U.S. patent application number 13/712040 was filed with the patent office on 2013-04-25 for production of soy protein product using calcium chloride extraction ("s702").
The applicant listed for this patent is Brandy Gosnell, Brent E. Green, Sarah Medina, Martin Schweizer, Kevin I. Segall. Invention is credited to Brandy Gosnell, Brent E. Green, Sarah Medina, Martin Schweizer, Kevin I. Segall.
Application Number | 20130101713 13/712040 |
Document ID | / |
Family ID | 42540626 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130101713 |
Kind Code |
A1 |
Segall; Kevin I. ; et
al. |
April 25, 2013 |
PRODUCTION OF SOY PROTEIN PRODUCT USING CALCIUM CHLORIDE EXTRACTION
("S702")
Abstract
A soy protein product having a protein content of at least about
60 wt % (N.times.6.25) d.b., preferably a soy protein isolate
having a protein content of at least about 90 wt % (N.times.6.25)
d.b., is prepared from a soy protein source material by extraction
of the soy protein source material with an aqueous calcium salt
solution, preferably calcium chloride solution, to cause
solubilization of soy protein from the protein source and to form
an aqueous soy protein solution, separating the aqueous soy protein
solution from residual soy protein source, concentrating the
aqueous soy protein solution while maintaining the ionic strength
substantially constant by using a selective membrane technique,
optionally diafiltering the concentrated soy protein solution, and
drying the concentrated and optionally diafiltered soy protein
solution.
Inventors: |
Segall; Kevin I.; (Winnipeg,
CA) ; Schweizer; Martin; (Winnipeg, CA) ;
Green; Brent E.; (Winnipeg, CA) ; Medina; Sarah;
(Winnipeg, CA) ; Gosnell; Brandy; (Winnipeg,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Segall; Kevin I.
Schweizer; Martin
Green; Brent E.
Medina; Sarah
Gosnell; Brandy |
Winnipeg
Winnipeg
Winnipeg
Winnipeg
Winnipeg |
|
CA
CA
CA
CA
CA |
|
|
Family ID: |
42540626 |
Appl. No.: |
13/712040 |
Filed: |
December 12, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12704078 |
Feb 11, 2010 |
|
|
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13712040 |
|
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Current U.S.
Class: |
426/330 ;
426/422; 426/431; 426/598; 426/656 |
Current CPC
Class: |
A23J 3/16 20130101; A23J
1/14 20130101; A23L 2/39 20130101; A23L 2/66 20130101; A23L 33/185
20160801; A23V 2002/00 20130101; A23V 2002/00 20130101; A23V
2300/34 20130101; A23V 2300/40 20130101 |
Class at
Publication: |
426/330 ;
426/431; 426/422; 426/656; 426/598 |
International
Class: |
A23J 1/14 20060101
A23J001/14 |
Claims
1. A method of producing a soy protein product having a soy protein
content of at least about 60 wt % (N.times.6.25), dry weight basis,
which comprises: (a) extracting a soy protein source with an
aqueous calcium salt solution to cause solubilization of soy
protein from the protein source and to form an aqueous soy protein
solution, (b) separating the aqueous soy protein solution from
residual soy protein source, (c) concentrating the aqueous soy
protein solution while maintaining the ionic strength substantially
constant by using a selective membrane technique, (d) optionally
diafiltering the concentrated soy protein solution, and (e) drying
the concentrated and optionally diafiltered soy protein
solution.
2. The method of claim 1 wherein said calcium salt is calcium
chloride.
3. The method of claim 2 wherein said calcium chloride solution has
a concentration of less than about 1.0 M.
4. The method of claim 3 wherein said calcium chloride solution has
a concentration of about 0.10 to about 0.15 M.
5. The method of claim 1 wherein said extraction step is effected
at a temperature of about 15.degree. C. to about 35.degree. C.
6. The method of claim 1 wherein said extraction step is carried
out at a pH of about 5 to about 11.
7. The method of claim 6 wherein said pH is about 5 to about 7.
8. The method of claim 1 wherein said aqueous soy protein solution
has a protein concentration of about 5 to about 50 g/L.
9. The method of claim 8 wherein said aqueous soy protein solution
has a protein concentration of about 10 to about 50 g/L.
10. The method of claim 1 wherein said aqueous calcium salt
solution contains an antioxidant.
11. The method of claim 1 wherein said aqueous soy protein solution
is treated with an adsorbent to remove colour and/or odour
compounds from the aqueous soy protein solution,
12. The method of claim 1 wherein said aqueous soy protein solution
is concentrated to a protein concentration of about 50 to about 400
g/L.
13. The method of claim 12 wherein said aqueous soy protein
solution is concentrated to a protein concentration of about 100 to
about 250 g/L,
14. The method of claim 1 wherein said concentration step is
effected by ultrafiltration using a membrane having a molecular
weight cut-off of about 3,000 to about 1,000,000 Daltons.
15. The method of claim 14 wherein said concentration step is
effected by ultrafiltration using a membrane having a molecular
weight cut-off of about 5,000 to about 100,000 Daltons.
16. The method of claim 1 wherein said diafiltration step is
effected using an aqueous calcium salt solution of about the same
pH and about equal or lower molarity than the extraction salt
solution on the soy protein solution before or after complete
concentration thereof.
17. The method of claim 16 wherein said diafiltration step is
effected using about 2 to about 40 volumes of diafiltration
solution.
18. The method of claim 17 wherein said diafiltration step is
effected using about 5 to about 25 volumes of diafiltration
solution.
19. The method of claim 16 wherein said diafiltration is effected
using a membrane having a molecular weight cut-off of about 3,000
to about 1,000,000 Daltons.
20. The method of claim 19 wherein said membrane has a molecular
weight cut-off of about 5,000 to about 100,000 Daltons.
21. The method of claim 16 wherein said diafiltration is effected
until no significant further quantities of contaminants or visible
colour are present in the permeate.
22. The method of claim 16 wherein said diafiltration is effected
until the retentate has been sufficiently purified so as, when
dried, to provide a soy protein isolate with a protein content of
at least about 90 wt % (N.times.625) d.b.
23. The method of claim 16 where an antioxidant is present during
at least part of the diafiltration step.
24. The method of claim 1 wherein said concentration step and
optional diafiltration step are carried out at a temperature of
about 2.degree. to about 60.degree. C.
25. The method of claim 24 wherein said temperature is about
20.degree. to about 35.degree. C.
26. The method of claim 1 wherein the concentration and optional
diafiltration step are operated in a manner favourable to the
removal of trypsin inhibitors.
27. The method of claim 1 wherein the concentrated and optionally
diafiltered soy protein solution is treated with an adsorbent to
remove colour and/or odour compounds.
28. The method of claim 1 wherein the concentrated and optionally
diafiltered soy protein solution is subjected to a pasteurization
step prior to drying.
29. The method of claim 28 wherein said pasteurization step is
effected at a temperature of about 55.degree. to about 70.degree.
C. for about 30 seconds to about 60 minutes.
30. The method of claim 29 wherein said pasteurization step is
effected at a temperature of about 60.degree. to about 65.degree.
C. for about 10 to about 15 minutes.
31. The method of claim 28 wherein said pasteurized, concentrated
and optionally diafiltered soy protein solution is cooled to a
temperature of about 15.degree. C. to about 35.degree. C. for
drying or further processing.
32. The method of claim 1 wherein the concentrated and optionally
diafiltered soy protein solution is acidified to a pH of about 2.0
to about 4.0 prior to drying.
33. The method of claim 32 wherein said acidified soy protein
solution is subjected to a heat treatment step to inactivate
heat-labile anti-nutritional factors prior to drying.
34. The method of claim 33 wherein the anti-nutritional factors are
heat-labile trypsin inhibitors.
35. The method of claim 33 wherein the heat treatment step also
pasteurizes the aqueous protein solution.
36. The method of claim 33 wherein said heat-treatment is effected
at a temperature of about 70.degree. to about 120.degree. C. for
about 10 seconds to about sixty minutes.
37. The method of claim 36 wherein said heat-treatment is effected
at a temperature of about 85.degree. to about 95.degree. C. for
about 30 seconds to about 5 minutes.
38. The method of claim 33 wherein the heat-treated clear acidified
soy protein solution is cooled to a temperature of about 2.degree.
to about 60.degree. C. for drying or further processing.
39. The method of claim 38 wherein the heat-treated clear acidified
soy protein solution is cooled to a temperature of about 20.degree.
to about 35.degree. C. for drying or further processing.
40. The method of claim 1 wherein a reducing agent is present
during the extraction step to disrupt or rearrange the disulfide
bonds of trypsin inhibitors to achieve a reduction in trypsin
inhibitor activity.
41. The method of claim 1 wherein a reducing agent is present
during the concentration and/or optional diafiltration step to
disrupt or rearrange the disulfide bonds of trypsin inhibitors to
achieve a reduction in trypsin inhibitor activity.
42. The method of claim 1 wherein a reducing agent is added to the
concentrated and optionally diafiltered soy protein solution prior
to drying and/or the dried soy protein product to disrupt or
rearrange the disulfide bonds of trypsin inhibitors to achieve a
reduction in trypsin inhibitor activity.
43. The method of claim 1 wherein said soy protein product has a
protein content of about 60 to about 90 wt % (N.times.6.25).
d.b.
44. The method of claim 1 wherein said soy protein product has a
protein content of at least about 90 wt % (N.times.6.25). d.b.
45. The method of claim 1 wherein said soy protein product has a
protein content of at least about 100 wt % (N.times.6.25). d.b.
46. A soy protein product produced by the method of claim 1.
47. An acidic solution having dissolved therein the soy protein
product of claim 46.
48. The aqueous solution of claim 47 which is a beverage.
49. The soy protein product of claim 46 which is blended with
water-soluble powdered materials for the production of aqueous
solutions of the blend.
50. The blend of claim 49 which is a powdered beverage.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 USC 119(e) from
U.S. Provisional Patent Applications Nos. 61/202,262 filed Feb. 11,
2009 and 61/213,663 filed Jun. 30, 2009.
FIELD OF INVENTION
[0002] The present invention is concerned with the preparation of
soybean protein products.
BACKGROUND TO THE INVENTION
[0003] In U.S. Provisional Patent Applications Nos. 61/107,112
filed Oct. 21, 2008, 61/193,457 filed Dec. 2, 2008, 61/202,070
filed Jan. 26, 2009, 61/202,553 filed Mar. 12, 2009, 61/213,717
filed Jul. 7, 2009, 61/272,241 filed Sep. 3, 2009, and U.S. patent
application Ser. No. 12/603,087 filed Oct. 21, 2009 the disclosures
of which are incorporated herein by reference, there is described
the preparation of a soy protein product, preferably a soy protein
isolate, which is completely soluble and is capable of providing
transparent and heat stable solutions at low pH values. This soy
protein product may be used for protein fortification of, in
particular, soft drinks and sports drinks, as well as other acidic
aqueous systems, without precipitation of protein. The soy protein
product is produced by extracting a soy protein source with aqueous
calcium chloride solution at natural pH, optionally diluting the
resulting aqueous soy protein solution, adjusting the pH of the
aqueous soy protein solution to a pH of about 1.5 to about 4.4,
preferably about 2.0 to about 4.0, to produce an acidified clear
soy protein solution, which may be optionally concentrated and/or
diafiltered before drying.
SUMMARY OF THE INVENTION
[0004] It has now been found that calcium chloride extracts of soy
protein source may be processed by alternative procedures to
provide substantially equivalent soy protein products, having a
protein content of at least about 60 wt % (N.times.6.25) d.b., that
are soluble in acidic media and produce transparent, heat stable
solutions at low pH values, and, therefore may be used for protein
fortification of, in particular, soft drinks and sports drinks, as
well as other aqueous systems, without precipitation of protein.
The soy protein product is preferably an isolate having a protein
content of at least about 90 wt %, preferably at least about 100%
(N.times.6.25) d.b.
[0005] In one aspect of the present invention, a soy protein source
material is extracted with aqueous calcium chloride solution at
natural pH and the resulting aqueous soy protein solution is
subjected to ultrafiltration and optional diafiltration to provide
a concentrated and optionally diafiltered soy protein solution,
which may be dried to provide the soy protein product. The level of
anti-nutritional trypsin inhibitors in the soy protein product may
be controlled by choosing the membrane processing conditions so as
to release the desired amount of inhibitors in the permeate
stream.
[0006] In another aspect of the present invention, a soy protein
source material is extracted with aqueous calcium chloride solution
at natural pH and the resulting aqueous soy protein solution is
subjected to ultrafiltration and optional diafiltration to provide
a concentrated and optionally diafiltered soy protein solution.
This soy protein may be fractionated by dilution into water,
yielding a precipitate rich in globulin proteins and a supernatant
rich in albumin proteins. The supernatant may be processed, as
described in detail below, to form soy protein products having a
soy protein content of at least about 60 wt %, preferably a soy
protein isolate having a protein content of at least about 90 wt %.
Trypsin inhibitors, which are proteins, are found primarily in the
supernatant fraction after dilution. The precipitate fraction may
be further processed or dried as is to provide the soy protein
product, but with a reduced level of trypsin inhibitors.
[0007] The soy protein isolate provided herein is soluble at acid
pH values to provide transparent and heat stable aqueous solutions
thereof. The soy protein isolate may be used for protein
fortification of, in particular, soft drinks and sports drinks,
without precipitation of protein.
[0008] In another aspect of the present invention, the concentrated
and optionally diafiltered soy protein solution, prepared as
described above is diluted into water, but all the proteins are
resolubilized by adjustment of the pH to about 1.5 to about 4.4,
preferably about 2.0 to about 4.0. The diluted and acidified
solution may then be optionally concentrated and/or diafiltered.
Reduction in the trypsin inhibitor level may be achieved by
judicious choice of the membrane processing parameters or
optionally employing a heat treatment step on the acidified
solution.
[0009] In accordance with one aspect of the present invention,
there is provided a method of producing a soy protein product
having a soy protein content of at least 60 wt % (N.times.6.25), on
a dry weight basis, which comprises: [0010] (a) extracting a soy
protein source with an aqueous calcium chloride solution to cause
solubilization of soy protein from the protein source and to form
an aqueous soy protein solution, [0011] (b) separating the aqueous
soy protein solution from residual soy protein source, [0012] (c)
concentrating the aqueous soy protein solution while maintaining
the ionic strength substantially constant by using a selective
membrane technique, [0013] (d) optionally diafiltering the
concentrated soy protein solution, and [0014] (e) drying the
concentrated soy protein solution.
[0015] The soy protein product is preferably an isolate having a
protein content of at least about 90 wt %, preferably at least
about 100 wt % (N.times.6.25) d.b.
[0016] A variation of this procedure may be adopted to produce the
product with a reduced content of albumin proteins and trypsin
inhibitors. In such a variation, the concentrated and optionally
diafiltered soy protein solution is diluted into water to yield a
precipitate with a reduced content of albumin proteins and trypsin
inhibitors. The precipitate may be collected and dried to yield the
product or the precipitate may be solubilized in water at low pH
and then dried. Alternatively, the solution formed by
re-solubilizing the precipitate in water at low pH may be
optionally heat treated and/or concentrated and/or diafiltered
before drying.
[0017] According to another aspect of the present invention, there
is described a method of producing a soy protein product having a
soy protein content of at least about 60 wt % (N.times.6.25), dry
weight basis, which comprises: [0018] (a) extracting a soy protein
source with an aqueous calcium salt solution to cause
solubilization of soy protein from the protein source and to form
an aqueous soy protein solution, [0019] (b) separating the aqueous
soy protein solution from residual soy protein source, [0020] (c)
concentrating the aqueous soy protein solution while maintaining
the ionic strength substantially constant by using a selective
membrane technique, [0021] (d) optionally diafiltering the
concentrated soy protein solution, [0022] (e) diluting the
concentrated soy protein solution into water to cause the formation
of a precipitate, [0023] (f) separating the precipitate from the
diluting water, termed the supernatant, and [0024] (g) drying the
separated soy protein precipitate.
[0025] Another variation of this procedure may be adopted to
produce the product. In such a variation, the concentrated and
optionally diafiltered soy protein solution is diluted into water
and the pH lowered. The resulting clear, acidified solution is
optionally concentrated and/or diafiltered and/or heat treated
before drying to yield the product.
[0026] According to a further aspect of the present invention,
there is provided a method of producing a soy protein product
having a soy protein content of at least about 60 wt %
(N.times.6.25), dry weight basis, which comprises: [0027] (a)
extracting a soy protein source with an aqueous calcium salt
solution to cause solubilization of soy protein from the protein
source and to form an aqueous soy protein solution, [0028] (b)
separating the aqueous soy protein solution from residual soy
protein source, [0029] (c) concentrating the aqueous soy protein
solution while maintaining the ionic strength substantially
constant by using a selective membrane technique, [0030] (d)
optionally diafiltering the concentrated soy protein solution,
[0031] (e) diluting the concentrated soy protein solution into
water to cause the formation of a precipitate, [0032] (f)
acidifying the mixture of precipitate and diluting water to
re-solubilize the protein and form in a clear soy protein solution,
[0033] (g) concentrating the clear acidified soy protein solution
while maintaining the ionic strength substantially constant by
using a selective membrane technique, [0034] (h) optionally
diafiltering the concentrated clear acidified soy protein solution,
and [0035] (i) drying the concentrated and optionally diafiltered
clear acidified soy protein solution.
[0036] Employing the procedures of the present invention allows the
option of production of the soy protein product in a natural pH
form. Generation of the soy protein product without an
acidification step allows easier, safer and more economical
processing, since there is no need for acids and their handling. In
addition, this procedure permits the beverage formulator to acidify
the protein and beverage with the acidifying agent of their choice,
given the differing strengths and flavour profiles of various
acids.
[0037] While the present invention refers mainly to the production
of soy protein isolates, it is contemplated that soy protein
products of lesser purity may be provided having similar properties
to the soy protein isolate. Such lesser purity products may have a
protein concentration of at least about 60% by weight
(N.times.6.25) d.b.
[0038] The novel soy protein products of the invention can be
blended with powdered drinks for the formation of aqueous soft
drinks or sports drinks by dissolving the same in water. Such blend
may be a powdered beverage.
[0039] The soy protein products provided herein may be provided as
an aqueous solution thereof having a high degree of clarity at acid
pH values and which is heat stable at these pH values.
[0040] In another aspect of the present invention, there is
provided an aqueous solution of the soy product provided herein
which is heat stable at low pH. The aqueous solution may be a
beverage, which may be a clear beverage in which the soy protein
product is completely soluble and transparent or an opaque beverage
in which the soy protein product does not increase the opacity.
[0041] The soy protein products produced according to the processes
herein lack the characteristic beany flavour of soy protein
isolates and are suitable, not only for protein fortification of
acid medium, but may be used in a wide variety of conventional
applications of protein isolates, including, but not limited to
protein fortification of processed foods and beverages,
emulsification of oils, as a body former in baked goods and foaming
agent in products which entrap gases. In addition, the soy protein
product may be formed into protein fibers, useful in meat analogs
and may be used as an egg white substitute or extender in food
products where egg white is used as a binder. The soy protein
product may be used as a nutritional supplement. Other uses of the
soy protein product are in pet foods, animal feed and in industrial
and cosmetic applications and in personal care products.
GENERAL DESCRIPTION OF INVENTION
[0042] The initial step of the process of providing the soy protein
product involves solubilizing soy protein from a soy protein
source. The soy protein source may be soybeans or any soy product
or by-product derived from the processing of soybeans including but
not limited to soy meal, soy flakes, soy grits and soy flour. The
soy protein source may be used in the full fat form, partially
defatted form or fully defatted form. Where the soy protein source
contains an appreciable amount of fat, an oil-removal step
generally is required during the process. The soy protein recovered
from the soy protein source may be the protein naturally occurring
in soybean or the proteinaceous material may be a protein modified
by genetic manipulation but possessing characteristic hydrophobic
and polar properties of the natural protein.
[0043] Protein solubilization from the soy protein source material
is effected most conveniently using food grade calcium chloride
solution, although solutions of other calcium salts may be used.
Where the soy protein product is intended for non-food uses,
non-food-grade chemicals may be used. In addition, other alkaline
earth metal salts may be also used, such as magnesium salts.
Further, extraction of the soy protein from the soy protein source
may also be effected using calcium salt solution in combination
with another salt solution, such as sodium chloride. Additionally,
extraction of the soy protein from the soy protein source may be
effected using water or other salt solution, such as sodium
chloride solution, with calcium salt, such as calcium chloride,
subsequently being added to the aqueous soy protein solution
produced in the extraction step. Precipitate formed upon addition
of the calcium salt then is removed prior to subsequent
processing.
[0044] As the concentration of the calcium salt solution increases,
the degree of solubilization of protein from the soy protein source
initially increases until a maximum value is achieved. Any
subsequent increase in salt concentration does not increase the
total protein solubilized. The concentration of the calcium salt
solution which causes maximum protein solubilization varies
depending on the salt concerned. It is usually preferred to utilize
a concentration value less than about 1.0 M, and more preferably a
value of about 0.10 M to about 0.15 M.
[0045] In a batch process, the salt solubilization of the protein
is effected at a temperature of from about 1.degree. C. to about
100.degree. C., preferably about 15.degree. C. to about 35.degree.
C., preferably accompanied by agitation to decrease the
solubilization time, which is usually about 1 to about 60 minutes.
It is preferred to effect the solubilization to extract
substantially as much protein from the soy protein source as is
practicable, so as to provide an overall high product yield.
[0046] In a continuous process, the extraction of the soy protein
from the soy protein source is carried out in any manner consistent
with effecting a continuous extraction of soy protein from the soy
protein source. In one embodiment, the soy protein source is
continuously mixed with the calcium salt solution and the mixture
is conveyed through a pipe or conduit having a length and at a flow
rate for a residence time sufficient to effect the desired
extraction in accordance with the parameters described herein. In
such a continuous procedure, the salt solubilization step is
effected rapidly, in a time of up to about 10 minutes, preferably
to effect solubilization to extract substantially as much protein
from the soy protein source as is practicable. The solubilization
in the continuous procedure is effected at temperatures between
about 1.degree. C. and about 100.degree. C., preferably between
about 15.degree. C. and about 35.degree. C.
[0047] The extraction is generally conducted at a p11 of about 5 to
about 11, preferably about 5 to about 7. The pH of the extraction
system (soy protein source and calcium salt solution) may be
adjusted, if necessary, to any desired value within the range of
about 5 to about 11 for use in the extraction step by the use of
any convenient acid, usually hydrochloric acid, or alkali, usually
sodium hydroxide, as required.
[0048] The concentration of soy protein source in the calcium salt
solution during the solubilization step may vary widely. Typical
concentration values are about 5 to about 15% w/v.
[0049] The protein solution resulting from the extraction step
generally has a protein concentration of about 5 to about 50 g/L,
preferably about 10 to about 50 L.
[0050] The protein extraction step with the aqueous salt solution
has the additional effect of solubilizing fats which may be present
in the soy protein source, which then results in the fats being
present in the aqueous phase.
[0051] The aqueous calcium salt solution may contain an
antioxidant. The antioxidant may be any convenient antioxidant,
such as sodium sulfite or ascorbic acid. The quantity of
antioxidant employed may vary from about 0.01 to about 1 wt % of
the solution, preferably about 0.05 wt %. The antioxidant serves to
inhibit the oxidation of any phenolics in the protein solution.
[0052] The aqueous phase resulting from the extraction step then
may be separated from the residual soy protein source, in any
convenient manner, such as by employing a decanter centrifuge,
followed by disc centrifugation and/or filtration, to remove
residual soy protein source material. The separated residual
protein source material may be dried for disposal. Alternatively,
the separated residual soy protein source may be processed to
recover some residual protein, such as by a conventional
isoelectric precipitation procedure or any other convenient
procedure to recover such residual protein.
[0053] Where the soy protein source contains significant quantities
of fat, as described in U.S. Pat. Nos. 5,844,086 and 6,005,076,
assigned to the assignee hereof and the disclosures of which are
incorporated herein by reference, then the defatting steps
described therein may be effected on the separated aqueous protein
solution. Alternatively, defatting of the separated aqueous protein
solution may be achieved by any other convenient procedure.
[0054] The aqueous soy protein solution may be treated with an
adsorbent, such as powdered activated carbon or granulated
activated carbon, to remove colour and/or odour compounds. Such
adsorbent treatment may be carried out under any convenient
conditions, generally at the ambient temperature of the separated
aqueous protein solution. For powdered activated carbon, an amount
of about 0.025% to about 5% w/v, preferably about 0.05% to about 2%
w/v, is employed. The adsorbing agent may be removed from the soy
solution by any convenient means, such as by filtration.
[0055] If of adequate purity, the resulting aqueous soy protein
solution may be directly dried to produce a soy protein product. To
decrease the impurities content, the aqueous soy protein solution
may be processed prior to drying.
[0056] The aqueous soy protein solution may be concentrated to
increase the protein concentration thereof while maintaining the
ionic strength thereof substantially constant. Such concentration
generally is effected to provide a concentrated soy protein
solution having a protein concentration of about 50 to about 400
g/L, preferably about 100 to about 250 g/L.
[0057] The concentration step may be effected in any convenient
manner consistent with batch or continuous operation, such as by
employing any convenient selective membrane technique, such as
ultrafiltration or diafiltration, using membranes, such as
hollow-fibre membranes or spiral-wound membranes, with a suitable
molecular weight cut-off, such as about 3,000 to about 1,000,000
Daltons, preferably about 5,000 to about 100,000 Daltons, having
regard to differing membrane materials and configurations, and, for
continuous operation, dimensioned to permit the desired degree of
concentration as the aqueous protein solution passes through the
membranes.
[0058] As is well known, ultrafiltration and similar selective
membrane techniques permit low molecular weight species to pass
therethrough while preventing higher molecular weight species from
so doing. The low molecular weight species include not only the
ionic species of the food grade salt but also low molecular weight
materials extracted from the source material, such as
carbohydrates, pigments, low molecular weight proteins and
anti-nutritional factors, such as trypsin inhibitors, which are
themselves low molecular weight proteins. The molecular weight
cut-off of the membrane is usually chosen to ensure retention of a
significant proportion of the protein in the solution, while
permitting contaminants to pass through having regard to the
different membrane materials and configurations.
[0059] The concentrated soy protein solution then may be subjected
to a diafiltration step, before or after complete concentration,
using calcium salt solution, such as a solution of calcium chloride
at the same pH and the same concentration of calcium salt as the
extraction solution. If a reduction in the salt content of the
retentate is desired, the diafiltration solution employed may be an
aqueous calcium salt solution at the same pH but lower salt
concentration than the extraction solution. However, the salt
concentration of the diafiltration solution must be chosen so that
the salt level in the retentate remains sufficiently high to
maintain the desired protein solubility. As mentioned, the
diafiltration solution is preferably at a pH equal to that of the
protein solution being diafiltered. The pH of the diafiltration
solution may be adjusted with any convenient acid, such as
hydrochloric acid or phosphoric acid or alkali, such as sodium
hydroxide. Such diafiltration may be effected using from about 2 to
about 40 volumes of diafiltration solution, preferably about 5 to
about 25 volumes of diafiltration solution. In the diafiltration
operation, further quantities of contaminants are removed from the
aqueous soy protein solution by passage through the membrane with
the permeate. The diafiltration operation may be effected until no
significant further quantities of contaminants or visible colour
are present in the permeate or until the retentate has been
sufficiently purified so as, when dried, to provide a soy protein
product with the desired protein content, preferably an isolate
with a protein content of at least about 90 wt % on a dry weight
basis. Such diafiltration may be effected using the same membrane
as for the concentration step. However, if desired, the
diafiltration step may be effected using a separate membrane with a
different molecular weight cut-off, such as a membrane having a
molecular weight cut-off in the range of about 3,000 to about
1,000,000 Daltons, preferably about 5,000 to about 100,000 Daltons,
having regard to different membrane materials and
configuration.
[0060] The concentration step and the diafiltration step may be
effected herein in such a manner that the soy protein product
subsequently recovered by drying the concentrated and diafiltered
retentate contains less than about 90 wt % protein (N.times.6,25)
d.b., such as at least about 60 wt % protein (N.times.6.25) d.b. By
partially concentrating and/or partially diafiltering the aqueous
soy protein solution, it is possible to only partially remove
contaminants. This protein solution may then be dried to provide a
soy protein product with lower levels of purity. The soy protein
product is still able to produce clear protein solutions under
acidic conditions,
[0061] An antioxidant may be present in the diafiltration medium
during at least part of the diafiltration step. The antioxidant may
be any convenient antioxidant, such as sodium sulfite or ascorbic
acid. The quantity of antioxidant employed in the diafiltration
medium depends on the materials employed and may vary from about
0.01 to about 1 wt %, preferably about 0.05 wt %, The antioxidant
serves to inhibit the oxidation of any phenolics present in the
concentrated soy protein solution.
[0062] The concentration step and the diafiltration step may be
effected at any convenient temperature, generally about 2.degree.
to about 60.degree. C., preferably about 20.degree. to about
35.degree. C., and for the period of time to effect the desired
degree of concentration and diafiltration. The temperature and
other conditions used to some degree depend upon the membrane
equipment used to effect the membrane processing, the desired
protein concentration of the solution and the efficiency of the
removal of contaminants to the permeate.
[0063] There are two main trypsin inhibitors in soy, namely the
Kunitz inhibitor, which is a heat-labile molecule with a molecular
weight of approximately 21,000 Daltons, and the Bowman-Birk
inhibitor, a more heat-stable molecule with a molecular weight of
about 8,000 Daltons. The level of trypsin inhibitor activity in the
final soy protein product can be controlled by manipulation of
various process variables.
[0064] For example, the concentration and/or diafiltration steps
may be operated in a manner favorable for removal of trypsin
inhibitors in the permeate along with the other contaminants.
Removal of the trypsin inhibitors is promoted by using a membrane
of larger pore size, such as about 30,000 to about 1,000,000
Daltons, operating the membrane at elevated temperatures, such as
about 30.degree. C. to about 60.degree. C. and employing greater
volumes of diafiltration medium, such as about 20 to about 40
volumes.
[0065] Further, a reduction in trypsin inhibitor activity may be
achieved by exposing soy materials to reducing agents that disrupt
or rearrange the disulfide bonds of the inhibitors. Suitable
reducing agents include sodium sulfite, cysteine and
N-acetylcysteine.
[0066] The addition of such reducing agents may be effected at
various stages of the overall process. The reducing agent may be
added with the soy protein source material in the extraction step,
may be added to the clarified aqueous soy protein solution
following removal of residual soy protein source material, may be
added to the concentrated protein solution before or after
diafiltration or may be dry blended with the dried soy protein
product. The addition of the reducing agent may be combined with
the membrane processing steps, as described above.
[0067] If it is desired to retain active trypsin inhibitors in the
concentrated protein solution, this can be achieved by utilizing a
concentration and diafiltration membrane with a smaller pore size,
operating the membrane at lower temperatures, employing fewer
volumes of diafiltration medium and not employing a reducing
agent.
[0068] The concentrated and optionally diafiltered protein solution
may be subject to a further defatting operation, if required, as
described in U.S. Pat. Nos. 5,844,086 and 6,005,076. Alternatively,
defatting of the concentrated and optionally diafiltered protein
solution may be achieved by any other convenient procedure.
[0069] The concentrated and optionally diafiltered aqueous protein
solution may be treated with an adsorbent, such as powdered
activated carbon or granulated activated carbon, to remove colour
and/or odour compounds. Such adsorbent treatment may be carried out
under any convenient conditions, generally at the ambient
temperature of the concentrated aqueous protein solution. For
powdered activated carbon, an amount of about 0.025% to about 5%
w/v, preferably about 0.05% to about 2% w/v, is employed. The
adsorbent may be removed from the soy protein solution by any
convenient means, such as by filtration.
[0070] The concentrated and optionally diafiltered soy protein
solution resulting from the optional defatting and optional
adsorbent treatment step may be subjected to a pasteurization step
to reduce the microbial load. Such pasteurization may be effected
under any desired pasteurization conditions. Generally, the
concentrated and optionally diafiltered soy protein solution is
heated to a temperature of about 55.degree. to about 70.degree. C.,
preferably about 60 to about 65'C, for about 30 seconds to about 60
minutes, preferably about 10 to about 15 minutes. The pasteurized
concentrated soy protein solution then may be cooled for drying or
further processing, preferably to a temperature of about 15.degree.
to about 35.degree. C.
[0071] In accordance with one aspect of the current invention, the
concentrated and optionally diafiltered clear aqueous soy protein
solution may be dried by any convenient technique, such as spray
drying or freeze drying to yield the soy protein product.
Alternatively, the concentrated and optionally diafiltered soy
protein solution may be adjusted in pH to about 2.0 to about 4.0.
The pH adjustment may be effected in any convenient manner, such as
by the addition of hydrochloric acid or phosphoric acid. The
resulting acidified soy protein solution then is dried. As a
further alternative, the pH adjusted soy protein solution may be
subjected to a heat treatment to inactivate heat labile
anti-nutritional factors, such as the trypsin inhibitors mentioned
above. Such a heating step also provides the additional benefit of
reducing the microbial load. Generally, the protein solution is
heated to a temperature of about 70.degree. to about 120.degree.
C., preferably about 85.degree. to about 95.degree. C., for about
10 seconds to about 60 minutes, preferably about 30 seconds to
about 5 minutes. The heat treated acidified soy protein solution
then may be cooled to a temperature of about 2.degree. C. to about
60.degree. C., preferably about 20.degree. to about 35.degree. C.
The resulting acidified, heat treated soy protein solution then is
dried.
[0072] In another aspect of the invention, the concentrated protein
solution resulting from the concentration step and optional
diafiltration step, optional defatting step, optional adsorbent
treatment step and optional pasteurization step, is diluted to
effect precipitate formation by mixing the concentrated protein
solution with water having the volume required to achieve the
degree of dilution desired. When the precipitated protein is to be
separated from the residual aqueous phase, termed the supernatant,
as is the case for this aspect of the current invention, the degree
of dilution is generally about 5 fold to about 25 fold, preferably
about 10 fold to about 20 fold. The water with which the
concentrated protein solution is mixed preferably has a temperature
of about 1.degree. to about 60.degree. C., preferably about
15.degree. to about 35.degree. C.
[0073] In a batch operation, the batch of concentrated protein
solution is added to a static body of water having the desired
volume, as discussed above. The dilution of the concentrated
protein solution and consequential decrease in ionic strength
causes the formation of the protein precipitate. In the batch
procedure, the protein precipitate is allowed to settle in the body
of water. The settling may be assisted, such as by centrifugation.
Such induced settling decreases the moisture content and the
occluded salt content of the precipitated protein.
[0074] Alternatively, the dilution operation may be carried out
continuously by continuously passing the concentrated protein
solution to one inlet of a T-shaped pipe, while the diluting water
is fed to the other inlet of the T-shaped pipe, permitting mixing
in the pipe. The diluting water is fed into the T-shaped pipe at a
rate sufficient to achieve the desired degree of dilution of the
concentrated protein solution.
[0075] The mixing of the concentrated protein solution and the
diluting water in the pipe initiates the formation of protein
precipitate and the mixture is continuously fed from the outlet of
the T-shaped pipe into a settling vessel, from which, when full,
supernatant is permitted to overflow. The mixture preferably is fed
into the body of liquid in the settling vessel in a manner which
minimizes turbulence within the body of liquid.
[0076] In the continuous procedure, the protein precipitate is
allowed to settle in the settling vessel and the procedure is
continued until a desired quantity of the precipitate has
accumulated in the bottom of the settling vessel, whereupon the
accumulated precipitate is removed from the settling vessel. In
lieu of settling by sedimentation, the precipitate may be separated
continuously by centrifugation.
[0077] By the utilization of a continuous process for the recovery
of soy protein precipitate as compared to the batch process, the
initial protein extraction step can be significantly reduced in
time for the same level of protein extraction. In addition, in a
continuous operation, there is less chance of contamination than in
a batch procedure, leading to higher product quality and the
process can be carried out in more compact equipment.
[0078] The settled precipitate is separated from the residual
aqueous phase or supernatant, such as by decantation of the
residual aqueous phase from the settled mass or by centrifugation.
The precipitate may be washed to remove residual supernatant, such
as with about 1 to about 10, preferably about 2 to about 3 volumes
of water and then the precipitate recovered again, as above. The
optionally washed precipitate may be used in the wet form or may be
dried, by any convenient technique, such as spray drying or freeze
drying, to a dry form. The dry precipitate has a high protein
content, in excess of about 60 wt % protein, preferably at least
about 90 wt % protein (N.times.6.25), and more preferably at least
about 100 wt % (N.times.6.25). The dry precipitate is low in phytic
acid content, generally less than about 1.5% by weight.
[0079] The supernatant arising from the dilution step may be
discarded or, if of sufficient purity, dried to produce a soy
protein product. To decrease the impurities content, the
supernatant may be processed, with acidification, such as to pH
about 1.5 to about 4.4, preferably about 2.0 to about 4.0, or
without acidification and dried by any convenient means to yield
one or more soy protein products. The supernatant stream is
enriched in trypsin inhibitors due to the fractionation occurring
on dilution. The supernatant may be processed to yield a dry
protein product high in trypsin inhibitor activity or the process
steps may be geared to reduce the trypsin inhibitor activity of the
protein derived from this stream. If processed without
acidification, heat treatment of the supernatant before or after
concentration may be employed to precipitate a fraction of heat
sensitive proteins, while the trypsin inhibitors stay largely in
solution. Alternatively, the supernatant may be concentrated at low
pH and then the sample adjusted in pH to about 6 to about 7, using
any convenient alkali, such as sodium hydroxide, prior to the
application of the heat treatment to precipitate the heat sensitive
proteins. Such a heat treatment may be effected at a temperature of
about 70.degree. C. to about 120.degree. C., preferably about
75.degree. C. to about 105.degree. C. for about 1 minute to about
30 minutes, preferably about 5 minutes to about 15 minutes. The
heat precipitated proteins may be removed in any convenient manner,
such as centrifugation or filtration or a combination thereof. The
precipitate then may be washed with about 1 to about 10, preferably
about 2 volumes of water to remove entrapped supernatant, then
recovered as above and dried by any convenient means to provide a
soy protein product with a reduced trypsin inhibitor content.
[0080] Heat treatment of the acidified supernatant may be used to
inactivate heat-labile trypsin inhibitors. Partially concentrated
or fully concentrated acidified soy protein solution may also be
heat treated to inactivate heat labile trypsin inhibitors.
Generally, the protein solution is heated to a temperature of about
70.degree. to about 120.degree. C., preferably about 85.degree. to
about 95.degree. C., for about 10 seconds to about 60 minutes,
preferably about 30 seconds to about 5 minutes. The heat treated
acidified soy protein solution then may be cooled to a temperature
of about 2.degree. C. to about 60.degree. C., preferably about
20.degree. to about 35.degree. C. for further processing.
[0081] The supernatant or the acidified and optionally heat treated
supernatant or the centrate resulting from the removal of proteins
deposited by heat treatment of the supernatant, which may
optionally be acidified after the removal of the precipitated
protein, such as to pH about 1.5 to about 4.4, preferably about 2.0
to about 4.0, may be concentrated to increase the protein
concentration thereof. Such concentration is effected using any
convenient selective membrane technique, such as ultrafiltration or
diafiltration, using membranes with a suitable molecular weight
cut-off permitting low molecular weight species, including salt,
carbohydrates, pigments, trypsin inhibitors and other low molecular
weight materials extracted from the protein source material, to
pass through the membrane, while retaining a significant proportion
of the soy protein in the solution. Ultrafiltration membranes
having a molecular weight cut-off of about 3,000 to 1,000,000
Daltons, preferably about 5,000 to about 100,000 Daltons, having
regard to differing membrane materials and configuration, may be
used. Concentration of the protein solution in this way also
reduces the volume of liquid required to be dried to recover the
protein. The protein solution generally is concentrated to a
protein concentration of about 50 g/L to about 400 g/L, preferably
about 100 to about 250 g/L, prior to drying. Such concentration
operation may be carried out in a batch mode or in a continuous
operation, as described above.
[0082] The soy protein solution may be subjected to a diafiltration
step, before or after complete concentration, using water or a
dilute salt solution. The water or dilute salt solution may be at
its natural pH or at a pH equal to that of the protein solution
being diafiltered or at any pH value in between. Such diafiltration
may be effected using from about 2 to about 40 volumes of
diafiltration solution, preferably about 5 to about 25 volumes of
diafiltration solution. In the diafiltration operation, further
quantities of contaminants are removed from the clear aqueous soy
protein solution by passage through the membrane with the permeate.
The diafiltration operation may be effected until no significant
further quantities of contaminants or visible colour are present in
the permeate or until the protein solution has been sufficiently
purified so as, when dried, to provide a soy protein product with
the desired protein content, preferably an isolate with a protein
content of at least 90 wt % (N.times.6.25) d.b. Such diafiltration
may be effected using the same membrane as for the concentration
step. However, if desired, the diafiltration step may be effected
using a separate membrane with a different molecular weight cutoff,
such as a membrane having a molecular weight cut-off in the range
of about 3,000 to about 1,000,000 Daltons, preferably about 5,000
to about 100,000 Daltons, having regard to different membrane
materials and configuration.
[0083] The concentration step and the diafiltration step may be
effected herein in such a manner that the soy protein product
subsequently recovered by drying the concentrated and diafiltered
retentate contains less than about 90 wt % protein (N.times.6.25)
d.b., such as at least about 60 wt % protein (N.times.6.25) d.b. By
partially concentrating and/or partially diafiltering the aqueous
soy protein solution, it is possible to only partially remove
contaminants. This protein solution may then be dried to provide a
soy protein product with lower levels of purity.
[0084] An antioxidant may be present in the diafiltration medium
during at least part of the diafiltration step. The antioxidant may
be any convenient antioxidant, such as sodium sulfite or ascorbic
acid. The quantity of antioxidant employed in the diafiltration
medium depends on the materials employed and may vary from about
0.01 to about 1 wt %, preferably about 0.05 wt %. The antioxidant
serves to inhibit the oxidation of any phenolics present in the
concentrated soy protein solution.
[0085] The concentration step and the optional diafiltration step
may be effected at any convenient temperature, generally about
2.degree. C. to about 60.degree. C., preferably about 20.degree. C.
to about 35.degree. C., and for the period of time to effect the
desired degree of concentration and diafiltration. The temperature
and other conditions used to some degree depend upon the membrane
equipment used to effect the membrane processing, the desired
protein concentration of the solution and the efficiency of the
removal of contaminants to the permeate.
[0086] The concentration and/or diafiltration steps may be operated
in a manner favorable for removal of trypsin inhibitors in the
permeate along with the other contaminants. Removal of the trypsin
inhibitors is promoted by using a membrane of larger pore size,
such as 30,000 to 1,000,000 Daltons, operating the membrane at
elevated temperatures, such as 30 to 60.degree. C. and employing
greater volumes of diafiltration medium, such as 20 to 40
volumes.
[0087] Acidifying and membrane processing the protein solution at a
lower pH (1.5 to 3) may also reduce the trypsin inhibitor activity
relative to processing the solution at a higher pH (3 to 4.4) or
without acidification. When the protein solution is concentrated
and diafiltered at the low end of the pH range, it may be desired
to raise the pH of the retentate prior to drying. The pH of the
concentrated and diafiltered protein solution may be raised to the
desired value, for example pH 3, by the addition of any convenient
food grade alkali such as sodium hydroxide.
[0088] Further, a reduction in trypsin inhibitor activity may be
achieved by exposing soy materials to reducing agents that disrupt
or rearrange the disulfide bonds of the inhibitors. Suitable
reducing agents include sodium sulfite, cysteine and
N-acetylcysteine.
[0089] The addition of such reducing agents may be effected at
various stages of the overall process. The reducing agent may be
added to the supernatant or the centrate arising from a heat
precipitation step, may be added to the concentrated solution
before or after diafiltration or may be dry blended with the dried
soy protein product. The addition of the reducing agent may be
combined with a heat treatment step and the membrane processing
steps, as described above.
[0090] If it is desired to retain active trypsin inhibitors in the
concentrated protein solution, this can be achieved by eliminating
or reducing the intensity of the heat treatment step, not utilizing
reducing agents, operating the concentration and diafiltration
steps at higher pH values, utilizing a concentration and
diafiltration membrane with a smaller pore size, operating the
membrane at lower temperatures and employing fewer volumes of
diafiltration medium.
[0091] The concentrated and optionally diafiltered aqueous protein
solution may be treated with an adsorbent, such as powdered
activated carbon or granulated activated carbon, to remove colour
and/or odour compounds. Such adsorbent treatment may be carried out
under any convenient conditions, generally at the ambient
temperature of the protein solution. For powdered activated carbon,
an amount of about 0.025% to about 5% w/v, preferably about 0.05%
to about 2% w/v, is employed. The adsorbent may be removed from the
soy protein solution by any convenient means, such as by
filtration.
[0092] The concentrated and optionally diafiltered aqueous soy
protein solution then may be dried by any convenient technique,
such as spray drying or freeze drying. The dry soy protein product
has a protein content of at least about 60 wt % (N.times.6.25)
d.b., preferably in excess of about 90 wt % (N.times.6.25) d,b.,
more preferably at least about 100 wt % (N.times.6.25), d.b. The
soy protein product is low in phylic acid content, generally less
than about 1.5% by weight.
[0093] As mentioned above, the settled protein precipitate formed
in the dilution step may be directly dried to yield the protein
product. Alternatively, the wet protein precipitate may be
re-suspended in water, such as about 2 to about 3 volumes, and
re-solubilized by adjusting the pH of the sample to about 1.5 to
about 4.4, preferably about 2.0 to about 4.0, using any convenient
acid, such as hydrochloric acid or phosphoric acid. The clear
protein solution then may be dried by any convenient technique,
such as spray drying or freeze drying to a dry form. The dry
protein product has a protein content in excess of about 60 wt %
protein, preferably at least about 90 wt % protein, more preferably
at least about 100 wt % protein (N.times.6.25)
[0094] As a further alternative, the clear, acidified,
re-solubilized soy protein solution may be subjected to a heat
treatment to inactivate any remaining heat labile anti-nutritional
factors. Such a heating step also provides the additional benefit
of reducing the microbial load. Generally, the protein solution is
heated to a temperature of about 70.degree. to about 120.degree.
C., preferably about 85' to about 95.degree. C., for about 10
seconds to about 60 minutes, preferably about 30 seconds to about 5
minutes. The heat treated, acidified soy protein solution then may
be cooled for further processing as described below, to a
temperature of about 2.degree. to about 60.degree. C., preferably
about 20.degree. to about 35.degree. C.
[0095] The acidified and optionally heat treated clear solution,
may be concentrated to increase the protein concentration thereof.
Such concentration is effected using any convenient selective
membrane technique, such as ultrafiltration or diafiltration, using
membranes with a suitable molecular weight cut-off permitting low
molecular weight species, including salt, carbohydrates, pigments,
trypsin inhibitors and other low molecular weight materials
extracted from the protein source material, to pass through the
membrane, while retaining a significant proportion of the soy
protein in the solution. Ultrafiltration membranes having a
molecular weight cut-off of about 3,000 to 1,000,000 Daltons,
preferably about 5,000 to about 100,000 Daltons, having regard to
differing membrane materials and configuration, may be used.
Concentration of the protein solution in this way also reduces the
volume of liquid required to be dried to recover the protein. The
protein solution generally is concentrated to a protein
concentration of about 50 g/L to about 300 g/L, preferably about
100 to about 200 g/L, prior to drying. Such concentration operation
may be carried out in a batch mode or in a continuous operation, as
described above.
[0096] The soy protein solution may be subjected to a diafiltration
step before or after complete concentration using water. The water
may be at its natural pH or at a pH equal to that of the protein
solution being diafiltered or at any pH value in between. Such
diafiltration may be effected using from about 2 to about 40
volumes of diafiltration solution, preferably about 5 to about 25
volumes of diafiltration solution. In the diafiltration operation,
further quantities of contaminants are removed from the clear
aqueous soy protein solution by passage through the membrane with
the permeate. The diafiltration operation may be effected until no
significant further quantities of contaminants or visible colour
are present in the permeate or until the retentate has been
sufficiently purified so as, when dried, to provide a soy protein
product with the desired protein content, preferably an isolate
with a protein content of at least about 90 wt % (N.times.6.25)
d.b. Such diafiltration may be effected using the same membrane as
for the concentration step. However, if desired, the diafiltration
step may be effected using a separate membrane with a different
molecular weight cut-off, such as a membrane having a molecular
weight cut-off in the range of about 3,000 to about 1,000,000
Daltons, preferably about 5,000 to about 100,000 Daltons, having
regard to different membrane materials and configuration.
[0097] The concentration step and the diafiltration step may be
effected herein in such a manner that the soy protein product
subsequently recovered by drying the concentrated and diafiltered
retentate contains less than about 90 wt % protein (N.times.6.25)
d.b., such as at least about 60 wt % protein (N.times.6.25) d.b. By
partially concentrating and/or partially diafiltering the aqueous
soy protein solution, it is possible to only partially remove
contaminants. This protein solution may then be dried to provide a
soy protein product with lower levels of purity. The soy protein
product is still able to produce clear protein solutions under
acidic conditions.
[0098] An antioxidant may be present in the diafiltration medium
during at least part of the diafiltration step. The antioxidant may
be any convenient antioxidant, such as sodium sulfite or ascorbic
acid. The quantity of antioxidant employed in the diafiltration
medium depends on the materials employed and may vary from about
0.01 to about 1 wt %, preferably about 0.05 wt %. The antioxidant
serves to inhibit the oxidation of any phenolics present in the
concentrated soy protein solution.
[0099] The optional concentration step and the optional
diafiltration step may be effected at any convenient temperature,
generally about 2.degree. to about 60.degree. C., preferably about
20.degree. to about 35.degree. C., and for the period of time to
effect the desired degree of concentration and diafiltration. The
temperature and other conditions used to some degree depend upon
the membrane equipment used to effect the membrane processing, the
desired protein concentration of the solution and the efficiency of
the removal of contaminants to the permeate.
[0100] As mentioned above, the level of trypsin inhibitor activity
in the final soy protein product can be controlled by manipulation
of various process variables,
[0101] As previously noted, heat treatment of the acidified aqueous
soy protein solution may be used to inactivate heat-labile trypsin
inhibitors. Partially concentrated or fully concentrated acidified
soy protein solution may also be heat treated to inactivate heat
labile trypsin inhibitors.
[0102] In addition, the concentration and/or diafiltration steps
may be operated in a manner favorable for removal of trypsin
inhibitors in the permeate along with the other contaminants.
Removal of the trypsin inhibitors is promoted by using a membrane
of larger pore size, such as 30,000 to 1,000,000 Daltons, operating
the membrane at elevated temperatures, such as 30.degree. to
60.degree. C. and employing greater volumes of diafiltration
medium, such as 20 to 40 volumes.
[0103] Acidifying and membrane processing the protein solution at a
lower pH (1.5 to 3) may reduce the trypsin inhibitor activity
relative to processing the solution at higher pH (3 to 4.4). When
the protein solution is concentrated and diafiltered at the low end
of the pH range, it may be desired to raise the pH of the retentate
prior to drying. The pH of the concentrated and diafiltered protein
solution may be raised to the desired value, for example pH 3, by
the addition of any convenient food grade alkali such as sodium
hydroxide.
[0104] Further, a reduction in trypsin inhibitor activity may be
achieved by exposing soy materials to reducing agents that disrupt
or rearrange the disulfide bonds of the inhibitors. Suitable
reducing agents include sodium sulfite, cysteine and
N-acetylcysteine.
[0105] The addition of such reducing agents may be effected at
various stages of the overall process. The reducing agent may be
added to the wet protein precipitate resulting from the dilution
step, may be added to the protein solution formed by acidifying and
re-solubilizing the precipitate, may be added to the concentrated
solution before or after diafiltration or may be dry blended with
the dried soy protein product. The addition of the reducing agent
may be combined with a heat treatment step and the membrane
processing steps, as described above.
[0106] If it is desired to retain active trypsin inhibitors in the
concentrated protein solution, this can be achieved by eliminating
or reducing the intensity of the heat treatment step, not utilizing
reducing agents, operating the concentration and diafiltration
steps at the higher end of the pH range (3 to 4.4), utilizing a
concentration and diafiltration membrane with a smaller pore size,
operating the membrane at lower temperatures and employing fewer
volumes of diafiltration medium.
[0107] The acidified, optionally concentrated and optionally
diafiltered clear aqueous protein solution may be treated with an
adsorbent, such as powdered activated carbon or granulated
activated carbon, to remove colour and/or odour compounds. Such
adsorbent treatment may be carried out under any convenient
conditions, generally at the ambient temperature of the protein
solution. For powdered activated carbon, an amount of about 0.025%
to about 5% w/v, preferably about 0.05% to about 2% is employed.
The adsorbent may be removed from the soy protein solution by any
convenient means, such as by filtration.
[0108] The acidified, optionally concentrated and optionally
diafiltered clear aqueous soy protein solution then may be dried by
any convenient technique, such as spray drying or freeze drying.
The dry soy protein product has a protein content of at least about
60 wt % (N.times.6.25) d.b., preferably in excess of about 90 wt %
(N.times.6.25) d.b., more preferably at least about 100 wt %
(N.times.6.25) d.b. The soy protein product is low in phytic acid
content, generally less than about 1.5% by weight.
[0109] In accordance with another aspect of the current invention,
the protein precipitated upon dilution into water may be processed
together with the supernatant. In such a case, the degree of
dilution is generally about 1 to 25 fold, preferably about 3 to
about 12 fold. The water with which the concentrated protein
solution is mixed has a temperature of about 1.degree. to about
60.degree. C., preferably about 15.degree. C. to about 35.degree.
C.
[0110] The dilution water, containing the deposited protein
precipitate, is adjusted in pH to about 1.5 to about 4.4,
preferably about 2.0 to about 4.0, using any convenient acid, such
as hydrochloric acid or phosphoric acid. The drop in pH causes the
resolubilization of the protein deposited by dilution yielding a
clear, acidified protein solution. The protein solution may be used
in the wet form or may be dried, by any convenient technique, such
as spray drying or freeze drying, to a dry form.
[0111] As a further alternative, the protein solution formed by
acidifying the mixture of protein precipitate and supernatant may
be processed utilizing the same steps as described above for the
isolated precipitate resolubilized by acidification.
[0112] The optionally concentrated, optionally diafiltered,
optionally heat treated, optional adsorbent treated clear aqueous
soy protein solution then may be dried by any convenient technique,
such as spray drying or freeze drying. The dry soy protein product
has a protein content in excess of about 60 wt % protein,
preferably at least about 90 wt %, more preferably about 100 wt %
(N.times.6.25) d.b.
[0113] The soy protein products produced herein are soluble in an
acidic aqueous environment, making the products ideal for
incorporation into beverages, both carbonated and uncarbonated, to
provide protein fortification thereto. Such beverages have a wide
range of acidic pH values, ranging from about 2.5 to about 5. The
soy protein products provided herein may be added to such beverages
in any convenient quantity to provide protein fortification to such
beverages, for example, at least about 5 g of the soy protein per
serving. The added soy protein product dissolves in the beverage
and does not impair the clarity of the beverage, even after thermal
processing.
[0114] The soy protein product may be blended with dried beverage
prior to reconstitution of the beverage by dissolution in water. In
some cases, modification of the normal formulation of the beverage
to tolerate the composition of the invention may be necessary where
components present in the beverage may adversely affect the ability
of the composition to remain dissolved in the beverage.
EXAMPLES
Example 1
[0115] This Example illustrates the production of a soy protein
isolate that is soluble, transparent and heat stable in acidic
solutions and is membrane processed at natural pH. The production
of this isolate does not involve a dilution step.
[0116] 20 kg of defatted, minimally heat processed soy flour was
added to 200 L of 0.15 M CaCl.sub.2 solution at ambient temperature
and agitated for 30 minutes to provide an aqueous protein solution.
The residual soy flour was removed and the resulting protein
solution was clarified by centrifugation and filtration to produce
169 L of filtered protein solution having a protein content of
1.68% by weight.
[0117] The filtered protein extract solution was reduced in volume
to 31 L by concentration on a PVDF membrane having a molecular
weight cutoff of 5,000 Daltons. The concentrated protein solution
was diafiltered with 62 L of 0.075M CaCl.sub.2. The resulting
diafiltered, concentrated protein solution had a protein content of
13.28% by weight and represented a yield of 95.2 wt % of the
initial filtered protein solution. The diafiltered, concentrated
protein solution was then dried to yield a product found to have a
protein content of 91.45% (N.times.6.25) d.b. The product was
termed S005-L11-08A S702.
[0118] A 3.2% w/v protein solution of 5702 was prepared in water
and the pH lowered to 3 with diluted HCl. The colour and clarity
was then assessed using a HunterLab ColorQuest XE instrument
operated in transmission mode.
[0119] The colour and clarity values are set forth in the following
Table 1:
TABLE-US-00001 TABLE 1 HunterLab scores for 3.2% protein solution
of S005-L11-08A S702 at pH 3 sample L* a* b* haze (%) S702 96.51
-0.82 11.45 0.8
[0120] As may be seen from Table 1, the colour of the S702 solution
at pH 3 was very light and the haze level was very low.
[0121] The colour of the dry powder was also assessed with the
HunterLab ColorQuest XE instrument in reflectance mode. The colour
values are set forth in the following Table 2:
TABLE-US-00002 TABLE 2 HunterLab scores for S005-L11-08A S702 dry
powder sample L* a* b* S702 85.11 0.37 11.11
[0122] As may be seen from Table 2, the dry colour of the S702
powder was very light.
[0123] The trypsin inhibitor activity of the isolate was determined
using the method of Kakade et al, Cereal Chem., 51:376-381 (1974),
The S005-L11-08A S702 was found to have a trypsin inhibitor
activity of 87 trypsin inhibitor units (TIU)/mg protein
(N.times.6.25).
Example 2
[0124] This Example contains an evaluation of the heat stability in
water of the soy protein isolate produced by the method of Example
1 (S702).
[0125] A 2% w/v protein solution of S005-L11-08A S702 in water was
produced and the pH adjusted to 3. The clarity of this solution was
assessed by haze measurement with the HunterLab ColorQuest XE
instrument. The solution was then heated to 95.degree. C., held at
this temperature for 30 seconds and then immediately cooled to room
temperature in an ice bath. The clarity of the heat treated
solution was then measured again.
[0126] The clarity of the protein solution before and after heating
is set forth in the following Table 3:
TABLE-US-00003 TABLE 3 Effect of heat treatment on clarity of S702
solution sample haze (%) before heating 5.0 after heating 0.6
[0127] As can be seen from the data in Table 3, the sample was heat
stable. The protein solution was initially very clear and the heat
treatment actually reduced the level of haze.
Example 3
[0128] This Example contains an evaluation of the solubility in
water of the soy protein isolate produced by the method of Example
1 (S702). Solubility was tested based on protein solubility (termed
protein method, a modified version of the procedure of Mon et al.,
J. Food Sci. 50:17154718) and total product solubility (termed
pellet method).
[0129] Sufficient protein powder to supply 0.5 g of protein was
weighed into a beaker and then a small amount of reverse osmosis
(RO) purified water was added and the mixture stirred until a
smooth paste formed. Additional water was then added to bring the
volume to approximately 45 ml. The contents of the beaker were then
slowly stirred for 60 minutes using a magnetic stirrer. The pH was
determined immediately after dispersing the protein and was
adjusted to the appropriate level (2, 3, 4, 5, 6 or 7) with diluted
NaOH or HCl. A sample was also prepared at natural pH. For the pH
adjusted samples, the pH was measured and corrected two times
during the 60 minutes stirring. After the 60 minutes of stirring,
the samples were made up to 50 ml total volume with RO water,
yielding a 1% w/v protein dispersion. The protein content of the
dispersions was measured using a Leco FP528 Nitrogen Determinator.
Aliquots (20 ml) of the dispersions were then transferred to
pre-weighed centrifuge tubes that had been dried overnight in a
100.degree. C. oven then cooled in a desiccator and the tubes
capped. The samples were centrifuged at 7800 g for 10 minutes,
which sedimented insoluble material and yielded a clear
supernatant. The protein content of the supernatant was measured by
Leco analysis and then the supernatant and the tube lids were
discarded and the pellet material dried overnight in an oven set at
100.degree. C. The next morning the tubes were transferred to a
desiccator and allowed to cool. The weight of dry pellet material
was recorded. The dry weight of the initial protein powder was
calculated by multiplying the weight of powder used by a factor of
((100-moisture content of the powder (%))/100). Solubility of the
product was then calculated two different ways:
[0130] 1) Solubility (protein method) (%) (% protein in
supernatant/% protein in initial dispersion).times.100
[0131] 2) Solubility (pellet method) (%) (1-(weight dry insoluble
pellet material/((weight of 20 ml of dispersion/weight of 50 ml of
dispersion).times.initial weight dry protein
powder))).times.100
[0132] The natural pH value of the protein isolate produced in
Example 1 in water (1% protein) is shown in Table 4:
TABLE-US-00004 TABLE 4 Natural pH of S702 solution prepared in
water at 1% protein Batch Product Natural pH S005-L11-08A S702
5.91
[0133] The solubility results obtained are set forth in the
following Tables 5 and 6:
TABLE-US-00005 TABLE 5 Solubility of S702 at different pH values
based on protein method Solubility (protein method) (%) Batch
Product pH 2 pH 3 pH 4 pH 5 pH 6 pH 7 Nat. pH S005- S702 98.2 95.8
100 94.2 15.1 11.2 10.9 L11-08A
TABLE-US-00006 TABLE 6 Solubility of S702 at different pH values
based on pellet method Solubility (pellet method) (%) Batch Product
pH 2 pH 3 pH 4 pH 5 pH 6 pH 7 Nat. pH S005- S702 98.5 100 97.3 26.6
10.2 32.0 28.3 L11-08A
[0134] As can be seen from the results of Tables 5 and 6, the S702
products were very soluble in the pH range of 2 to 4.
Example 4
[0135] This Example contains an evaluation of the clarity in water
of the soy protein isolate produced by the method of Example 1
(S702).
[0136] The clarity of the 1% w/v protein solution prepared as
described in Example 3 was assessed by measuring the absorbance at
600 nm, with a lower absorbance score indicating greater clarity.
Analysis of the samples on a HunterLab ColorQuest XE instrument in
transmission mode also provided a percentage haze reading, another
measure of clarity.
[0137] 101161 The clarity results are set forth in the following
Tables 7 and 8:
TABLE-US-00007 TABLE 7 Clarity of S702 solution at different pH
values as assessed by A600 A600 Batch Product pH 2 pH 3 pH 4 pH 5
pH 6 pH 7 Nat. pH S005- S702 0.012 0.019 0.094 >3.0 2.201 2.422
2.283 L11-08A
TABLE-US-00008 TABLE 8 Clarity of S702 solution at different pH
values as assessed by HunterLab analysis HunterLab haze reading (%)
Batch Product pH 2 pH 3 pH 4 pH 5 pH 6 pH 7 Nat. pH S005- S702 0.0
2.2 16.0 97.3 97.6 100.1 101.9 L11-08A
[0138] As can be seen from the results of Tables 8 and 9, solutions
of S702 were very clear at pH 2 and 3, but were slightly hazy at pH
4.
Example 5
[0139] This Example contains an evaluation of the solubility in a
soft drink (Sprite) and a sports drink (Orange Gatorade) of the soy
protein isolate produced by the method of Example I (S702). The
solubility was determined with the protein added to the beverages
with no pH correction and again with the pH of the protein
fortified beverages adjusted to the level of the original
beverages.
[0140] When the solubility was assessed with no pH correction, a
sufficient amount of protein powder to supply I g of protein was
weighed into a beaker and a small amount of beverage was added and
stirred until a smooth paste formed. Additional beverage was added
to bring the volume to 50 ml, and then the solutions were stirred
slowly on a magnetic stirrer for 60 minutes to yield a 2% protein
w/v dispersion. The protein content of the samples was analyzed
using a LECO FP528 Nitrogen Determinator then an aliquot of each of
the protein containing beverages was centrifuged at 7800 g for 10
minutes and the protein content of the supernatant measured in each
sample.
Solubility (%)=(% protein in supernatant/% protein in initial
dispersion).times.100
[0141] When the solubility was assessed with pH correction, the pH
of the soft drink (Sprite) (3.39) and the sports drink (Orange
Gatorade) (3.19) without protein was measured. A sufficient amount
of protein powder to supply 1 g of protein was weighed into a
beaker and a small amount of beverage was added and stirred until a
smooth paste formed. Additional beverage was added to bring the
volume to approximately 45 ml, and then the solutions were stirred
slowly on a magnetic stirrer for 60 minutes. The pH of the protein
containing beverages was measured and then adjusted to the original
no-protein pH with HCl or NaOH as necessary. The total volume of
each solution was then brought to 50 ml with additional beverage,
yielding a 2% protein w/v dispersion. The protein content of the
samples was analyzed using a LECO FP528 Nitrogen Determinator then
an aliquot of the protein containing beverages was centrifuged at
7800 g for 10 minutes and the protein content of the supernatant
measured.
Solubility (%)=(% protein in supernatant/% protein in initial
dispersion).times.100
[0142] The results obtained are set forth in the following Table
9:
TABLE-US-00009 TABLE 9 Solubility of S702 in Sprite and Orange
Gatorade no pH correction pH correction Solubility Solubility
Solubility (%) Solubility (%) (%) in in Orange (%) in Orange Batch
Product Sprite Gatorade in Sprite Gatorade S005-L11-08A S702 100
100 96.4 100
[0143] As can be seen from the results of Table 9, the S702 protein
was extremely soluble in both the Sprite and the Orange Gatorade.
Note that the S702 is a neutral pH product but the slightly higher
pH of the non-corrected beverage samples did not appear to
negatively affect the solubility.
Example 6
[0144] This Example contains an evaluation of the clarity in a soft
drink and sports drink f the soy protein isolate produced by the
method of Example 1 (S702).
[0145] The clarity of the 2% w/v protein dispersions prepared in a
soft drink (Sprite) and a sports drink (Orange (liatorade) in
Example 5 were assessed for clarity using the methods described in
Example 4. For the absorbance measurements at 600 nm, the
spectrophotometer was blanked with the appropriate beverage before
the measurement was performed.
[0146] The results obtained are set forth in the following Tables
10 and 11:
TABLE-US-00010 TABLE 10 Clarity (A600) of S702 in Sprite and Orange
Gatorade no pH correction pH correction A600 in A600 in A600 in
Orange A600 in Orange Batch Product Sprite Gatorade Sprite Gatorade
S005-L11-08A S702 0.209 0.520 0.158 0.204
TABLE-US-00011 TABLE 11 HunterLab haze readings for S702 in Sprite
and Orange Gatorade no pH correction pH correction haze haze (%) in
haze haze (%) in (%) in Orange (%) in Orange Batch Product Sprite
Gatorade Sprite Gatorade no protein 0.0 44.0 0.0 44.0 S005-L11-08A
S702 35.7 80.8 32.6 65.6
[0147] As can be seen from the results of Tables 10 and 11, despite
the excellent solubility, Sprite and Orange Gatorade samples
containing S702 were somewhat hazy. Correcting the pH reduced the
haze level only slightly.
Example 7
[0148] This Example was conducted to extract the soy protein source
with calcium chloride solution at various pH values.
[0149] Three samples of defatted, minimally heat processed soy
flour (10 g each) were extracted with 0.15M CaCl.sub.2 (100 ml) for
30 minutes at room temperature with a magnetic stirrer/stir bar.
One sample was extracted at natural pH, one sample was adjusted to
pH 2.98 with dilute HCl and the third sample was adjusted to pH
8.55 with dilute NaOH. The pH of the extraction systems was
adjusted immediately after wetting the flour. After the extraction,
the samples were centrifuged at 10,200 g for 10 minutes to separate
extract from the spent meal. The supernatant was then further
clarified by filtration through a 0.45 .mu.m pore size syringe
filter. Filtrates were analyzed for pH, conductivity, clarity
(A600) and protein content (Leco). A sample of filtrate was also
diluted 1:1 with an equal volume of RO water and the A600 measured
again, Diluted and undiluted filtrate samples were acidified to pH
3 with diluted HCl and the A600 measured again.
[0150] The properties of the filtrates obtained are set forth in
the following Table 12:
TABLE-US-00012 TABLE 12 Properties of initial extracts sample A600
% protein Extractability (%) cond. (mS) natural pH 0.072 3.00 55.2
22.9 pH 2.98 0.109 3.88 71.5 27.9 pH 8.55 0.139 3.46 63.7 23.0
[0151] As may be seen in Table 12, the low pH conditions extracted
the highest amount of protein. However, the extractability was
quite good at all the pH conditions evaluated.
[0152] The clarity of the acidified, full strength extracts is set
forth in the following Table 13:
TABLE-US-00013 TABLE 13 Effect of acidification on clarity of full
strength extracts sample initial pH final pH final A600 natural pH
5.44 2.94 0.052 pH 2.98 3.10 3.10 0.109 pH 8.55 8.18 2.78 0.140
[0153] As can be seen from Table 13, upon acidification, all of the
extracts were quite clear, but the sample extracted at natural pH
was the clearest.
[0154] The clarity of the acidified, diluted extracts is set forth
in the following Table 14:
TABLE-US-00014 TABLE 14 Effect of acidification on clarity of
diluted extracts sample initial pH initial A600 final pH final A600
natural pH 5.53 2.582 2.93 0.046 pH 2.98 3.22 0.056 2.81 0.050 pH
8.55 8.14 2.756 3.05 0.112
[0155] As may be seen from Table 14, when the samples were diluted
1:1 with water and then acidified, all samples again were quite
clear. However, the clarity of the samples extracted at natural and
acidic pH was better than the sample extracted at high pH.
Example 8
[0156] This Example illustrates the production of soy protein
isolate that is soluble, transparent and heat stable in acidic
solutions and is membrane processed at natural pH then fractionated
by a dilution step.
[0157] `a` kg of soy `b` was added to `c` L of 0.15 M CaCl.sub.2
solution at ambient temperature and agitated for 30 minutes to
provide an aqueous protein solution. The residual soy protein
source was removed and the resulting protein solution was clarified
by centrifugation and filtration to produce L filtered protein
solution having a protein content of `e` % by weight.
[0158] `f` L of the protein extract solution was reduced to `g` on
a `h` membrane having a molecular weight cutoff of `i` Daltons,
producing a concentrated protein solution with a protein content of
`j` % by weight. The concentrated protein solution was then
diafiltered with `k` L of 0.15M CaCl.sub.2 solution on the same
membrane used for the initial concentration step. The diafiltered
protein solution was then further concentrated to `l` kg on the
same membrane used for the initial concentration and diafiltration
steps, producing a concentrated protein solution with a protein
content of wt %.
[0159] `n` kg of the concentrated or concentrated and diafiltered
protein solution at `o`.degree. C. was then diluted into reverse
osmosis (RO) purified water having a temperature of `q`.degree. C.
A white cloud formed immediately and was allowed to settle. The
supernatant was removed by centrifugation and the precipitated
protein was recovered in a yield of wt % of the filtered protein
solution. The recovered `s` kg of protein precipitate was then
washed with about volumes of water and the water decanted. `u` of
the washed precipitate was then resolubilized in about `v` volumes
of water with sufficient diluted hydrochloric acid added to adjust
the sample pH to An additional `x` kg of pH 3 RO water was added to
thin the resolubilized precipitate to facilitate spray drying. kg
of the re-solubilized precipitate was then spray dried. The dried
protein was found to have a protein content of `z`% (N.times.6.25)
d.b. The product was given the designation `aa` S7300. Another `ab`
kg of the re-solubilized precipitate fraction was heated to
90.degree. C. for 1 minute and then diluted with about `ac` L of RO
water to facilitate spray drying. The dried protein was found to
have a protein content of `ad`% (N.times.6.25) d.b. The product was
given a designation `aa` S7300H. The other `ae` of the washed
precipitate was resolubilized in about `af` volumes of water with
sufficient diluted phosphoric acid added to adjust the sample pH to
`ag`. `ah` kg of the re-solubilized precipitate fraction was then
spray dried. The dried protein was found to have a protein content
of `ai`% (N.times.5.25) d.b. The product was given a designation
`aa` S7300-02. The parameters `a` to `ai` are shown in the
following Table 15.
TABLE-US-00015 TABLE 15 Parameters for runs to produce S7300
products S013/ aa S005-C19-09A S013-J06-09A S013-J27-09A 15-K30-09A
a 20 50 40 40 b flour (defatted, white flake white flake white
flake minimally heat processed) c 200 500 400 400 d 172.9 276.4 325
330 e 2.25 2.47 2.44 2.38 f 172.9 275 325 330 g 19.7 kg 25.48 kg 22
kg 67 L h PES PES PES PES i 100,000 100,000 100,000 100,000 j 16.36
22.06 not determined 9.74 k n/a n/a n/a 335 l n/a n/a n/a 23.2 m
n/a n/a n/a 23.7 n 19.7 25 22 22.7 o 31.5 27 25.2 30 p 1:10 1:15
1:15 1:15 q 2.4 17.3 14.9 13 r 61.7 67.1 57.1 53.6 s 5.01 8.26 9.78
10.7 t 0 2 2 2 u all all half all v 1 2 2 1.7 w 1.97 3.20 2.81 3 x
8.5 0 0 0 y 18.5 11.36 16.2 26 z 98.76 101.74 100.92 100.73 ab n/a
12.57 n/a n/a ac n/a 26 n/a n/a ad n/a 101.60 n/a n/a ae n/a n/a
half n/a af n/a n/a 2 n/a ag n/a n/a 2.76 n/a ah n/a n/a 12.4 n/a
ai n/a n/a 94.32 n/a n/a = not applicable
[0160] 3.2% protein solutions of the S7300, S7300H and S7300-02
products were prepared in water and the colour and clarity assessed
using a HunterLab ColorQuest XE operated in transmission mode. The
pH of the solutions was measured with a pH meter.
[0161] The pH, colour and clarity values are set forth in the
following Table 16.
TABLE-US-00016 TABLE 16 pH and HunterLab scores for 3.2% protein
solutions of S7300, S7300H and S7300-02 batch sample pH L* a* b*
haze (%) S005-C19-09A S7300 2.27 97.10 -1.88 11.04 0.0 S013-J06-09A
S7300 3.01 95.08 -0.67 10.08 7.4 S013-J06-09A S7300H 2.99 88.50
-0.29 9.00 42.4 S013-J27-09A S7300 2.72 92.50 -0.60 10.17 29.6
S013-J27-09A S7300-G2 2.75 91.94 -0.23 9.51 36.3 S013/15-K30-G9A
S7300 2.92 95.90 -0.44 8.01 10.4
[0162] As may be seen by the results of Table 16, the pH of the
S005-C19-09A product ended up lower than the target pH of 3. This
could be remedied by simply adding less acid when re-solubilizing
the precipitate. Generally, these products produced lightly
coloured solutions with high degrees of transparency. The haze
values obtained for the solution of S013-J06-09A S7300H and the
solutions of the S013-J27-09A products were surprisingly high. It
is thought that the haze present in these samples may have arisen
from some difficulty in the spray drying process. The feed streams
for these samples entering the spray dryer were quite clear as
assessed by A600 measurement (data not shown). When the same 3.2%
w/v protein solutions of the 57300 products were evaluated on the
HunterLab again, one hour after preparation, the solutions were
notably clearer as set forth in the following Table 17.
TABLE-US-00017 TABLE 17 pH and HunterLab scores for 3.2% protein
solutions of S7300, S7300H and S7300-02 with measurement made one
hour after solution preparation batch sample L* a* b* haze (%)
S013-J06-09A S7300H 93.15 -0.40 9.13 22.8 S013-J27-09A S7300 95.27
-0.80 9.62 10.0 S013-J27-09A S7300-02 94.63 -0.46 8.95 18.1
[0163] The colour of the dry powders was also assessed with the
HunterLab in reflectance mode. The colour values are set forth in
the following Table 18.
TABLE-US-00018 TABLE 18 HunterLab scores for S7300, S7300H and
S7300-02 dry powders batch sample L* a* b* S005-C19-09A S7300 86.43
-1.91 12.70 S013-J06-09A S7300 87.38 -1.09 10.61 S013-J06-09A
S7300H 88.81 -0.82 8.00 S013-J27-09A S7300 88.11 -1.04 11.97
S013-J27-09A S7300-02 88.09 -0.73 11.31 S013/15-K30-09A S7300 88.17
-0.70 10.19
[0164] As may be seen from Table 18, the dry products were very
light in colour.
[0165] The trypsin inhibitor activity of the S7300 products was
determined using the method of Kakade et al, Cereal Chem.,
51:376-381 (1974). The results obtained are shown in the following
Table 19.
TABLE-US-00019 TABLE 19 Trypsin Inhibitor Activity (TIA) for S7300,
S7300H and S7300-02 in TIU/mg protein (N .times. 6.25) batch sample
TIA S005-C19-09A S7300 49 S013-J06-09A S7300 11.8 S013-J06-09A
S7300H 3.1 S013-J27-09A S7300 37.7 S013-J27-09A S7300-02 36.6
S013/15-K30-09A S7300 47.5
[0166] As may be seen from Table 19, the products prepared from the
precipitate formed upon dilution of the concentrated protein
solution had a lower trypsin activity than was found in Example 1
for a product (S702) prepared similarly, but without the dilution
step. The value of washing the precipitate with water before
re-solubilizing and drying is unclear based on the variability in
the results. A very low TIA was obtained by heat treating the
re-solubilized precipitated protein. Comparing the results in Table
19 to the trypsin inhibitor activity values for the supernatants
from the same dilution steps illustrates that the dilution does
fractionate the precipitated protein away from the trypsin
inhibitors. The trypsin inhibitor activities of the supernatants
are shown in Table 20.
TABLE-US-00020 TABLE 20 Trypsin Inhibitor Activity (TIA) for
unprocessed supernatants in TIU/mg protein (N .times. 6.25) batch
TIA S005-C19-09A not determined S013-J06-09A 294.0 S013-J27-09A
219.2 S013/15-K30-09A 272.6
[0167] As may be seen from Table 20, the TIA of the supernatants
was notably higher than the precipitate derived products.
Example 9
[0168] This Example illustrates methods of processing the
supernatant streams arising from the procedures of Example 8 to
form additional soy protein products.
[0169] The pH of the supernatant from the dilution step was
adjusted from `a` to `b` by the addition of diluted HCl. `c` L of
supernatant was then reduced to `d` kg on a `e` membrane with a
molecular weight cutoff of `f` Daltons. The concentrated protein
solution had a protein concentration of `g` wt %. With additional
protein recovered from the supernatant, the overall recovery of the
filtered protein solution was `h`%. kg of the concentrated
supernatant was spray dried to form a product with a protein
content of `j` (N.times.6.25) d.b. The product was given the
designation `k` S7200. `l` kg of the concentrated supernatant was
adjusted to pH `m` with diluted sodium hydroxide solution. kg of
the concentrated supernatant was then heat treated at 85.degree. C.
for 10 minutes, which precipitated about `o`% of the protein
associated with the concentrated supernatant. `p` kg of
precipitated protein was recovered by centrifugation and washed
with about `q` volumes of RO water then recovered by centrifugation
again. `r` kg of washed precipitate was freeze dried to form a
product with a protein content of `s` % (N.times.6.25) d.b. This
product was designated `k` S7200P. The centrate containing the
protein not precipitated by the heat treatment was filtered and
then spray dried to form a product with a protein content of %
(N.times.6.25) d.b. This product was designated `k` S7200H.
Parameters `a` to T are set forth in the following Table 21.
TABLE-US-00021 TABLE 21 Parameters for the production of S7200
products from the dilution supernatants prepared as shown in
Example 8 S013/ k S005-C19-09A S013-J06-09A S013-J27-09A 15-K30-09A
a 6.26 5.66 5.74 5.82 b 3.16 n/a 1.96 n/a c 200 370 355 335 d 5.34
19.96 20 19.74 e PES PES PES PES f 10,000 100,000 100,000 100,000 g
7.32 3.34 3.77 3.30 h 71.7 76.9 66.6 61.9 i 5.34 n/a n/a n/a j
91.66 n/a n/a n/a l n/a n/a 19.3 n/a m n/a n/a 6.57 n/a n n/a 19.96
19.3 19.74 o n/a 61.2 71.6 69.2 p n/a 2.42 3.08 2.58 q n/a 0 2 2 r
n/a 2.06 2.70 2.14 s n/a 99.78 98.06 101.61 t n/a 81.49 70.24 not
determined n/a = not applicable
[0170] 3.2% protein solutions of the S7200 and S7200H products were
prepared in water and the colour and clarity assessed using a
HunterLab ColorQuest XE operated in transmission mode. The pH of
the solutions was measured with a meter. The S7200P was poorly
soluble and so the colour and clarity of this sample was not
tested.
[0171] The pH, colour and clarity values are set forth in the
following Table 22.
TABLE-US-00022 TABLE 22 pH and HunterLab scores for 3.2% protein
solutions of S7200 and S7200H batch sample pH L* a* b* haze (%)
S005-C19-09A S7200 3.04 95.86 -1.07 9.95 3.4 S013-J06-09A S7200H
5.80 95.82 -1.36 11.44 42.9 S013-J27-09A S7200H 6.24 96.18 -0.93
9.82 23.9 S013/15- S7200H not K30-09A determined
[0172] As may be seen from Table 22, all the supernatant derived
products yielded lightly coloured solutions. However, the
S013406-09A and S013-J27-09A products were hazier than the
S005-C19-09A product. This difference may be attributable to many
different factors such as differences in pH, processing and soy
protein source. However, the spray drying issues mentioned in
Example 8 may have played a role. The centrates arising from the
removal of the heat deposited protein from the concentrated
supernatant were filtered and quite clear as assessed by A600
measurement prior to the drying step.
[0173] The colour of the dry powders was also assessed with the
Hunter ab in reflectance mode. The colour values are set forth in
the following Table 23.
TABLE-US-00023 TABLE 23 HunterLab scores for S7200 and S7200H dry
powders batch sample L* a* b* S005-C19-09A S7200 87.30 -0.21 8.13
S013-J06-09A S7200H 86.99 -0.34 8.47 S013-J27-09A S7200H 85.97
-0.22 7.20 S013/15-K30-09A S7200H not determined
[0174] As may be seen from Table 23, the dry products were very
light in colour.
[0175] The trypsin inhibitor activity of the supernatant derived
products was determined using the method of Kakade et al. Cereal
Chem., 51:376-381 (1974). The results obtained are shown in the
following Table 24.
TABLE-US-00024 TABLE 24 Trypsin Inhibitor Activity (TIA) for S7200,
S7200P and S7200H in TIU/mg protein (N .times. 6.25) batch sample
TIA S005-C19-09A S7200 482 S013-J06-09A S7200P 78.6 S013-J27-09A
S7200P 8.7 S013/15-K30-09A S7200P 40.1 S013-J06-09A S7200H 296.7
S013-J27-09A S7200H 209.8 S013/15-K30-09A S7200H not determined
[0176] As may be seen from Table 24, the S7200P products had
notably lower trypsin inhibitor activities than the S7200H
products. This suggests that the trypsin inhibitors remain soluble
when the concentrated supernatant is fractionated by heat induced
precipitation. Lower TIA values for the S7200P were obtained when
the protein precipitate was washed with water before drying. The
particularly low value obtained for the S013-J127-09A S7200P may
also be related to the pH regimen employed in that trial.
Example 10
[0177] This Example illustrates the production of soy protein
isolate that is soluble, transparent and heat stable in acidic
solutions that employs membrane processing at natural pH and a
dilution step, but the protein fractions are not separated after
dilution.
[0178] `a` ml of diafiltered and concentrated retentate from
process run S013/S015-K30-09A, prepared as described in Example 8,
at approximately `b`.degree. C. was diluted with `c`ml of RO water
at approximately `d`.degree. C. A white cloud formed but when the
pH of the sample was lowered to `e` with diluted HCl the protein
re-solubilized. The protein content of the diluted and acidified
solution was `f` wt %. The diluted and acidified protein solution
was reduced from a volume of `g` ml to approximately `h` g on a `i`
membrane with a molecular weight cutoff of `j` Daltons, providing a
concentrated protein solution with a protein content of `k` wt %.
After removing a small sample of the concentrated protein solution
for analysis, `l` g of the concentrated protein solution was freeze
dried to provide `m` g of a product termed `n` S7301-01, which had
a protein content of `o` wt % w.b. The remaining `p` ml of
concentrated protein solution was diafiltered with `q` ml of RO
water on the same membrane as used for the concentration step. A
total of `r` g of diafiltered and concentrated protein solution was
obtained, having a protein content of `s` wt %. `t` g of this
solution was freeze dried to yield `u` g of a product termed `n`
S7301-02, which had a protein content of `v`% w.b. Parameters `a`
to `v` are shown in the following Table 25.
TABLE-US-00025 TABLE 25 Parameters for the production of S7301
products n trial 1 trial 2 a 250 120 b 20 24 c 750 1320 d 22 22 e
3.16 3.06 f 6.35 2.27 g 980 1422 h 492 257 i PES PES j 10,000
10,000 k 12.12 11.40 l 218.92 114.12 m 26.86 12.03 o 91.27 99.69 p
250 120 q 1250 120 r 223.42 119.70 s 12.85 11.17 t 198.80 105.02 u
25.83 10.78 v 95.19 100.40
[0179] 3.2% protein solutions of the S7301 products were prepared
in water and the colour and clarity assessed using a HunterLab
ColorQuest XE operated in transmission mode.
[0180] The colour and clarity values are set forth in the following
Table 26.
TABLE-US-00026 TABLE 26 HunterLab scores for 3.2% protein solutions
of S7301-01 and S7301-02 batch sample L* a* b* haze (%) trial 1
S7301-01 93.67 -0.21 9.93 15.7 trial 1 S7301-02 94.13 -0.01 8.74
13.4 trial 2 S7301-01 94.76 -0.19 8.41 15.9 trial 2 S7301-02 94.78
-0.13 8.36 15.5
[0181] As may be seen from Table 26, all the S7301 solutions had
light colour and quite low haze values. The S7301-02 samples, which
were diafiltered, were lighter, less green, less yellow and clearer
than the S7301-01 samples, which were not diafiltered. This effect
of diafiltration was more pronounced in trial 1, where the initial
dilution volume was lower and more diafiltration volumes were
employed. However, the samples of trial 2, which had a larger
dilution volume and only one volume of diafiltration were overall
lighter, less yellow and higher in protein content.
Example 11
[0182] This Example contains an evaluation of the heat stability in
water of the soy protein isolates produced by the methods of
Example 8 (S7300) and Example 10 (S7301).
[0183] 2% w/v protein solutions of S013/15-K30-09A S7300 and trial
1 S7301-02 in water were produced and the pH adjusted to 3 with
HCl. The clarity of the solutions was assessed by haze measurement
with the HunterLab ColorQuest XE instrument. The solutions were
then heated to 95'C, held at this temperature for 30 seconds and
then immediately cooled to room temperature in an ice bath. The
clarity of the heat treated solutions was then measured again.
[0184] The clarity of the protein solutions before and after
heating is set forth in the following Table 27:
TABLE-US-00027 TABLE 27 Effect of heat treatment on clarity of
S7300 and S7301 solutions haze (%) after product haze (%) before
heating heating S013/15-K30-09A S7300 6.4 4.2 trial 1 S7301-02 12.0
5.2
[0185] As can be seen from the data in Table 27, the samples were
heat stable. The protein solutions were initially quite clear and
the heat treatment actually reduced the level of haze
SUMMARY OF THE DISCLOSURE
[0186] In summary of this disclosure, the present invention
provides an alternative method based on extraction of soy protein
from source material using aqueous calcium chloride solution, to
obtain a soy protein product which is soluble in acidic media and
forms heat stable, transparent solutions therein. Modifications are
possible within the scope of this invention.
* * * * *