CA1091079A - Process for improving the functonal properties of protein material - Google Patents

Abstract

A,PROCESS FOR IMPROVING TIIE FUNCTIONAL
PROPERTIES OF PROTEIN MATERIAL
ABSTRACT OF THE DISCLOSURE
Protein-containing materials are treated at specified temperature and pH conditions for a suitable length of time to yield products which replace material such as egg solid and nonfat dry milk.

Description

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jl This inventioll relates generally to tlle lmprovement of the ~unctional 1~ properties of proteinaceous materials 8uch as single-cell proteins, plant proteins, whey solids, and mixtures thereof. More precisely, this o invention involve's subjecting the protein-containing materlal to a con-trolled pH, temperature, and time treatment which results in the improvement of the functional properties. For purposes of this ! invention, yeasts are considered as being separate from the plant , proteins and are included within the single-cell protein category.
' In recent years much attention has been directed toward the develop-1l ment of protein materials which can be incorporated in foods or food !i addltives suitable for human consumption. Looking at plant proteins ~' available today, it has been observed that these materials contribute to the off flavor, after flavor, undesirable color, unbalanced nutrients, zo ,i !l or unacceptability in various food products. Similarly, untreated single-!i cell protein materials have been observed to have adverse effects on i, .
dough property and the bread quality. As would be expected, mixtures of single-cell and plant protein material have undesirable functional characteristics from each of the separate protein source materials.
2s The use of single-cell materials as a source for protein and the problems associated therewith can be better understood by looking more closely at a member selected from this class of materials, such as yeast cells. Yeast cells have the characteristic flavor and aroma which are affected to some extent by the growth conditions and the after-harvest lO~

, processing conditions. They have a complicated organoleptic profile which consists of both pleasing and unpleasant flavors. One of the reasons limiting the use of yeast materials in food systems is the i deleterious effect of its "yeasty" flavor. Where it is desirable to use i!yeast material at high levels for protein enrichment, a product of bland taste is preferred. Although the majority of yeasty flavor components l can be easily removed from the yeast cells by a hot water extraction l~ method, the use of such a process results in the 1088 of 15 to 20~ in !! product yield. Furthermore, the extracted cells will retain some ,Ibitter, beany, and metallic off-taste. The 1088 in yield may be com-pensated by the value of the meat-flavored extract as a by-product, but Il the poor flavor of the cell product would need definite improvement. In !l addition, the hot water-extracted yeast cells contain about 0.6 to 1.0%
¦phosphorus and 0.01 to 0.02% calcium. In order to achieve a nutritional ¦balance of the calcium-phosphorus ratio for a food system in which such yeast is u6ed, additional calcium may be necessary.
Particular attention has been directed to the use of single-cell protein materials, such as yeast, as a replacer for egg solids and ~¦ nonfat dry milk (NFDM). For example, in the bakery industry, 2 to 3X
!i Il nonfat dry milk i8 normally used as an additive to improve the physical li and nutritional quality of bread. However, in view of the increasing i' coYt and decreasing availability of milk, many bakers are looking for a " substitute. Although certain products derived from soy protein have i! gained some acceptance, the active search by food technologists for a ~I suitable substitute for mllk in food products continues.
In this regard we have observed that during the fermentation and i baking of bread dough, the wheat protein (gluten) formæ the -Qtructure to hold the small bubbles of gas which are generated. This functional property permits the bread to rise and results in the production of bread ~

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having good volume and fine crumb structure. However, when untreated single-cell materials, such as dried inactive yeast, are added to bread Idough to replace 2% nonfat dry milk, undesirable changes are observed ¦lin the property of the dough which adversely affect the bread quality.
! Typically, dough which contains untreated yeast is soft, stringy, ¦'sticky and moist to the extent of rendering it difficult to handle. In ~fact, the dough has poor machinability characteristics which are detectable from the mixing to the final proofing stage. The inferior property of the dough is probably due to the poor water absorption and 0 !~the strong reducing property of the thiol group in the yeast cell which '~damages the gluten structure. We have now found that materials such jas yeast, plant, whey solids and combinations thereof can be treated ¦according to the process of this invention to yield products highly ¦suitable for replacing egg solids and nonfat dry milk. During the ,Itreatment of the yeast cells in accordance with the present process, ¦several things happen which improve the functional property of the cell.
¦The yeasty off-flavor is greatly reduced and cell material becomes ¦significantly bland in taste by heat:ing the yeast cells under controlled ~pH reaction conditions. A large amount of buffering materials are 1 released from the cell by the heating process, which increase the ~,buffering capacity of the food system when they are incorporated as dry -yeast cell material. The saponification of lipid material gives rise ~ to a soap material which is a good emulsifier. Also, heating under ¦ alkaline pH conditions will enhance the auto-oxidation of the thiol ll groups and the water holding capacity.
! SUMMARY OF THE INVENTION
; According to this invention, there is provided a process for treating ,~ protein materials such as single-cell protein material, plant protein !! material, whey solids, or mixtures thereof in a manner whereby the color, f1~vor, nutritional vs1ue, and functions1 properties of 3aid

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materials are improved for food use. Where a mixture is being used, the amount of the single-cell protein component can vary from about 1 to about 99 percent. Moreover, the aqueous slurry can be treated with a baslc compound, preferably a calcium compound, and fortified with an amino acid such as methionine or cystine. An aqueous slurry of the protein material is prepared and heated to a temperature of from about 75 to about lOO~C. and the pH of the heated protein material is ad~usted within the range of about 6.6 to about 8.0, preferably about 7.2 to about 7.6, by adding a pH ad~usting compound. The pH adjusting compound can be selected from among the group consisting of anhydrous ammonia, ammonium hydroxide, calcium hydroxide, sodium hydroxide, sodium bicarbonate, calcium sulfate, potassium carbonate, calcium carbonate, sodium carbonate, potassium hydroxide, magnesium hydroxide, and mixtures thereof, especially mixtures of calcium hydroxide and calcium carbonate or calcium sulfate. Additionally, the pH adjustment can be accompanied by the agitation and oxidation of the single-cell protein. The pH
ad~usted solution is maintained at temperature for a period of about l to about 120 mlnutes and then dried. Alternatively, the pH
adjusted slurry is separated into (1) a protein extract and (2) a base-treated protein material, particularly with a basic calcium compound, wherein the base-treated protein material is removed, water washed and dried with or without the addition of amino acids. The protein extract can be heated to an increased concentration and dried for use as a seasoning ingredient.
By the practice of this invention one can prepare a proteinaceous material having improved functional properties.
Thus the present invention provides a process for improving the functional properties of protein-containing materials comprising the steps of:
(a~ preparing an aqueous slurry of a protein-containing material selected from the group consisting of (1) single-cell protein, (2) plant protein, (3) whey material, and (4) mixtures of single-cell protein with 10910`~

plant protein, whey solids, or both plant protein and whey solids, said mixtures containing from about l to about 99 weight percent of the single-cell protein component;
(b) heating the aqueous slurry to a temperature of from about 75 to about 100C.;
(c) adjusting the pH of the heated slurry to within the range of about 6.6 to about 8.0 by adding a compound selected from the group consisting of anhydrous ammonia, ammonium hydroxide, calcium hydroxide, sodium hydroxide, sodium bicarbonate, calcium sulfate, potassium carbonate, calcium carbonate, sodium carbonate, potassium hydroxide, magnesium hydroxide and mixtures thereof;
(d) maintaining the heated, pH-adjusted slurry at said conditions ~-for a time period of from about l to about 120 minutes; and (e) drying the material from step (d).
; DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process of this invention provides a method for improving the functional properties of single-cell protein, plant protein, whey solids, or mixtures thereof.

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It is believed that any microbial cell material, plant protein, whey solution, or mixtures thereof can be treated according to the ~process of this invention, although this invention is particularly ! ~, suited for processing yeasts such as Candida utilis. In a fully integrated, continuous system, microbial cells are conveniently grown in a first fermenting stage where oxygen and a suitable substrate, such as liquid or gaseou~ hydrocarbons or oxygenated hydrocarbons such as carbohydrates or alcohols, together with a nutrient solution containing minerals are fed to a stirred reactor containing the microorganisms. In 0 a continuous fermentation at steady state, a portion of the reacting , mixture is withdrawn at a constant concentration of microorganisms. The concentration of the cells is typically increased by mechanical or evaporative means. As the microorganism concentration increases, a portion of the reacting mixture i9 withdrawn from the stirred reactor jj and the microorganisms are separated from the withdrawn reaction mixture.
By way of illustration, bacteria such as those listed in TABLE I, yeasts such as those listed in TABLE II, and fungi such as those listed in TABLE III are suitable single-cell protein materials for use as starting materials in the practice of this invention.
TABLE I - Suitable Bacteria Acetobacter sp.
Arthrobacter sp.
Bacillus subtili6 ! CorYnebacterium Sp.

I Micrococcus sp.

Pseudomonas sp.

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TABLE II - Suitable Yeasts Candida curvata . Candida lipolytica ; Candida Pulcherima 5 1l Candida utilis . Hansenula anomala li ; ,I Pichia farinosa . Oidium lactis Saccharomyces carlsbergensls 0 ~ Saccharomyces cerevisiae Saccharomyces fraRilis ' Trichosporon cutaneum ~j TABLE III - Suitable Fun~i 15 j, A~pergillus niger Il Asper~illus ~ilaucus ,j Aspergillus oryzae A~pergillus terreus I Aspergillus itaconicus 20 1 Penicillium notatum :, -~
~, Penicillium chrysogenum !I Penicillium glaucum !, Penicillium griseofulyum Candida utilis, Saccharomyces cerevisiae, Saccharomyces fragilis, 25 1l or Saccharomyces carlsbergensis are suggested ~lngle-cell starting : ¦¦ component materials for the process of this invention, because each is . approved by the U.S. Food and Drug Administration as suitable for use in food products.
The plant protein material is advantageously selected from oil seed protein materials such as soy flour, defatted soy flour, soy flakes, , .
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80y protein isolates and concentrates, cotton seed flour, cotton 6eed protein isolates and concentrates, peanut flour, peanut protein isolates and concentrates, sesame seed flour, sesame seed protein isolates and concentrates, corn grits, corn protein isolates and concentrates, gluten, cereal protein isolates and concentrates, rapeseed flour and rapeseed protein isolates and concentrates.
The whey material can be whey solids in the form of an a~ueous solution, condensed suspension of crystals, or a dried powder. The whey may be derived from the processing of Cheddar, Brick, Edam, Parmesan, Gouda, Emmenthaler (Swi9s), or other cheeses-The following schematic diagrams (FIGURES 1 to 3), TABLES IV to VIII, and EXAMPLES I to XI are illustrative, without implied limitation, of this invention. In the drawings that accompany this specification, Figure 1 shows comparative processes for preparing a yeast plant or yeast-plant product, Figure 2 is a process flow sheet and Figure 3 shows production of modified plant protein.

EXAMPLE I
The following three testing samples were prepared from a 10% solids yeast cell slurry under the condition as described in the diagram shown in Figure 1.
(a) untreated spray-dried cells (b) heated at 95C. and pH 5.9 for 30 minutes (c) heated 95C. and pH 7.5 (0.88g. NaOH/100 g dry cell) for 30 minutes.
The samples were submitted for bread-baking test. The re6ults are su~marized in TABLE IV. The best result, as it i~ comparable to that of NFDM, is from the sample prepared by heating at pH 7.5. The most significant improvement is in its tough property. The baking test results indicate the importance of the pH effect during the heat treat-ment.

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TABLE IV
Performance in Dough Handling A~ Additive 2%) Characteristics ¦I NFDM Good in mixer, rounding, and moulder.
5 , Normal into oven.

, Untreated Cells Not tolerant to mixer. Sti_k-, and stringy off mixer. Recovered for rounding. Flst into oven.

Cells treated* The same as that of untreated cells.
at pH 5.9 Cells treated* Equal to that of NFDM.
at pH 7.5 ;l *Heating at 95C. for 30 minutes under open air with constant agitation.
As previously mentioned, untreated yeast cells have a high content of thiol groups. Soluble compounds such as glutathione and cystine, as ; well as the thiol group in the water soluble protein are active materials l~ which will weaken the gluten structure by the sulfhydryl-disulfide interchange reaction during the dough mixing and proofing. The thiol group is readily oxidized, especially under heating at increased pH
with trace amounts of metal ions, Experimental results in TABLE V
illustrates the effect of heating at increased pH in order to achieve ~ the auto-oxidation of thiol in Candida utilis cells. Two things are indicated: (l) the thiol may be oxidized to various compounds beyond the less oxidized form of disulfide as indicated by the data showing that 61% of the total thiol in yeast is lost through the auto-oxidation from heating at the pH of 7.5, while only 30.5% is lost at the pH of 2s 5.9, and (2) almost all of the remaining thiol groups are in reactive form which apparently represents the thiol groups of insoluble protein ; existing intracellularly and unreacted. These residual thiol groups in the treated yeast cell are most probably inactive during bread-making 3r when the cells are mixed into the dough. Only soluble thiol compounds ` such as gultathione and cystine will affect the gluten structure.

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TABLE V
Effect of Heating At Increased pH To (1) The Auto-oxidation of Thiol iD Yeast Cells j Reactive SH Total SH
5 Cell (milli-equivalents/ (milli-equivalents SH Loss Treatment ~ram) gram) X
,Untreated 21.6 30.7 0 , pH 5.9( ) 12.9 21.3 30.5 j, pH 7.5( ) 10.4 12.0 61.0 (1) Candida utilis ATCC 9256. Continuous culture grown on ethanol 0 at 2 ~ limiting condition.
, (2) Heating at 95C. for 30 minutes under open air with constant agltation.
~i (3) Analyzed by the method of C. C. Tsen and J, A. Anderson ("Determina-tion of Sulfhydryl and Disulfide Groups in Flour and Their Relation to Wheat Quality" Cereal Chem. 40: 314-323, 1963).
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5 li EXAMPLE II
' A sample was prepared by digesting a 10% torula yeast cell slurry ' at 75C. and pH 7.0 for one hour. The baking test results as summarized !, below indicate that it6 quality is comparable to NFDM as an additive to '~
! bread-baking.
I Sample Bread Score Dou h Property ; Untreated cell 83 sticky and wet Treated cell 97 normal i; NFDM 98 normal EXA~LE III
The experiment of calcium treatment was carried out as outlined in Figure 2.
Aliquots of 200 ml of yeast cream which contains lOX cell by weigh~, are dispensed into each of the 400 ml beakers, with or without the ~ addition of variou6 calcium compounds as listed in TABLE ~I. The amount L~
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of calcium added is calculated from the basis of 2X phosphorus in the , aliquot of cell material and of a ratio of calcium to phosphorus of one.
The slurry was heated rapidly to 80C. by a submerged steam coil under constant stirring. At the end of lO minutes' cooking period, the heated material was quickly cooled down to room temperature by circulating the cooling water through the coil~ The pH of the treated slurry was measured and adiusted, as necessary, to a value of 6.7. The cell material was separated, washed, and dried. The yeast extract was directly 0 subjected to sensory test without further treatment. The results of the treatment using various calcium compounds as compared to the control are summarized in TABLES VI, VII, and VIII.
The experiment results indicate that:
l. A bland-taste cell material is obtainable by cooking the yeast with CaC03, where the pH is close to the neutral. Bad flavors are produced when the cells are reacted with Ca(OH)2 at an alkaline pH, or with CaCl2 at an acidic pH.
2. The yeast extracts obtained from the treatment with various ; calcium compound are significantly different in their color, odor, and 2' taste from that of the control. The best choice is still the one from ; the CaC03 treatment.
3. Tasting of the unfractionated products prepared from the above calcium treatments indicated that calcium carbonate (CaC03) treated material gave the best flavor. This means that a control of pH close to 7 is very critical to the flavor of the treated yeast products.

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i TABLE VI
The Calcium-Treated Yeast Cells(l) Treatment(2) ~(3) Yield(4) Color Flavor(5) j ;Control 6.2 84.3 Whitish Slightly bitter 5.0% CaCO3 6.7 85.0 Whitish Bland 3.7% Ca(OH)2 9.2 80.0 Cream Fairly bit~er 5.5% CaCl2 5.6 84.4 Pinkish Fairly bitter and astringent (l) Cooked at 80~C. for l0 minutes, washed, and dried (2) The weight of calcium compound added is based on the dry weight of yeast cell which contains 2% P. The ratio of Ca/P i8 about l.
(3) Unad~u~ted pH reading of the cooked slurry.

(4) After the pH of the slurry is adjusted to 6.7.
'j (5) Sensory test of a 5% suspension in water.
TABLE VII

5 ' The Yeast Extract From Various Calcium Treatment( ) Treatment(2) Color Color Odor Off-Flavor(3) , Control Orange ~ Yeasty Yeasty and beany 5.0% CaCO3 Yellowish + Hydroly- ~ot ~ate detected 3,7% Ca(OH)2 Yello~-ish + Butyrous Slightly ' beany 5.5% CaC12 Orange- ++ Yeasty Slightly Yellowish beany , (l) Cooked at 80C. for l0 minutes, separated from the cell material.
, (2) The weight of calcium compound added i9 based on the dry weight of yeast cell.
(3) All of the samples give pleasing meaty flavor.

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~ TABLE VIII
, The Comparison of Egg Replacement ~uality Between Calcium-treated and Untreated Blend Products In Yellow Cake Tests at 50% EÆg Replacement Level li Total Score* Expert 5 j! Composition of Samples Yellow Cake Panel Comments !' 80% ~ull Fat Soy Flour 90 Bright color, i'20% inactive dry yeast finer crus~b, -~
; (treated according to egg taRte, 1 Example XI) excellent body 80% Full Fat Soy Flour84 Dry texture, lacks , 20% inactive dry yeast flavor, soy taste, (untreated) crumbles, burning aftertaste 10 .:
80% Defatted Soy Flour96 Excellent body, , 20% inactive dry yeast well defined i (treated according to crumb structure ! Example IX) clean flavor 80% Defatted Soy Flour74 Poor body, good 20% inactive dry yeast flavor, dry mouth-(untreated) feel, open structur,e 80% Triticale Flour 94 Excellent body, 20% inactive dry yeast sweet egg flavor, (treated according to good structure j Example X) 3l 80% Triticale Flour 90 Gray color, gummy ~¦ 20% inactive dry yeast (untreated) l5 * Yellow cake score. Maximum pos~ible score is 100 for best overall 3 quality. The score for yellow cakes with 100% egg ranges from 94 to 96.

EXAMPLE IV
Yeast cream (containing 10-19% cell by weight) was heated to 80C.
The pH of the flowing stre3m was adjusted to within the range of 7.2 to ~1 7.6 by blending with an aqueous suspension 1.7 weight percent calcium ,, hydroxide (Ca(OH)2 and 8.5 weight percent calcium carbonate (CaCO3).
5 The stream was held at temperautre and pH for 2 to 4 minutes, then i spray dried at rates up to 2,500 lbJhr. of dry product.

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EXAMPLE V
Mixtures of yeast cream (10-19% cell by weight) and cheese whey (5-40% total solids by weight) were blended to levels of 27 to 47~ whey ¦ (dry basis, by weight). The mixed stream was heated to 80C, then ¦treated with a combined aqueous suspension of calcium carbonate (CaCO3, 8.5% by weight) and calcium hydroxide (Ca(OH)2, 1.7% by weight~ to effect a system pH within the range of 7,0 to 7.6. The process stream was held at 80C and 7.0 - 7.6 pH for 2-4 minutes, then spray dried at rates up Ito 80 lb/hr. of dry product output.
10 ¦ EXAMPLE VI

The process of Example V was repeated using sodium hydroxide (NaOH, 5.6% by weight) to adjust the pH to within the range of 6.8 to 7Ø

EXAMPLE VII
Figure 3 outlines the process of the production of modified plant protein.
Calcium carbonate and calcium hydroxide is added to an aqueous ¦ soy protein solution until the pH is between 6.5 and 7.5. The aqueous ¦ suspension is heated 90C. for 30 to 60 minutes and then dried.

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EXAMPLE VIII
The same as Example VII except that methionine is added before the aqueous suspension is h'eated.
EXAMPLE IX
Twenty grams of Torutein (inactive dried yeast) was mixed with eighty grams of defatted soy flour. Eight hundred grams of wa~e- was adted to form an aqueous mixture of Torutein and defatted soy flour.
1.7 grams of calcium hydroxide (Ca(OH)2) and 3.6 grams of calcium carbonate (CaC03~ was added to the aqueous mixture. The aqueous mixture was heated up to 190F. over a period of 40 minutes, the temperature was maintained at 190F. for 60 minutes, and allowed to cool to 70F.
over a period of 20 minutes. The cooled product was dried by freeze drying.
EXAMPLE X
The same as EXAMPLE IX except that triticale flour is used in place i of defatted soy flour.
EXAMPLE XI
i, The same as EXAMPLE IX except that full fat soy flour is used in ; place of defatted soy flour.
2;; ; The many uses and advantages of the treated products produced in accordance with this invention become apparent when it is realized that such products replace egg yolk and/or nonfat dry milk in an extensive array of food products. More particularly, it has been observed that the said products can replace nonfat dry milk in formulations which ~5 include such bakery goods as brownies, chocolate cake, chocolate krinkles, chocolate puddings, cinnamon rolls, cinnamon swirl loaf, coffee cake chemically leavened, coffee cake yeast raised, fudge, hamburger buns, high ratio yellow cake, nut fingers, pancakes, pecan loaf, pound cake, shortbread cookies, waffles, wheat flour tortillas, dough-nut, yellow cake mix and related products B

Claims (26)

We claim:

1. A process for improving the functional properties of protein-con-taining materials comprising the steps of:
(a) preparing an aqueous slurry of a protein-containing material selected from the group consisting of (1) single-cell protein, (2) plant protein, (3) whey material, and (4) mixtures of single-cell protein with plant protein, whey solids, or both plant protein and whey solids, said mixtures containing from about 1 to about 99 weight percent of the single-cell protein component;
(b) heating the aqueous slurry to a temperature of from about 75° to about 100°C.;
(c) adjusting the pH of the heated slurry to within the range of about 6.6 to about 8.0 by adding a compound selected from the group consisting of anhydrous ammonia, ammonium hydroxide, calcium hydroxide, sodium hydroxide, sodium bicarbonate, calcium sulfate, potassium carbonate, calcium carbonate, sodium carbonate, potassium hydroxide, magnesium hydroxide and mixtures thereof;
(d) maintaining the heated, pH-adjusted slurry at said con-ditions for a time period of from about 1 to about 120 minutes; and (e) drying the material from step (d).

2. The process of Claim 1 wherein the protein-containing material in step (a) is a mixture of yeast and whey.

3. The process of Claim 2 wherein the aqueous slurry is maintained at a pH of about 7.0-7.6 for from about 2 to about 4 minutes.

4, The process of Claim 3 wherein the aqueous slurry is maintained at about 80°C.

5. The process of Claim 4 wherein the pH is adjusted by adding calcium carbonate and calcium hydroxide.

6. The process of Claim 1 wherein the protein-containing material in step (a) is a mixture of yeast and whey and the aqueous slurry is maintained at a pH in the range of 6.8 to 7Ø

7. The process of Claim 6 wherein the aqueous slurry is heated to about 80°C for from about 2 to about 4 minutes.

8. The process of Claim 7 wherein the pH is adjusted by adding sodium hydroxide.

9. The process of Claim 1 wherein the protein-containing material in step (a) is plant protein material.

10. The process of Claim 9 wherein the plant protein material is a soybean material.

11. The process of Claim 10 wherein the aqueous slurry of soybean material is maintained at a pH of from about 6.5 to about 7.5 for about from 30 to about 60 minutes.

12. The process of Claim 11 wherein the pH is adjusted by the addition of calcium carbonate and calcium hydroxide.

13. The process of Claim 12 wherein the temperature of the slurry is heated to about 90°C.

14. The process of Claim 13 wherein an amino acid such as methionine or cystine is added to the slurry prior to heating.

15. The process of Claim 1 wherein the protein-containing material in step (a) is a mixture of yeast and defatted soy flour.

16. The process of Claim 1 wherein the protein-containing material in step (a) is a mixture of yeast and full fat soy flour.

17. The process of Claim 1 wherein the protein-containing material in step (a) is a mixture of yeast and triticale flour.

18. A process for improving the functional properties of a yeast material comprising the steps of:
a) preparing an aqueous slurry of the yeast material;
b) heating the slurry to a temperature of from about 75 to about 100°C.;
c) adjusting the pH of the slurry to from about 7.2 to about 7.6;
d) maintaining the heated, pH-adjusted slurry at said temperature and pH for from about 1 to about 10 minutes; and e) drying the slurry.

19. The process of Claim 18 wherein the yeast is Candida utilis.

20. The process of Claim 18 wherein the slurry is heated to about 80°C.

21. The process of Claim 18 wherein the pH is adjusted by the addition of calcium hydroxide and calcium carbonate.

22. The process of Claim 18 wherein the slurry is maintained at said temperature and pH for about 2 minutes.

23. A process for improving the functional properties of Candida utilis yeast comprising the steps of:
(a) preparing an aqueous slurry of the yeast material;
(b) treating the slurry by maintaining the slurry at a pH in the range of 7.2 to 7.6 and a temperature of about 80°C.
for about 2 minutes, wherein the pH is adjusted by the addition of calcium hydroxide and calcium carbonate; and (c) drying the treated slurry.

24. The dried yeast material product having improved functional properties, whenever prepared by the process of Claim 1.

25. The dried yeast material product having improved functional properties, whenever prepared by the process of Claim 18.

26. The dried yeast material product having improved functional properties, whenever prepared by the process of Claim 23.