Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3!39
Case 2946
IMPROVED HEAT GELLABLE PROTEIi' ISOLATE
-
- The present invention relates to novel heat
gellable protein isolates which are suitable for use as
substitutes or extenders for egg white.
In our Canadian Patent No. 1,151,156, there
are described heat set gels having hardness values which
are at least those of heat set gels formed from
dispersions of egg white in water having the same
dispersion concentration.
Such heat set gels are formed from dispersions
of certain undenatured vegetable protein isolates
containing at least about 90% by weight of vegetable
protein (as determined by Kjeldahl nitrogen x 6.25),
known as protein micellar mass, or PMM. The protein
15 dispersions are manipulated as to pH and ionic strength
values, so as to provide dispersions having an ionic
strength of at least about 0.2 molar and a pH of up to
about 6Ø
Heat set gels produced from 20% w/w egg white
20 dispersions typically have hardness values of about 35 to
40 texturometer units (T.U.), as determined by the G.F.
Texturometer. The G.F. Texturometer and its operation
are described in detail ir: an article entitled "The
Texturometer - A New Ins rument for Objective Texture
25 Measurement" by H.H. Friednan et al published in J. of
Food Science, vol. 28, p.l30 (1963).
It has now surprisingly been found that the
substitution of small amounts of gellable starch for the
protein micellar mass in the dispersions from which the
30 heat set gels are formed leads to an increase in the gel
hardness of the gel which is formed upon heat setting the
dispersion, at the same dispersion concentration.
The substitution of increasing amounts of
starch for protein micellar mass results in increasing
35 values of gel hardness until a maximum gel hardness value
is achieved, beyond which further increasing amounts of
starch result in decreasing values of gel hardness.
Substitution for up to about 30% of the protein micellar
, ~
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mass by starch in the dispersion may be effected without
significantly adversely affecti~g the gel hardness value
which may be attained upon gelation of the dispersion.
The surprising synergistic result of the
mixture of protein micellar mass and starch enables gels
5 of egg white hardness to be achieved using lower
concentrations of protein isolate. A cheap raw material
is used to replace the more costly protein micellar mass,
thereby realizing a cost saving while at the same time
providing a material which may be used as an egg white
10 replacement or extender in food systems which employ egg
white to provide gelation.
The present invention is based on the
synergistic effect of starch and a protein micellar mass,
in combination with manipulation of pH and ionic
15 strength.
In United States Patents Nos. 4,169,090,
4,208,323, 4,296,026 and 4,307,014, assigned to the
applicant of this application, there are described
procedures for isolating protein from protein source
20 materials by solubilizing the protein by contact of the
protein source material with sodium chloride solution
under critical pH and ionic strength conditions and
diluting the protein solution with water to a lower ionic
strength to cause the formation of protein micelles in
25 the aqueous phase which settle and are collected as an
amorphous protein micellar mass. The protein solution
may be subjected to ultrafiltration prior to the dilution
step and the settling may be enhanced by centrifugation.
The protein micellar mass produced by this
30 procedure is a novel protein isolate and represents the
vegetable protein isolate with whlch the starch is mixed
to form the heat gellable dispersions herein. The novel
protein isolate is described in detail in United States
Patent No. 4,285,862, assigned to the applicant of this
35 application.
As described in more detail therein, the novel
protein isolate is a substantially undenatured protein
isolate product containing at least about 90% by weight
,~
,
~7~9~
of vegetable protein, (as determined by Kjeldahl nitrogen
x 6.25) and in the form cf a protein micellar mass which
is formed by settling an aqueous dispersion of protein
micelles consisting of homogeneous amphiphilic protein
moieties and formed from at least one vegetable protein
5 source material, thereby collecting an amorphous protein
mass. ~he protein isolate product has substantially no
lipid contant, substantially no lysinoalanine content and
substantially the same lysine content as the storage
protein in the source material. The isolate product may
10 be provided in dry form by drying the amorphous protein
mass.
The aqueous dispersion of protein micelles from
which the isolate is settled may be formed, in accordance
with the procedure of U.S. Patent No. 4,169,090, by
15 solubilizing the protein in the vegetable protein source
material at a temperature of about 15 to 35C using a
food grade salt solution having a concentration of at
least 0.2 molar ionic strength and a pH of 5.5 to 6.3 to
form a protein solution, , and diluting the protein
20 solution to an ionic strength of less than 0.1 molar to
cause formation of the dispersion.
The aqueous dispersion of protein micelles also
may be formed, in accordance with the procedure of U.S.
Patent No. 4,208,323, by solubilizing the protein in the
25 vegetable protsin source material at a temperature of
about 15 to about 35C using a food grade salt solution
having a concentration of at least 0.2 molar ionic
strength and a pH of about 5 to about 6~8 to form a
protein solution, increasing the protein concentration of
30 the protein solution while maintaining the ionic strength
thereof substantially constant, and diluting the
concentrated protein solution to an ionic strength below
about 0.2 molar to cause formation of the dispersion.
In the latter process, the food grade salt
35 solution preferably has an ionic strength of about 0.2 to
about 0.8 molar and a pH of about 5.3 to about 6.2. In
addition, the protein concentration step is preferably
effected by a membr'ane technique at a volume reduction
J ~74~3~g
factor about 1.1 to about 6.0, as determined by the ratio
of volume of pr~tein solution and the volume of
concentrated protein solution.
Further, the dilution of the concentrated
protein solution is preferably effected by passirg the
5 concentrated protein solution into a body of water having
a temperature below about 25C and a volume sufficient to
decrease the ionic strength of the concentrated protein
solution to a value of about 0.06 to about 0.12 molar.
In one embodiment of the latter process, the
10 food grade salt solution has a pH of about 5 to about 5.5
and the phosphorus content of the protein solution is
decreased prior to the dilution step.
The food grade salt used in the above-described
solubilization procedures usually is sodium chloride,
15 although other salts, such as, potassium chloride or
calcium chloride may be used.
As is set forth in U.S. Patent 4,296,026, the
purity of isolate which is obtained from soybeans may be
improved by the presence of millimolar amounts of calcium
20 chloride in the aqueous sodium chloride solution. As
described therein, the protein is solubilized by contact
with an aqueous sodium chloride solution having an ionic
strength of at least about 0.2 molar and containing about
0.001 to about 0.01 M calcium chloride and having a
25 temperature of about 15 to about 75C.
Further, as is set forth in U.S. Patent No.
4,307,014, the yield of isolate which is obtained ~from
soybeans may be improved by effecting the protein
solubilization at a temperature of about 15 to about
30 75C using an aqueous food grade salt solution of ionic
strength of at least 0.2 M and a pH of about 5.6 to about
7.0, preferably about 6.0 to about 6.4, and then
adjusting the pH of the protein solution to a pH of about
4.8 to about 5.4, preferably about 5.1 to about 5.3,
35 prior to dilution of the pH-adjusted protein solution.
As is set forth in our prior Canadian Patent
No. 1,151,156, referred to above, the heat gelation
properties of dispersions of the protein isolate in water
:;`
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are improved by incorporating in such dispersions
sufficient a- least one food grade salt to provide an
ionic strength of the dispersion of at least about 0.2
molar and sufficient at least one food grade acidifying
agent to provide a pH of the dispersion of less than
5 about 6Ø That procedure, in effect, is a
post-manipulation of the product of U.S. Patent No.
4,285,862, formed by the processes of U.S. Patents Nos.
4,169,090 and 4,208,323, as improved upon for soybeans in
accordance with the processes of U.S. Patent Nos.
10 4,296,026 and 4,307,014, by the simultaneous actions of
food grade salt and food grade acid to impart heat
gelation properties to the isolate which are comparable
to or exceed those of egg white, which properties are not
possessed by the isolate itself.
In accordance with the present invention, a
proportion of the protein isolate in the dispersion is
replaced by a gellable starch. The replacement of the
protein isolate preferably is effected using sufficient
starch to produce an enhanced gel hardness upon gelation
20 of the dispersion. Usually, about 1 to about 20% by
weight, preferably about 5 to about 15% by weight, of
starch of the total weight of protein isolate and starch.
The proportion of starch generally does not
exceed about 30% by weight of the total weight of protein
25 i~olate and starch. At such concentrations, the~hardness
values of the gels are not significantly different from
those of gels produced from the protein isolate above
and, beyond such concentration, the gel hardness values
decline rapidly.
The comparisons of gel hardness which are made
herein are all made with respect to gels produced from
dispersions having the same dispersion concentration.
Usually, 20% w/w dispersions are used in such
comparisons.
Even though the presence of as much as 30 wt~
starch does not result in any advantage from the
viewpoint of gel properties, nevertheless the decreased
proportion of the more costly protein isolate achieved
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thereby results in the obtaining, at a lower cost, of
desire~ gel hardness properties, preferably at least
those of heat set gels produced from dispersions of egg
white in water at the same dispersion concentration.
Further, at lower starch concentrations, the
5 enhanced gel hardness in comparison to egg white, is
ach_eved at a lower overall protein concentration than is
the case with egg white. Hence, to obtain the same gel
hardness as is achieved with egg white, a lower
dispersion concentration, and hence even lesser
10 concentration of vegetable protein isolate, may be used!
with consequential economy of use of protein isolate. - ~
The starch and vegetable protein isolate may be
provided in the dispersion in any convenient manner. For
example, the vegetable protein isolate and starch may be
15 separately dispersed in the aqueous phase.
Alternatively, the starch may be mixed with wet or dry
PMM and the resulting mixture dispersed in the aqueous
phase.
As noted above, the pH and ionic strength of
20 the dispersion is manipulated to achieve a dispersion
having improved gelation properties. pH manipulation is
achieved using at least one food grade acidifying agent
while ionic strength manipulation is achieved using at
least one food grade salt. Where the starch is
2S separately added to the dispersion, such addition may be
effected before or after such pH and ionic strength
manipulation.
The ionic strength of the dispersion provided
by the added at least one food grade salt usually varies
30 from the lower limit of about 0.2 molar up to about 1.5
molar and preferably is in the range of about 0.3 to
about 0.75 molar for the reasons discussed in detail
below. While such ionic strength values represent a
relatively high salt concentration in terms of the heat
35 gellable dispersion, the overall salt concentration in a
food composition incorporating the heat gellable
dispersion will inevitably be very much lower and
invariably within tolerable levels.
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The pH of the dispersions provided by the
addition of food grade acidifying agents may vary from
the upper limit of about 6.0 down to about 3.5 and
preferably is in the range of about 4.5 to about 5.5 for
the reasons discussed in detail below.
The incorporation of the food grade salt and
food grade acidifying agent into the protein dispersion
may be effected in a number of ways. One manner of
incorporation is to dissolve the food grade salt and food
grade acidifying agent directly in an aqueous dispersion
10 of the vegetable protein isolate which may also contain
the starch. ~ -
Alternatively, the food grade salt and food
grade acidifying agent, in the required proportions, may
be uniformly mixed with the settled protein mass from the
15 isolation procedure after separation from the residual
aqueous phase along with the starch, the mixture
thereupon dried and the dispersion formed from the dried
mixture. Such a dried mixture also may be formed by dry
mixing the food grade salt, food grade acidifying agent,
20 dried isolate and starch.
The relative proportions of protein, starch,
food grade salt and food grade acidifying agent in such
intermixed dry compositions depends on a number of
factors, including the intended protein concentration in
25 ~he aqueous heat gellable dispersion to be formed
therefrom, the proportion of the protein to be replaced
by the starch, the form of the acidifying agent and the
source of the food grade salt.
For example, the food grade acidifying agent
30 may be such as to provide part of the food grade salt.
A so, the overall food grade salt concentration may be
intended to be provided in part by the food system with
which the protein dispersion is to be used.
In general, for each 100 parts by weight of
35 mixture of dry vegetable protein isolate and starch,
there may be mixed therewith about 0.5 to about 4.0 parts
by weight of food grade acidifying agent and up to about
2.5 parts by weight of food grade salt. Such a
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399
composition is capable of dispersing in water to form a
dispersion of protein concentration of about 10 to about
30% w/w wherein the isolate and starch are dispersed in
an aqueous phase having an ionic strength of at least
about 0.2 molar and a pH of up to about 6Ø
S The food grade salt used in this invention to
provide the required ionic strength usually is sodium
chloride, although other food grade salts, such as,
potassium chloride or calcium chloride may be used.
The food grade acidifying agent used in this
10 invention to provide the required pH value may be any
desired food grade acid, usually hydrochloric acid, b~
also including phosphoric acid, citric acid, malic acid
and tartaric acid. The food grade acidifying agent may
be of such a nature that it provides part of the ionic
15 strength in the dispersion, for example, sodium tartrate
or sodium citrate.
It has been found that an increase in the ionic
strength of the di~persion above about 0.2 molar leads to
an increased hardness of heat set gel formed from the
20 diqpersion up to a maximum at a given pH up to about 6.0,
before once again decreasing.
Further, as the pH is decreased, an increased
gel hardness is observed for the same ionic strength
value above about 0.2 molar to a peak beyond which
25 further decreases in pH value lead to decreases in gel
strength. As the ionic strength of the dispersion
increases, the peak gel hardness occurs at a lower pH
value.
There is a broad spectrum of ionic strength and
30 pH values over which the gel strength does not
significantly change and the gel strength value usually
is at least about 35 T.U. and preferably at least about
40 T.U. and hence at least as good as egg white gels (35
to 40 T.U.) produced from the same 20% w/w dispersions
35 thereof.
For example, for soy PMM gels with no added
sodium chloride in the pH range of 4.5 to 7.5, the gels
were generally soft, exhibiting hardness values of 4 to 8
A
1~74~3~9
T.U. with the hardest gel (21 T.U.) being produced at pH
6.5 (from 20% w/w dispersions thereof). These values
compare with hardness values for egg white gels (35 to 40
T.U.) formed at the same dispersion concentration.
As the concentration of added sodium chloride
5 increased, the magnitude of the gel hardness values
obtained increased, reaching a maximum value (from a 20%
w/w dispersion) in excess of egg white of 40 T.U. at pH
5.0 and 0.5 M NaCl, with the maximum value increasing
significantly to above 50 T.U. at 10 to 20% substitution
10 of starch for isolate. Increased concentrations of
sodium chloride in the range of 0.75 to 1.0 M over the pH
range caused a slight decrease in gel hardness from this
maximum. A broad region of high gel hardness was
observed at sodium chloride levels above 0.3 M and gels
15 with hardness values above 40 T.U. from 20% w/w
dispersions thereof were obtained in the pH range of 4.5
to 5.5. With increasing sodium chloride concentration,
the pH at which maximum gel hardness occurs decreased
from pH 6.5 at 0 M NaCl to pH 5.0 at 0.5 M NaCl and pH
20 4.5 at 1.0 M NaCl.
The presence of the added salt substantially
increases the dispersibility of the proteins. At low
ionic strength values, from 0 to 0.1 M, dispersibility is
low, ranging from 10 to 30% and gels produced under these
25 conditions are extremely soft. At 0.2 M NaCl and above,
dispersibility increases markedly to greater than 70% and
is relatively insensitive to NaCl concentration and
changes in pH. The gel hardness of the heat set gels,
however, is independent of the dispersibility above about
30 30% and both hard and soft gels may be attained under
conditions where the protein dispersibility exceeds 70%.
The manipulation of the dispersions formed from
the protein isolate and starch by the addition of sodium
chloride and pH adjustment enables heat-set gels to be
35 formed which have hardness values which are as good as or
exceed those of egg white produced at the same dispersion
concentration. This result enables the dispersions or
dry mixes of the isolate, starch, food grade salt and
~,..
food grade acidifying agent to be used in various food
systems more efficiently than the unmodified isolate as a
substitute or extender for egg white, where the egg white
is used for its gelation properties.
The food system in which the compositions of
5 this invention find particular utility include various
meat analogs, including bacon analogs, such as that
described in U.S. Patent No. 3,840,677, assigned to
General Foods Corporation. The broad spectrum of pH and
salt concentration values over which the high gel
10 hardness values are attained permits flexibility from a
processing standpoint. The presence of the starch
enables the amount of protein isolate which is required
to be decreased.
Egg white is multifunctional over a wide range
15 of conditions and often is used in meat analogs for both
gelation and emulsiflcation properties. The PMM isolate,
however, exhibits functionality which is much more
sensitive to environmental conditions, so that the
conditions which favour optimum gelation properties, as
20 set forth herein, may not necessarily be those conditions
which favour emulsification, so that the composition of
this invention often cannot be substituted directly into
a formulation which has been optimized for egg white
multifunctionality. -
The protein source material from which the
protein isolate is formed may be any convenient
salt-extractable vegetable protein source, usually an oil
seed, preferably soybeans, or a legume, preferably
fababeans and field peas. The responses of the isolates
30 from differing protein sources are similar and any
differences in gelation behaviour result from differences
in specific characteristics, such as, amino acid
composition, between the protein sources.
The starch material which is used may be any
35 convenient gellable starch material, including
cornstarch, tapioca and peas. Starch is a cheap, readily
available material and the ability to utilize the same in
synergistic admixtures with PMM enables there to be
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11
produced gels which compare with or exceed hardness
values of egg white gels while using decreased quantities
of vegetable protein isolate.
The present invention is illustrated by the
following Examples:
5 Example 1
This Example illustrates the effect of starch
on the gel hardness of gels produced from dispersions of
soy PMM.
A protein isolate was formed from soybeans
10 following the procedure of U.S. Patent No. 4,208,323.
Soybean concentrate (about 50 wt% protein) was mixed wi*h-
Imperial gallons of 0.35 molar sodium chloride
solution at a 15% w/v concentration at a temperature of
about 25C. The mixture was stirred for about 30 minutes
15 at a pH of about 5.8. The aqueous protein extract was
separated from residual solid matter.
The extract was concentrated on an
ultrafiltration unit using a "ROMICON" (Trademark) type
XM50 and a Romicon type PM50 cartridge for a time
20 sufficient to achieve a volume reduction factor of four
times. The Romicon ultrafiltration cartridges are
manufactured by Rohm and Haas Company, the designation
"50" referring to a molecular weight cut-off of 50,000
Daltons. -
The concentrate was diluted into cold wat~r
having a temperature of 7C to an ionic strength of 0.1
molar whereupon a white cloud of protein isolate formed
in the dilution system. The protein dispersion was
allowed to settle as a highly viscous amorphous
30 gelatinous precipitate (wet PMM) in the bottom of the
dilution vessel. The wet PMM was separated from the
residual aqueous phase.
Samples of the dry isolate were mixed with
varying amounts of cornstarch and were formed into 20%
35 w/w aqueous dispersions. The ionic strength of such
dispersions was adjusted to 0.5 M using sodium chloride
and the pH of the dispersions also was adjusted to
varying values by the addition of hydrochloric acid.
. ~
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12
Samples were dispersed for 30 minutes at ambient
temperature (20 to 25C).
The protein dispersions were poured into
stainless steel gel tubes (2~ in x 3~ in I.D.) with
removable stainless steel caps after greasing to
5 facilitate removal of the gel. The gel tubes were heated
in a boiling water bath for 45 minutes and then cooled to
20C for a minimum of 20 minutes. The gels were removed
from the tubes immediately before testing, to minimize
water loss from the surface.
lQ Each gel was sliced into 3/4 inch length
cylinders and tested for hardness on the G.P;
Texturometer using a 2 inch diameter disc plunger. Each
sample was compressed twice and the peak heights
measured. The hardness was calculated according to the
15 method of Friedman et al (mentioned above) from the
formula:
millivolts
Hardness = Heiqht of first peak x 2
~T.U.) voltage
The hardness values obta ned for the various gels are
reproduced in the following Table I:
TABLE I
Components Gel Hardness (T.U.~
Soy PMM(g) Cornstarch (g) pH 5 5.5 6.0
:
25 10 0 41 30 35
9 1 59 38 43
8 2 52 35 35
7 3 31 32
6 4 21 28
0 10 12 12
As may be seen from the results of Table I,
significantly increased gel hardness was attained at a 10
wt% replacement of starch for protein, while at a 30 wt%
replacement of starch for protein there was no
significant decrease in gel hardness.
35 Example 2
This Example illustrates the effect of starch
on the gel hardness of gels produced from egg white
dispersions.
~3~7~ 9
13
The gel hardness determination procedure of
Example 1 was repeated with egg white replacing the soy
PMM in the 20% w/w dispersions. The pH was adjusted to
6.0 and the salt concentration to 0.5 M NaCl. The
results obtained are reproduced in the following Table
S II:
Table II
Components Gel Hardness
Egg White (g) Cornstarch (g) (T.U.)
10 10 0 45
9 1 48
8 2 50
7 3 45
0 10 12
The results of the above Table II demonstrate
15 the same effect is attained with egg white as is attained
~ith soy PMM.
Example 3
This Example illustrates the effect of starch
on gel hardness of gels produced from other PMM
20 dispersions.
PMM from fababeans was formed following the
proce~ure outlined in Example 1 and gel hardness was
determined following the procedure of ExampLe 1 at 0.3 M
sodiu.n chloride and pH 6Ø The results cbtained are set
25 forth in the following Table III:
TABLE III
Components Gel Hardness
Fababean PMM ( g) Cornstarch(g) (T.U.)
20 0 29
3018 1 332
17 3 29
16 4 25
As may be seen from the results of Table III,
fababean PMM exhibits similar behaviour when low
35 concentrations of starch are used to replace protein, but
the effects are not as pronounced as those observed for
soy PMM.
A
9~
14
Example 4
This Example illustrates the effect of added
starch on protein gelation.
The gel hardness determination procedure of
Example 1 was repeated for gels produced from dispersions
5 formed from increasing amounts of cornstarch added to lOg
samples of various protein materials and adjusted to pH
5.5 and ionic strength 0.5 M sodium chloride. The
results obtained are reproduced in the following Table
IV:
lQ TABLE IV
Amount of Cornstarch Hardness Values (T.U.) ~
(g) SoyFaba Egg
PMM PMM White*
0 30 29 40
1 37 31
2 39 35 42
4 47 - 51
6 43 34 57
* Determined for gels at pH 6.0, 0~3 M NaCl
The results of Table IV show that the addition
20 of starch to constant concentrations of protein isolates
increases gel hardness values significantly.
Example 5
This Example illustrates t}e use of differing
types of starch in the formation of gels.
The gel hardness determination procedure of
Example 1 was repeated using differing starch materials
in dispersions adjusted to pH 5.5 and 0.5 M NaCl. The
results obt~ined are reproduced in the following Table V:
TABLE V
30 Components Starch Type
Soy Starch Amioca( ) Hylon( ) Baka Snak(3) Tapioca
PMM(g) (g) Hardness Values (T.U.)
0 30 30 30 30
19 1 32 35 33 33
35 18 2 30 32 31 37
17 3 26 34 18 30
16 4 28 28 8 27
Notes: (1) A waxy maize starch containing no
A amylose
- ~7~ 9
(2) A high amylose cornstarch (55
amylose)
(3) A pregelatinized waxy maize starch.
(4) AMIOCA, HYLON and BAKA SNAK are
trade marks of National Starch
Company.
As may be seen from the results of the above
Table, the effects of Hylon are comparable to those seen
with cornstarch and tapioca starch also improves the
gelation when used at low levels. Baka Snak showed some
10 improvements in gel hardness at low concentrations but
gel hardness values fell rapidly at replaceme~
concentrations of 15% and higher.
In summary of this disclosure, the present
invention provides gels of improved hardness by utilizing
15 starch in combination with protein isolates.
Modifications are possible within the scope of the
invention.
