CA1080026A

CA1080026A - Process for producing a refined soy protein product

Info

Publication number: CA1080026A
Application number: CA280,152A
Authority: CA
Inventors: Peter J. Lillford; Roland P. Carpenter; Graham W. Rodger; Mervyn T.A. Evans; Peter Harris
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1976-06-11
Filing date: 1977-06-09
Publication date: 1980-06-24
Also published as: IT1083508B; BE855597A; IE45421L; GB1580051A; JPS52154553A; FR2354055A1; FR2354055B1; DE2726185A1; LU77524A1; JPS5612421B2; NL7706381A; IE45421B1; SE7706793L

Abstract

Abstract of the Disclosure A process for producing a foodstuff mainly consisting of highly functional vegetable protein sub-stantially free of off-flavour components and pigments, which comprises subjecting vegetable protein containing material to alkaline conditions in the presence of an alkali metal halide and separating released pigments and off-flavour components from the protein by ultra-filtration or iso-electric precipitation.

Description

~L08q)0Z6 This invention relates to a process for the preparation of a proteinaceous foodstuff.
For the production of various food systems oil seed proteins are often used in the form of flours, concentrates or isolates, which have been subjected to some treatment in order to remove undesirable components such as off-flavours, pigments, typsin inhibitors and flatulence factors.
The products obtained after removal of the undesirable components are often denatured and not very useful especially in the case where a relatively high functionality is required.
There is thus a need for a process resulting in a product combining a high functionality with good organoleptic properties.
We have found a process enabling a facilitated release of pigments and off-flavour components from soy protein-containing material.
The present invention provides a process for producing a refined soy protein concentrate substantially free of off-flavour components and pigments, comprising the steps of:
a) forming an aqueous slurry of defatted soy protein- ~ `
containing materia:L;
b) subjecting said slurry to alkaline conditions in the presence of an alkali metal halide for a time sufficient to obtain a mixture in which said pigments and off-flavour components are substantially completely released from said soy protein-containing material by adjusting the pH of said slurry to a pH
of 9 to 12, and adding an amount sufficient of said alkali metal halide such that the concentration of said alkali metal halide in said slurry is 0.2 to 1

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8~0~6 Molar; and c) separating the released pigments and off-flavour components from the soy protein-containing material by either apply~ng ultra-filtration to obtain a retentate which contains the soy protein and a filtrate containing off-flavour components and pigments, or by precipitating the soy protein at its isoelectric point and separating the precipitated protein from the supernatant containing said off-flavour components and pigments.
The starting soy vegetable protein material is defatted prior to use, using e.g. solvent extraction. Extraction with e.g. hexane gives excellent results. The aqueous slurry of the starting material is easily prepared by thoroughly mixing the defakted material with suitable amounts o~ water. The applied ratio of solids to water can vary within wide limits but preferably a ratio of solids to water from 1:5 to l:30 is used. -The alkaline conditions can be obtained by using a base, preferably an alkalimetal hydroxide such as sodium- or potassium-hydroxide, which can be added in solid form to the aqueous slurry or in the form of concentrated aqueous solution in a proportion suf~icient to give a pEI ~rom 9 to 12 and preferably ~rom 10 to 11.
The alkali metal halide is pre~erably a sodium- or potassium halide, ideally sodium chloride is used.
The concentration of the alkali metal halide should range from O.2 to 1 M,~preferably from 0.35 to 0.70 M.
The treatment of~the vegetable protein-containin~ material under alkaline conditions in the presence of the alkali metal ~ ~ , halide can be performed after removal of insoluble material,

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~inly consisting o~ carbohydrates or in the presence thereo~.
We have found that an effective removal of off-flavour components and pigments is obtained if the treatment (step a) is carried out in the absence of the insoluble material (mainly consisting of carbohydrates), rather than in the presence thereof, in the case where the treatment of the starting material is followed by an ul'tra-filtration operation (step b) which is carried out in order to separate the released off-flavour components and pigments from the rest of the material.,However in the case where step (b) consists of an isoelectric precipitation it is more advantageous to perform the treatment ~step a) in the presence of the insoluble material.
The alkali metal halide can be added either before or after ad~justing the pH of the aqueous slurry of vegetable protein-containing material to the desired value which,as already stated,lies between 9 and 12. ;' In some instances it has been ~ound advantageous to first raise the pH of the aqueous slurry to a pH value within ' the given range andthen to add the alXali metal halide.
The treatment under alkaline conditions in the presence of the alkali metal halide is carried out for a sufficiently long time to achieve a sufficient dissociation of pigments and release of off-flavour components. A suitable method for assessing the released amount of off-flavour components is GL chromatography.
The duratlon of the treatment and the temperature should be such that the treated protein remains substantially

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Q 556 (R) -^ 10~ 26 undenatured by which term is meant that the functionality of the protein ~solubility, heat-setting properties, etc.) remains practically unchanged.
Usually a treatment of less than one hour and preferably from 1 to 15 minutes at a temperature ranging from 20 to 40C will be adequate. -Anyho~ the man skilled in the art will easily find the ideal conditions in each particular case.
Separation of the undesirable components such as off-flavour components and pigments from the rest of the materialcanbe achieved by usirlg conventional techniques.
Preferably isoelectric precipitation or ultrafiltration is applied. When startin~ from e.g. an aqueous slurr-y of de~atted soy ~lakes or soymeal lsoelectric precipitation f the protein is carried out at a pH ~rom 1l.5 to 5.5, preferably at a pH from 4.5 to 4.8.
Dilution of the aqueous slurry prior to isoelectric precipitation is sometimes required to facilltate the separation of the insoluble carbohydrate and to effectively perform the isoelectric precipitation, especially if relatively high concentrations of the alkali metal halide have been used.
Depending on whether the desired end-product is a protein concentratehavingaprotein concentration of about 70% or a protein isolate having a protein concentrati~no~ about 90%, the isoelectric precipitation is performed in the presence or in the absence of insoluble material mainly consisting of carbohydrates.
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' ' ' , : . ' . :' ' ~ , Q 556 (R) 8~110Z~i A preferred embodiment of the process according to the invention involves:
i) forming an aqueous slurry of defatted soymeal;
ii) subjecting said slurry to alkaline condibions at a pH from 9 to 12 in the presence o~ 0.2 M to 1 M of an alkali metal halide to obtain a mixture i.n which pigments and off-flavour-components are substantially completely released;
iii) diluting said mixture with water to obtain a mixture in which the molarity of the alkali metal .
halide is less than 0.2 M; -iv) precipitating the protein at a pH ranging from 4.5 .
to 5.5;
v) separatin~ the insoluble mater:ial consisting of carbohydrate~ and protein from the liquid, to obtain a soyprotein concentrate.
Another preferred embodiment of the process according to the invention involves:
i) forming an aqueous slurry of defatted soymeal; .
ii) subjecting said slurry to alkaline conditions at a pH from 9 to 12 in the presence of 0~2 ~ to 1 M
of an alkali metal hal:i.de to obtain a mixture in which pigments and off-f:Lavour components are ~ .
substantially completely released;
iii) diluting said mixture wlth water to obtain a mixture in which the molarity of the alkali metal :
halide is less than 0.2 M;
iv) separatine the insoluble material, mainly - 6 - ~;

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consisting of carbohydrates from the ~ixture to obbain a clarified protein solution;
v) precipitating the protein at a pH ranging from 4.5 to 5.5 from the solution to obtain a protein isolate.
According to the invention the undesirable off-flavour components and pigments can ~ separated from the rest of the material byusing ultra-filtration. Ultra-filtrationcan be carried out preferably after lowering the pH of the vegetable protein containlng mixture from the alkaline value to a value from 6-8, by using conventional membranes having a molecular weight cut-off limit of not less than 1000 daltons and preferably not less than 5000 daltons. ~epending on which end-product is envisa~,e~ (protein concentrate or protein isolate),the ultrafiltration can be carried out in the presence or in the absence of the insoluble carbohydrate.
A particularly preferred embodiment of the process according to the invention for the preparation of a soy-protein isolate involves:
i) forming an aqueous slurry of defatted soymeal;
ii) removing insoluble material,mainly consisting of carbohydrates, from said slurry to obtain a clarified solution; -iii) subjecting said clarified solution to alkaline conditions at a p~ ranging from 9 to 12 in the presence of 0.2 M to 1 ~ of an alkali metal halide, to obtain a mixture in which pigments and off-flavour components are substantially ::

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completely released; : ' iv) lowering the pH of the mixture to a value ranging -from 6 to 8; and v) ultra-filtering said mixture on a membrane having :
a molecular weight cut-off limit of not less than ~., 1000 daltons, to obtain a soyprotein isolate.
Another particularly ~referred embodiment of the process according to the invention for the preparation of a soyprotein isolate involves: "' i) forming an aqueous slurry of defatted soymeal, , ii) subjecting said slurry to alkaline condi.tions at a , pH ranging from 9 to 12~ in the presence of 0.2 M ' '' to 1 M of an alkali meta]. halide, to achleve a substantlally complete release of pi~ments and off-flavour components;
iii) lowering the pH of the slurry ,to a value ranging from 6 to 8;
iv) removing insoluble material mainly consisting of carbohydrates from said slurry to obtain a :
clarified solution, v) ultra-filtering said clarified solutlon on a membrane having a molecular weight cut-off limit ,'' of not less than 1000 daltons, to obtain a soy , , protein-isolate.
A particularly preferred embodiment of the process : .
according to the invention for the preparation of a soyprotein concentrate involves: .' , l) forming an aqueous slurry of defatted soymeal; ':

Q 556 (R) ~8~;26 ii) subJecting said slurry to alkaline conditions at a pH ran~ing from 9 to 12, in the presence of 0.2 ~ ;
to 1 M of alkali metal halide;
iii) lowering the pH of the slurry to a value ranging from 6 to 8;
iv) ultra-filtering the slurry on a membrane having a molecular weight cut-off limit of not less than 1000 daltons, to obtain a protein concentrate.
The products obtained according to the invention can be used in several food systems and particularly in those where good functional and organoleptic performance isrequired, like dairy desserts, simulated meat, or fish etc.
The followlng Examples illustrate the invention.
Example I
Production of a soyprotein concentrate by ultra-filtration One part by weight of defatted soybean meal was mixed with 10 parts by weight of water to form an aqueous slurry.
Solid sodlum chloride was added to the aqueous slurry in a proportion sufficient to obtain o.6 M dissolved NaCl.
The pH of the mixture was raised to 10.0 using sodium hydr-oxide. After 10 minutes the pH was lowered to 6.5 by adding hydrochloric acid. The mixture was concentrated two-fold in a conventional tubular module ultra-filtration plant at 55C using a membrane cast from a solution of , .
cellulose acetate in dimethylsu~hoxide, of a molecular weight cut-off limit of more than 5.000 daltons. The inlet pressure was 90 psig. and the outlet pressure 40 psig.
The concentrated slurry was diluted with an equal - _ g ''"

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volume of water and then reconcentrated by ultra-filtration `
in order to remove the sodium chloride, water soluble sugars, and other low-molecular weight impurities. This washing step was repeated until atleast 90%of the low-molecular weight impuritieshadbeenremoved. The concentrate obtained was spray-dried to yield a white powder containing about 70% of . protein and 30% of insoluble carbohydrate.
Example II .
Production of a soyprotein isolate by ultrafiltration The procedure of Example I was followed except that the insoluble material (mainly consistin~ of carbohydrates) present in the acidified mixture (pH 6.5) was centrifuged off and the clarified solution was ultra-filtered to yield aprotein isolate having a protein concentration of' about ~0%.
~
Production of a soyprotein isolate by ultrafiltration The general procedure of e~ample II was followed except that the insoluble materi~l was removed from the aqueous slurry bef'ore the addition of salt and sodium hydroxide Example IV
_ duction of asoyproteln concentrateby isoelectricprecipitation . . .
One part by welght of defatted soybean meal was mlxed with 10 parts by weight of water. Sodium chloride was dissolved in the aqueous extract to give a concentration f 0.25 molar and the pH of the mixture was ad,justed to 10.0 by adding sodium hydroxide. After 10 minutes the mixture wasdiluted with 22 volumes of water and the p~ adjusted to 4.8 by adding hydrochloric acld. The insoluble material .

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consisting of precipitated protein and insoluble carbohdrate~
was centrifuged off and spray-dried.
Example V
Production of soyprotein isolate by isoelectric precipitation The general procedure of example IV was followed except that the pH was first lowered from 10.0 to 6.5, and the insoluble material, mainly consisting of carbohydrate, was removed by centrifugation before performing the isoelectric precipitation of the protein at pH 4.8.
The precipitated protein was washed once with water and spray-dried to yield a white bland protein powder with a protein concentrat`lon of about 90%.
Example VI
Preparation of a proteinaceous ingredient for meat or fish analogues A fibrous ingredient useful for producing extended meat or fish products or full analogues was prepared starting from an isolate prepared according to example II.
Following the procedure outlined in US patent 3,987,213 drops of 0.05 ml of an aqueous solution containing about 25% soyprotein were added to a laminar flow of water of 9llC to coagulate the protein added. The product was collected and used for the production of 1) a seafood analogue and 2) a beef analogue.
Production of a seafood analogue 100 g. of the coagulated soyprotein were mixed with 200 ml. of a flavouring composition, pH 5.8-6.2 consist- `
ing of 3% natural seafood extracts, 1.5% seafood flavours, - 11 - ,, . . ,, ............ . : . . : .:
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Q 556 (R) ~O~I~Z6 0.1% salt and 95.4% water. The liquid was subsequently drained and the drained material was mixed with a dressing made of 94.9% mayonaise, 5% tomato ketchup and 0.1% lemon juice.
Production of beef analogue A mould was filled with collected soyprotein coagulates and the material was compressed at 55O kN/m2 between paper towelling to avoid a glossy surface on the final material.
The compressed sheet of material having a thickness of 3 - 5 mm was soaked for a few minutes in a flavour/
texturising bath. The sheet was drained and then heat-set in steam for 10 minutes.
When cooked in gravy and vegetables the analo~ue looked, chewed and swallowed like a slice of beef.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for producing a refined soy protein concentrate substantially free of off-flavour components and pigments, comprising the steps of:
a) forming an aqueous slurry of defatted soy protein-containing material;
b) subjecting said slurry to alkaline conditions in the presence of an alkali metal halide for a time sufficient to obtain a mixture in which said pigments and off-flavour components are substantially completely released from said soy protein-containing material by adjusting the pH of said slurry to a pH of 9 to 12, and adding an amount sufficient of said alkali metal halide such that the concentration of said alkali metal halide in said slurry is 0.2 to 1 Molar; and c) separating the released pigments and off-flavour components from the soy protein-containing material by either applying ultra-filtration to obtain a retentate which contains the soy protein and a filtrate containing off-flavour components and pigments, or by precipitating the soy protein at its isoelectric point and separating the precipitated protein from the supernatant containing said off-flavour components and pigments.

2. A process according to claim 1, wherein said defatted soy protein-containing material is soymeal.

3. A process according to claim 1, wherein the solids to liquid ratio of said slurry is 1:5 to 1:30.

4. A process according to claim 1, wherein said pH is adjusted by adding an alkali metal hydroxide to said slurry.

5. A process according to claim 1, wherein said pH is 10 to 11.

6. A process according to claim 1, wherein said alkali metal halide is sodium chloride.

7. A process according to claim 6, wherein the concentration of said sodium chloride is 0.35M to 0.70M.

8. A process according to claim 7, wherein said slurry has a temperature of 20°C to 40°C, and said time is less than one hour.

9. A process according to claim 1, wherein the pH of said mixture is adjusted to a pH of 6 to 8 prior said ultrafiltration.

10. A process according to claim 1, wherein:
(i) insoluble material mainly consisting of carbohydrates, is removed from said slurry to obtain a clarified solution prior to subjecting said clarified solution to alkaline conditions in the presence of an alkali metal halide;
(ii) the pH of said mixture is adjusted to a pH
of 6 to 8; and (iii) said released pigments and off-flavour components are separated from said soy protein containing material by ultrafiltering said mixture on a membrane having a molecular weight cut-off limit of not less than 1000 daltons, to obtain a soy protein isolate.

11. A process according to claim 1, wherein:
(i) the pH of said mixture is adjusted to a pH of from 6 to 8;
(ii) insoluble material mainly consisting of carbohydrates is removed from said slurry to obtain a clarified solution; and (iii) said released pigments and off-flavour components are separated from said soy protein containing material by ultra-filtering said clarified solution on a membrane having a molecular weight cut-off limit of not less than 1000 daltons, to obtain a soy protein isolate.

12. A process according to claim 1, wherein:
(i) the pH of said mixture is adjusted to a pH of 6 to 8; and (ii) said released pigments and off-flavour components are separated from said soy protein containing materials by ultra-filtering said slurry on a membrane having a molecular weight cut-off limit of more than 1000 daltons, to obtain a protein concentrate.

13. A process according to claim 1, wherein said ultra-filtration is performed on a membrane having a molecular weight cut-off limit of more than 5000 daltons.

14. A process according to claim 1, wherein:
(i) said mixture is diluted with water so that the molarity of said alkali metal halide is less than 0.2M;
(ii) said protein is precipitated by adjusting the pH of said mixture to a pH of 4.5 to 5.5; and (iii) said precipitate is separated to obtain a soy protein-concentrate.

15. A process according to claim 1, wherein:
(i) said mixture is diluted with water so that the molarity of said alkali metal halide is less than 0.2M;
(ii) insoluble material, mainly consisting of carbohydrates is separated from the mixture to obtain a clarified protein solution; and (iii) said protein is separated by precipitation by adjusting the pH of said solution to 4.5 to 5.5 to obtain a protein isolate.

16. A process for producing proteinaceous foodstuffs such as meat or fish analogues, which comprises replacing at least part of the original protein by a product prepared according to claim 1.

17. Foodstuffs, produced according to claim 16.

18. A soybean protein foodstuff substantially free of off-flavour components and pigments as produced by the process of

claim 1.