A process for producing a proteinaceous foodstuff with a fibrous structure.

The invention relates to a process for producing a proteinaceous foodstuff with a fibrous structure, starting from a mixture of vegetable protein-containing material and water by extruding said mixture, shredding the extrudate, incorporating the shreds thus obtained in a protein binder and heat-setting the mixture thus obtained.

A similar process has been described in French Patent Application No. 7,624,989. This process, however, displays a number of drawbacks. During the shredding step fines are formed which have to be recirculated. The formation of an unacceptable proportion of fines is due to evaporation of water from the extrudate as soon as it leaves the extrusion die, whereby the water content of the extrudate drops to 20% or less. Shredding such a relatively dry extrudate causes the disintegration of the extrudate into particles of far too small dimensions for these to be useful as a structure- imparting component. Moreover the extrudate has a texture which lacks a certain resilience or toughness.

Applicants have found a process which alleviates to a great extent the above disadvantages.

The process according to the invention involves <ul id="ul0001" list-style="none"><li>a) producing a mixture mainly consisting of (i) 50-80 wt.% of a vegetable protein-containing material having a protein content of at least 25%, (ii) 20-50 wt.% water, (iii) 0.5-8 wt.% lipids and (iv) an effective proportion of an edible agent imparting toughness to the protein material;</li><li>b) extruding said mixture while ensuring that an extrudate is obtained having a moisture content of at least 30 wt.%;</li><li>c) shredding said extrudate;</li><li>d) incorporating the shreds in a protein binder, and</li><li>e) heat-sutting the mixture consisting of binder and shreds.</li></ul>

The vegetable protein-containing material in step (a) may consist of material originating from oleaginous seeds such as rapeseed-, cottonseed- or soya meal and the like, which has been defatted by extraction with an organic solvent such as hexane. It is very useful to use a protein concentrate which is a meal which has further been refined by extraction with a polar solvent, such as a mixture of ethanol and water, whereby sugars and other undesirable components are removed.

The vegetable protein-containing material may partly consist of a protein isolate which is usually produced by precipitation of protein from an aqueous suspension of meal at the isoelectric point of the protein.

In the process according to the invention a soya protein concentrate or soya meal is preferably used.

The toughening agent to be incorporated in the mixture in step (a) comprises a calcium salt such as calcium chloride or calcium lactate in a proportion of at least 0.05 and preferably 1-3 wt.% and/or a sufficient proportion of an acid such as citric acid, lactic acid or sulphuric acid to achieve a ^pH in the mixture which is approximately equal to the isoelectric point of the protein present therein. When soya protein is present the proportion of acid to be used should be such as to achieve a pH of about 5.0.

Step (b) of the process according to the invention can be carried out using a conventional plastic extruder such as a Wenger X20 or X200. Extrusion is usually carried out at a temperature ranging from 110-165°C at a pressure ranging from 5 to 50 atm.

The moisture content of the extrudate being critical, it is essential to carefully select the water content of the mixture in step (a) and the extrusion conditions. A way for obtaining an extrudate having a moisture content of at least 30% and preferably of at least 50% consists in preventing evaporation of water from the extrudate leaving the extrusion die by keeping the extrudate immediately after it is leaving the extrusion die under superatmospheric pressures until its temperature sufficiently drops to a value at which under atmospheric pressure water does not evaporate quickly enough to render the extrudate unuseful. A simpler way of achieving the desired moisture content in the extrudate consists in contacting the extrudate with water, for instance by spraying water on it, or by allowing the extrudate to rehydrate in a vessel containing a sufficient amount of water. The temperature of the water may vary from 4 to 100°C. Although rehydration is quicker at the higher temperatures of this range, for practical reasons it is preferred under conditions prevailing in a factory to use tap water.

Applicants have surprisingly found that rehydration rates are improved by incorporating in the mixture to be extruded an efficient proportion of a hydrophilic emulsifier, which means an emulsifier having an HLB value (hydrophilic/lypophilic balance) of at least 8. Such emulsifiers are well-known commercial products and are described in "Emulsion", Paul Becher, Reinhold Publishing Corporation 1957, Chapter 6.

Useful examples of such emulsifiers are lecithin, sodiumstearoyl lactylate and sucrose monopalmitate.

The useful proportion of the emulsifier can be established in each particular case. In most instances a proportion ranging from 1 to 4 wt.% will suffice.

The preferred emulsifier is lecithin. It is believed that lecithin at a level of 1-4 wt.% offsets the hydrophobic action of the fat incorporated as a lubricant in the mixture to be extruded.

Lecithin can be added as a powder to the mixture. Preferably a mixture of lecithin and soybean oil in a proportion of preferably 9:1, which has a relatively low viscosity, is sprayed on the mixture. Lecithin can be used to replace at least part of the lipids used in the mixture to be extruded as an extrusion aid. Applicants have established that the use of lecithin allowed rehydration values of 100-300X (subject to the shape and dimensions of the extrudate) to be achieved within 5 minutes in cold tap water. The rehydration values indicate the percentage of water absorbed by the extrudate based on the weight of the extrudate.

In the process according to the invention the extrudate is shredded in an apparatus exerting shearing forces, such as a Pallman or Eirich mill. The clearance between the rotating plates of the apparatus is chosen to be such that shreds of the desired dimensions are obtained. For producing meat substitutes shreds having a thickness of at least 0.2 mm and preferably 0.3-1 mm and a length of at least 2 mm and preferably 4-25 mm, are produced.

The binder in which the shreds are incorporated contains fats and proteins. Preferably a binder is used which comprises 10-50% fat, 3-20% protein, 1-10% potato pulp powder as a rehydration aid and water up to 100%. The fat may consist of vegetable and/or animal fats such as soybean oil, cottonseed oil, sunflower oil, lard and tallow.

The protein may consist of vegetable and/or animal proteins such as soy protein, rapeseed protein or meat proteins.

The mixture consisting of binder and shreds is subsequently shaped into the desired form and heated at a temperature which is sufficiently high to set the protein. Mostly a temperature from 60-120°C will be adequate. The heat-set product is subsequently cut to the desired dimensions and is optionally dried to a moisture content of e.g. 3-6%. The product is eminently suitable for use in dry meals, soups and filled sauces, particularly of the instant-type.

The invention will now be illustrated in the following Examples.

Example I

A mixture of the following composition was produced:

<tables id="tabl0001" num="0001"><img file="EP0010798A1_D0001.tif" /></tables>This mixture was fed into a Wenger extruder type X20 and was extruded at 130°C.

The moisture content of the extrudate was raised to 50% by spraying water of 90°C on it.

Rehydration was completed after 5 minutes.

The rehydrated extrudate was shredded in a Pallman apparatus in which the clearance between the rotating plates was about 3.5 mm, to obtain shreds of a thickness ranging from 0.2-lmm and of a length ranging from 4-25 mm.

The proportion of fines was almost nil.

A binder of the following composition was prepared. <tables id="tabl0002" num="0002"><img file="EP0010798A1_D0002.tif" /></tables>

1 Part of shreds was mixed with 2 parts of binder. A plank was formed from this mixture. The plank was heated at 100 C to coagulate the protein. The heated plank was subsequently cut into dice of 8 x 12 x 25 mm which were finally air-dried to a moisture content of 5 wt.%. The dice were incorporated in a dry meal composition. On rehydration the dice were found to have excellent chewability and fibrosity similar to real meat.

Example II

The procedure outlined in Example I was repeated, using instead of calcium chloride a proportion of citric acid sufficient to achieve a pH of about 5.0.

The dice obtained had an excellent texture and the proportion of fines formed during shredding was negligeable.

Examples III and IV

The procedure outlined in Examples I and II was repeated but using an extrudate having a moisture content of 70%.

The results were as satisfactory as in the previous Examples.

The following Examples illustrate the effect of the use of specific emulsifiers according to the invention on the rehydration proporties of the extrudate.

Examples V-VIII

Examples I to IV were repeated, using 3% of a lecithin powder (HLB=14). The extrudates were all rehydrated in cold tap water. Within 5 minutes a rehydration percentage of approximately 120% was achieved.

Examples IX-XII

Examples I to IV were repeated, using 1.5% of a native mixture of soya lecithin consisting of 90% lecithin and 10% soybean oil. The extrudates were all rehydrated in cold tap water. Within 5 minutes a rehydration percentage of approximately 170% was achieved.

Example XIII

The procedure outlined in Example I was repeated, using 3% sodiumstearoyl lactylate (HLB 12). A rehydration percentage of the extrudate of approximately 105% was achieved within 5 minutes in cold tap water.

Example XIV

The procedure outlined in Example I was repeated, using 3% sucrose monopalmitate (HLB 12). A rehydr_dtion percentage of the extrudate of approximately 80% was achieved within 5 minutes in cold tap water.

Comparative Examples XV and XVI

The procedure outlined in Example I was repeated, while rehydration was carried out in cold tap water. The rehydration percentage obtained after 5 minutes was insufficient. The procedure outlined in Example I was repeated, using sorbitan monostearate (HLB 5).

The rehydration percentage obtained after 5 minutes in cold tap water was 40%, which is considerably lower than the percentage obtained when an emulsifier having an HLB value&gt;8 was used.