Method for reducing acrylamide formation in thermally processed foods

Method for reducing the formation of acrylamide in hot processed food

BACKGROUND OF THE INVENTION Cross-referenced related applications This application is a partial follow-up application of pending US patent application 10/247,504 filed on September 19, 2002.

Technical field

The invention relates to a method for reducing the amount of acrylamide in thermally processed foods. The food produced by the invention can greatly reduce the content of acrylamide. The method relies on the addition of divalent or trivalent cations such as calcium, magnesium, copper, iron, zinc or aluminum salts found in the dough formulations of foods.

Description of Related Art The chemical acrylamide has been used in the industry for a long time in the form of a polymer. It can be used in water treatment, concentrated oil recovery, papermaking, flocculant, thickener, ore treatment and non-iron fiber products. Acrylamide is used as a white crystalline solid. It is odorless and has high water solubility (2155g/L at 30°C). Homologues of acrylamide include 2-propenamide, ethylenecarboxamide, acrylic amide, vinyl amide and acrylic amide. The molecular weight of acrylamide is 71.08, the melting point is 84.5°C, and the boiling point at 25mmHg is 125°C.

Recently, acrylamide monomer has been tested positive in many different foods. In particular, acrylamide has been found in carbohydrate foods that are heated or processed at high temperatures. Examples of foods that test positive for acrylamide include coffee, cereals, biscuits, potato chips, crackers, fried potato chips, bread and rolls, and breaded fried meat. In contrast to undetected levels in unheated and boiled foods, generally lower levels of acrylamide are found in heated protein-rich foods, while higher levels of acrylamide are found in carbohydrate-rich foods. The reported acrylamide content found in different similar processed foods includes: potato chips in the range of 330-2,300 (ug/kg), French fries in the range of 300-1100 (ug/kg), and corn flakes in the range The range of 120-180 (ug/kg), and the content in different breakfast cereals ranges from undetected to 1400 (ug/kg).

It is currently believed that the formation of acrylamide is due to the presence of amino acids and reducing sugars. For example, it is believed that acrylamide in most fried foods is produced by the reaction of free asparagine with reducing sugars. Asparagine is an amino acid commonly found in raw vegetables. In raw potatoes, the amount of asparagine accounts for about 40% of the total free amino acids, about 18% in high-protein rye, and about 14% in wheat.

The formation of acrylamide by amino acids other than asparagine is also possible, but it has not been confirmed. For example, it has been reported that some acrylamide has been found by experimenting with glutamic acid, methionine, cysteine and aspartic acid as precursors. However, these findings are difficult to confirm due to the potential asparagine impurities in the raw amino acids. Nevertheless, asparagine has been identified as the amino acid precursor most likely to form acrylamide.

Since acrylamide in food is a recently discovered phenomenon, the exact mechanism of its formation has not yet been confirmed. However, it is now believed that the most likely way to form acrylamide involves the Maillard reaction. Maillard reaction is recognized as one of the most important chemical reactions in food processing in food chemistry, and affects food flavor, color and nutritional value. The Maillard reaction requires heating, humidity, reducing sugars and amino acids.

Maillard reaction is a series of complex reactions including multiple intermediates, but it can usually be described as including three steps. The first step of the Maillard reaction involves the combination of free amino groups (from free amino acids and/or proteins) with reducing sugars (such as glucose) to form Amadori or Heyns rearrangement products. The second step involves the degradation of Amadori or Heyns rearrangement products via different alternative pathways, including the production of deoxyosones, cleavage, or Streker degradation. A series of complex reactions-including dehydration, elimination, cyclization, cleavage and fragmentation-lead to the synthesis of fragrance intermediates and fragrance compounds. The third step of the Maillard reaction is characterized by the formation of brown nitrogen-containing polymers and copolymers. Using the Maillard reaction as the most likely way to form acrylamide, Figure 1 depicts a simplified possible way to start forming acrylamide with asparagine and glucose.

Acrylamide is still not sure that it is harmful to humans, but it exists in food, especially in food at a high content is undesirable. As noted earlier, higher acrylamide concentrations are found in heated or thermally processed foods. The reduction of acrylamide in such foods can be achieved by reducing or eliminating the precursor compounds that form acrylamide, thereby inhibiting the formation of acrylamide during food processing, and decomposing or reacting acrylamide monomers once formed in the food. Or, remove acrylamide from the product before consumption. It is understandable that each type of food has unique challenges to achieve any of the above options. For example, without destroying the cell structure, the food that is sliced and cooked as a sticky piece is not easily mixed with different additives, and the cell structure gives the food a unique flavor during cooking. Other processing requirements for special foods are also incompatible or very difficult with acrylamide reduction strategies.

As an example of heating food, this example illustrates the unique challenge of reducing the content of acrylamide in the final product, making snacks from dough. The term "synthetic snack" means a snack food that uses some starch raw materials that are different from the original and unchanged starch as the starting ingredients. For example, synthetic snacks include the use of dehydrated potato products as raw materials to synthesize potato chips, and moist masa as the raw materials to synthesize corn flakes. Note that the dehydrated potato may be potato flour, potato flakes, potato granules, or any other form of dehydrated potato. When any of these terms are used in this application, it is understood that all various changes can be included. The predecessor of synthetic potato chips is, for example, thin potato chips, which are mixed with water and other auxiliary ingredients to form a dough. The dough is made into sheets and cut before the cooking step. The cooking step includes frying or drying. Then the flakes are seasoned and packaged. The mixing of potato dough usually makes it easy to add other ingredients by itself. In contrast, adding such ingredients to unprocessed foods such as potato slices requires the discovery of a mechanism for the ingredients to penetrate the porous structure of the product. However, any ingredients added during the mixing step must take into account that the ingredients can adversely affect the dough sheeting characteristics and the final potato chip characteristics, such as flavor, texture, and color.

There is a need to develop one or more methods to reduce the acrylamide content in the final product of heated or thermally processed food. Ideally, this method should sufficiently reduce or eliminate acrylamide in the final product without negatively affecting the quality and performance of the final product. In addition, the method should be easy to implement, especially adding almost no cost to the entire process.

SUMMARY OF THE INVENTION In the method of the present invention, before cooking, divalent or trivalent cations or mixtures of the cations are added to the synthetic food in order to reduce the formation of acrylamide. During grinding, dry mixing, wet mixing or other mixing, divalent or trivalent cations can be added so that the cations are present in the whole food. In a preferred embodiment, the added cation may be selected from calcium, magnesium and aluminum salts, and less suitably, from the group of iron, zinc and copper salts. The amount of cations added to the dough should be sufficient to reduce the acrylamide formed in the final product to the desired level.

The added divalent or trivalent cations effectively reduce the amount of acrylamide found in the final product of heated or thermally processed food, and at the same time minimize the quality and characteristics of the final product. In addition, the method of reducing acrylamide is usually easy to implement, and hardly adds any cost to the entire process.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features brought about by the performance of the present invention are described in the following claims. However, the present invention itself, its preferred mode of use, and other objectives and advantages will be well understood by referring to the following drawings in conjunction with the detailed description of illustrative embodiments, in which: Figure 1 is the formation of acrylamide in food A schematic diagram of possible chemical pathways; and Fig. 2 is a schematic diagram of a method for making synthetic potato chips from potato chips, granules or powder according to an embodiment of the present invention.

A detailed description of the formation of acrylamide in thermally processed food requires a carbon source and a nitrogen source. It is assumed that carbon is provided by a carbohydrate source and nitrogen is provided by a protein or amino acid source. Many food ingredients derived from plants, such as rice, wheat, corn, barley, soybeans, potatoes and oats, contain asparagine, and the main carbohydrates contain less amino acids. Generally speaking, such food ingredients have a small amino acid library, and the amino acid library contains other amino acids in addition to asparagine.

By "thermal processing" is meant to heat food or food ingredients, here refers to food ingredients, such as a mixture of food ingredients, at a minimum of 80°C. Preferably, the thermal processing of the food or food ingredient is carried out at a temperature of about 100°C to 205°C. The food ingredients can be individually processed at elevated temperatures before the final food is made. An example of a heat-processed food ingredient is potato chips, which are made by exposing raw potato materials to temperatures as high as 170°C. (The terms "potato flakes," "potato granules, and "potato flour" are used interchangeably here and mean any dehydrated potato-based product.) Other thermally processed food ingredients include processed oats, semi-cooked and dried rice , Cooked soybean products, corn mash, roasted coffee beans, and roasted cocoa beans. Alternatively, food ingredients can be used in the preparation of the final food, the production of the final food includes a heating step. The final food is the raw material produced by the heating step An example of processing is the production of potato chips from raw potato slices. This processing is carried out by a step of frying at a temperature of about 100°C to 205°C or by producing fried potato chips at a similar temperature.

However, according to the present invention, when the amino acid asparagine is heated in the presence of reducing sugars, it has been found that a large amount of acrylamide is formed. In the case of reducing sugars such as glucose, heating other amino acids such as lysine and alanine does not cause the formation of acrylamide. Surprisingly, the addition of other amino acids to the asparagine sugar mixture can increase or decrease the formation of acrylamide.

When it has been determined that acrylamide is formed rapidly when asparagine is heated in the presence of reducing sugars, the reduction of acrylamide in thermally processed foods can be achieved by reducing the activity of asparagine. By "reducing activity" is meant to remove acrylamide from food through conversion or binding to another chemical that interferes with the formation of acrylamide from asparagine, or to make asparagine not follow the path of acrylamide formation. React.

In the present invention, it is achieved by adding divalent or trivalent cations to the recipe of the snack food before cooking or heat processing the snack food. Chemists understand that cations do not exist in isolation, but exist together with anions of the same valence. Although the salts referred to here include salts of divalent and trivalent cations, by reducing the solubility of asparagine in water, it is believed that the presence of cations in the salt can reduce the formation of acrylamide. Here, these cations are regarded as cations having at least two valences. Interestingly, the use of a single valence cation has no effect in the present invention. Choose an appropriate compound that includes at least two valence cations combined with anions. The relevant factors are water solubility, food safety, and minimal changes in the performance of special foods. A combination of different salts can be used, although only one is discussed here. Kind of salt.

Chemists talk about the valence of an atom as a measure of its ability to combine with other elements. In particular, divalent atoms have the ability to form two ionic bonds with other atoms, while trivalent atoms can form three ionic bonds with three atoms. A cation is a positively charged ion, that is, an atom loses one or more electrons, giving it a positive charge. Divalent or trivalent cations are indeed positively charged ions, which have two or three ionic bonds, respectively.

A simple model system can be used to test the effects of divalent or trivalent cations on the formation of acrylamide. Acrylamide can be produced by heating asparagine and glucose in a molar ratio of 1:1. It has a quantitative comparison with the acrylamide content without added salt, and measures the salt's ability to promote or inhibit the formation of acrylamide. Two sample preparation and heating methods are used. One method involves mixing the dry ingredients, adding equal amounts of water, and heating in an open bottle. When heating causes most of the water to separate, the reagent is concentrated and the cooking state is repeated. Thick syrup or tar can be produced, complex recovery of acrylamide. These experiments are shown in Examples 1 and 2 below.

The second method using pressure vessels allows more control trials. The solutions of the test components are combined under pressure and heated. The test ingredient can be added at a concentration found in food, and the buffer can double the pH of ordinary food. In these experiments, there was no water detachment and the recovery of acrylamide was simplified, as shown in Example 3 below.

Example A 120ml (ml) glass bottle containing L-asparagine monohydrate (0.15g, 1mmole), glucose (0.2g, 1mmole) and water (0.4ml) were covered with aluminum foil and raised by 20°/ The minute rate is heated in a gas chromatography (GC) furnace. The heating is scheduled to be heated from 40° to 220°C, stay at 220°C for two minutes, and cool from 220° to 40° at a rate of 20°/min. The residue was extracted with water and analyzed for acrylamide by gas chromatography mass spectrometry (GC-MS). Analysis found close to 10,000ppb (parts/billion) acrylamide. Two additional bottles include L-asparagine monohydrate (0.13g, 1mmole), dextrose (0.2g, 1mmole), anhydrous calcium chloride (0.1g, 1mmole), and water (0.4ml) It is heated and analyzed. Analysis found that with 7 and 30ppb acrylamide, more than 99% of acrylamide was reduced.

The surprising result is that calcium salt strongly reduces the formation of acrylamide, and further screening of salts shows that divalent and trivalent ions (magnesium, aluminum) have similar effects. Note that similar experiments with monovalent cations, namely 0.1/0.2 grams of sodium bicarbonate and ammonium carbonate (same as ammonium carbamate and ammonium dichromate) increased the formation of acrylamide, as shown in Table 1 below.

Table 1

Example 2

In the second experiment, an experiment similar to the above was performed, but instead of using anhydrous calcium chloride, two different diluted solutions of each of calcium chloride and magnesium chloride could be used. The bottle contains L-asparagine monohydrate (0.15g, 1mmole) and glucose (0.2g, 1mmole) mixed with one of the following solutions: 0.5ml water (control group), 0.5ml 10% calcium chloride solution (0.5 mmole), 0.05 ml of 10% calcium chloride solution (0.05 mmole) and 0.45 ml of water, 0.5 ml of 10% magnesium chloride solution (0.5 mmole), or 0.05 ml of 10% magnesium chloride solution (0.05 mmole), and 0.45 ml of water.

The same two samples were heated and analyzed as described in Example 1, and the results were averaged and summarized in Table 2 below.

Table 2

Example 3 As shown above, the test did not include water lost from the container, but was operated under pressure. The vial contains 2ml of buffer raw material solution (15mM asparagine, 15mM glucose, 500mM phosphate or acetate) and 0.1ml salt solution (1000mM) at a rate of 20°/min. Parr high pressure placed in the GC furnace It is heated in the gas cylinder, and the heating rises from 40° to 150°C according to the planned procedure, and stays at 150°C for two minutes. The high-pressure gas cylinder was removed from the furnace and cooled for 10 minutes. The content was extracted with water and analyzed for acrylamide by the following GS-MS method. For each combination of pH and buffer, a control group was performed without adding salt, or three different salts were added. The results of repeated experiments were averaged and summarized in Table 3 below.

table 3

Through the use of the three salts, the greatest reduction occurred at pH 7 acetate and pH 5.5 phosphate. Acetate at pH 5.5 and phosphate at pH 7 found only a small decrease.

Example 4 is the result of the following model system, running a small-scale laboratory test in which calcium chloride is added to potato chips before heating. Three kinds of 0.4%, 2%, or 10% calcium chloride solutions by mole were added to 3 grams of potato chips. In the control group, 3 grams of potato chips were mixed with 3 milliliters of deionized water. The pieces were mixed to form a relatively uniform paste, and then heated in a sealed small glass tube at 120° for 40 minutes. Acrylamide was measured by GC-MS after heating. Before heating, the control potato chips included 46 ppb of acrylamide. The test results are reflected in Table 4 below.

Table 4

From the above results, in the experiments conducted, calcium salt was added to the formula of synthetic snack foods to bake synthetic potato chips. The method of manufacturing baked synthetic potato chips includes the steps shown in FIG. 3. Dough preparation step 31 combines the potato chips with water, cation/anion pair (here, calcium chloride) and other auxiliary materials, and the ingredients are thoroughly mixed to form a dough. (In addition, the term "potato flakes" is here intended to include the entire dry potato flakes, granules or powder, regardless of particle size.) In the sheeting/slicing step 32, the dough is passed through the sheeting machine to flatten the dough and be Cut into individual pieces. In the cooking step 33, the formed pieces are cooked to a specific color and water content. The synthesized piece is seasoned in the seasoning step 34 and packaged in the packaging step 35.

The first embodiment of the present invention is illustrated by the method of baking synthetic potato chips described above. To illustrate this example, the composition and method of synthetic potato chip dough were compared between the control group and the test batch using commercial drying. The test and control batches were carried out according to the formula listed in Table 5. The only difference between the batches is that the test batch contains a calcium chloride solution.

table 5

In all batches, the dry ingredients are mixed together first. Then the oil is added to the dry mixture and mixed. The calcium chloride is dissolved in the water before being added to the dough. The water content of the dough before the tableting is 40% to 50% by weight. The dough is pressed into slices with a thickness of 0.020 to 0.030 inches, cut into potato chip sizes, and dried.

After cooking, determine the moisture, fat, and color according to the Hunter Lab color difference system. The sample is tested to obtain the acrylamide content of the final product. Table 6 shows the results of these analyses.

Table 6

As shown in these results, adding calcium chloride to the dough at a ratio of about 1:125 by weight of calcium chloride to potato chips can significantly reduce the content of acrylamide in the final product, reducing the final acrylamide content from 1030 ppb to 160ppb. In addition, the percentage of oil and water in the final product is not affected by the addition of calcium chloride. However, it should be noted that depending on the amount used, calcium chloride can cause changes in the taste, structure and color of the product.

The amount of divalent or trivalent cations added to food to reduce acrylamide can be expressed in many ways. For commercial needs, the amount of cation added should be added at least 20%, so as to be sufficient to reduce the final content of acrylamide. More preferably, the content of acrylamide should be reduced to the range of 35% to 95% (35-95%). More preferably, the content of acrylamide should be reduced to a range of 50% to 95% (50-95%). In order to express it in a different way, the added amount of divalent cations or trivalent cations can be given as the ratio between the moles of cations and the moles of free asparagine in the food. The molar ratio of the divalent or trivalent cation to the free asparagine should be at least 1:5 (1;5). More preferably, the ratio is at least 1:3 (1:3); and more preferably 1:2 (1:2). In the present preferred embodiment, the molar ratio of cations to asparagine is about 1:2 and 1:1. In the case of magnesium, which has less effect on the taste of the product than calcium, the molar ratio of cation to asparagine can be two to one (2:1).

Run other experiments, using the same steps as above, but with different batches of potato chips including different levels of reducing sugar added and varying amounts of calcium chloride added. In Table 7 below, as in the above test, the potato chips of batch 1 have 0.81% reducing sugar, batch 2 has 1.0%, and batch 3 has 1.8% reducing sugar.

Table 7

As shown in the table, the added calcium chloride continues to reduce the acrylamide content of the final product, even when the weight percentage of the added calcium chloride to the potato chips is less than 1:250.

Many salts that form divalent or trivalent cations (or the other methods that produce cations with at least two valences) can be used in the present invention disclosed herein, as long as the adjustment can have an indirect effect on the additional ingredients. The effect of reducing the content of acrylamide appears to originate from the divalent or trivalent cation, rather than the anion paired with it. The limitation of the cation/anion pair is not the valence, but the acceptability in food, such as safety, solubility and the influence of their taste, smell, appearance and structure. Suggested cations include calcium, magnesium, aluminum, iron, copper and zinc. Suitable salts of these cations include calcium chloride, calcium citrate, calcium lactate, calcium malate, calcium gluconate, calcium phosphate, calcium acetate, calcium sodium tetraacetate, calcium glycerophosphate, calcium hydroxide, calcium lacturonate, Calcium oxide, calcium propionate, calcium carbonate, calcium stearoyl lactate, magnesium chloride, magnesium citrate, magnesium lactate, magnesium malate, magnesium gluconate, magnesium phosphate, magnesium hydroxide, magnesium carbonate, and magnesium sulfate, aluminum chloride Hexahydrate, aluminum chloride, aluminum hydroxide, ammonium alum, potassium aluminum sulfate, aluminum sulfate, ferric chloride, ferrous gluconate, ferric ammonium citrate, ferric pyrophosphate, ferrous fumarate, ferrous lactate, Ferrous sulfate, copper chloride, copper gluconate, copper sulfate, zinc gluconate, zinc oxide, zinc sulfate. The preferred embodiment of the present invention utilizes calcium chloride, although it is believed that its requirements can be met by the combination of one or more suitable cationic salts. Many salts, such as calcium salts, especially calcium chloride, are relatively inexpensive and are commonly used in foods. Calcium chloride can be used in combination with calcium citrate, thus reducing the indirect effect of calcium chloride on flavor. In addition, any number of calcium salts can be used in combination with one or more magnesium salts. Those skilled in the art understand that the adjustment of the specific composition of the salt required depends on the characteristics of the food and the desired end product.

It should be understood that changes in the characteristics of the final product, for example, color, flavor, and density can be adjusted by different methods. For example, the color characteristics of potato chips are adjusted by controlling the amount of sugar in the starting product. Some flavor characteristics can be changed by adding different flavor agents to the final product. The physical structure of the product can be adjusted by adding yeast or different emulsifiers.

With reference to one or more embodiments, although the present invention is partially shown or described, those skilled in the art should understand that the different methods for reducing acrylamide when heat-processed food do not depart from the essence and scope of the present invention. For example, although the method has been disclosed for potato products, the method can also be used in food processing made from corn, barley, rye, rice, oats, millet, and other starch-based cereals. In addition to synthetic potato chips, the present invention can be used to make corn flakes and other types of snack chips, and can also be used in cereals, biscuits, crackers, breads, small breads, fried meat breads with breadcrumbs, and other products containing Asparagine and reducing sugar food. In each of these foods, cations can be added during the mixing of the dough to make the product, so that the added cations can be obtained during the cooking process, thereby providing a reduction in the content of asparagine. In addition, the added divalent or trivalent cations can be combined with other methods to reduce acrylamide in order to produce acceptable acrylamide content without affecting the flavor, color, smell or other characteristics of individual foods.