates the meat after slaughter and manufacturing. This oxygen is eliminated by the activities of the OCR / MRA. Likewise, these activities facilitate the predominance of the deoxymyoglobin form of the myoglobin molecule. It is believed, but without wishing to be bound by any theory, that the activities of the OCR / MRA also facilitate the reduction of nitrites to nitric oxide when sodium nitrite is used as the producing agent of the red color of myoglobin. In this case, the formation of deoximioglobin and nitric oxide allows the development of nitroximioglobin. Oxygen itself is a red producing agent because it causes the formation of oxythioglobin, as described hereinbefore. However, oxygen interferes with the reactions that form desoximioglobin and nitric oxide. Therefore, it interferes with the development of the red color in the presence of nitrites. Therefore, a preferred aspect of the present invention is to select and configure an oxygen barrier layer to protect the surface of the meat from the entry of atmospheric oxygen during the formation of the desired red color of the meat.

Producers of the myoglobin red color

In a first embodiment, producing agents of the myoglobin red color are provided. "Agent producing the red color of myoglobin" (abbreviated "MBA"; from Myoglobin Blooming Agent) refers to any agent (or precursor to it) that binds or interacts with any structure that contains denatured myoglobin (included, but not characterized limiting, oximioglobin, methioglobin, carboximioglobin and myoglobin-nitric oxide) present in a fresh meat product to produce or preserve a desired color, such as a red color indicative of fresh meat. The myoglobin red producing agent can also interact or cause an interaction with the hemoglobin present in a meat product to produce, maintain or increase, that is, to "fix" a desired color. Therefore, the myoglobin red color producing agent is not a colored additive but acts as a color fixer.

In a preferred embodiment, the myoglobin red producing agent is a "nitric oxide donor compound" ("NO donor") that provides a nitric oxide (NO) molecule that binds to the myoglobin present in a product of meat to maintain or favor a redness or shine or other favorable coloring of the meat product. A nitric oxide donor compound releases nitric oxide or is a precursor, for example, a nitrate, which acts as an intermediate that causes the formation of nitric oxide that binds to a myoglobin molecule present in a meat product. Examples of nitric oxide donor compounds include nitrosodisulfonates, including, for example, Fremy salt [NO (SO3Na) 2 or NO (SO3K) 2].

Other suitable nitric oxide donor compounds that can act as producing agents of the myoglobin red color are described in US Pat. Nos. 6,706,274 to Herrmann et al. (filed January 18, 2001), 5,994,444 from Trescony et al. (filed on October 16, 1997) and

6,939,569 to Green et al. (filed June 18, 1999), as well as in published U.S. patent application number US2005 / 0106380 of Gray et al. (filed on November 13, 2003). Optionally, the myoglobin red producing agents may contain materials that promote the conversion of other materials to NO, such as nitrate reductases or nitrosothiol reductases catalytic agents, including materials described in WIPO Publication No. WO 02/056904 of Meyerhoff et to the. (filed on January 16, 2002).

Other examples of nitric oxide donor compounds include nitrosoderivative organic compounds (containing a functional group -NO bonded to a carbon), including 3-ethyl-3-nitrosopentane-2,4-dione, and nitroderivative organic compounds (containing a functional group –NO2 attached to a carbon), including nitroglycerol and 6

nitrobenzo [α] pyrene.

Other examples of nitric oxide donor compounds include O-nitrosylated compounds (-O- NO), S-nitrosylated compounds (-S-NO), also known as nitrosothiols, including S-nitrosothioglycerol, Snitrosopenicillamine, S-nitrosoglutathione, glutathione, derivatives S-nitrosylated captopril, S-nitrosylated proteins, S-nitrosylated peptides, S-nitrosylated oligosaccharides, S-nitrosylated polysaccharides and Nnitrosylated compounds (-N-NO), including N-nitrosoamines, N-hydroxy-N-nitrosoamines and N-nitroimines.

Additional examples of nitric oxide donors include nonoate compounds that include the functional group -N (O) -NO, also referred to in the art as N-oxo-N-nitroso compounds, Nhydroxy-N'-diazenium oxides, diazeniodiolates and NONO- atos, including 3,3,4,4-tetramethyl-1,2-diazetine-1,2-dioxide.

Other examples of nitric oxide donor compounds include transition nitrous metal complexes, including sodium nitroprusside; dinitrosyl-iron-thiol complexes, iron nitrosyl-sulphide, ruthenium-nitrosyl, transition nitrous-heme-metal complexes, ferrous nitroso-protoporphyrin complexes, furoxanes including 1,2,5-oxadiazole N-oxide, benzofurans, oxatriazole -5-imines including 3-aryl-1,2,3,4-oxatriazol-5-imine, sydnonimines including molsidomine, oximes including cyclohexanone oxime, hydroxylamines, N-hydroxyguanidines and hydroxyureas.

The nitric oxide donor compounds can donate one or more nitric oxide molecules. In some aspects, the nitric oxide donor compound can be a polymeric material that contains several nitric oxide donor compounds, so it can release several nitric oxide molecules. Preferably nitric oxide is released from the polymer chain. For example, U.S. Patent No. 5,525,357 describes a polymer with a nitric oxide releasing functional group attached to the polymer. United States Patent Number

5,770,645 describes a polymer in which a NOx group is covalently linked to the polymer by a linker group. US Patent No. 6,087,479 describes polymer derivative materials derived by derivatization, including nitric oxide adducts. It should be understood that polymeric materials containing a nitric oxide donor compound or a nitric oxide donor functional group chemically bonded to the polymer chain are within the scope of the present invention.

In any case, the nitric oxide donor compound is different from sodium nitrate or sodium nitrite.

In any case, the nitric oxide donor compound is different from an inorganic nitrate or an inorganic nitrite.

In one embodiment the nitric oxide donor compound is different from a nitrosodisulfonate.

Other agents that produce the red color of myoglobin within the scope of the present invention include inorganic cyanides (MCN) in which suitable positive ions (M +) include alkali metal ions (e.g., sodium, potassium), alkaline earth metals (by example, calcium) and transition metals, primary, secondary or tertiary protonated amines, quaternary amines or ammonium; inorganic fluorides (MF) in which suitable positive (M +) ions include alkali metal ions (e.g., sodium, potassium), alkaline earth metals (e.g., calcium) and transition metals, primary, secondary or tertiary protonated amines, quaternary amines or ammonium; isothiocyanates including mustard oil; bacterial cultures that fix nitrogen providing a source of nitric oxide, including xanthine oxidases, nitrate reductases and nitrite reductases; Betanin, erythrocin and cochineal extracts.

Other agents producing the red color of myoglobin include heterocycles and their derivatives. Examples of suitable nitrogen heterocycles include pyridines, pyrimidines (for example, dipyridamole), pyrazines, triazines, purines (for example, nicotinamide), nicotinates, nicotinamides, niacin (also known as nicotinic acid), isoquinolines, imidazoles and derivatives and salts thereof. compounds. It should be understood that these nitrogen heterocycles can be substituted or unsubstituted. In the case of pyridines and isoquinolines, compounds substituted with a carbonyl group in position 3 are preferred. Preferably the nitrogen heterocycle is a pyridine, pyrimidine or imidazole. More preferably the nitrogen heterocycle is an alkali metal or alkaline earth metal salt or a nicotinic acid ester and may include esters such as methyl nicotinate, ethyl nicotinate, propyl nicotinate, butyl nicotinate, pentyl nicotinate, hexyl nicotinate, isonicotinate of methyl, isopropyl isonicotinate and isopentyl isonicotinate. More preferably the nitrogen heterocycle is an alkali metal or alkaline earth metal salt or an nicotinamide or imidazole ester. In another aspect, the nitrogen heterocycle is pyridine, pyrimidine, histidine, N-acetylhistidine, 3-butyrylpyridine, 3-valeroylpyridine, 3-caproylpyridine, 3-heptylpyridine, 3-capriloylpyridine, 3-formylpyridine, nicotine-nmidamide, nicotine-nidamide diethylnicotinamide, isonicotinic acid hydrazide, 3-hydroxypyridine, 3-ethylpyridine, 4-vinylpyridine, 4-bromoisoquinoline, 5-hydroxyisoquinoline or 3-cyanopyridine.

The agents that produce the red color of myoglobin also include any compound that acts as a ligand for myoglobin and causes the formation of the desirable color or any compound that acts as a substrate that causes the formation of said ligand. For example, the myoglobin red producing agent may be a carbon monoxide donor compound. It is known that carbon monoxide complexes with the heme group of myoglobin forming a desirable appearance in meat. A carbon monoxide donor compound is any compound that releases carbon monoxide or acts as a substrate that causes the formation of carbon monoxide. Alternatively, the myoglobin red producing agent may be a sulfur monoxide donor compound (SO), a nitrous oxide donor compound (N2O), an ammonia donor compound (NH3) or a hydrogen sulfide donor compound. Such compounds donate the specific ligand or act as a substrate that causes the formation of the specific ligand. The compounds include transition ligand-heme-metal complexes and ferrous ligand-protoporphyrin complexes, including, for example, carbon monoxide-ferrous protoporphyrin complexes. Carbon monoxide donor compounds, sulfur monoxide donor compounds, nitrous oxide donor compounds and hydrogen sulfide donor compounds include polymeric materials with the appropriate donor functional groups chemically bonded to the polymer chain.

The myoglobin red producing agent is preferably present at the desired concentration in contact with a meat product. The food contact layer of a packaging film preferably contains the myoglobin red producing agent at a concentration high enough to produce or preserve the desirable appearance in a meat product. Preferably the myoglobin-red producing agent is present in the food contact layer at a concentration sufficient to convert at least 50% of the myoglobin molecules present in a contact meat surface to a binding state. With a desired ligand. The concentration of the myoglobin red producing agent is preferably selected to bind ligands that produce the desirable appearance or color of the meat to the myoglobin molecules in the outer 6 mm or less of the meat product. For example, a nitric oxide donor agent is desirably present at a concentration sufficient to convert at least 50% of the myoglobin molecules present on the contact surface of the meat to myoglobin-nitric oxide.

When the myoglobin red producing agent is niacin, the chosen concentration of niacin is greater than the concentration of niacin naturally present in meat. According to Richardson et al. [Composition of Foods. Sausage and Luncheon Meats (Raw, Processed, Prepared) Handbook No. 8-7, USDA, Science and Education Administration, Washington, DC, 1980] Niacin is present in red and poultry meat at a concentration of approximately 0.05 -0.09 mg / g. In the present invention, when niacin is used as the producing agent of the myoglobin red color and is incorporated into the meat product, it is typically used in amounts greater than 0.1 mg / g of meat.

The myoglobin red producing agent can be coated on the inner layer of a polymeric film by spraying, dusting or any other means of application or it can be incorporated into the inner layer.

In other aspects, the myoglobin red producing agent is incorporated into the fresh meat product that contains myoglobin or is coated on the surface of the fresh meat product that contains myoglobin. The myoglobin-red producing agent can be coated on the fresh meat product that contains myoglobin, prior to packaging, by spraying, sprinkling or any other means of application. The producing agent of the red color of myoglobin can be incorporated into the fresh meat product containing myoglobin by mixing it directly with meat, such as minced meat. Alternatively, an aqueous composition of the myoglobin red producing agent can be prepared and mixed with the meat. The aqueous composition may be an aqueous suspension or an aqueous solution of the myoglobin red producing agent.

In addition to the myoglobin red producing agent, other additives known to those skilled in the art can be added. These additives can be added directly to the meat product or to the packaging film, by direct incorporation into said products or by coating or sprinkling on its surface. Examples of these other additives include monosodium glutamate, salt, cereals, soy flour, soy protein concentrate, lactose, corn syrup solids, antifungals (which eliminate the development of yeasts and molds), antibiotics, sugar, glycerol, acid lactic acid, ascorbic acid, erythorbic acid, α-tocopherol, phosphates, rosemary extract and sodium benzoate.

The agents that produce the red color of myoglobin and its solutions or dispersions may be colorless, such as sodium nitrate, or they may have an intrinsic pale color (that is, they may not be completely colorless), such as sodium nitrite, but this Color does not typically have sufficient intensity in itself to act as a significant colored dye or additive. However, this does not prevent the use of colored agents that provide the red color of myoglobin and that impart an intrinsic color or the combination of a producing agent of the red color of myoglobin together with one or more natural dyes, pigments and flavorings and / or artificial, such as annato, bixin, norbixin, beet powder, caramel, carmine, cochineal, turmeric, hot pepper, liquid smoke, erythrosine, betanin, one or more FD & amp; C dyes, etc.

It is believed that the producing agent of the myoglobin red color causes an interaction with the myoglobin present in meat products, thus maintaining, promoting or increasing a desirable color of the meat. Myoglobin includes a non-protein portion called heme and a protein portion called globin. The heme portion includes an iron atom in a flat ring. The globin portion can provide a three-dimensional structure that surrounds the heme group and stabilizes the molecule. The heme group provides an open binding site that can bind to the iron atom certain ligands that have the appropriate electronic form and configuration. When a ligand enters and binds to the heme portion, the electronic configuration of the ligand can change the shape of the globin portion of the molecule in a manner that affects the light absorption characteristics of the heme group. Therefore, the presence or absence of a ligand, such as oxygen, in the heme group and the ligand itself can cause visible color changes in myoglobin.

When there is no ligand in the heme group, myoglobin is called deoximioglobin, which has a purple color (sometimes characterized as purple, deep red, dark red, reddish blue or bluish red). Molecular oxygen (O2) ("oxygen") acts as a ligand that binds to the heme group, allowing the biological transport of oxygen from the blood stream to the mitochondria of the cells. When oxygen is attached to the heme group, the purple deoximioglobin becomes red oxythioglobin. When the oxygen ligand dissociates from oxythioglobin, the iron atom oxidizes leaving the iron in a ferric state. The oxidation of the iron atom makes the molecule unable to normally bind oxygen. When the chemical state of iron changes from ferrous (Fe2 +) to ferric (Fe3 +), the three-dimensional structure of the globin portion can change in a way that allows the binding of water molecules to the heme group. The binding of a water molecule to the heme group containing ferric iron affects the light absorption of the heme group. The oxidized form of myoglobin with a water molecule in the heme group is called methioglobin and its color is brown. It is believed that oxidation of the iron atom causes a brown color. For example, the presence of carbon monoxide (CO) can cause fresh meat that has a desirable bright red color similar to the presence of oxygen. Although it has been suggested that nitric oxide (NO) may cause a dull red or stable pink color in the case of cured meat that also contains sodium chloride, it has been found that, in the absence of oxygen, NO can produce a bright red color desired similar to that caused by oxygen in uncooked meat, especially in fresh, raw, unprocessed or cured meat. It has been found that the development of this desired bright red color may take many hours and typically may take 1 to 5 days and that initially the color of the meat in a vacuum container that has an oxygen barrier may change to a brown color. undesirable until the unexpected transformation to the desired red color takes place.

Other variables that affect the stability of the globin portion also affect the affinity of the heme group for oxygen and the tendency of the chemical state of the iron atom to be oxidized. The acidity and a high temperature, such as that associated with cooking, can denature the globin portion and, therefore, cause instability of the heme group. In the absence of stabilizing ligands, iron oxidation of the heme group is automatic when globin is denatured.

Polymeric films for food packaging

In the present invention, articles for packaging food and oxygen barrier are provided which include food contact surfaces comprising a producing agent of the myoglobin red color. "Food contact surface" refers to the portion of a packaging material designed to contact the surface of the packaged meat product. Preferably, the food packaging article includes a food contact surface comprising a producing agent of the myoglobin red color in an amount effective to promote or maintain a desirable color after contact with a meat product. The myoglobin red (MBA) producing agent preferably contacts the surface of the meat to a sufficient extent to produce a desired red color that preferably does not penetrate an undesirable length of the thickness of the food under reduced oxygen conditions (this color it may take a while to develop, for example, 1 to 5 days). Beneficially, the MBA may be present on the surface of the food contact film (or on the surface of the food containing myoglobin) in an amount of about 0.0015-0.465 to 0.775-1.55 μmol / cm2 and in 0.1 μmol increments. Higher or smaller amounts of MBA can be used so that the color intensity may vary depending on the presence or relative absence of myoglobin.

Therefore, the food contact surface of the food packaging article contains an MBA at a concentration high enough to produce and / or maintain a desired coloration on the surface of a fresh meat product, but low enough to avoid an undesirable extension of the color inside the meat product. Preferably, the MBA is present on the surface of contact with the food at a sufficient concentration after contact with the surface of a meat to convert at least 50% of the myoglobin molecules to a binding state to a desired ligand. The available amount or concentration of MBA is preferably selected to bind ligands that produce a desirable coloration of the meat to myoglobin molecules at 0.42, 0.32, 0.25, 0.21, 0.16 or 0.13 cm outside or less of the meat product although, if desired, deeper penetrations can be achieved. For example, desirably the nitric oxide is present at a concentration sufficient to convert at least 50% of the myoglobin molecules present in the contact surface of the meat into myoglobin-nitric oxide. The MBA may be coated in the form of a single layer film or it may be in the inner layer of a multilayer film or it may be incorporated into said film.

Preferably the myoglobin red producing agent is uniformly distributed on the food contact surface. The minimum amount required to cause the desired coloration depends on the concentration of myoglobin present in the meat product. For example, beef containing 10 mg of myoglobin per gram of meat may require 10 times more MBA than poultry meat that contains 1 mg of myoglobin per gram of meat. Also, if the desired depth of penetration is 0.63 cm, then, to affect all myoglobin molecules (the molecular weight of myoglobin is approximately 17,000 g / mol) present in 1 cm2 of beef to a depth of 0.63 cm, It will take at least 0.0775 micromoles (μmol) of the MBA available to transfer across the surface of 1 cm 2 of film [1 cm 2 of beef with a height of approximately 0.63 cm are approximately 0.635 grams of meat (meat specific weight 1 g / cm3)] Sodium nitrite, which is the preferred MBA, has a molecular weight of 69 g / mol. Therefore, 2.4 μmol of sodium nitrite weighs 0.166 mg and the total amount of myoglobin in 0.635 grams of meat containing 10 mg / g is 6.35 mg. Beef typically contains myoglobin at a level of 3-10 milligrams per gram of meat. The preferred amount of MBA that should be present in the article is 0.112-0.372 μmol / cm2. Similarly, pork contains myoglobin at a level of 1-3 milligrams per gram of meat. A packaging article for this application must provide 0.037-0.112 μmol / cm2. Poultry meat that has less than 1 milligram of myoglobin per gram of meat should preferably use a packaging article that provides less than 0.037 μmol / cm2, for example, 0.019 μmol / cm2. An article that uses sodium nitrite (molecular weight 69 g / mol) as MBA should preferably provide 0.007-0.026 mg / cm2 in the case of beef, 0.003-0.007 mg / cm2 in the case of pork and less than 0.026 mg / cm2 in the case of poultry meat. An article that provides 0.026 mg / cm2 will be suitable for a variety of types of fresh meat.

In the case of darker colored muscles that may contain higher levels of myoglobin, a larger amount of the producing agent of the myoglobin red color may be preferred. When the myoglobin-red producing agent is incorporated into the polymer matrix comprising the food contact layer of a single-layer or multi-layer packaging film, only a portion thereof can effectively migrate from the surface. from the film to the surface of the product to interact with myoglobin. Film inclusion levels of up to 20 times or more of the amount required for effective color fixation are assumed.

Therefore, the amount of myoglobin red producing agent per unit area of ​​the food contact surface can be selected to provide a desired coloration of the surface of the packaged fresh meat product. For example, the food contact layer may include from about 7.75x10-4 to about 0.139 mg / cm2 of sodium nitrite, preferably from about 1.55x10-3 to about 0.062 and most preferably from about 0.015 to about 0.046 mg / cm2 In the case of beef, the food contact layer may include, for example, from about 0.031 to about 0.039 mg / cm 2 of sodium nitrite whereas, in the case of pork, concentrations of about 0.015 to about 0.023 mg / cm2.

A uniform dispersion or coating having a particle size of 35 micrometers (μm) or less, preferably 10 μm or less, is desirable. Although also

Even larger particle sizes can be used, the film before use is less aesthetically pleasing. If the particle size is too large, an irregular initial appearance with granules may occur although it tends to be more uniform over time and this desirable uniformity of color (i.e., absence of granules or spots) frequently occurs after transformation. from brown to red. Advantageously, the myoglobin-red producing agent can be applied in a manner that moistens the surface of the contact layer with the food of the film using film-forming agents, surfactants, binding agents and other use compounds. suitable. For example, the myoglobin red producing agent according to the present invention can be sprayed on the surface of the film in contact with the food. Tubular films and casings can also be coated by other methods (including the well known immersion and blasting methods). Typical agents producing the red color of myoglobin do not easily pass through the wall of the film and, therefore, it is preferable to apply them inside the tube and / or on the inner surface of the tube, for example, during an operation of pursed by a sprayer, because the external application (for example, by immersion) may require a complex and more expensive operation of turning the tube upside down to provide contact between the myoglobin-red producing agent and the meat contact surface. The application of other additives and coating compositions by spraying in solution during or just before purging is convenient and economical and facilitates obtaining a regular measured distribution of a coating on the inner surface of the tube. For example, lubricants and other compositions have been applied by various means, such as blasting, spraying or contact coating of the inner surface of a tubular polymeric shell by a puckering mandrel and such means are well known [see, for example, patents United States numbers

3,378,379 (Shiner), 3,451,827 (Bridgefort), 4,397,891 (Kaelberer et al.), 5,256,458 (Oxley et al.), 5,573,800 (Wilhoit) and 6,143,344 (Jon et al.) ]. The packages prepared in accordance with the present invention can be coated with the myoglobin red color producing agent of the present invention by blasting, to provide a coating of uniform thickness.

Tubular or non-tubular shapes (e.g., sheets or bands) of the food packaging film can be coated by wet or dry spray, dusting, roller coating, coating using a Mayer bar or blade, printing (e.g., using flexographic or photogravure printing) or using electrostatic transfer. Also, it can be applied at various points in the manufacturing process, including, for example, mixing, incorporation into a masterbatch or addition to the polymeric layer before extrusion or by dusting, spraying or coating during or after extrusion or during tube formation or during winding or manufacturing of the bags, for example, in a spraying and dusting stage.

In one embodiment of the invention, it is contemplated that the food contact layer may comprise between about 1,000 ppm (0.1%) and about 50,000 ppm (5.0%) of a myoglobin red producing agent, more preferably between about 5,000 and about 25,000 ppm and most preferably between about 7,500 and about 20,000 ppm. Typically, a food contact layer comprises about 1.5% to about 2.0% by weight (15,000 to 20,000 ppm) of a nitrite salt to package a fresh minced beef product or about 0, 75 to about 1.5% by weight of a nitrite salt to package a fresh pork product. Advantageously amounts in the range of 0.75 to 2.25% by weight can be used in the case of a variety of meats.

According to the invention, single layer films can be provided for food packaging, which comprise a myoglobin-red producing agent. In another embodiment, the food packaging film can also be a multilayer film. The films of the present invention for food packaging can have any suitable composition or configuration. Preferably, the food packaging film meets several functional requirements that may be present in one or more layers or in a combination of layers. For example, a single layer film may combine the oxygen barrier and contact functions with a myoglobin-red producing agent with one or more additional functions, such as puncture resistance, wear resistance, fitness printing, moisture barrier, heat sealing ability, transparency, high brightness, low toxicity, high temperature resistance, low temperature flexibility, etc. Alternatively, several layers can be used to add some functionality. The present invention can be used in a wide variety of commercially available packaging films, such as those sold by Curwood Inc. under the trademarks ABP, Clear-Tite, Cook-Tite, Perflex, Pro-Guard, Pro-Tite, Curlam®, Curlon® and Surround; and for others, for example, those marketed by Alcan, Asahi, Cryovac, Kureha, Vector, Pactiv, Printpack, Viskase and Wipab, under the trademarks or registered names Cryovac® T-Series, Cryovac® E-Seal Materials, Alcan Q ® Series, Alcan Peel Rite® Peel Systems, Alcan Q4 Forming Films, Krehalon®, Alcan Mara Flex® Non-Forming Films, Wipak Combitherm, Wipak Bialon, Wipak Biaxer and Wipak Biaxop. A typical beneficial film for packaging food according to embodiments of the present invention may have an inner layer of contact with the food, which also acts as a sealant layer, an outer layer resistant to heat and wear and a central layer between the two comprising an oxygen barrier material. Another suitable common film has adhesive layers on each face of the oxygen barrier layer to connect it with the surface layers.

In another embodiment of the invention, the food package may comprise a food containing myoglobin, such as fresh meat, having a water content of at least 5% by weight, and a receptacle comprising a thermoplastic barrier film against the oxygen and having a polymeric layer of contact with food and a tray; wherein the receptacle contains the food in an atmosphere with a reduced oxygen content, and the food is maintained in a modified atmosphere comprising an MBA containing nitrogen or sulfur, or mixtures thereof. The MBAs described herein can also be used in this embodiment. In various embodiments of the present invention it is also contemplated that gaseous or non-gaseous MBAs can be used, as well as combinations thereof.

Embodiments of multilayer films for packaging food of the present invention may have an outer surface and an inner surface and include 2, 3, 4, 5, 6, 7, 8, 9 or more layers of polymeric films.

Film thickness

The food packaging article may be in the form of a single layer or multilayer film having a total thickness less than μm.

that about 254 µm, more preferably about 13 to 254 Advantageously, many embodiments may have a thickness of about 25 to 127 µm, certain embodiments having a thickness of about 38 to 76 µm. For example, pels or multilayer or

Individual particles of any single layer of a multilayer film may have any suitable thickness, including 25, 51, 76, 102, 127, 152, 178, 203, 229 or 254 μm, or any increase of 2.5 or 0.025 μm between those values. Thicker and thinner films are also provided. Although films suitable for packaging foods as thick as 102 μm or more or as thin as 25 μm or less can be made, it is assumed that the most common films will have a thickness between approximately 38 and 76 μm. Especially preferred films for food packaging are films in which the multilayer film has a thickness between 51 and 76

μm. Such films may have good wear resistance and good aptitude to be worked.

The food packaging article may be in the form of a single layer or multilayer sheet having a

total thickness of at least 254 μm, mμm and m

preferably from about 254 to 1,270, more preferably from about 254 to 762 µm.

Food contact layers / heat sealed

It is essential that the food packaging film of the present invention has a food contact layer. The food contact cover can also act as a heat sealant layer and facilitate the formation of hermetically sealed containers although plastic tubular envelopes can also be used and then closed, for example, by staples, as is well known in the art. Preferred films of the present invention use a food contact layer that has heat sealing properties.

The terms "heat sealant layer" or "sealant layer" are used interchangeably to refer to a layer that is heat sealable, that is, capable of melt bonding by conventional indirect heat media that generate sufficient heat on at least one contact surface of the film for its conduction to the contact surface of an adjacent film and the formation of a bonding interface between the two without loss of the integrity of the film. The bonding interface between adjacent inner layers preferably has sufficient physical strength to withstand the packaging process and subsequent handling, including, for example, stresses resulting from concomitant stretching or contraction with the presence of a food contained in the package using a film It has a heat sealable layer. Advantageously, preferably the bonding interface is sufficiently thermostable to prevent gas or liquid leakage through it when exposed to temperatures greater or less than room temperature, for example, during one or more of the following operations: packaging, storage , handling, transport, exposure or processing of food. Thermal seals must be designed to meet the different expected conditions of use and various thermal sealing formulations that can be used in the present invention are known in the art. In certain optional embodiments, the heat seals can be subjected to pasteurization and cooking temperatures and conditions, for example, in a sealed bag, fine vacuum sealed container or sealed tray. When used in cooking applications, heat seals must withstand high temperatures of up to about 71-82 ° C or higher, for example, 100 ° C, for long periods of time, for example, up to 4-12 hours, in environments that may vary from humid hot air or steam to hot water immersion. Preferably, the heat-sealed or food contact layer is heat sealable in itself but can be sealable to other objects, films or layers, for example, to a tray when used as a cover film, or to an outer layer in the sealing of a coating or in certain embodiments of upper wrappers of trays. Also, in certain embodiments, the contact layer with the food and containing the agent that produces the red color of myoglobin does not need to be heat sealable.

Preferably the sealable layer is located at or near the inner surface of the packaging film and can be the layer of an inner surface that allows a single layer or multi-layer film to be transformed into a resulting container, for example, when used as a clam shell type receptacle, sealed to a tray, for example, when used as a cover film, or sealed to a cover film, for example, when used as a tray. The sealant layer may comprise a myoglobin-red producing agent and a suitable heat sealable polymer, such as an ethylene / α-olefin copolymer, mixtures of nylon or an ionomer. The outer layer can also be a heat sealable layer and used instead of (or in addition to) the inner layer for this purpose.

The food contact layer may comprise a sealant layer and may comprise a heat sealable polymeric material, such as a polyolefin or a mixture of polyolefins, for example, polyethylenes, such as low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene / α-olefins copolymers including, for example, elastomers, very low density polyethylene (VLDPE) and linear low density polyethylene (LLDPE), or polypropylene homopolymers, polypropylene copolymers or homogeneous polyolefin resins, such as those made with forced geometry catalysts or single-site catalysts of the type of metallocenes included, for example, ethylene or propylene copolymers with at least one C4-8 α-olefin or higher (for example, butene-1, hexene-1, octene-1 or combinations of these olefins) with a majority of polymer units derived from ethylene or propylene. Ethylene-vinyl acetate (EVA) copolymers, ethylene-butyl acetate (EBA) copolymers, ethylene-methyl acetate (EMA) copolymers, ethylene-methacrylic acid (EMAA) copolymers and ethylene-ethyl acrylate copolymers (EEA) are also suitable materials to form the inner surface of the heat sealable layer. The food and / or sealant contact layer may also comprise an ionomer that is essentially a metal salt of a copolymer of ethylene and acrylic acid or methacrylic acid. Suitable materials of the sealant / food contact layer often include ionomers, polyolefins or mixtures thereof, such as those described in U.S. Patent Nos. 6,964,816, 6,861,127, 6,815,023, 6,773,820, 6,682,825, 6,316,067, 5,759,648 and 5,663,002 and in U.S. Patent Application Publications Nos. 2005/129969 (Schell et al.) And 2004/0166262 (Busche et al.), Which are incorporated herein as reference. The sealant and / or food contact layer may also comprise nylon, polyesters such as polyethylene terephthalate (PET), polycarbonates, cyclic olefin copolymers, polyacrylonitriles or copolymers or mixtures thereof. The food contact layer may constitute 100% of the total structure thickness. The sealant and food contact layers of a multi-layer structure can be of any thickness, with thicknesses in multi-layer structures ranging from 1-5% to 15-50% or more of the total thickness contemplated. Preferred examples of sealable resins constituting a sealant and / or food contact layer include copolymers of ethylene and an α-olefin commercially available from Dow Chemical Company under the trade names "AFFINITY", "ATTANE" or "ELLITE" (which include hexene1 as α-olefin) and from Exxon Mobil Oil Co. under the trade name "EXACT" (which includes hexene-1, butene-1 and octene-1 as a comonomer); and commercially available ionomers from DuPont Company under the trade name Surlyn®.

Barrier layers

Barrier layers can be made comprising a producing agent of the red color of myoglobin. The barrier layer preferably functions as a gas barrier layer although other types of barriers, such as moisture barrier layers, may also include the myoglobin-red producing agent. The gas barrier layer is preferably an oxygen barrier layer and is preferably a central layer located between the first and second layers. For example, the oxygen barrier layer may be in contact with a first surface and with an adhesive layer or it may be interposed between two tie layers and / or two surface layers.

In order to achieve all the benefits of the present invention it is essential to use the film of the producing agent of the red color of myoglobin together with an atmosphere with reduced oxygen content. The barrier layer can provide a suitable barrier against oxygen during the desired preservation of the item to be packaged under anticipated storage conditions. In one aspect, an oxygen barrier layer is used in the meat container or packaging film that is maintained in an atmosphere with reduced oxygen content. The oxygen barrier is preferably selected to provide oxygen permeability sufficiently diminished to allow inducing or maintaining a desirable color in packaged meat. For example, a film may comprise an oxygen barrier having an oxygen permeability low enough to reduce the myoglobin reducing activity of methioglobin reducing enzymes present in the meat and / or maintain an atmosphere with reduced oxygen content in contact with meat to reduce oxygen binding to myoglobin on the surface of fresh packaged meat.

The oxygen barrier layer may comprise any suitable material, such as nylon, EVOH, PVOH, polyvinylidene chloride, polyamides, polyesters, poly (alkylene carbonates), polyacrylonitriles, nanocomposites, a metallized film, such as aluminum vapor deposited on a polyolefin, etc., as is well known to those skilled in the art. The oxygen barrier layer of a film may preferably comprise EVOH, although oxygen barrier layers comprising polyvinylidene chloride-vinyl chloride (PVDC or VDC-VC) copolymers or copolymers of oxygen may also be preferable. vinylidene chloride-methyl acrylate (VDC-MA) or mixtures thereof. The barrier layer can also provide desirable optical properties when oriented by stretching, including transparency and low brightness, and a stretching behavior compatible with the surrounding layers. It is desirable to select the thickness of the barrier layer to provide the desired combination of the desired functional properties, for example, with respect to oxygen permeability, contraction values ​​(especially at low temperatures), ease of orientation, resistance to de-stratification and optical properties. The suitable thickness in a multi-layer film is less than 15%, for example, 3 to 13% of the total thickness of the film and preferably less than about 10% of the total thickness of the multi-layer film. Higher thicknesses can be used; however, oxygen barrier polymers tend to be relatively expensive and, therefore, it is assumed that less expensive resins will be used in other layers to impart desirable properties as soon as a suitable thickness is used to achieve the desired barrier property. against gases in the combination of film layers. For example, the thickness of a central oxygen barrier layer may be advantageously less than about 11.43 µm and greater than about 1.27 µm, including thicknesses of 2.54, 5.08, 6.35, 7, 62, 10.16 or 11.43 μm.

Preferably, multilayer films include a central oxygen barrier layer. Any suitable material can be used to form an oxygen barrier layer. The oxygen barrier layer of a film may preferably comprise EVOH, although oxygen barrier layers comprising polyvinylidene chloride-vinyl chloride (PVDC or VDC-VC) copolymers or copolymers of oxygen may also be preferable. vinylidene chloride-methyl acrylate (VDC-MA), as well as mixtures thereof. A preferred EVOH used as a barrier material is E151B resin containing 44 mol% EVOH, marketed by Eval Company of America under the trade name Eval® LCE151B. Another example of an EVOH that may be acceptable can be purchased from Nippon Gohsei (or Soarus, LLC in the United States) under the trade name Soarnol® AT (EVOH with 44 mol% ethylene) or Soarnol® ET (EVOH with 38% in moles of ethylene). Oxygen barrier films, for food packaging, which comprise EVOH and contain a myoglobin red-producing agent can be formed by methods described in US Pat. Nos. 7,018,719, 6,815,023, 6,777,046 , 6,511,688, 5,759,648, 5,382,470 and 4,064,296, all of which are incorporated in their entirety as a reference.

Nylon or mixtures of suitable nylon can also be used to impart oxygen barrier properties. Mixtures of barrier materials can also be used. For example, several layers of nylon and EVOH barrier are often used to impart suitable barrier properties in meat and food containers. These and other known materials can also be used to form an oxygen barrier layer.

In perishable food containers, desirably the oxygen permeability (O2) should be minimized. Typical oxygen barrier films tend to have an O2 permeability of less than approximately 310 cm3 / m2 over a period of 24 hours at 1 atmosphere, 0% relative humidity and 23 ° C, preferably less than 75 cm3 / m2.day, more preferably less than 20 cm3 / m2 day. Barrier resins of the central layer, such as PVDC or EVOH resins, must be adjusted by mixing compatible polymers to vary orientation parameters or gas permeability, for example to O2, of the films. The thickness of the central layer should also be varied, which can be beneficially from about 1.3 to about 7.62 µm.

Wear resistant outer layer

As the outer surface of the film is seen by the users / consumers, in embodiments of the single layer and multi-layer packaging film, it should improve the optical properties of the film and preferably should have a high gloss. Also, it must withstand contact with sharp objects and provide abrasion resistance, which is why it is often referred to as a wear resistant layer. This wear-resistant outer layer may or may not be used as a heat sealable layer. As a layer of the outer surface of the film, most frequently this layer is also the outer layer of the container, bag, bag, tray or any other receptacle made of the film of the invention and, therefore, is subject to handling and wear, for example, by machinery during the packaging operation, and rubbing against other containers and shipping containers and storage shelves during transport and storage. This contact causes abrasion forces, stresses and pressures that can erode the film causing printing defects, worse optical characteristics or even perforations or breaks in the integrity of the package. Therefore, the outer surface layer is typically made of materials chosen to be resistant to abrasion and perforation forces and other stresses and wear that the container must withstand during use. The outer surface layer must be easy to be worked on (that is, easy to feed and be worked by machines, for example, transport, packaging, printing, etc., as part of the film or bag manufacturing process) . It should also facilitate stretch orientation when a highly contractile film is desired, particularly at low temperatures, such as 90 ° C or less. Also, stiffness, flexibility, flexural cracking resistance, modulus, tensile strength, friction coefficient, printing aptitude and suitable optical properties are often designed in the outer layers by an appropriate selection of materials. This layer should be selected so that it has adequate characteristics to create the desired heat sealants that must be resistant to combustion, for example, by pulse sealants, or that can be used as heat sealing surface in certain packaging embodiments, for example, using overlap seals.

The outer layer can be formed from a mixture similar to that of the inner layer. In one embodiment, at least one of the inner and outer layers use polyolefin resins, preferably a mixture of (i) EVA, (ii) EAO (such as VLDPE), and (iii) an ethylene / hexene-1 copolymer that have a melting point of up to 80-98 ° C, preferably 80 to 92 ° C. Each of these three polymers typically constitutes 20 to 40% by weight of the layer. When EVA is used in the outer layer, it preferably has a vinyl acetate content of 3 to 18% by weight to provide good shrinkage properties, if desired. Mixtures of EAO are also usefully employed in the outer layer.

The outer layer typically has a thickness of 12.7 to 25.4 μm. Thinner layers will be less effective in terms of wear resistance; however, thicker layers, although more expensive, can be advantageously used to produce films having desirable properties of very high puncture and wear resistance. In demanding applications, thicker films, typically 127 to 178 μm or more, are necessary, which are usually achieved with complex and expensive laminated film structures and / or with secondary packaging materials, such as bone shield, pads or top wraps.

In one embodiment of the barrier layer of the present invention, a layer of the multi-layer wrapping film is on the opposite side of a central layer of the inner layer and in direct contact with the environment. In a suitable three layer embodiment, this outer layer is adhered directly to the central layer, which is preferably an oxygen barrier layer.

Intermediate layers

Intermediate layer is any layer between the outer layer and the inner layer and may include oxygen barrier layers, tie layers or layers that have useful functional qualities for the structure of the film or for its programmed uses. Intermediate layers can be used to improve, impart or modify in any way a multitude of features, for example, printing aptitude in the case of printed structures, contractility, orientation aptitude, processing aptitude, processing aptitude, tensile properties, draping, flexibility, rigidity, module, designed de-stratification, easy opening characteristics, tearing properties, resistance, elongation, optical properties, barrier against moisture, oxygen or other gases, barrier radiation, for example, ultraviolet wavelengths, etc.

Bonding layers

In addition to the outer layer, the inner layer and the intermediate layers, such as a barrier layer, a multi-layer packaging film may further comprise one or more adhesive layers, also known in the art as "tie layers", which can be they can select to provide adhesion of adjacent layers to each other or to another layer in a multilayer film and avoid undesirable de-stratification. A multifunctional layer is preferably formulated to aid the adhesion of one layer to another layer without the need to use different adhesives, given the compatibility of the materials of that layer with those of the first and second layers. In some embodiments, the adhesive layers comprise materials present in the first and second layers. Conveniently the adhesive layer may constitute less than 10%, and preferably between 2 and 10% of the total thickness of the multi-layer film. Adhesive resins are often more expensive than other polymers, so usually the thickness of the bonding layer is kept to a minimum consistent with the desired effect. In one embodiment, a multilayer film comprises a three layer structure, with an adhesive layer located between and in contact with the first layer and the second layer. In another embodiment, a multilayer film comprises a multilayer structure comprising a first adhesive layer located between and in direct contact with the outer layer and a central oxygen barrier layer; and preferably and optionally has a second adhesive layer between and in direct contact with the same central oxygen barrier layer and the inner layer to produce a five layer film.

The multilayer films may comprise any suitable number of adhesive or bonding layers of any suitable composition. Various adhesive layers are formulated and placed to provide the desired level of adhesion between specific layers of the film according to the composition of the layers contacted by the bonding layers.

For example, the adhesive layers in contact with a layer comprising a polyester, such as PET, preferably comprise a suitable mixture of polyolefins with other adhesive polymers. A preferred component of an adhesive layer in contact with a PET polyester layer is EMAC SP 1330 [indicating that it has a density of 0.948 g / cm 3, a melt flow rate of 2.0 g / 10 min, a melting point of 93 ° C, a softening point of 49 ° C and a methyl acrylate (MA) content of 22%].

The inner, outer, intermediate or joining layers can be formed of any suitable thermoplastic material, for example, polyamides, polystyrenes, styrenic copolymers (for example, styrene-butadiene copolymer), polyolefins and in particular members of the polyethylene family (such as LLDPE, VLDPE, HDPE and LDPE), ethylene-vinyl ester or ethylene-acrylate copolymers, polypropylenes, ethylenepropylene copolymers, ionomers, polybutylenes, α-olefins polymers, polyesters, polycarbonates, cyclic olefin copolymers, polyurethanes, polyacrylamides, anhydride modified polymers, acrylate modified polymers, poly (lactic acid polymers) or various mixtures of two or more of these materials.

In another embodiment, the inner, outer and / or one or more intermediate layers may comprise or consist essentially of a composition of a mixture of nylon. Preferably, the composition of the nylon mixture comprises at least one amorphous nylon, such as 6I / 6T nylon, combined with at least one semi-crystalline nylon, such as 6/12 nylon, 6/69 nylon, 6/66 nylon, MXD6 nylon , nylon 6, nylon 11 or nylon 12.

In another embodiment of the invention, one or more of the inner, outer and / or one or more intermediate layers comprise at least one polyester polymer. Preferred polyester polymers comprise aromatic polyesters and more preferably are homopolymers or copolymers of poly (ethylene terephthalate) (PET), poly (ethylene naphthalate) and mixtures thereof. Suitable polymers may have an intrinsic viscosity of about 0.60 to about 1.2, preferably between 0.60 and 0.80. The polyester may be an aliphatic polyester resin but preferably it is an aromatic polyester resin. For example, polyester materials can be derived from dicarboxylic acids, including terephthalic acid and isophthalic acid as preferred examples, and can also be dimers of unsaturated aliphatic acids. Examples of diols for synthesizing polyester can include polyalkylene glycols (such as ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, diethylene glycol, polyethylene glycol and polytetramethylene glycol), cyclohexane-1,4-dimetanol and 1,3-diol-1,3-propane. More specifically, examples of constituent dicarboxylic acids of the polyester resin may include terephthalic acid, isophthalic acid, phthalic acid, 5-t-butylisophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, oxalic acid, acid Malonic, succinic acid, azelaic acid, sebacic acid and dimer acids comprising dimers of unsaturated fatty acids. These acids can be used alone or as a combination of two or more species.

In some aspects, polyester compositions comprising an aromatic polyester resin comprising an aromatic dicarboxylic acid may be preferred including, for example, polyesters formed by terephthalic acid (such as dicarboxylic acid) and diols having a maximum of 10 carbon atoms, such as poly (ethylene terephthalate) and poly (butylene terephthalate). Particularly preferred examples of these polyesters include: copolyesters obtained by replacing a portion, preferably 30 mol% maximum, more preferably 15 mol% maximum, of the terephthalic acid with another dicarboxylic acid, such as isophthalic acid; copolyesters obtained by replacing a portion of the diol, such as ethylene glycol, with another diol, such as cyclohexane-1,4-dimethanol (for example, "Voridian 9921", manufactured by the Voridian division of Eastman Chemical Co.); and polyester-ether copolymers comprising polyester as the predominant component (for example, a polyester-ether formed by a dicarboxylic acid comprising mainly terephthalic acid and / or its ester derivative and a diol comprising mainly tetramethylene glycol and tetramethylene glycol oxide, which preferably contains the polytetramethylene glycol oxide glycol moiety in a proportion of 10-15% by weight). It is also possible to use two or more different polyester resins mixed. Examples of preferred polyesters are available under the trademarks Voridian 9663, Voridian 9921 and EASTAR® 6763, all of them from Eastman Chemical Corporation, Kingsport, Tenn. (U.S). U.S. Patents Nos. 6,964,816 to Schell et al. and 6,699,549 from Ueyama et al. describe multi-layer structures comprising a polyester layer and a polyamide layer.

Optional layer additives

Various additives may be included in the polymers used in one or more of the outer, inner and intermediate or bonding layers of food containers comprising them. For example, a layer can be coated with an antilock powder. Also, antioxidants, anti-blocking additives, polymeric plasticizers, moisture or gas eliminators (such as oxygen), gliding agents, dyes, pigments, organoleptic agents, etc., can be added to one or more layers of the film or they can be exempt from said added ingredients. If the outer layer is corona treated, a sliding agent may or may not be used, but said layer must contain or be coated with an anti-blocking powder or with an agent such as starch or silica. Typically, processing aids are used in amounts less than 10%, preferably less than 7% and more preferably less than 5% of the weight of the layer. A preferred processing aid used in the outer layer of the film includes one or more of fluorinated elastomers, stereamides and silicates.

Preferred films also provide a beneficial combination of one or more or all of the following properties: low turbidity, high brightness, high or low shrinkage values ​​at 90 ° C or less, good workability, good mechanical strength and good barrier properties against oxygen and water permeability.

Manufacturing methods

The single-layer or multi-layer film for containers of the present invention can be manufactured by conventional processes modified to include a myoglobin-producing agent. These processes for producing flexible films include, for example, blown or molten film processes. Single-layer or multi-layer films may be manufactured by methods well known in the art as modified herein to include a myoglobin-red producing agent. Descriptions of suitable film manufacturing and orientation processes are found in U.S. Patent Nos. 5,759,648, 6,316,067 and 6,773,820, and in U.S. Patent Application Publication No. 2004/0166262 (Busche et al. .) entitled “Easy opening heat shrink containers”.

As is apparent to those skilled in the art in view of the present specification, various manufacturing methods can be used. For example, U.S. Patent No. 4,448,792 (Schimer) describes a method comprising the steps of coextrusion, biaxial orientation and irradiation, and U.S. Patent Number

3,741,253 (Brax et al.) Describes a method of extrusion, irradiation, coating / de-stratification by extrusion and biaxial orientation. The processes can be modified by eliminating uniaxial or biaxial orientation or by adding a subsequent annealing step to form a non-contractile film.

In a preferred process for making films, the resins and additives are introduced into an extruder (in general, a film extruder), in which the resins are plasticized by fusion forming a tube and / or a flat sheet. In general, the temperatures of the extruder and the nozzle depend on the particular resin or resin mixtures that are processed. Suitable temperature ranges for commercially available resins are generally known in the art or are indicated in the technical bulletins provided by the resin manufacturers. Processing temperatures may vary depending on other selected process parameters. However, there may be variations that depend on factors such as selection of polymeric resins, use of other resins, for example, mixed or in layers other than the multilayer film, manufacturing process and particular equipment used and other processing parameters. used. Actual process parameters, including process temperatures, can be set by those skilled in the art without undue experimentation from the present description.

As generally admitted in the art, the properties of the resins can be further modified by mixing two or more resins and it is contemplated that various resins including, for example, homopolymers and copolymers, can be constituted or mixed to form individual layers of the film of several layers or can be added as additional layers. Such resins include polyolefins, such as ethylene-unsaturated ester copolymer resins, especially vinyl ester copolymers, such as EVA, or polymers of other esters, very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), polyethylene low density (LDPE), high density polyethylene (HDPE), ionomers, polypropylenes or mixtures thereof. Other polymers that can be included as separate or combined layers include polyamides, such as nylon, PVDC, EVOH and PET. These and other resins can be mixed by well known methods using rotating drums or mixers.

Also, if desired, known additives, such as antioxidants, processing aids, slip agents, anti-blocking and anti-fogging agents, colorants, color enhancers, flavoring, odorants, organoleptic agents, coefficient modifying agents, can be incorporated into the film of friction, lubricants, surfactants, encapsulating agents, oxygen scavengers, pH modifying agents, film-forming agents, emulsifiers, polyphosphates, humectants, drying agents, antimicrobial agents, chelating agents, binders, starches, stabilizers, buffer substances, phospholipids, oils, fats, proteins, polysaccharides, transfer agents or combinations thereof. Examples of particular compositions that may be added include: α -tocopherol, alcohol, annato, ascorbic acid, beet powder, BHA, BHT, bixin, caramel, carmine, carotenoid pigment, casein, cochineal, cyclodextrin, dextrin, erucamide, mono and ethoxylated diglycerides, fluorinated elastomers, food grade oil, glycerol, lecithin, liquid smoke, nisin, norbixin, pediocin, polysorbate, potassium chloride, rosemary extract, shellac, sodium chloride, sodium erythorbate, starch, trisodium polyphosphate, turmeric, water, water soluble cellulose ether and zein. Examples of dyes include methionine, cysteine ​​and cooked cured meat pigments. Cooked cured meat pigments comprise a complex of mononitric oxide and ferrous protoporphyrin. Cooked cured meat pigments can be formed by reacting red blood cells with a nitrosating agent and a reducer at elevated temperatures, as described in US Patent Nos. 5,230,915, 5,443,852 and 5,425,956.

Various polymeric modifiers can be incorporated to improve stiffness, orientation ability, dilatability and / or other film properties. Modifiers that can be added include modifiers that improve toughness at low temperatures or impact resistance and modifiers that reduce modulus or stiffness. Examples of modifiers include styrene-butadiene, styrene-isoprene and ethylene-propylene copolymers.

Here, the term "longitudinal direction", abbreviated "MD", refers to the direction "along" the film, that is, in the direction in which the film is formed during its extrusion and / or coating . Here, "transverse length", abbreviated "TD", refers to the "wide" direction of the film, perpendicular to the longitudinal direction.

Typically, the films are made heat shrinkable by stretching orientation. Stretching orientation can be performed by various known methods. For example, the orientation in the longitudinal direction is preferably performed using sets of pressure rollers that rotate at different speeds to stretch the film, sheet or tube in the longitudinal direction whereby they cause an elongation in the longitudinal direction, which is stabilized by cooling. Other methods include tensioning commonly used to orient blades or the well-known bubble or double-bubble technique occluded to orient tubes, described for example, in US Patent No. 3,456,044 (Pahlke). In the bubble technique, an extruded primary tube exiting a tubular extrusion nozzle is cooled, collapsed and then oriented by reheating and inflation forming an expanded secondary bubble, which cools and collapses again. This collapsed stretched film can be wound on a tube-shaped mandrel or can be cut into continuous sheets or bands and wound or further processed, for example, by annealing or irradiation as described below.

Typically heat shrink films stretch biaxially. The orientation in the transverse direction is carried out by the aforementioned method of inflation to radially lengthen the hot film which is then cooled to stabilize the film in expanded form or by dragging the film in the transverse direction during tensioning. The orientation can be in one or both directions. Preferably, a primary tube is stretched biaxially radially (transversely) and longitudinally at the same time, to produce a multilayer film that is heat shrinkable at temperatures below the melting points of the main polymer components, for example, 90 ° C or less. The stretch ratio during orientation should be sufficient to provide a film with a total thickness of 254 μm or less, preferably films with a thickness less than 127 μm, typically between about 25.4 and 101.6 μm. The stretch ratio in the longitudinal direction is typically 2.5-6 and in the transverse direction it is also typically 2.5-6. A total stretch ratio (longitudinal stretch ratio x cross stretch ratio) of approximately 6.25-36 is suitable.

The general annealing process by which biaxially stretched heat shrink films are heated under reduced controlled tension to reduce or eliminate shrinkage values ​​is well known in the art. If desired, the films can be annealed to produce lower shrinkage values ​​as desired for the particular temperature. Accordingly, using an annealing process, heat shrink films can be transformed into non-heat shrink films suitable for use in certain embodiments described herein.

Optionally, the films of the present invention can be subjected to a variety of irradiation treatments. In the irradiation process, the film is subjected to an irradiation energy treatment, such as corona discharge, plasma, flame, ultraviolet rays, X-rays, beta rays and treatment with high-energy electrons. These irradiation treatments can be performed for a variety of reasons including, for example, modifying surface characteristics to improve the adhesion of the surface to a variety of substances, such as meat or printing ink, or to improve the adhesion of the layer interior to improve adhesion between layers and avoid undesirable de-stratification. An important known use of irradiation is to induce cross-linking between molecules of the irradiated material. The irradiation of polymeric films to induce favorable properties, with cross-linking, is well known in the art and is described in US Patent Nos. 4,737,391 (Lustig et al.) And 4,064,296 (Bornstein et al.). Bornstein et al. describe the use of ionizing radiation to crosslink the polymer present in the film. In some preferred embodiments, it is preferred to crosslink the entire film to widen the heat sealing range. This is preferably done by irradiation with an electron beam at dosage levels of at least about 2 megarads and preferably in the range of 3 to 8 megarads, although larger doses may be used. Irradiation can be done on the primary tube, with or without additional layers coated on it, or after biaxial orientation. The latter, called post-irradiation, is described in US Patent No. 4,737,391 (Lustig et al.). An advantage of post-irradiation is that a relatively thin film is treated instead of a relatively thick primary tube, so that the energy requirements for a given level of treatment are reduced.

Alternatively, crosslinking can be performed by adding a chemical crosslinking agent or using irradiation together with a crosslinking modifier added to one or more layers as described, for example, in U.S. Patent No. 5,055,328 (Evert et to the.).

Fundamental to the present invention is to include a producing agent of the red color of myoglobin with an oxygen barrier film. Packaging films may have any suitable structure but it is essential that the myoglobin-red producing agent be on or on the surface of contact with the film food or be able to migrate thereto.

Whether the myoglobin-red producing agent is coated or incorporated into an inner layer of food contact, it can be applied by any suitable method, for example, as described above, including dry spray or wet, dusting, mixing, coating, for example, with transfer rollers, blasting, inclusion in a mother bath, printing, etc. Preferably the myoglobin-red producing agent is dispersed uniformly over the contact surface of the layer and / or throughout the entire layer to allow any length of film that is incorporated into the layer to include approximately similar amounts of compound in the layer. sealing layer during a uniform transfer to the meat through the contact surface.

When the agent producing the red color of myoglobin is coated on the surface of the food contact layer, it can be applied at various times. For example, the agent can be applied on the surface of the meat, for example, by dipping or spraying, just before packaging or during a bag manufacturing operation with or without mixing with starch used as a means to facilitate the subsequent opening of the bag. It can be applied during simultaneous winding operations to cutting operations or during bag making

or tubes It can be applied with or instead of starch using electron beam irradiation and / or corona treatment as described in US Patent No. 5,407,611 (Wilhoit et al.). Many myoglobin-producing agents are soluble in water or alcohol and solutions of a myoglobin-producing agent can be coated onto a film, alone or incorporated with other agents, such as wetting agents and / or film-forming agents. or other materials, such as zein, casein, dextrin, starch, shellac, etc., used, for example, in connection with bixin transfer, as described in U.S. Patent No. 6,143,344 (Jon et al.). The agent can also be applied in aqueous solution on a film whose contact surface with the food has been modified to be hydrophilic or adapted or modified in any other way to absorb or adsorb water or oily liquids containing a red color producing agent. myoglobin In accordance with the present invention, in one aspect, films containing a transferable modifier can be used to transfer producing agents of the myoglobin red color using, for example, films having a formulation of the food contact layer suitable for make the transfer, as described in U.S. Patent Nos. 5,288,532 (Juhl et al.), 5,374,457 (Huhl et al.), 5,382,391 (Juhl et al.) and 6,667,082 (Bamore et to the.).

When the myoglobin red producing agent is incorporated into the inner layer, it can be added to a base polymer before or during extrusion of the film. The base polymer can be any suitable polymer, for example, a polyolefin, such as a polyethylene, and can be very low density polyethylene (VLDPE or ULDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), EVA, polypropylene, ionomer, nylon, PVDC, PET, etc. Melt blending is a suitable method for mixing the base polymer and the myoglobin red producing agent. Individual component materials can be combined in a high intensity mixing device, such as an extruder. The base polymer melts to form a viscous or "molten" liquid. The myoglobin red producing agent can be combined with the polymer before, during or after melting. The high intensity mixing device is used to uniformly disperse the producing agent of the myoglobin red color in the base polymer. The quality and functionality of the dispersed agent may depend on the selection of the producing agent of the myoglobin red color, composition of the base polymer and mixing device. It is desirable to achieve good mixing to uniformly disperse the red-producing agent of myoglobin into the melt. The presence of agglomerations of poorly humidified particles is not desirable. It may be desirable to include additives in the mixture, such as antioxidants and anti-blocking agents or glidants.

The myoglobin red producing agent can be added directly to the base polymer or can be provided in solution, as an aqueous or oily solution that is added to the polymer before or during the molten state of the polymer. In the case of direct addition of a solid or granular or particulate agent, it is assumed that the grinding of the solid agent to produce smaller particles provides a more uniform dispersion. It is assumed that in the case of a water-soluble material, providing the myoglobin-producing agent in the form of an aqueous solution can provide a better dispersion of the compound in the polymer than the addition of the undissolved agent. An aqueous solution can be prepared from a soluble agent that produces the red color of myoglobin, preferably at concentrations close to saturation, and the solution may include between about 20 and about 42% by weight of the compound that acts as the producing agent. of the red color of myoglobin. This aqueous solution can be introduced directly into the molten polymer, for example, in an extruder heated to a temperature greater than 150 ° C to facilitate mixing. If added as a solution, try to evacuate water vapor from the extruder. The mixture of the polymer and the producing agent of the red color of myoglobin can be extruded into granules or directly into films.

The myoglobin red producing agent can be mixed with a carrier resin or base polymer to form a masterbatch. The granules obtained from the mother mixture may be suitable for later use to manufacture articles. The granules obtained from the mother mixture can also be mixed with the base polymer or with another polymer during the film formation process.

When used to create a masterbatch, a sufficient amount of the solution can be introduced into the molten polymer to obtain a mixture having a high concentration of the myoglobin red producing agent, for example, between about 2 and about 10 % by weight, preferably between about 4 and about 6% by weight.

Single layer barrier films

In one embodiment of the invention, single-layer oxygen barrier films are provided for food packaging, comprising a food contact layer that includes a myoglobin-red producing agent. The agent may be coated on the surface of the single layer film or incorporated therein, for example, during the extrusion process. Said film provides an oxygen barrier and may have a red-producing agent of myoglobin coated on it or incorporated therein.

Multi-layer barrier films

Multi-layered oxygen barrier films having a myoglobin-red producing agent that contacts the surface of a packaged meat product can promote, preserve or increase a desirable mitigated red color of myoglobin.

In one aspect of the embodiment, a myoglobin-red producing agent is included in the food contact layer, which is preferably a sealing layer. Multi-layer films can advantageously use one or more additional layers to provide beneficial properties of the film. Multi-layer films have greater application flexibility than single-layer films because specific layers can be provided to incorporate specific features. Sometimes, in a multi-layer construction, materials may be advantageously used that may not be suitable when used alone. For example, the EVOH polymer has oxygen barrier properties that are very sensitive to moisture, so it affects them negatively but, when protected from moisture contact by adjacent moisture barrier layers, it can provide a film that It has excellent oxygen barrier properties. The oxygen barrier layers may be located between an abrasion or wear resistant layer and a food contact layer containing the myoglobin red producing agent to protect the oxygen barrier and allow layers of thinner oxygen barrier. When EVOH is used as a barrier material, it is contemplated that a layer containing polyamide may optionally be in contact with the EVOH polymer. Non-limiting examples of various preferred multi-layer film configurations include the following:

wear-resistant (outdoor) / oxygen barrier / food contact & amp; sealant (inside),

wear-resistant (exterior) / central / oxygen barrier / central / sealant (interior),

wear-resistant (exterior) / joint / central / oxygen barrier / central / sealant (interior),

wear-resistant (exterior) / joint / central / oxygen barrier / central / joint / sealant (interior),

wear-resistant (exterior) / central / joint / oxygen barrier / joint / central / sealant (interior),

wear-resistant (exterior) / joint / oxygen barrier / joint / sealant (interior),

wear-resistant (exterior) / nylon core / oxygen barrier / core / sealant (interior),

wear-resistant (exterior) / nylon core / oxygen barrier / nylon core / sealant (interior),

wear-resistant (exterior) / joint / central / oxygen barrier / nylon core / sealant (interior), and

wear-resistant (exterior) / joint / central / oxygen barrier / nylon core / joint / sealant (interior).

Some embodiments provide a film with 3, 4, 5, 6, 7, 8, 9 or more co-extruded layers, with desirable levels of wear resistance and oxygen barrier in a multilayer film structure.

Referring now to the drawings, Figure 1 represents an example of an embodiment of a three layer film structure of the present invention, generally designated by reference number 10. This embodiment relates to a multilayer composite material comprising an outer layer 12, which is an outer layer 102 comprising a material such as a polyolefin, PET or a nylon composition, and an outer layer 14 which is a sealing layer 122 , each attached to opposite faces of a central oxygen barrier layer 112 comprising, for example, EVOH. The sealing layer 122 comprises a producing agent of the red color of myoglobin. The multilayer film 10, which can be heat shrinkable or not, is designed to package food and can be used, for example, to wrap a tray or a vacuum-thin container.

Referring now to Figure 2, the cross section of an example of a five layer oxygen barrier film 20, having an outer layer 22 which is a wear resistant layer 102 joined by a first tie layer is shown 112 to a central and barrier layer 26 of polyamide, comprising one or more nylon polymers 104, the other face of the central layer 26 being joined by a second joining layer 114 to an inner layer 24 which is a sealing layer 122 comprising a producing agent of the myoglobin red color.

Placing one or more central layers of nylon in contact with an EVOH oxygen barrier layer can provide films with better processing ability. In certain embodiments, the nylon may be mixed with EVOH or may be included as adjacent layers. For example, when the EVOH used as an oxygen barrier material has an ethylene content of about 44 mol% or less, at least one and more preferably two central layers of polyamide in contact with the EVOH layer can be included to facilitate processing.

Referring now to Figure 3, the cross section of an example of a seven layer film 30 is shown. The film 30 may comprise an outer layer 32 that is a wear-resistant layer 102 that has high gloss and good printing ability and is in direct contact with a first tie layer 112 and connected thereto to a first core layer 36 of polyamide comprising one or more nylon polymers 104. The nylon layer 36 is in direct contact with an oxygen barrier layer 35. Similarly, the other side of the oxygen barrier layer 35 comprising EVOH 120 is bonded to a second central polyamide layer 38 comprising one or more more nylon polymers 104, whose other face is attached to a second tie layer 116. The inner layer 34 is a food contact layer 122 which can also be heat sealable and which comprises a polyethylene, such as ULDPE, and a myoglobin-red producing agent. The sealing layer in contact with the food is attached to a second bonding layer 116. Preferably the seven layers are coextruded layers, but they can also be formed by dispersion coating, emulsion coating, solution coating or stratification, for example, by extrusion stratification, thermal stratification, adhesive stratification, dry bond stratification, stratification without solvent, coating stratification or extrusion coating, or by a combination of these methods.

The first layer bonding 112 promotes or provides adhesion between a wear-resistant layer 102, which is an outer layer 32, and a central polyamide layer 104. Similarly, layer 116 promotes or provides adhesion between a second layer of polyamide 28 and a layer of contact with food 122, which is an inner layer 34. Layers 112 and 116 may be identical or different and may include a wide range of polyolefins with anhydride grafts, including those based on ethylene-vinyl acetate copolymer, polypropylene, linear low density polypropylene and very low density polyethylene. Preferably, the layer compositions are based on linear low density polyethylene or elastomers, such as metallocene catalyzed polyethylene. Examples of resins used in bonding layers are manufactured by Equistar Chemical Company under the trade name Plexar®.

Some embodiments provide a multi-layer, easy-opening and oxygen barrier wrap, or a multi-layer food packaging film that is preferably coextruded at least partially or more preferably fully coextruded. Optionally, although not shown, the film of Figure 3 may be heat stratified or by adhesion to a single rigid or semi-rigid polypropylene film to be used to form a rigid or semi-rigid tray. The multilayer film provides appropriate oxygen barrier and heat seal characteristics. Other examples of such rigid and semi-rigid trays are described by Lischefki et al., In the patent application entitled "Rigid and semi-rigid articles for packaging", which is incorporated herein by reference.

Referring now to Figure 4, the cross section of an example of a rigid or semi-rigid film 40 of five stratified layers is shown, for use in an oxygen barrier container comprising an outer layer 42 which is preferably a layer of Polyester 202 compressed layered to a barrier layer 46 which is preferably a PVDC layer 212. The PVDC layer 212 is coated by extrusion on a three layer blown film. The coextruded blown film includes an outer layer 45 preferably comprising a polyolefin 230 as a mixture of ULDPE and LLDPE polyethylenes, a central layer 47 preferably comprising a mixture of EVA and PB, and a heat-sealing outer layer 44 preferably comprising a mixture of EVA, LLDPE and a producing agent of the red color of myoglobin. The outer layer 44 containing the myoglobin red producing agent is a heat sealable layer 222.

Also in another embodiment of the invention, the PVDC coated three layer blown film of the embodiment of Figure 4 can be replaced by a six layer structure having an EVOH oxygen barrier layer, such that it includes a outer layer structure / joint / EVOH / joint / core / sealant, as described with the laminated films illustrated above.

Examples of films for packaging foods that can be combined with a myoglobin-red-producing agent according to the present description include those described in U.S. Patent Nos. 6,514,583, Re35,285, 4,755,403, 6,299. 984, 6,221,470, 6,858,275, 4,755,419, 5,834,077, 6,610,392, 6,287,613, 6,074,715, 6,511,568, 6,753,054, 4,610,914, 4,457,960, 6,749,910, 6,815,023, 5,593,747, 5,382,470 and 6,565,985, as well as in published U.S. patent application number US 2005/0129969. Preferably, the myoglobin red producing agent is included in the food contact layer of the packaging film, which is preferably a heat sealable layer.

Training movies

Multi-layer thermoformable films are useful for forming dimensionally stable structures for packaging food and other products. The structures or receptacles are made by softening a portion of the film by heat application, deforming the softened film to form a desired shape and cooling the film to stabilize the shape. Ordinarily, hot dogs are stored in receptacles made of thermoforming films. The thermoformable films described herein can be used in accordance with the present invention including a myoglobin red producing agent in the inner layer of food contact.

The thermoformable films can be made by mono or coextrusion with flat nozzle, mono or coextrusion with groove nozzle or single bubble blow coextrusion. The films made by these processes can be non-oriented or oriented by tensioning in an extension that allows further orientation / stretching. Suitable non-oriented thermoformable films may have a shrinkage value of less than about 5% at 90 ° C in one or both directions (longitudinal and transverse), measured before thermoforming.

A typical thermoformable film may include an outer layer comprising a mixture of a very low density polyolefin, an ethylene-vinyl acetate copolymer and a compatibilizer; an intermediate layer comprising a mixture of a nylon copolymer and an amorphous nylon; an inner layer comprising a polyolefin and an ionomeric polymer; and at least one adhesive that joins said outer, intermediate and inner layer. In U.S. Patent Nos. 6,861,127 of Glawe et al. Examples of such films are described.

Another thermoformable film may include a first polyester layer, the polyester being selected from the group consisting of a homopolymer or copolymer of ethylene terephthalate, ethylene naphthalate and mixtures thereof; a second layer of an adhesive, and a third layer comprising a mixture of nylon, the third layer being preferably a mixture between about 100% by weight and about 71% by weight of a nylon selected from the group consisting of nylon 4.6 [poly (tetramethylene adipamide)], nylon 6 (polycaprolactam), nylon 6.6 [poly (hexamethylene adipamide)], nylon 6.9 [poly (hexamethylene nonanediamine)], nylon 6.10 [poly / hexamethylenensecamide)], nylon 6,12 [poly (hexamethyleneddecanediamide)], nylon 6/12 [poly (caprolactam-dodecanediamide)], nylon 6,6 / 6 poly (hexamethyleneadipamide-co-caprolactam)], nylon 11 (polyundecanolactam), nylon 12 (polylauryl -lactam) and alloys or mixtures thereof; and between about 0% by weight and about 29% by weight of an amorphous nylon; in which the first layer, the second layer and the third layer are transformed into a flexible film by a coextrusion process that forms a film having a heat shrinkage value, measured before the thermoforming, less than about 5% in the longitudinal direction at 90 ° C and less than about 5% in the transverse direction at 90 ° C, and an elongation at break at room temperature greater than about 250% in the longitudinal direction and greater than about 250% in the transverse direction. Optionally, the second layer and the third layer have a combined thickness of 254 μm or less. In U.S. Patent No.

No. 6,964,816 from Schell et al. Examples of such films are described.

Also, other thermoformable films include a seven layer structure comprising, in sequence, layers of nylon, adhesive, nylon, adhesive, nylon, adhesive and a polymeric sealing material. Preferably, the polymeric sealing material is selected from the group consisting of low density polyethylene, linear low density polyethylene, very low density polyethylene, ethylene vinyl acetate copolymer, ethylene methacrylic acid copolymer, ethylene acrylate copolymer of methyl, ethylene-acrylic acid copolymer, an ionomer and combinations thereof. Preferably, the film does not include a central EVOH layer. The movie can

have a thickness between 127 and 254 μm. In United States patents n

6,068,933 and 6,562,476 of Shepard et al. Examples of such films are described. If said films include a central layer of EVOH, it is preferable that the multilayer structure includes, in sequence, layers comprising nylon, adhesive, nylon, EVOH, mixture of nylon and adhesive, and a heat sealable polymer. Nylon layers may include two or more coextruded nylon layers forming a single layer of nylon. The film may include an ionomer layer between the heat sealable polymer and the adhesive layer. The film may include an outer layer comprising an anhydride modified polyolefin. In U.S. Patent No. 6,942,927 to Shepard et al. Examples of such films are described.

Although thermoformable films can retain flexibility after being shaped, certain films may also have, after being shaped, sufficient rigidity to serve as packaging trays. Said rigid trays often have flexible films exfoliably sealed to flanges extending from the top of the trays. To make tall trays, thermoforming techniques such as vacuum forming, pressure forming, and mechanical or plug forming are useful. To effectively soften the multilayer sheet so that it can be easily transformed into receptacles having a uniform wall thickness, the films are often preheated to a temperature between about 190 and about 218 ° C. In United States Patent Number

4,810,541 of Newman et al. Examples of such exfoliable trays and covers of films are described.

The packaging trays can also be made of cardboard composite materials and extruded thermoformable laminated films, with the lid sealed to the flanges around the top of the tray. In U.S. Patent No. 6,651,874 to Pedersen et al. Examples of such trays are described. Such containers may be useful for modified atmosphere (MAP) containers, in which the air in the sealed container has been replaced or supplemented with a gas, such as carbon monoxide. In accordance with the present invention, it should be understood that the aforementioned forming films can be used alone or in combination with other films, for example, oriented polyethylene terephthalate, as a non-forming film. Non-limiting examples of various configurations of non-forming films that can be used as a cover include the following:

OPET (outside) / junction / sheet / junction / PE (inside)

OPET (outdoor) / PVDC / junction / PE or ionomer (indoor)

OPET (exterior) / junction / PE / junction / EVOH / junction / sealant (inside)

OPET metallic (exterior) / junction / PE (interior)

Oriented PP (outside) / joint / PE / joint) EVOH / joint / sealant (inside)

Biaxially oriented nylon (exterior) / joint / PE / joint / EVOH / joint / sealant (interior)

Biaxially oriented nylon (exterior) / PVDC / joint / PE or ionomer (interior)

Food containers

In another embodiment, food containers are provided comprising a fresh meat product containing myoglobin. Food containers preferably include a polymeric film comprising a red producing agent and an oxygen barrier.

The fresh meat product can be any meat suitable for human consumption that contains a molecule that contains myoglobin. References to "total myoglobin" in a meat include any structure that contains myoglobin, including any ligand present in the myoglobin structure (for example, deoxythioglobin, oxythioglobin, methioglobin, carboximioglobin and myoglobin-nitric oxide). Preferably, the meat product contains a level of myoglobin sufficient to provide or maintain a desirable appearance or color. Examples of suitable meats include ox, veal, pork, lamb, poultry, chicken, duck, turkey, goose, game, fish and seafood. The concentration of myoglobin varies in different types of meat products, but preferably it is sufficient to provide the desired color when approximately 50% of the myoglobin structures of the meat has become a binding state of the ligand that produces the desired color. . Typically, the ox contains approximately 3-10 mg of myoglobin per gram of meat, the pig contains approximately 1-3 mg of myoglobin per gram of meat, and the chicken contains approximately 1 mg of myoglobin per gram of meat. For example, the total concentration of myoglobin compounds can be between about 3 and about 20 mg per gram of fresh meat. In other embodiments, the total concentration of myoglobin compounds may be between about 1 and about 5 mg per gram of fresh meat. Also in other embodiments, the total concentration of myoglobin compounds is at least 1 mg per gram of fresh meat. Also in other embodiments, the total concentration of myoglobin compounds is less than 1 mg per gram of fresh meat.

The uncooked fresh meat product is desirably a fresh meat product supplied in a post mortem period of time that provides a desired level of freshness and safety. Preferably, a food comprising myoglobin is packaged less than 20 days post mortem, more preferably less than 14, 12, 10, 6, 5, 4, 3, 2 or 1 day post mortem. Typically, the food is fresh meat packaged between about 2 days and 14 days post mortem, more preferably between about 2 and about 12 days post mortem.

Typically, meat comprises moisture (water), protein and fat. Fresh meat can include approximately 60 to 80% moisture content, typically lean meats having a higher moisture content. Fresh meat products, such as ox, chicken and pork, often have a moisture content of approximately 68 to 75%, depending on the fat content of the meat (meats with higher fat content tend to have lower moisture content and vice versa). Cured meats often have a higher moisture content due to the injection of aqueous preservative compounds. For example, pork sausages may have a moisture content of approximately 40% or more. Preferably, the packaged meat product may have a moisture content of at least about 5, 10, 15, 20, 30, 40, 50, 60, 70, 80% or more.

The food package preferably includes a polymeric oxygen barrier film comprising a red producing agent, but may also include a film together with a food whose surface has been coated with a myoglobin red producing agent before pack it The food package may further comprise an oxygen barrier layer as part of the film that forms the food container. The oxygen barrier layer may comprise any suitable material and, in a multi-layer embodiment, is preferably located between the wear-resistant outer layer and the inner food contact layer. An oxygen barrier layer may be an ethylene-vinyl alcohol (EVOH) or PVDC copolymer. The gas barrier layer of the food container has been described above with reference to multi-layer films for containers. One or more tie layers can also be included. The tie layers of the food container have been described above with reference to multi-layer films for packages.

Preferably, the food package comprises a prepared and packaged meat product comprising a fresh meat product that includes myoglobin. Prepared and packaged meat products can generally be defined as fresh meat that has been pre-packaged and optionally pre-labeled at a centralized point and supplied to the retailer for final sale. Meat products such as beef, turkey and chicken products supplied by US domestic supermarkets for retail sale are increasingly supplied as prepared and packaged meat ready for consumption. In many supermarkets, especially in the so-called “large surfaces”, prepared and packaged meat products provide not only savings in minimizing or eliminating cutting and packaging on site but also better sanitary conditions and lower incidence of waste.

Containers that retain the desirable color of meat, especially fresh meat, can promote the marketing and interest of the meat product by consumers. To meet the growing demand for prepared and packaged meat products, they should preferably provide a predetermined weight and / or volume of a common meat product, such as chicken breast and minced meat. The prepared and packaged meat product may include a polymeric film to maintain its freshness, such as a film as described herein. The meat product can be supplied fresh, frozen, refrigerated, thawed, improved, processed or cooked and the films advantageously provide protection at various temperatures. The selection of films for food packaging may include considering criteria such as barrier properties, cost, duration, puncture resistance, resistance to flex cracking, compliance with food packaging standards, for example, approval by Food & amp ; Drug Administration (FDA) of the United States, ability to be worked with machines, optical properties such as turbidity and gloss, printing ability, sealing ability, contractility, contraction force, toughness and resistance. Containers that retain the desirable coloration of the meat can promote its commercialization.

In another aspect, the packaged food product includes a fresh meat in contact with a thin plastic film containing a producing agent of the myoglobin red color on the food contact surface, extended around a foam tray containing to the product The film is preferably a multilayer film sufficiently impermeable to oxygen so that the desirable color of the meat (eg, red) can be preserved for more than about 3 days, preferably for 5, 7, 10, 15 or more days . Preferably the meat product is packaged in vacuum receptacles, such as thermo-shrinkable or non-heat shrinkable bags or sacks, shaped chambers, stapled trays or envelopes, which are vacuum sealed and avoid oxygen contact with the meat until the container is opened. The vacuum receptacle includes a food contact surface, a surface that includes the myoglobin red-producing agent.

In prepared and packaged meat applications ready for prior art consumption, sometimes the meat product is packaged in a modified atmosphere ("MAP") container in which the meat is kept in a sealed chamber containing a space superior with an atmosphere different from ambient air. For example, a MAP can keep red meat in carbon dioxide, with a very low oxygen content, for example, in a multiple package in which the main package is subsequently opened and the individual packages contained in oxygen permeable films are exposed to the atmosphere with what originates that the meat acquires a red color. Also, the preferred color of fresh meat can be promoted and maintained using a MAP with an oxygen enriched content. Similarly, a MAP with low concentrations of carbon monoxide (CO) can be used to originate and maintain a preferred red color of fresh meat. Methods of treating fresh meat with carbon monoxide have also been developed for packaging applications before packaging. The bright red myoglobin-CO complex is called carboximioglobin. The presence of carbon monoxide can also adversely affect the sale of meat products containing CO to consumers.

It is contemplated that the present invention may be used in conjunction with a MAP. For example, in a tray-type container in which the film contacts an important portion of the surface, but not all, that is seen from the food, an atmosphere containing CO can be used to cause a desirable color in the food surfaces that are not in direct contact with the film of the container. This embodiment can be beneficially used, for example, in certain types of upper wrap trays, in which the film may typically be in contact with the upper surface of the food but not in all places, or in containers of the type of trays or other than trays of irregularly shaped items that have empty spaces between adjacent meat surfaces, such as those of products such as whole birds or products with a certain shape, Like ribs for roasting.

Food containers typically comprise a multilayer polymeric film. Food containers preferably include one or more central layers of polyamide in contact with the multilayer oxygen barrier, of EVOH-polyamide, in accordance with the first embodiment. Food containers may include a three-layer oxygen barrier formed from an EVOH layer in contact with one face with a first polyamide layer and the opposite side with a second polyamide layer. The food package may also include a heat resistant layer, a sealant layer and one or more layers of adhesive having a suitable composition, as described in relation to the second embodiment.

The polyamide layers in contact with the EVOH barrier layer may essentially comprise or consist of a polyamide composition or polyamide mixture, described in relation to the first embodiment. Preferably, the polyamide layers have the same composition as the heat resistant outer layer comprising a blend composition of various types of nylon.

Preferably, the heat resistant layer may comprise or consist essentially of a mixture of an amorphous nylon copolymer, a low temperature polyamide and a high temperature polyamide. The heat resistant layer is preferably located at or near the outer surface of the packaging film and may be an outer layer, but it can also form a polyamide layer. In some embodiments, the food package may further comprise a sealant layer located on or near the inner surface of the container, for example, as an inner layer. The sealing layers of the food container have been described above in relation to multi-layer films for packaging.

The sealing layer is preferably located on or near the inner surface of the container, for example, as an inner layer. The adhesive layers may also be included between a heat resistant outer layer and the first polyamide layer or between the sealant layer and the second polyamide layer. In some embodiments, the food container may be a container that can be heated, preferably when the food package comprises a sealant layer formed of a material compatible with the cooking conditions.

If desired, food containers can be heat shrinkable. Food packages preferably include a multilayer oxygen barrier component and, if heat shrinkable, preferably have a total free shrinkage measured at 90 ° C of at least 30, 40 or 50% in at least one of the two directions ( longitudinal and transverse). Food containers preferably have a free shrinkage at 90 ° C of at least 30%, more preferably at least 30% in both directions, each direction meaning the longitudinal direction and the transverse direction. Even more preferably, the food package has a free shrinkage of at least 40% in a first direction and at least 50% in a second direction. Food containers are preferably biaxially oriented, heat shrinkable or both. Preferably, food containers have a free shrinkage value at 90 ° C between about 80 and about 120% at 90 ° C. In some embodiments, food containers may have a total free shrinkage at 90 ° C of at least about 90%, more preferably of at least about 95%, even more preferably of at least about 100% and most preferably of at least about 105%.

Food containers preferably comprise at least one heat resistant layer comprising

or consists essentially of a mixture of an amorphous nylon copolymer, a low temperature polyamide and a high temperature polyamide. The heat resistant layer may be located at or near the outer surface of the packaging film and may be an outer layer. The heat resistant layer may have been biaxially oriented. Some embodiments may provide a heat-shrinkable and heat-resistant five-layer container or bag, formed from coextruded multi-layer films. Food containers can also be formed of seven coextruded layers that can be contractile or non-heat shrinkable and heat resistant. In some embodiments, the thermo-shrinkable food container may be a container that can be heated, preferably when the food package does not comprise a sealant layer. "That can be heated" is the term used to indicate a film or bag in which a food is cooked or pasteurized. This film or bag is used to contain, protect and / or form the food form by a food processor (manufacturer) during the cooking or pasteurization process after which the film can be removed (sometimes referred to as "remove") or it can be left as a protective barrier during transport and, optionally, left during retail sale.

In the present invention, food containers formed from multi-layer films having two to fourteen layers are contemplated, in which each layer is selected from the group consisting of: layers comprising a heat-resistant composition and a mixture of various Nylon types, adhesion layers, oxygen barrier layers, moisture barrier layers, bulky layers and sealing layers. Preferably, the outer surface layer comprises a blend composition of various types of nylon, which has an amorphous nylon copolymer and a low temperature polyamide. Also preferably, the inner surface layer is a sealant layer.

Referring now to Figure 5, the schematic sectional cut of a tray 50 containing meat is shown. Tray 51 has a bottom 52 with integral side walls 52a and 52b that support a cut of meat 53, such as pork, for retail sale. The film 54 seals the top of the tray 51 and provides a seal 55a and 55b along the edges of the side walls 52a and 52b. The film 54 is vacuum sealed or sealed in a modified atmosphere with the surface 57 of contact with the food containing a producing agent of the red color of myoglobin in intimate contact with the surface 58 of the meat. The lateral surfaces 59a and 59b of the meat are not in contact with the layer 57 in contact with the meat but are exposed to an atmosphere 56 modified with a gas, such as carbon monoxide. The tray has an inner surface 60 that can also be coated with a myoglobin red producing agent to fix the color on the bottom surface 61 of the meat.

Referring now to FIG. 6, a top view of a container 62 represents a food 63 containing myoglobin, such as a boneless cut of meat on a substrate and covered under a thin vacuum packaging film 64 that has contact with the meat a contact surface coated with a producing agent of the red color of myoglobin. The film is transparent to allow to perceive the color and characteristics of the surface of the meat.

With reference now to Figure 7, the schematic sectional cut of a shaped receptacle 70 containing meat and having a fresh meat cut 71 containing myoglobin disposed in the thermoformed bag 72 that is heat sealed to a non-oriented film 73 around the meat cut in heat seal 74a is depicted which is continuous and joins the heat seal 74b forming a vacuum-tight container that has a reduced oxygen atmosphere with intimate contact between the surfaces of the film 72 and 73 which they contain the agent that produces the red color of myoglobin.

Vacuum packed with a thin film

Vacuum packed with a thin film (VSP) is another process well known in the art that uses a thermoplastic material to store a product. In US Patents Nos. 3,835,618, 3,950,919 and Re30,009, all of them of Perdue, various apparatus and processes are described. In one sense, the vacuum packaging process with a thin film is a type of thermoforming process in which an article to be packaged serves as a mold for the thermoforming. An article is placed on a support member, rigid or semi-rigid cardboard or any other bottom and then passed to a chamber where a top film is sucked up against a hot dome and then dropped onto the article. The movement of the plastic top film is controlled by vacuum and / or air pressure and, in a vacuum packaging arrangement with a thin film, the vacuum is made inside the receptacle before the final sealing of the film superior to the support. As a top film and bottom support, a thermoformable material can be used, together with an intermediate support for products held on either side of the support as indicated, for example, in US Patent No. 3,966,045.

In vacuum packaging with a thin film, the product to be packaged is placed on a support member. The product serves as a mold for a thermoformable polymeric film. The thermoformable film is formed around the product by means of a differential air pressure. However, the term "vacuum packed with a thin film" (hereinafter "VSP") refers not only to the fact that a thermoformable film is formed around the product by vacuum or differential air pressure but also to the fact that that the product is packaged under vacuum, the vacuum being made during packaging in the volume containing the product.

Vacuum packaging processes with a thin film use a vacuum chamber with an open top. The product (on a waterproof bottom board through which vacuum is not aspirated) is placed on a platform inside the vacuum chamber. The upper part of the chamber is covered with a sheet of film that is held firmly against the camera forming an air tight closure. The vacuum is made in the chamber while the film is heated to its formation and softening temperature. The platform is then lifted to carry the product in the softened film and the air reintroduced into the chamber can be used around the film to force it intimately around the product.

In vacuum packaging with a thin film, it is well known to remove the vacuum and allow ambient air to enter the chamber after having made the vacuum in the chamber and carrying the product in the heat softened film, or vice versa. In this way, the thermoplastic film is molded more or less on and against the product since there is a certain vacuum inside the container, and ambient air pressure or pressure greater than that of the ambient air immediately outside the container.

Vacuum containers with a thin film generally use a rigid tray, such as one made of a thermoformable film, to support a product. The transparent top film, such as one made of a thermoformable film, which may or may not be a biaxially oriented film, is formed or dropped around the product during vacuum packaging procedures. The film forms a skin around the entire surface of the product. Preferably, the food contact layer of the transparent top film includes a red forming agent. Optionally, the tray can also include a red forming agent in the food contact layer. In U.S. Patent Nos. 4,611,456 to Gilliotos et al., 5,846,582 to Mayfield et al. and 5,916,613 to Stockley describe examples of trays, films and processes for vacuum packaging with a thin film.

Packaging methods

In another aspect of the invention, methods of packaging a food containing myoglobin are provided. In one embodiment of the invention, a method of manufacturing a vacuum package of fresh meat is provided, a method comprising: providing a receptacle comprising a film having a layer comprising a myoglobin-red producing agent, film which is substantially impermeable to oxygen; place a cut of meat in the receptacle for retail sale; eliminate the atmosphere inside the receptacle; make a transparent portion of the film in direct contact with at least a portion of the meat surface; tightly close the receptacle to enclose fresh meat and avoid its contact with oxygen from outside the receptacle; provide a compact package that has an internal oxygen level sufficiently reduced to promote a surface of the meat that favors the formation of deoximioglobin or methioglobin instead of oxythioglobin and the corresponding purple and brown colorations associated with those; and store the container under refrigeration conditions for a sufficient time to allow the reducing activity of the enclosed meat that favors the formation of nitroximioglobin on the surface of the meat to a degree where the corresponding red color associated with that producing a surface is formed. of visibly red meat.

Variations of this embodiment may utilize the wide selection of MBA, polymers, films, attributes and parameters described herein and recognized by those skilled in the art in view of the present description.

The meat product must be packaged in a suitable food container and / or in a film suitable for packaging, such as the containers and films described herein. Preferably, the meat product is in contact with the surface of the contact container with the food containing the myoglobin red producing agent. The myoglobin red (MBA) producing agent will preferably contact the surface of the meat to a sufficient extent to produce the desired red color that preferably does not penetrate an undesirable length of the thickness of the food under reduced oxygen conditions (this color may need to develop, for example, 1 to 5 days). Beneficially, the MBA may be present on the surface of the food contact film (or on the surface of the food with myoglobin) in an amount of approximately 0.008-0.465 to 0.775-1.550 μmol / cm2 and in increments of 0.1 μmol. Higher and smaller amounts of MBA may be used and the intensity of the color may vary depending on the presence or relative absence of myoglobin. The food contact layer preferably has between about 1.55x10-4 and about 0.139 mg of an MBA, such as NaNO2, per cm2. The package must also keep the food in a reduced oxygen medium that has a reduced partial pressure of gaseous oxygen. The reduced oxygen package may comprise an oxygen barrier layer having an oxygen transmission rate of less than about 310, 200, 100, 75, 50, 40, 30, 20, 10, 5 or 3 cm3 / m2. 24 h, measured at 23 ° C and 0% relative humidity. Preferably, the oxygen barrier layer has an oxygen transmission rate of less than about 310 cm3 / m2.24 h, measured at 23 ° C and 0% relative humidity, more preferably less than about 75 cm3 / m2.24 h and more preferably less than about 20 cm3 / m2.24

h. It may also be desirable to bring the package with the food contained at a temperature of about 4 ° C or more to facilitate the formation of the red color, after which the temperature can be adjusted to the optimum temperature desired for storage, transport or presentation.

In many packaging applications, such as vacuum packaging, heat sealable films are desirable for food packaging. Said bags or bags can be made with heat sealable layers. A typical bag for food packaging can include three heat-sealed sides by the manufacturer, leaving one side open to allow product insertion. Flexible receptacles for food packaging, such as bags or sacks, can be made by transversely cutting a single-layer or multi-layer tubular film material and cutting the portion of the tube containing the sealed end; superimposing flat sheets of film and sealing on three sides; or by folding a flat sheet and sealing on two sides. A manufacturer may then insert, for example, fresh, frozen, chilled, thawed, raw, enhanced, cured or processed meat, ham, poultry, primary or subprimary cuts, minced meat or other products containing myoglobin, and making a final seal to tightly enclose the product in the bag. Preferably the final sealing is done after gas removal (for example, vacuum removal). Flexible receptacles for food packaging, such as bags or sachets, can be made by transversely sealing a single-layer or multi-layer tubular film material and cutting the portion of the tube containing the sealed end; making two sealed seals in the tubular material and cutting the open side of the tube; superimposing flat sheets of film and sealing on three sides; or by folding a flat sheet and sealing on two sides. The final seal after inserting the food can be a stapling but is usually a heat seal similar to the initial seals produced by the bag manufacturer although the actual heat sealing equipment may vary. Heat sealing and pulse sealing devices are commonly used for heat sealing.

The food packaging film can also be used in embodiments using trays, for example, as a cover film or a tray wrap. Sealing equipment such as those manufactured by Ossid Corporation (of Rocky Mount, North Carolina) or ULMA Packaging Inc. (of Woodstock, Georgia) can be used to package poultry meat or other meats. Tray packaging may optionally involve replacing the gaseous medium present inside the container with one or more gases that provide some advantage, such as helping to preserve the product, but, to enjoy the preferred benefits of the present invention, at least a portion of the oxygen barrier film must be in contact with a food surface under reduced oxygen conditions to fix the color on that contact surface so that a potential consumer or buyer can see the surface of the meat with the color set through a transparent portion of the film.

Conveniently at least 10%, preferably at least 20% and more preferably at least 30 or 50% or more of the surface of the oxygen barrier film is transparent to allow visual perception of food color After being packaged. It is believed that meats that have a bright red color are more visible and have greater definition to distinguish the physical topography, texture and color variation of meat such as that found, for example, in a marbled. It is also believed, without wishing to be bound by any theory, that the targets of meat components such as fats, skin and white muscle fibers, are intensified by having nearby myoglobin bound by producing agents of the myoglobin red color that fix a Bright red color as opposed to purple, bluish or brownish colors. Therefore, whites appear whiter in poultry meat or in other meats, including beef and pork. This, in turn, causes consumers to have a perception of greater transparency of the meat surface, which increases consumer confidence in their purchase with respect to meats that have less visible surface characteristics.

Examples

The following are examples and comparative examples.

The experimental results and the presented properties of the following examples are based on the following test methods or substantially similar test methods, unless otherwise indicated.

Oxygen gas transmission rate: ASTM D-3985-81

Water vapor transmission rate: ASTM F 1249-90

Thickness: ASTM D-2103

Melt flow index: ASTM D-1238, condition E (190 ° C) [except for propene-based polymers (C3 content greater than 50%)].

Melting point: ASTM D-3418; differential scanning calorimetry (DSC) with a heating rate of 5 ° C / min.

Contraction values: the contraction values ​​are defined as values ​​obtained by measuring the free contraction of a square sample of 10 cm on the side submerged in water at 90 ° C (or at the indicated temperature, if different) for five seconds. Four test specimens are cut from a given sample of the film to be tested. The specimens are cut into squares 10 cm long in the longitudinal direction and 10 cm long in the transverse direction. Each test tube is completely immersed for 5 seconds in a 90 ° C water bath (or at the indicated temperature if it is different). The specimen is removed from the bath and the distance between the ends of the contracted specimen is measured in both directions (longitudinal and transverse). The difference between the distance measured in the original specimen and the contracted specimen is multiplied by 10 to obtain the percentage of contraction of the specimen in each direction. The average contraction value of the four specimens in the longitudinal direction and the average contraction value of the four specimens in the transverse direction are calculated. Here, the term "heat shrink film at 90 ° C means a film that has a free shrinkage value of at least 10% in at least one direction.

Contraction force: the contraction force of a film is the force or tension required to avoid the contraction of the film and is determined in samples taken from each film. Four samples of the 2.54 cm wide and 17.8 cm long film in the longitudinal direction and 2.54 cm wide and 17.8 cm long in the transverse direction are cut. The average thickness of the film samples is measured and recorded. Each sample is then fixed between two jaws separated by 10 cm. One jaw is in a fixed position and the other is connected to the transducer of a strain gauge. The fixed sample of the film and the jaws are then immersed in a silicone oil bath maintained at a constant high temperature for a period of five seconds. During this time, the force in grams expressed by the shrinkage tension of the film at the elevated temperature is noted. At the end of this time, the sample is removed from the bath and allowed to cool to room temperature, after which the force in grams at room temperature is also noted. The contraction force of the film sample is determined by the following equation, in which the results are obtained in grams per millimeter of thickness:

Contraction force = F / T

F being the force in grams and T the average thickness in millimeters of the film samples.

The following references provide other useful tests: United States patent application number 09 / 652,591 entitled "Biaxially oriented irradiated film" by Scott Idlas, and United States patents numbers 6,777,046 and 5,759,648.

Non-limiting examples of the compositions, films and packages described herein are provided below. In all of the following examples, unless otherwise indicated, film compositions are generally produced using the apparatus and method described in United States Patent Number

3,456,044 (Pahike), which describes a type of double bubble method coextrusion, and in addition to the above detailed description. All percentages are by weight, unless otherwise indicated.

Single and multi-layer tubular films are manufactured by an orientation process with biaxial stretching. Movies of five or more layers are also contemplated. The multi-layer films of the present invention may include additional layers or polymers to add or modify various properties of the desired film, such as heat sealing ability, adhesion between layers, adhesion to the surface of the food, contractility, contraction force, resistance to wrinkled, puncture resistance, printing ability, stiffness, gas or water barrier properties, abrasion resistance and optical properties, such as gloss, turbidity, absence of lines, stripes or gels. These layers can be formed by any suitable method, including coextrusion, extrusion coating and stratification.

Example 1

A solution of an agent that produces the red color of myoglobin (MBA), as described above, is prepared by dissolving an adequate amount of MBA in a solvent. A suitable concentration of MBA is approximately 0.60 moles of MBA in 60 g of solvent. The solution is prepared at room temperature by gently stirring the MBA / solvent mixture.

Very low density polyethylene (VLDPE) ATTANE® (obtained from Dow Chemical Company, Midland, MI) is loaded into the hopper of a gravimetric dosing unit placed to feed the polymer to the main feed mouth of a two rotating propeller extruder 50 mm MP2050 (from APV Extrusion Systems). The feeder is configured to dose the ATTANE at a flow rate of 41 kg / h. The mixing elements of the twin-screw extruder are arranged in such a way that they allow the feeding and fusion of the VLDPE, injection and mixing of the MBA / solvent solution, solvent removal, pressurization of a nozzle and formation of continuous filaments of a homogeneous mixture of VLDPE / MBA.

The two-propeller extruder is electrically heated so the feed zone is at 93 ° C and the rest of the extruder at 165 ° C. When the extruder zones reach the programmed temperatures, the drive motor that rotates the extruder's propellers is started at a speed of approximately 578 rpm. The VLDPE ATTANE is dosed to the main feeding mouth at a flow rate of 41 kg / h. Once a homogeneous stable extrudate is achieved, the MBA / solvent mixture is injected into the injection mouth in the molten VLDPE. A gear pump is used to provide the MBA / solvent solution to the injection nozzle. The injection point is located in a section of the extruder configured to have high free volume and low pressure. The flow rate of the solution is calculated by changing the mass of the MBA / solvent mixture over time. The programmed concentration of 5% is achieved by adjusting the pump speed. A suitable pump speed is approximately 33 rpm. Preferably, the contribution rate of the MBA / solvent mixture is approximately 5.4 kg / h.

The mixing elements of the extruder are arranged in such a way that the return of the MBA / solvent solution to the main feed port is avoided. Holes with punched holes are used to prevent such return movement.

After injection, the temperature of the MBA / solvent solution is rapidly increased. The solvent in the solution evaporates and finally boils. The resulting solvent escapes through the purge outlet at atmospheric pressure. Some solvent may also escape from the main feeding mouth. After a mixing section, the VLDPE / MBA mixture enters the pressurization section and finally into an eight-hole nozzle. Upon exiting the nozzle, the resulting continuous filaments are cooled in a water bath. At the exit of the water bath, an air knife removes some of the moisture attached to the surface of the filaments. After leaving the influence of the air knife, the filaments are cut into discrete granules by a rotary granulator of the type of blades. These granules are subsequently dried in a convection oven at approximately 50 ° C, packed in aluminum foil bags and stored for use (these granules are called matrix granules). Non-limiting examples of various techniques for preparing basic mixtures are described in US patent application, pending processing together with this, number 11 / 408.221 entitled "Process for introducing an additive into a polymer melt", by Nelson et al.

Films are prepared from the matrix granules. The loading level of the matrix granules to produce VLDPE films with an effective concentration of MBA is varied and packages are prepared using the film as an inner layer.

Foods, in particular meat products, are vacuum packed and observed for a period of time.

Example 2

Matrix granules of Example 1 with VLDPE ATTANE 4201 resin (from Dow) are used to make the inner layer of a multi-layer thermoformable film. The film has the layers of 85% nylon 6 - 15% nylon 6I / 6T (11% by weight) / adhesive (20% by weight) / 85% nylon 6 - 15% nylon 6I / 6T (8, 5% by weight) / EVOH (9.4% by weight) / 85% nylon 6 - 15% nylon 6I / 6T (8.5% by weight) / adhesive (20% by weight) / 70% VLDPE

- 30% of matrix granules (22.6% by weight). The film is manufactured in a simple bubble process to make a non-oriented thermoforming film.

Examples 3a, 3b and 3c

A steer was sacrificed and three days post mortem meat was cut from the shredded shoulder. Approximately 2,270 grams of this minced meat was distributed in vacuum bags and the meat was crushed to a thickness of 2 cm. After 7 days of refrigerated storage, the meat was cut into rectangular samples measuring 6.3 x 8.9 cm. In Example 3a, a 300 m dietary tablet produced by Vitamin World and containing 100 mg of nicotinic acid together with bicalcium phosphate, cellulose, vegetable stearic acid, silica and vegetable magnesium stearate was placed in one of the meat samples It was packed with a Multivac T200 machine using a VSP polyolefin based film that had an EVOH layer as an oxygen barrier and a food contact polyethylene layer. The bright color of the meat began to proliferate from the meat closest to the tablet after 24 hours of refrigerated storage.

In example 3b, a second rectangular sample of minced meat was sprayed with an aqueous solution of niacin and packaged as described in example 3a. The niacin solution was obtained by dissolving a similar niacin tablet in water. A bright red color developed on the surface of the meat sample. However, the intensity of the red color was less than that formed around the tablet.

In example 3c, a control example was performed by packaging a third sample of minced meat as described above in example 3a but without adding niacin. The color on the surface of the sample was purple without formation of the red color observed in examples 3a and 3b.

After 15 days, the three packages prepared in examples 3a, 3b and 3c were opened and examined. After opening the containers, the meat of each container acquired a uniform red color. Roasting on a gas-heated grill produced non-distinguishable results in all three examples. The interior color of the treated and untreated samples was a pink color. No persistent pink appearance was observed in meat treated with niacin.

Examples 4a, 4b and 4c

Four days after sacrificing the animal, lean shoulder meat containing approximately 5% visual fat was crushed. The minced meat was distributed in flexible oxygen barrier bags and vacuum packed with a Koch chamber machine. The color of the meat changed from red to dark purple in 4 hours. In Example 4a, after 24 hours of refrigerated storage, one of the vacuum containers of minced lean meat was opened and niacin was mixed with a portion of the meat to produce minced meat containing 0.025% by weight of niacin. This mixture was then placed in a white polypropylene oxygen barrier tray, which contained an EVOH barrier layer. Similarly, in example 4b, another portion of the packaged meat was opened and placed in the same type of tray without the addition of niacin. The two minced meat trays were packaged with a thin film in a Multivac T200 machine with a thin packaging film that had an EVOH barrier against oxygen. In Example 3c, another portion of the packaged meat was opened and placed on a tray without adding niacin. The tray was then packaged in the Multivac T200 machine with a thin film containing a sealant layer with 2% by weight sodium nitrite. After 24 hours of refrigerated storage, the niacin-treated meat sample (Example 4a) acquired the preferred red color while the untreated meat sample (Example 4b) had a characteristic dark purple color of vacuum-packed fresh meat. The meat of the third tray with the nitrite-containing film (Example 4c) acquired a grayish-purple color during the initial 24 hours, after which time the color changed to bright red.

The color of the meat treated with niacin was darker than that of the meat in the container with the film containing nitrite. The face of the bottom and the central parts of the meat treated with niacin had the same intense red color as the surface. The red color of the meat in the nitrite-containing film penetrated approximately 1.6 to 1.4 mm from the surface of the meat.

After 1 week of refrigerated storage, the three meat samples were removed from the containers. The meat samples were then placed on a gas heated grill. They were roasted slowly at 93-121 ° C for approximately 45 minutes, turning them every 5-10 minutes, to achieve a well-done cooking level. The color of the roasted surfaces and inner portions of the meat treated with niacin and packaged with the thin oxygen barrier film and the color of the untreated meat packaged with the thin oxygen barrier film were the same. On the upper surface that is in contact with the meat film that did not contain added niacin and that was packed with the nitrite-containing film (Example 4c), a red smell persisted at the same penetration depth and that observed in the product raw. The color of the opposite surface and the central portion of this sample were the same as that of the control (Example 4b) and that of the sample treated with niacin (Example 4a).

Example 5

Nicotinic acid powder (obtained from Sigma Aldrich Chemical Company, Milwaukee, WI) was mixed with a VLDPE ATTANE® 4203 granules (0.5 dg / min; 0.912 g / cm3; ethylene and octene copolymer; obtained from Dow Chemical Company, Midland MI) until the powder uniformly coated the surface of the granules. The amounts were selected so that the nicotinic acid content was 5% by weight (14.25 VLDPE and 0.75 kg nicotinic acid). The mixture was loaded into the hopper of a gravimetric dosing unit located to feed the polymer into the main feed mouth of a 50 mm MP 2050 rotating propeller extruder (from APV Extrusion Systems). The feeder is configured to dose the nicotinic acid / VLDPE mixture at a flow rate of 36 kg / h. The mixing elements of the twin-screw extruder are arranged to accommodate the feeding of the nicotinic acid mixture (VLDPE, intensive mixing of the nicotinic acid in the VLDPE, pressurization of a nozzle and continuous filament formation of the homogeneous mixture.

The two propeller extruder is electrically heated so that the feed zone is at approximately 93 ° C and the rest of the extruder at approximately 160 ° C. The nicotinic acid / VLDPE mixture is dosed in the main feeding mouth at a flow rate of approximately 36 kg / h. Once a stable homogeneous extrudate is achieved, the continuous filaments are cooled by transporting them through a water bath. At the exit of the water bath, an air knife removes some of the moisture attached to the surface of the filaments. After leaving the influence of the air knife, the filaments are cut into discrete granules by a rotary granulator of the type of blades. The resulting granules have a brown color. Over time, an accumulation of a powdery mass is observed at the exit of each of the nozzle holes.

Example 6

Example 5 is repeated except that nicotinic acid is substituted by nicotinamide (obtained from Sigma Aldrich Chemical Company, Milwaukee, WI). It is observed that the resulting granules are brown.

Example 7

Example 6 is repeated except that the rotation speed of the extruder propellers is reduced to approximately 200 rpm. The color of the granules is very light brown and they have very bright surfaces. The filaments are stable and the manufacturing efficiency is much greater than that of example 6.

Example 8

Example 5 is repeated except that the speed of rotation of the extruder propellers is reduced to approximately 200 rpm. As in example 7, the color of the granules is much lighter. The degree of accumulation of the powdery mass around the holes of the nozzle is substantially less than that observed in example 5.

The MBA-containing resins of Examples 5-8 can be used to form receptacles suitable for packaging foods containing myoglobin and maintaining a stable surface color therein.

Films, bags and packages may also employ combinations of the features described in one or more embodiments.