CA1151938A - Functional characteristics of protein bearing materials - Google Patents

Abstract

ABSTRACT Disclosed is a process for improving the func-tional characteristics of protein materials. In a preferred embodiment, soy grits are slurried in a aqueous, alkaline media containing a water-dispers-ible high polymer such as polyvinyl pyrrolidone, and the aqueous media is then neutralized. The treated soy grits arc then mixed in combination with other protein materials and a farinaceous component and extruded to form an expanded pet food product. The treatment of the soy grits according to this inven-tion provides improved product expansion, hardness, hydration resistance and water binding, and de-creases energy consumption during extrusion/ expansion.

Description

IMPROVED E~JNCTIONAL CHARAC113RISTICS
OF PROTEIN_BEARING MAll~RIALS
~ESCRIPTION

113C~INICAL FIEID
05 The present invention provides a process for functionally improving protein materials, and pro-ducts produced according to this process.
While protein plays an essential role in human and animal ~utrition, it is not of great importance nutxitionally as to the exact source of the protein materials. What is important to proper growth and nutrition is that the protein be supplied in the diet in sufficient quantities and with an adequate balance of the essential amino acids. Thus, it is not important for nutrition that great quantities of meat be consumed where the diet contains other nutritional proteins.
Through the years, the diets of humans and domesticated pets such as dogs and cats have relied heavily upon meat as the source of protein. This is probably due to its taste and availablity. Un~or-tu~ately, it is fairly well established that our reliance upon meat as a source of protein is ecolo-gically inefficient. Animals convert vegetable protein into meat protein in an extremely ineffi-cient manner. Moreover, it has become apparent that the continued reliance upon meat in such diets will soon become economically inefficient.

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To avoid the problems associated with the use of meat as a prime protein source, there have been many at~empts in recen~ years to convert vegetable protein directly into food products which have the 05 appearance and general attractiveness of meat.
While these attempts have been successful to a good degree, they all rely upon the use of highly func-tional protein. That is, in order to provide meat simulating products from vegetable protein mater-ials, the vegetable protein must either have theability to be processed to form highly cohesive and resilient products, or it must be employed in com-bination with a binder material which will supply these important fu~ctional characteristics. And, even where a protein is highly functional, the use of it with other necessary dietary components such as non-proteinaceous filler materials such as star-ches, flours, and bulk dietary fibers, may substan-tially decrease the overall meat-like character-istics of product prepared from it.
Among the properties important when a meatsubstitute for human consumption is desired, are the properties of resilience, bite resistance, fibrosity and cohesiveness. On the other hand, when the dry, crunchy characteristics familiar to dry pet foods are desired, it is important to have a product of a relatively high degree of expansion, good hardness, and the capability of being rehydrated without becoming mushy.
The need for functional protein presents another supply problem. Those vegetable protein raw materials, concentrates and isolates which are highly func-tional, are in great demand and relatively high in cost, while relatively non-functional, but nutri-tionally good proteins are now being inefficiently utilized.

~ ~19 38 The probl~ms associated with protein func-tionali~y have a staggering impact on the world's ability to provide adequate nutrition to all of its inhabitants in forms which are attractive and palat-05 able. There is clearly a present need in the art toimprove the functionality of a wide variety of protein materials.
BACXG~OUND OF T~E INV~TION
Accordingly, it is an object of the present invention to provide a process capable of improving the functional characteristics of protein materials.
It is a function of the present invention to provide a process capable of improving the cohesive-ness of products prepared from proteinaceous materials.
It is a function of the present invention to provide a process for improving the hydration resis-tance of dry protein based pet foods.
It is still another function of the present invention to provide a process for treating a pro-teinaceous material which will improve the expansion of products prepared therefrom.
It is a yet further function of the present invention to provide a process for improving the hardness of dry protein based products.
It is another function of the present invention to provide a process for treating proteinaceous material which will affect the density of products thereby allowing another degree of process control.
It is a further aspect of the present invention to provide a process for increasing the water bindingcapability of protein materials.

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It is ano~her aspect of the present invention to provide a process for treating a protein material which will improve the efficiency with which that material can be ultimately processed such as by 05 extrusion.
These and other objects are accomplished accord-ing to ~he present invention which provides a method for functionally improving a protein material com-prising contacting the protein with an agueous, alkaline media containing a water-dispersible high polymer material and then reducing the p~ of the combined mixture of protein and aqueous media to a level effectiYe to entrap a portion of the high polymer material within the protein.
The present invention is concerned with improv-ing the ~unctionality of protein materials. It is especially useful for low quality proteins which are to be employed in extrusion procedures for forming food products. These extrusion procedures are carried out at elevated temperatures and pressures.
The temperature will be at least high enough to coagulate the protein and typically will be in excess of about 100C. Pressure drops from the extruder that are low enough to simply ena~le expul-sion of the product can be employed but typically vary from a few atmospheres up to as high as about 50 atmospheres. Generally, those products extruded at pressures above 7 atmospheres have a highly expanded texture. Processes involving extrusion without expansion are shown in U.S. Patent 3,814,823 to Yang and U.S. Patent 3,866,299 to Feldbrugge et al. Typical of the processes which extrude under relatively high pressures to form an expanded product are U.S. Patent 3,488,770 to Atkinson, and U.S.
Patent 3,940,495 to R.J. Flier. Also representative ~ 3 8 of processes which can be improved by employing protein materials processed in accordance with ~h~
present invention are those for preparing e~panded dry pet foods such as described in u.s. Patent 05 3,119,691 to Ludington et al, U.s. Patent 3,447,929 to ~ale, and U.S. Patent 3,139,342 to Linskey.
For the purpose of simplifying the following disclosure, but with no intention of being limited to compositions of a particular type, the following detailed description will be directed to the prepa-ration of a dry expanded pet food of the type de-scribed in the above-referenced Ludington et al patent. The disclosures of all of the above-referenced patents are incorporated by reference herein to show the detail of other suitable product forms and processing schemes, it being understood that in each case the protein or a portion of it as is called for by those references can be protein-aceous materials treated according to the present invention.
SUMMARY OF T~E INVENTION
According to a preferred embodiment, a dry, particulate, porous, expanded pet food product is prepared from a mixture comprising farinaceous and proteinaceous materials wherein at least a portion of the proteinaceous materials are treated in accor-dance with the present invention. The proteinaceous ingredients used in the mixture may be of vegetable or animal origin, and typically include soy bean meal, soy grits, meat meal or fish scrap. Typ-ically, the proteinaceous ingredients comprise from about 20% to 50% by weight of the total mixture.
The farinaceous ingredients employed according to this embodiment may be wheat, corn, barley, oats, ~lg38 their derivatives such as corn meal, hominy, andother like ingredients. Typically, the total amount of farinaceous ingredients based on the weight of farinaceous/proteinaceous mixture is between 35% to 05 70% by weight.
The balance of the mixture may comprise salts, 1avorings, colorings, vitami~ supplements and other like ingredients to form a nutritionally balanced animal food product.
In preparing an animal food according to the teachings of the present invention, at least a portion of the proteinaceous materials are processed to improve their functional properties. To accom-plish this, the protein material is contacted with an aqueous, alkaline media containing a water-dis-persible high polymer material, following this, the pH of the total mixture is reduced to a level effec-tive to entrap a portion of the hi~h polymer within the protein.
Typically, the protein material such as soy grits or soy bean oil meal are added to a mixing vessel along with sufficient water to form a mixable slurry. Preferably, the protein material will be present in an amount of from about 10 to about 50%
by weight of the slurry. The water-dispersible high polymer material is mixed with the slurry to cause complete dispersion. While in most cases it is preferable to add and disperse the high polymer material prior to raising the slurry pH to within the alkaline range, it may sometimes be desirable to reverse the order of addition and add sufficient amounts of a base to raise the pH prior to addition of the high polymer material. It is also desirable in some situations to add both the base and the high polymer material at the same time.

~ 938 Once slurried, the ingredients are maintained under sufficie~t agitation for a period of time sufficient to allow the high polymer material to come into close association with the alkaline treated 05 protein wherein the helic~l protein molecule has become unfolded and opened sufficiently to allow partial ingress ~f the high polymer internally in the helical mole~ule. After a sufficient period of holding in contact in this manner, the pH of the solution is reduced to a level effective to entrap a portion of the high polymer material within the protein helix. Typically, the p~ is reduced to on the order of from about pH 5 to less than pH 8.
Among the bases suitable for increasing the pH
of the solution according to the present invention are potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonium hydroxide, sodium hydroxide, calcium hydroxide and the like. Sodium hydroxide and calcium hydroxide are most desirably employed.
The base should be employed in sufficient amounts to raise the p~ of the slurry to well within the alkaline range, of pH 8 to 12 and preferably in the range of from about p~ 9 to p~ 10. The entire alkaline range of from about p~ 8 to approaching p~ 14 is however useful to varying degrees and therefore can be employed according to the present invention. To date, the best results have been achieved at p~
values of around 9, and this level is therefore considered preferred. It is posæible and indeed likely, however, that proteinaceous materials in com~ination with high polymer materials other than those specifically employed in the tests referred to, will show optimum results at levels different from this.

The high polym~r material can be any polymer which has the ability to be dispersed in water at the pH conditions employed, and which also has the ability to become entrapped within the alkaline 05 treated protein material upon reduction of the slurry pH to effect change in the functional prop-erties of the protein. Generically, the preferred high polymer materials can be described as long, straight chained combination of a single monomer that is capable of binding to protein sites.
Typical of polymers of this type are polyvinyl-pyrrolidone, carboxymethylcelluloses (CMC), hydroxy propylcellulose (KlucelTM), methyl cellulose and polysaccharides (preferably those that have a charged monomer unit; (e.g. pectic acid, pectin etc.) and combination of these. Molecular weights of the order of from about 10,000 to about 450,000 have been found useful, and in the case of polyvinyl pyrrolidone, molecular weight of around 360,000 has been found to provide the best results obtained to date. Any amount of polymer to effect a change in protein functionality can be employed. Levels of about 0.2% to 4% by weight of slurry appear to provide good results, but amounts outside this range can be employed under conditions where they will be effective. For polyvinylpyrrolidone, it is preferrable ~hat levels of about 0.5% to 2% by weight of slurry appear to provide good results when using molecular weight of 360,000. It is not likely that the definition of one numerical range can be universally applied to all the possible polymers which are intended to be employed across the broad spectrum of protein substrates potentially applicable to the present invention.
Accordingly, the above ranges are given only to guide the person of ordinary skill in the art to those exemplary situations which we have at this time folmd to be especially desirable.
After allowing sufficient time for the base and the high polymer to adequately modify the protein 05 material and allow entry of the high polymer within the protein helix, the pH of the slurry is reduced to entrap the polymer within the protein. This can be accomplished by adding a suitable acid in an amount sufficient to reduce the pH or by mixing the treated protein with the other ingredients of the product to ~e made where they can reduce pH due to their acidity, buffering or dilution effect. Normally, reduction of the pH to below about pH 8 is effective, but desirably it is reduced to below about pH 7.
The most preferred acidic materials for pH
reduction are those which either alone or as the salt of the acid with the base employed for raising the pH of the slurry, form an important nutritional contribution to the final product wherein they are employed. It is of course possible to employ acid and base combinations which provide no nutrition, taste or other advantageous end result or even to employ acid/base combinations which would be dele-terious to some respect; however, most desirably they will form an important nutritional contribution to the food product. Thus, where sodium hydroxide is employed as the base, hydrochloric acid can be employed as the acid portion, and these two mate:rials together will supply the total requirement for sodium chloride necessary in a full feeding dog food. Other suitable acid/base combinations would be phosphoric acid in combination with calcium hydroxide or a combination of calcium, sodium, and/or potassium hydroxides along with a combination of hydrochloric, phosphoric or other suitable edible ~ 38 acid. Typical of ~hese o~her acid ma~erials are citric, acetic, and malic acids.
The treated protein material is employed in preparing the final pet food or other ~ood product 05 in conventional manner. In the specific instance of the dry pet food, the proteinaceous materials, farinaceous materials, and other added components are mixed together and then mechanically worked under elevated temperatures and pressures, generally in an extruder apparatus, to form an expanded porous product. Typically, the temperatures in the ex-truding zone are above 100C. Steam and/or water is generally injected to control the moisture and temp-erature. The residence time of the mixture in the extruder is relatively short and generally on the order of 15 seconds to 120 seconds. The mixture exits an extruder into the atmosphere throu~h an extruder die orifice. As the material issues from the die it expands into a porous expanded product due to the pressure drop across the die and the flashing off of the water as steam. The extrudate, typically in rope form, having a moisture content of about 20% to 35% by weight, is then cut into desired kib size and dried to a stable moisture content, generally about 10% and lower. A more complete discussion of the processing for the formation of dry dog foods or pet foods of this type can be found in U.S. Patents 3,119,691, 3,139,342 and 3,447,929, The following examples are presented for the purpose of further illustrating and explaining the present invention and are not to be taken as limit-ing in any regard. Unless otherwise indicated, all parts and percentages are by weight.

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3~3 EXA~PL~ I

This ex~mple shows that, in certain cases, ~he palatability o a pet food can be improved by the process of this invention. A dry pet food is pre-05 pared from the following materials:
Parts Soy bean oil meal (44% protein) 42 Whole ground corn 83 Wheat midlings 45.5 Meat meal 22 Wheat Red dog 3.78 Sodium chloride 2.6 Vitamin premix 0.05 Color 0-05 Zinc oxide 0.16 Polyvinylpyrrolidone (molecular weight 360,000) 0.55 About 81.5 parts of water were added to an approxi-mately 190 liter (approximately 50 gallon) kettle with a scraped surface agitator. To this, the polyvinylpyrrolidone was added and mixed sufficiently to cause complete dispersion. The soy bean oil meal was then added to the water and mixed sufficiently to cause its dispersion. Once dispersion of the total slurry was obtained, 4 N sodium hydroxide was added until a ~ of 12.0 was attained while mixi~g was continued. After about 30 minutes of mixing, the remainder of the formula was added to a ribbon blender and blending begun. The slurry was then added thereto and mixed for about 10 minutes. The p~ of the combined mixture was 7.8. The material from the ribbon blender was collected and extruded through an Anderson expander at a temperature of approximately 107C (approximately 225F). No water was added during the extrusion cooking step. Upon exiting the expander, the ma~erial was cut into kibbled form and run throu~h a belt dryer held a1 a 05 temperature of appro~imately 121C (approximatelv 250F) for 20 minutes. A single pass through the dryer reduced the moisture content to about 4 to 7%.
The resulting dried kibbled product was then coa1:ed with bleachable fancy tallow to an amount of 3.5%
based on the weight of the total product.
This product (3) was fed to a sixty dog panel to compare it to a commercial product (2) having the same formulation and processed in essentially the same manner but eliminating the pretreatment of the protein as done according to the present invention.
Another control product (l) was also employed thi.s time pretreating the protein material with base clS
described above but without employing the polyvi~yl-pyrrolidone. The samples were all mixed with an equal weight of water for feeding, and the result~
are as follows:

(2) was no different to (l)

(3) was significantly preferred to (l) (3) was significantly preferred to (2) EXAMPLE II

To illustrate how the process of the present:
invention can be employed to increase the water binding capability of a proteinaceous material, l~0 grams of soy grits was added to 300 ml of water, and mixed to form a slurry. Sodium hydroxide was added to raise the slurry pH to 12. At this point, 3 grams of polyvinylpyrrolidone (M.W. 360,000) was added and the slurry was stirred for an additional 30 minutes at 25C. Following this, sufficient hydrochloric acid was added to reduce the slurry p~

~ ~193 8 to 6Ø The solids were filtered from the slurry, washed and dried. The water activity (aw~ of 20%
moisture-containing material was 0.82, as compared to an untreated portion of soy ~rits having the same 05 moisture which had an aw of 0~93~

EXAMPLE III

To illustrate the improved expansion which can be obtained from an extruded product employing a proteinaceous material treated by the process of this invention, a pet food was prepared from the ingredients listed in Example I according to the following procedure.
About 81.5 parts of water, 3.8 parts of 3N NaOH
and 42 parts 44% soybean oil meal were added to a round bottom kettle with a scraped surface agitator.
The soybean oil meal had been ground so that it passed through a 20 mesh screen. The mixture was agitated until uniform and the pH was measured.
Sufficient additional NaOH was added to bring the pH
to 11.5 to 12.0 and about .S5 parts of polyvinyl-pyrrolidone (M.W. 360,000) was added. Agitation was continued for an additional 30 minutes at which time the slurried mixture was added to a dry ingredient ribbon blender which contained the other dry ingre-dients. These other dry ingredients had also been pre-ground so that they passed through a 20 mesh screen. The mixture was blended for about 10 minutes after which the pH was about neutral (pH 6.0 to 7.0). The blended mixture was then fed to an Ander-son extruder-cooker having 1/4 inch (approximately 6.4 mm) die holes and 140 psig (approximately 9.8 Kg/cm2 gage pressure) steam on the jacket. 80 psig (approximately 5.6 Kg/cm2 gage pressure) steam was ~ ~5~38 injected into the last e~truder section about 6-8 inches the orifice. The product at the die face had a temperature of approximately 121C (approximately 225F). A~ter dryin~, the product had a density of 05 about 269 Kg/m3 (abou~ 16.8 lb/ft3) as compared to the same formulation processed in the same manner, but without pre-treatment of the soybean oil meal, which had a density of about 352-368 Kg/m3 (about 22-23 lb/ft3).
E~AMPLE IV
To illustrate the effect of process pH on the characteristlcs of a product employing a protein-aceous material processed in accordance with this invention, a series of pet food products were pre-pared according to the formulation and the process set forth in Example I, varying the slurry pH as set forth in Table I below. The products were evaluated for effect on exp~nsion (i.e. density), rehydration rate (i.e % water uptake after 10 minutes), and hardness (after rehydration). ~ardness after re-hydration is increased beyond control sample which is a desireable characteristic of dry pet food.
Hardness is shown in both metric units as well as English units. Rehydration was effected by placing the sample with an equal amount of water in a dish at room temperature. ~ardness was measured by an Instron pressure tester.
TABIE I
. .
3 Hardness Product Rehydration After After Densi~y Rate Rehydra- Rehydra- 3 Slurry pH__ (g/c ) (%/10 min.) tion (Kg/m3) tion (lb/in ) 11.5 .40 40.0 7,753 .28 35 9.0 .39 34.2 12,734 .46 8.0 .36 31.5 6,g20 .25 Control-tpH 10 no NaOH
no pvp) .37 44.5 4,710 .17 _ ~ 38 EXAMPLE V

To illustrate the effect of process temperature on the characteristics of a product employing a proteinaceous material processed in accordance with 05 this invention, a series of pet food products were prepared according to the formulation and process set forth in Example I, varying the temperature at which the soybean oil meal is slurried at elevated pH with the polyvinylpyrrolidone. This effect is tested at slurry pH values of 8, 9 and 11.5. The results are illustrated in Table II.
TABLE II

_ Hardness 15 Slurry Product Rehydration After After temp. Slurry ~ensi~y Rate Rehydra- Rehydra-C PH tg/c ) (%/10 min.) tio~ (Kg/m3) tio~ ( 8.0 .39 38.6 3,875 .14 9.0 .38 37.0 ~,304 .30 11.5 .40 40.8 6,643 .24 71 8.0 .36 31.5 6,920 .25 9.0 .38 34.2 12,732 .46 11.5 .40 4~.0 7,750 .28 EXAMPLE VI

Based on Examples IV and V, it appears that a pH of 9, at a temperature of 71C provides an espec-ially favorable increase in functional character-istics of the soybean oil meal treated wth poly-vinylpyrrolidone. To illustrate the effectiveness of the process of the present invention on a variety of proteinaceous materials, the tests summarized in Table III were carried out employing the formulation and procedure set for~h in Example I, but employing 05 the listed proteins at a pH of 11.5 and a tempera-ture of 25C. In each case, a control ca~e carried out wherein no pre-treatment of the protein was effected. As c~n be seen from the following data, hydration resistance is improved over the control.
This results in a dry pet food which provides more resistance to pet mastication despite rehydration of product. It is also noted that hardness values are significantly increased over the respective control protein employed.

TABLE III
_ Hardness Product Rehydration After After Densi~y Rate Rehydra- 3 Rehydra- 3 20 Protein _ tg/CJ) (%/10 min.) tion (lb/in ) tion (Kg/m ) Meat Meal .33 38 .25 6,920 Control Meat Meal .33 49. 7 .10 2,768 . . .
Corn Gluten Meal .32 30.3 1.23 34, 045 Control Corn Gluten Meal .33 49.7 .10 2,768 _ Feather Meal .36 50.5 . 60 16,607 Control Feather Meal .33 49.7 .10 2,768 . . _ . . _ EXAMPLE VII

To illustrate the effectiveness of the process of the present invention employing a variety of different polymers, the tests summarized in Table IV
05 were carried out employing the formulation and procedure set forth in Example I, but employing the listed polymers at a pH of 11.5 and a temperature of 25C. From this table, the effect of product density can be observed.

1~ TABLE IV
.
Hard~ess Product Rehydration After After Polymer _ De~si~y Rate Rehydra-3 Rehydra- 3 TyE~_Mol. Wt. (g/c ) (%/10 min.) tion (Xg/m ) tion (lb/in ) pvp360,000 .37 38.9 13,286 .48 lO,000 .36 40.9 4,705 .17 300 .37 47.5 4,429 .I6 Klucel360,000 .34 44.6 5,536 .20 .
CMC360,000 .36 38.3 4,705 .17 gM31~
Control .34 37.6 7,750 .28 EXAMPLE VIII
To illustrate the effect of reaction time on the process of the invention a number of pet food samples were prepared from the formulation and according to the procedure of Example I varying the time the protein slurry, having the polyvinylpyr-rolidone added thereto, is maintained at various elevated pH values and temperatures. The results are summarized in Table Y below.

TABLE V

Hardness Reaction Slu~ry Product Rehydratios After Re- After Re-05 Time Temp. Slurry Dens~ty Rate hydrat~on hydrat~o~
(min.) (C) PH (g/c ) (%/10 min.) (lb/in ) (Kg/m ) 8.0 .39 _ 33.5 .4~ 11,072 9.0 .39 28.0 - -_ ll.S _ .40 37.5 .76 21~03~
71 8.0 .34 34.3 .24 6,643 9.0 .39 32.8 .28 7,750 11.5 .37 40.4 .21 ~ 5,~13 _ _ _. _ . _ _ 25_ 8.0 _ .3g 38.6 .14 3,875 ~ 9.0 .38 37.0 .30 _8 304 11.5 .40-- ---40.8 .24 6 643 71 8.0 .3634.5 .25 6,920 9.0 .38-- 34.Z .46 12 732 11.~ .4040.0 .28 7 750 _ _ . _ Control .37 37.5 .17 4 705 EXAMPLE IX
To illustrate the effect of different bases employed for p~ adjustment, pet food samples are prepared from the formulation and according to the procedure of Example I, changing only the type of base employed. The results are summarized in Table VI below.
It has been found that when the reduction of the pH of the solution is to be effected by mixing the treated protein with other ingredients of the product, the use of calcium hydroxide as the base used to increase the p~ of the solution significant-ly increases the hardness of the product of the invention as compared to using sodium hydro~ide.
However, it has also been found that if the reduc-tion of the pH of the solution is to be effected by ~13LS1938 the adding of a suitable acid, the use of sodium hydroxide as the base used to increase the pH of the solution, significantly increases the hardness of the product of this invention as compared to using 05 calcium hydroxide.

TABLE VI
Hardness Product Rehydration After After NaCl Slurry Den~ity Rate Rehydra- 3 Rehydra- 3 Base % p~ (g/c ) (%/10 min.) tion ~lb/în ) tion ~Kg/m ) NaOH 2.0 11.5 .34 43.5 .31 8,581 Ca ~OH)2 .29 28.0_ .40 _11,072 The above description is for the purpose of teaching those skilled in the art how to practice the present invention and is not intended to detail all those modifications and variations of the present invention which would become apparent to the person of ordinary skill in the art upon reading the dis-closure. It is intended, however, that all such obvious modifications and variations be included within the scope of the present invention which is defined by the following claims.

Claims (10)

1. A method for functionally improving a protein material comprising forming a mixable protein slurry, mixing a water dispersible high polymer material to cause complete dispersion in said slurry, raising the pH of the slurry to within the alkaline range to a level effective to allow ingress of the high polymer material internally in the protein helix, and reducing the pH of the slurry from about pH 5 to less than pH 8 to entrap a portion of the high polymer material within the protein helix.

2. The method of Claim 1 wherein the protein material will comprise from about 10% to 50% by weight of the slurry.

3. The method of Claim 1 wherein the raising of the pH of the slurry is in the range from pH 8 to pH 12.

4. The method of Claim 3 wherein the raising of the pH of the slurry is in the range from pH 9 to pH 10.

5. The method of Claim 1 wherein the high polymer material is selected from the group consist-ing of polyvinylpyrrolidone, carboxymethylcelluloses (CMC), hydroxy propylcellulose (KlucelTM), methyl cellulose and polysaccharides and combination thereof.

6. The method of Claim 5 wherein the poly-saccharides have a charged monomer unit.

7. A method for functionally improving a protein material comprising forming a mixable protein slurry, mixing polyvinylpyrrolidone having a molecular weight from 10,000 to 450,000 to cause complete dispersion in said slurry, raising the pH of the slurry to within the alkaline range to a level effective to allow ingress of the polyvinylpyrrolidone internally in the protein helix, and reducing the pH
of the slurry to a level effective to entrap a portion of polyvinylpyrrolidone within the protein helix.

8. The method of Claim 7 wherein the level of polyvinylprrolidine used to effect a change in protein functionallty is in the range from 0.2% to 4% by weight of the slurry.

9. The method of Claim 1 which further comprises using the treated protein slurry to form a dry, particulate, porous, expanded, pet food product.

10. The pet food product of Claim 9 wherein the proteinaceous ingredients comprise from about 20% to 50% by weight of the total mixture and the total amount farinaceous ingredients based upon the weight of the farinaceous/proteinaceous mixture is between 35% to 70% by weight.