GB2085273A - Foamed proteinaceous snack products - Google Patents

Abstract

A foamed, crispy snack product, produced by extrusion and based on protein with a content of casein protein, contains 51 to 95% dry weight of protein, the protein comprising 30 to 70% by weight of caseinate and optionally casein, 2 to 25% by weight of cereal protein and 10 to 70% by weight of soya protein, referred to the total protein content, and has a specific weight of from 0.1 to 0.4 and a maximum water content of 12%. A process for the production of such a snack product, comprises mixing acid casein with sufficient alkali to adjust the pH to between 5.3 and 8, incorporating the other proteins and extruding.

Description

SPECIFICATION Snack product based on protein The present invention is concerned with a foamed, crispy snack product produced by extrusion and based on protein and with a process for the production thereof.

It is known to produce snacks by extruding casein and caseinate under certain conditions. The extrusion of caseinate admittedly gives snack-like products but it is a disadvantage that the products obtained are not brittle enough and sometimes, because of their toughness, they are too difficult to chew in order to be useful as crispy snacks. Federal Republic of Germany Patent Specification No.2,910,665 discloses a solution to this problem in which the casein or caseinate dry mass is modified with certain amounts of aldehyde, a crispy, brittle product being obtained. However, such a chemical modification can encounter prejudices and resentments which may impair the commercial success of such a product. Therefore, it would, if possible, be desirable to produce such a snack only from conventional nutriments and foodstuff components, without chemical modification.

The present invention solves this problem by providing a foamed, crispy snack product, produced by extrusion and based on protein with a content of casein protein, wherein it contains 51 to 95% dry weight of protein, the protein comprising 30 to 70% by weight of caseinate and optionally casein, 2 to 25% by weight of cereal protein and 10 to 70% by weight of soya protein, referred to the total protein content, has a specific weight of from 0.1 to 0.4 and a maximum water content of 12%.

The present invention is based upon the surprising discovery of the fact that casein, cereal protein and soya protein, when they are present in definite amount ratios, can, on the one hand, be readily extruded and, on the other hand, under the extrusion conditions, give a brittle, crispy product of the above-described kind in which there is no danger that, in the case of storage, undesired properties arise, such as insufficient brittleness and difficult chewability.

The snack product according to the present invention preferably contains 70 to 85% by weight of protein in the dry mass, the remainder comprising ash, raw fibres, carbohydrates and fat, these components being, in particular, introduced into the product by the soya protein and the cereal protein. Therefore, the amount of these components also depends upon the quality and composition of the particular soya protein or cereal protein used. The cereal protein used is preferably gluten. In the case of the soya protein, products containing from 50% to more than 90% by weight of protein can be used as starting materials. Depending upon the amount of high percentage proteins used, snacks are obtained containing over 90% by weight of protein in the dry mass.If flavour-imparting foodstuffs or extrudable starch carriers are also used, the undesirable characteristics of the product according to the present invention are not impaired, provided that the proportion of protein present therein is more than 50% by weight of the dry mass.

Of the amount of protein in the snack according to the present invention, preferably 30 to 60% consists of caseinate, which can still contain undigested casein. The preferred amount of soya protein is from 35 to 65% by weight and the preferred amount of cereal protein is from 2 to 15% by weight, in each case referred to the total amount of protein present.

In the scope of the composition according to the present invention, the good extrudability is, in particular, determined by the caseinate content. It is assumed that the caseinate acts as a lubricant for the extrusion of the soya protein.

For the production of the product according to the present invention, casein is used as starting material, alkali being added in such an amount that, during the extrusion process, digestion also takes place with the formation of caseinate. Thus, the present invention provides a process for the production of the above-described snack product, wherein casein alone, before admixing with the other proteins, or casein in admixture with the cereal protein and/or the soya protein, is mixed with an aqueous alkali solution containing an amount of alkali which, by reaction with the casein alone, would give a pH value of 5.4 to 8, any still missing plant proteins are then admixed and, together with the alkali solution or after separation thereof, so much water is admixed that a water content of the mixture, before or during the extrusion, of at least 13% is obtained, whereafter the so obtained mixture is extruded at a temperature above 1 00 C. and under pressure into a zone of lower pressure and lower temperature.

The aqueous alkali solution is preferably sprayed on to the casein before admixing the two plant proteins.

However, it is also possible first to premix the casein with one or both of the other proteins and then to add the alkali solution. When soya and wheat proteins with a certain alkali capacity are used, it can be necessary to add thereto more alkali than that determined for the casein. This can, however, be determined in a preliminary experiment.

The amount of water introduced into the initial paste for the extrusion depends upon the conditions in the extruder, especially the temperature, which, in turn, determines the vapour pressure, the extruder construction, which can result in a more or less large escape of water vapour during heating up, and possibly also the flow characteristics in the extruder. Thus, in general, in the case of a two-screw extruder, a smaller water content is necessary for the extrusion than in the case of a single-screw extruder. However, in any case, by means of a few preliminary experiments, it is easily possible to determine that amount of water which must be added in order that the end product, after extrusion, has the above-mentioned water content and displays the desired consistency and density.

The process according to the present invention leads directly to the desired crispy-brittle consistency, without a special post-treatment step, for example an after-drying, being necessary. However, in the case of a product with a water content lying on the upper limit of the admissible water content, it is still possible to carry out a post-drying, a further improvement of the consistency thereby being achieved.

Furthermore, the specific density of the snack, which should be from 0.1 to 0.4 and preferably from 0.1 to 0.25, is also determined by the extruding conditions and the water content before or during the extruding.

The extrusion temperature used is preferably at least 11 0 C., the best results having been achieved at temperatures above 1 600C., for example 170 to 200"C. It is also possible to extrude in several stages at different temperatures, in which case the above-mentioned temperatures apply to the last extrusion step.

The casein used is preferably acid casein. Foaming is achieved by the expansion which occurs during passage from the extruder mouth piece into a zone of lower temperature and lower pressure, the water vaporising under the temperature conditions employed and the carbon dioxide liberated during the extrusion thereby acting together. The alkali used is preferably one which splits off carbon dioxide under the temperature and pressure conditions of the extruder employed, preferably an alkali metal carbonate or bicarbonate or an alkaline earth metal carbonate or bicarbonate. The carbonates and bicarbonates can also be used together with hydroxides and/or edible acids. Thus, by appropriate combination, any desired pH value in the above-given range can be achieved.As already mentioned above, the amount of alkali used is so chosen that, with the casein alone, under the usual conditions of caseinate production, it gives rise to a product with a pH value of from 5.4 to 8 and preferably of from 5.8 to 6.5. When using potassium carbonate, typical amounts of alkali lie, for example, from 2 to 5% by weight, referred to the amount of acid casein. The amount of alkali necessary for the achievement of a particular pH value can easily be determined by titration in a simple preliminary experiment. In the accompanying drawing, the Figure shows a typical titration curve of acid casein for the determination of the amount of alkali to be added.

The snack according to the present invention is admittedly preferably produced in the above-described manner, starting from casein and alkali, but it is also possible to start directly from caseinate, for example from sodium caseinate. In this case, the total water content of the mixture to be extruded is also adjusted to the range of from 13 to 18 and preferably from 15 to 17% by weight.

The following Examples are given for the purpose of illustrating the present invention: Example 1 50 Parts by weight of acid casein (protein content 86%, dry mass 90%) were sprayed with 3.3 parts by weight of potassium carbonate, referred to the acid casein, in the form of an aqueous solution. The water content of the solution was such that the total mixture had a water content of 16%, including the moisture already contained in the proteins. 64 Parts by weight of soya protein (64% protein, 91% dry mass) and 4 parts by weight of gluten (83% protein, 91% dry mass) were then thoroughly incorporated.

The mixture obtained was extruded in a single-screw extruder with two zones, the temperature of the first zone being 11 0,C. and that of the second zone being 1 80 C. The rate of revolution was 180 rpm and the extruder nozzle was of 3 mm. diameter. The extrusion took place smoothly and, after the emergence from the second zone into the surrounding atmosphere, the product expanded to give a foam-like, brittle substance with a density of 0.115 and water content of 8%.

Example 2 The process of Example 1 was repeated but 49 parts by weight of soya protein and 1 part by weight of gluten were incorporated. Extruding was difficult and the product obtained was deficient to unsatisfactory.

Example 3 The process of Example 1 was repeated with the use of 48 parts by weight of soya protein and 2 parts by weight of gluten. Extruding took place smoothly and the product obtained was acceptable. Density 0.15, water content 7.5% Example 4 40 Parts by weight of sodium caseinate were mixed with 50 parts by weight of soya protein and 10 parts by weight of gluten. The water content was adjusted to 16%. Extruding took place under the conditions of Example 1. The product obtained had the desired brittle, foamy character. Density 0.17, water content 8%.

Repetition of the process with 15 or 17% water content gave a qualitatively equal foamed, crispy snack product with a density of 0.17 or 0.18, respectively, and a water content of 7.0 or 9.0%, respectively.

Example 5 35 Parts by weight of acid casein were mixed with 60 parts by weight of soya protein and 5 parts by weight of gluten and sprayed with 3.8% potassium carbonate, referred to the casein, in aqueous solution. The water content was adjusted to 16%. Extruding took place under the conditions given in Example 1. The extrudability was good and the product had the desired brittle foam structure. Density 0.18, water content 9.5%.

Similar results were achieved with 15 and 17% water content and with a temperature in the last extruder stage of 1 600C. Density 0.18 or 2.0, respectively, water content 9.0 or 10.2, respectively.

Example 6 Under the same conditions as used in Example 1, there were extruded: 40% acid casein, 55% soya protein and 5% gluten. Alkali addition 3.3%, referred to acid casein, of potassium carbonate. Density of the extruded product 0.145, water content 8.5%.

The process was repeated but with the use of 4.5% potassium carbonate and 5.0% potassium bicarbonate, products of comparable density and water content being obtained.

Example 7 Under the same conditions as used in Example 1, there were extruded: 30% acid casein, 60% soya protein and 10% gluten. Alkali addition, referred to casein, 3.0% potassium carbonate. Water content adjustment to 13%. Density of the extruded product 0.18, water content 7.5%.

Example 8 Under the same conditions as used in Example 1, there were extruded: 30% acid casein, 60% soya protein, 5% gluten and 5% maize grit. Alkali addition, referred to casein, 3.3% potassium carbonate. Water content adjustment to 15%. Density of the extruded product 0.17, water content 8.2%.

In the following Table, the compositions described in the above Examples are given in tabular form. TABLE Ex acld casein soya protein produet wheat protein product total total total ample dry pro- pro amount dry prot- propor- amount dry pro- propor- amount dry pro- propor- mass tein tein mass ein tion of mass tein tion of mess tein tion of inel. in pro- pro- alkali dry tein tein mass 1 50 45 42.5 56.5 48 41.9 29.4 39.1 4 3.7 3.3 4.4 92.1 75.2 81.7 2 50 45 42.5 56.6 49 44.6 31.4 41.8 1 0.9 0.8 1.1 92.0 75.1 81.6 3 50 45 42.5 56.7 48 43.7 30.7 41.0 2 1.8 1.7 2.3 92.0 74.9 81.4 4 40 36 34 45.8 50 45.5 32 43.1 10 9 8.3 11.2 92.0 74.3 80.8 5 25 22.5 21.25 33.3 60 54.5 38.4 60.1 5 4.5 4.2 6.6 83.2 63.9 76.8 6 40 36 34 46.3 55 50.0 35.2 48.0 5 4.5 4.2 5.7 92.0 73.4 79.8 7 30 27 25,5 35.3 60 64.6 38.4 53.2 10 9 8.3 11.5 92.8 72.2 78.6 8 30 27 25,5 37.4 60 54.6 38.4 56.4 5 4.5 4.2 6.2 92.1 68.1 73.9 % with out inc unding added water

Claims (16)

1. A foamed, crispy snack product, produced by extrusion and based on protein with a content of casein protein, wherein it contains 51 to 95% dry weight of protein, the protein comprising 30 to 70% by weight of caseinate and optionally casein, 2 to 25% by weight of cereal protein and 10 to 70% by weight of soya protein, referred to the total protein content, has a specific weight of from 0.1 to 0.4 and a maximum water content of 12%.

2. A snack product according to claim 1, wherein it contains 70 to 85% by weight of the dry mass of protein.

3. A snack product according to claim 1 or 2, wherein it contains 30 to 60% by weight of caseinate and optionally of casein, referred to the total protein content.

4. A snack product according to any of the preceding claims, wherein, as cereal protein, it contains 2 to 15% by weight of gluten, referred to the total protein content.

5. A snack product according to any of the preceding claims, wherein it contains 35 to 65% by weight of soya protein, referred to the total protein content.

6. A snack product according to any of the preceding claims, wherein, in addition to the mentioned protein products, it contains other flavouring and/or consistency-imparting foodstuff components.

7. A snack product according to claim 1, substantially as hereinbefore described and exemplified.

8. A process for the production of a snack product according to any of claims 1 to 7, wherein casein alone, before admixing with the other proteins, or casein in admixture with soya protein and/or cereal protein, is mixed with an aqueous alkali solution containing an amount of alkali which, by reaction with casein alone, would give a pH value of from 5.3 to 8, any still missing plant proteins are then admixed and, together with the alkali solution or after separation thereof, so much water is admixed that a water content of the mixture, before or during the extrusion, of at least 13% is obtained, whereafter the so obtained mixture is extruded at a temperature above 100"C. and under pressure into a zone of lower pressure and lower temperature.

9. A process for the production of a snack product according to any of claims 1 to 7, wherein casein alone or in admixture with the cereal protein and/or the soya protein is mixed with so much water that the mixture, before or during the extrusion, has a water content of at least 13% and the so obtained mixture is extruded at a temperature above 100"C. and under pressure into a zone of lower pressure and lower temperature.

10. A process according to claim 8, wherein the amount of alkali added is one which, in the case of reaction with the casein alone, would give a pH value of 5.8 to 7.

11. A process according to any of claims 8 to 10, wherein extrusion is carried out at a temperature of over 150"C.

12. A process according to any of claims 8, 10 and 11, wherein the alkali used is a compound which splits off carbon dioxide under the temperature and pressure conditions of the extruder employed.

13. A process according to claim 12, wherein an alkali metal carbonate or bicarbonate is used.

14. A process according to claim 13, wherein the carbonate or bicarbonate is used together with an edible acid.

15. A process for the production of a snack product according to any of claims 1 to 7, substantially as hereinbefore described and exemplified.

16. A snack product, whenever produced by the process according to any of claims 8 to 15.