IE46561B1 - Textured food product - Google Patents

Abstract

To prepare a textured foodstuff or animal food, an aqueous mixture which contains nutrient components and an ionic gelling agent is prepared. A gel is produced in the mixture by reacting the gelling agent with a non-toxic divalent or polyvalent metal ion, either by means of directly treating discrete particles of the mixture in a solution which contains the abovementioned ions, or by including the abovementioned ions in the mixture. The mixture is frozen slowly so that not less than 2 hours elapse before the mixture is frozen completely. Ice crystals are formed in the mixture, resulting in a fibrous, layer-like or strip-like structure. This structure is sufficiently stable to allow the product to be processed for example by sterilising or canning, even on an industrial scale.

Description

This invention relates to a textured food product with a fibrous or striated appearance, resembling for example the appearance of fibrous meat and provides a process for the production of such food.

It is known to impart a lamellar structure to protein solutions, emulsions and dispersions by freezing the mixture followed by setting the structure by means of the proteins present. For instance, heat coagulation of the protein is described in U.S. Patent No. 3 870 808 and in Belgian Patent 838 907. However these products are often too weak to be used in large scale manufacturing processes, and furthermore are limited by the requirement of a functional protein, i.e one that on coagulation in aqueous solution or dispers15 ion yields a coherent body. A further disadvantage with these processes is the high energy requirement of the thawing and heat coagulation stages.

British Patent Specification No. 1 311 581 describes a method of producing a protein-containing food imitating lamellar-structure meat products by forming a gelatinous food preparation, diffusing ions of a polyvalent metal from a solution of a salt thereof into the gelatinous preparation through a semipermeable membrane to form an ionotropic gel, freezing the said gel and then defrosting the frozen gel to form elements of lamellar structure, impregnating said elements of 4656 - 3 lamellar structure with an edible binding agent and bond ing together the impregnated elements.

We have now discovered that a food product with meat-like fibrous, lamellar or striated texture, which is sufficiently tough to withstand factory handling, can be prepared by a process which comprises a method of making textured food product which comprises: preparing a mixture including nutritious ingredients and an ionic gelling agent; forming a gel in the mixture by causing the gelling agent to react with a non-toxic divalent or polyvalent metal ion through either direct treatment of discrete pieces of the mixture in a solution containing the said ions or inclusion of the said ions in the mixture; and freezing the mixture at a slow rate such that it is not fully frozen until at least 2 hours has elapsed, thereby forming ice crystals therein and generating a fibrous, lamellar or striated structure in the mixture.

A wide variety of ionic gelling agents and reactive metal ions can be employed. The gels produced by divalent or polyvalent metal ions when used in sufficient concentration have considerable stability and in particular can form thermally stable fibrous or lamellar structures that are resistant to sterilizing heat, for example in a canning process, even in the absence of heat coagulable substance such as protein.

The majority of ionic gelling agents are acidic polysaccharides. The acidic groups may be carboxyl groups as in the case of pectates, alginates and carboxylmethyl celluloses, or they may be sulphate groups as in the case of carragheenin.

Although the fibrous, striated or lamellar structure achieved by this process is of particular value in conferring a meat-like texture on products containing edible proteinaceous material, whether of Ο5δ1 - 4 animal or vegetable origin, so as to provide a meat substitute or analogue, the formation of the textured structure does not ultimately depend on the presence of protein in the mixture.

The product may, if required, be preserved by canning, sterilisation or freezing or by incorporation or infusion of sugars, glycerol or other humectants and fungistats such as potassium sorbate. Alternatively the product may be preserved by lowering its pH to a bacteriostatic level and including fungistats.

In the preferred process for preparing the food product of this invention proteinaceous materials and preferably also fat or oil are formed into a solid matrix by the reaction of a non-toxic salt of a metal ion and the salt of an acidic polysaccharide. A lamellar structure is induced by freezing the solid matrix at temperatures less than 273 K and controlling the freezing rate to allow the temperature to fall to below 273 K over a period of 2 hours or more to promote large ice crystal formation.

The proteinaceous materials can be of meat, vegetable or bacterial origin, typical examples being fish flesh, muscle flesh, meat offal, meat by-products, gluten (vital or devital), defatted soya flours, soya concentrates, peanut flour, soya isolate, bacterial protein, yeast protein, fungal protein, meat meals, dried blood, structural animal or vegetable protein fibres, greaves, fish meals, blood, bone and keratin.

The inclusion of fats and oils is preferred, but the fat may ba an integral part of one or more of the ingredients instead of or as well as a separate ingredient. Emulsifiers may be added to assist emulsification. if desired, although it may be advantageous to have evident lumps of fat embedded in the matrix. Inert fillers such as micro-crystalline cellulose or silica may be added to absorb free fat or oils.

The non-toxic salt employed in this invention is preferably a calcium, magnesium or aluminium salt, but more generally may be any non-toxic di- or polyvalent metal salt. The salt employed will depend upon the method used to set up the protein food. For example, a highly soluble salt such as calcium chloride can be used if the forming process is one of contact between the reactive protein mix and a metal salt solution. On the other hand a less soluble salt such as calcium sulphate is preferred if the setting up process occurs in situ after intimate mixing of all the ingredients.

The preferred acidic polysaccharides for the purposes of this invention are pectates and the prefer15 red forming process is one of an in situ reaction between the metal salt and the acidic polysaccharide. By pectate is meant a very low methoxyl pectin with a degree of esterification (DE) of less than 20% and especially crude pectin sources which contain pectin of a degree of esterification less than 20%. Providing the degree of esterification is less than 20% any pectin source may be used at a preferred concentration of 0.1% to 5.0% of pectin based on the weight of product. Citrus peel or pulp which has been treated to produce a pectin of very low methoxyl content is a good example of such crude pectin. However, sodium pectates and potassium pectate may be used. Similarly, soluble salts of alginic acid and carboxy methyl cellulose may be used.

Hydrophilic gums and mucilages may be incorpora30 ted in the formulation to reduce syneresis of the product which may occur upon thawing.

Suitable colouring agents such as blood, natural and synthetic dyestuff, e.g. caramel, may be added at any stage. Flavourings and flavour enhancers may also be added. 46001 - 6 Sequesterants may be used either to extract pectin from the crude pectin sources or to slow down the rate of the gelation process. The sequesterant may be any non-toxic salt capable of sequestering or chelating with, or making unavailable for gelation, the metal ion causing gelation. Examples are sodium or potassium salts of tripolyphosphate, citrate, pyrophosphate, orthosphosphate and EDTA.

We have also found that application of this ionic gelling and freezing process of this invention markedly enhances the fibrous character of formed structures which prior to freezing already possess some fibrous character. For instance, extremely fibrous products are obtained by this process when hashed fibrous meats are used and are set up using a pectate in situ forming process. It has also been found that added water has a beneficial effect on the structure.

A product with a high added water content exhibits a more fibrous structure after freezing than does a similar product with lower water content.

The process of this invention provides best results when the ice crystal formation takes place slowly The slower freezing process presumably produces larger ice crystals which provide a more marked structuring effect. An improved product texture is obtained also if the product is maintained at sub-freezing temperatures for a prolonged period. The inclusion of hydrophilic colloids to reduce the volume of drip loss during the thawing process surprisingly does not appear to affect the extent of structuring brought about during the freezing process.

The process of this invention induces or increases the fibrous appearance of food products which have been set up by ionic gelling agents presumably as a result of their freeze-thaw instability and the - 7 structure formed is not thermo-reversible. This instability to freeze-thaw cycling is interesting since the sodium salts of the polysaccharides are used to provide freeze-thaw stability in items such as ice creams.

Mixes which have not been formed” prior to freezing, but which contain sufficient metal ions to allow gelation with time, react during the freezing process and after thawing exhibit the fibrous appearance.

The following Examples further illustrate the invention but are given by way of example only. Percentages are quoted on a weight basis unless the context otherwise requires. Example 1 describes the present preferred product.

Example 1 % Meat offcuts (2mm mince) 40.0 Water 26.5 Caramel 0.5 Gravy 33.0 100.0 Gravy formulation Treated citrus peel (DE 10%)* 6.0 Sodium tripolyphosphate 1.2 Water ¢373 K) 92.8 100.0 * Calacturonic acid content 30% sufficient calcium. and containing The gravy was prepared by mixing the ingredi4 6 5 01 - 8 ents in a high speed mixer or homogeniser until an homogeneous viscous solution vzas produced.

The meat offcuts vzere hashed through a 2-mm plate and mixed with the other ingredients except for the gravy in a bowl mixer with a spade attachment.

The above noted proportion of gravy was rapidly mixed into the meat, water, and caramel mixture and the resulting mixture poured into trays to solidify. After 2 hours the solidified blocks, which were approximately 1¾ inches deep, were placed in a freezer controlled at 258 K for 8 weeks. The temperature of the block centre reached 273 K after 2 hours and was at 258 K after 8 weeks.

The blocks were conditioned to between 273 K and 278 K before being cubed and sterilised in a typical meat-in-jelly petfood product in metal cans. After cooling, the cans were opened and the product examined. The product of the invention was very tough with a marked fibrous appearance similar to high quality fibrous muscle meat.

The control product prepared in an identical manner but not subjected to the freezing process, after sterilisation in jellymeat pet-food product, did exhibit some fibrosity due to the meat but to a very much smaller degree. Also the meat analogue which had been subjected to the process was significantly tougher with a more meat-like mouthfeel and chew characteristics than the control. - 9 Example 2 Gravy formulation % Treated citrus peel 2.0 Tetron (sequesterant) 0.4 Water (373 K) 31.1 33.5 Product formulation 2 nun hashed meat offcuts 66.0 Caramel 0.5 Gravy 33.5 100.0 The gravy was prepared by high shear mixing together of all ingredients before adding to the meat/ carmel mixture. After mixing, the mixture was extruded intermittently into a solution of 10% calcium chloride and allowed to stand in the solution for 25 minutes, after which time the chunks were thoroughly washed with running water. The chunks resulting have a tough skin but a soft unreactai centre. After being stored for 5 hours at room temperature the chunks were solid throughout as a result of calcium penetration. The solid chunks were placed in a deep freeze set at 258 K for 24 hours, after which time they were allowed to thaw. The chunks when cut exhibited a fibrous structure which was stable to sterilisation when canned in a meat in gravy product.

The control product which was not treated to the freezing had a dense non-fibrous appearance similar to lung or kidney. After sterilisation in a meat and gravy formulation the control material remained dense - 10 with no evidence of fibrosity. The meat analogue which had been subjected to the freezing process and subsequently sterilised in a similar meat and gravy food product had in contrast the appearance of a good quality fibrous muscle meat, especially when cut open or deformed.

Example 3 % Sodium alginate 1.33 Guar gum 0.67 10 Water (293 K) 32.00 Meat offcuts (2 mm hashed) 66.00 100.0 Sodium alginate, guar gum and water were mixed in a Z-blade mixer to produce a viscous solution. The 2 mm hashed meat offcuts were mixed in to provide an homogeneous mixture which was then extruded into a weir of 10% calcium chloride solution and cut off with a rotary knife to produce spherical lumps of meat mix with a tough outer skin and soft centre. The chunks were allowed to soak in 10% calcium chloride solution for 25 minutes before being washed thoroughly. At this point the chunks had a tough skin but a very soft unreacted centre.

The chunks were placed in a deep freeze compart25 ment controlled at 258 K for 24 hours and thereafter allowed to thaw at room temperature.

The thawed chunks were solid throughout and when cut open exhibited a lamellar structure, which was stable to sterilisation in a meat-based product, giving it the appearance of good quality fibrous meat. - 11 In contract the control product which had been treated similarly but not subjected to the freezing process had a dense lung-like appearance and texture.

Example 4 Product Formulation % Meat mix 67.0 Gravy mix 33.0 Meat mix Pasteurised meat offcuts 63.0 Lactobacillus culture 3.0 Calcium sulphate 21^0 1.0 67.0 Gravy mix Treated citrus peel 6.0 Tetrasodium pyrophosphate 1.2 Sugar 9.0 Potassium sorbate 1.2 Caramel 4.5 Dye 1.5 Water 76.6 100.0 The meat mix was prepared by adding the Lactobacillus casei culture to the pasteurised meat offcuts, which had been heated at 373 K for 15 minutes, hashed through a 2 mm plate, and cooled to 313 K. The calcium sulphate was added and the three ingredients were mixed in a bowl mixer using a dough hook.

The Lactobacillus starter culture vzas prepared by growing the desired strain of microorganism for 20LH in MRS Broth at 3O3K.

The gravy mix at 323 K was added to the meat mix (313 K) whilst mixing in the bowl mixer for approximately 30 seconds and the contents were then transferred to a 2-inch deep tray. After 5 minutes, when a pH of approximately 6.4 vzas achieved, the solid meat block was cut into chunks, packaged in PVDC pouches and incubated at 303 K for 18 hours by which time the pH of the chunks had fallen to 4.3. The formed meat vzas firm, having a fibrous appearance similar to stewed steak but was bacteriologically stable.

The product was then deep frozen at 258 K for 36 hours. After thawing out, the chunks exhibited a highly lamellar structure which was superior to the unfrozen material.

Example 5 Product Formulation % Vital gluten 15.4 Caramel 0.5 Water (353 K) 9.1 Gravy 75.0 100.0 Gravy Formulation Treated citrus peel 4.5 Sodium tripolyphosphate 0.5 Water (373 K) 95.0 100.0 - 13 The gravy was prepared as in Example 1. To 75 parts of gravy the remaining ingredients of the product formulation were folded in under high shear, e.g. in a jar homogeniser, and the mix was poured into 1%-inch deep trays to form. After 2 hours, the solid blocks were placed in a deep freeze at 258 K for 24 hours. Before freezing the chunks were dense, with a lung-like appearance, but after the freezing process had been carried out the thawed chunks had a sponge-like fibrous texture which was stable to sterilisation in metal cans in a meat and gravy formulation.

Claims (12)

1. CLAIMS;

1. A method of making textured food product which comprises: preparing a mixture including nutritious ingredients and an ionic gelling agent; forming a 5 gel in the mixture by causing the gelling agent to react with a non-toxic divalent or polyvalent metal ion through either direct treatment of discrete pieces of the mixture in a solution containing the said ions or inclusion of the said ions in the mixture; and freezing 10 the mixture at a slow rate such that it is not fully frozen until at least 2 hours has elapsed, thereby forming ice crystals therein and generating a fibrous, lamellar or striated structure in the mixture.

2. A method according to claim 1 in which the 15 mixture is extruded to form as discrete pieces which are immersed in a solution of calcium chloride.

3. A method according to claim 1 in which the mixture contains calcium ions and the rate of gelation is controlled by the inclusion of a sequesterant. 20

4. A method according to claim 1, 2 or 3 in which the mixture is maintained at a temperature below its freezing point for a period after being frozen.

5. A method according to any preceding claim wherein the gelling agent is an acidic polysaccharide. 25

6. A method according to claim 5 wherein the gelling agent is a pectate.

7. A method according to any preceding claim wherein the said mixture includes proteinaceous material.

8. A method according to claim 7 wherein the - 15 mixture contains fibrous meats conferring some fibrous character thereon, and the gel formation and freezing enhances the fibrous character of such mixture.

9. A method according to any preceding claim 5 wherein the product after freezing is subjected to a sterilization or canning process, the fibrous, lamellar or striated structure being retained in the now sterilized product.

10. A method of making a textured food product 10 substantially as described in any one of Examples 1, 4 or 5 herein.

11. A method of making a textured food product substantially as described on either Example 2 or Example 3 herein.

12. 15 12. A textured food product made by a method according to any preceding claim.