Soy protein product and process

A novel aqueous process for the production of soy protein concentrates which possess many of the functional attributes of soy protein isolates. In producing the soy concentrate, parameters are controlled in the aqueous leaching and separating, neutralization, pastuerization and drying steps which are performed in the order recited.

BACKGROUND OF INVENTION 
This invention relates to an aqueous process for producing soy protein 
concentrates and, more particularly, to concentrates that possess many of 
the functional properties of soy protein isolates. 
Although food-grade soybean flours and grits have been available since the 
1930's, it has been only within the last twenty years that soy protein 
products have been used at an accelerating rate for the manufacture of 
processed food. During this period, there has been a proliferation of 
improved products, including soy protein concentrates (minimum 70% 
protein), isolates (minimum 90% protein), and textured products. 
In most instances, the nutritional quality of a protein ingredient for food 
is a vital factor. However, in many cases, the functional properties of 
the ingredient is an over-riding factor since the product must contribute 
to, or at least not detract from the overall character of the food being 
processed. This is true of both conventional foods and newly designed 
foods. All foods, old and new, must conform to some prevalent pattern of 
consumer acceptability in order to achieve successful commercialization. 
In the food field, functionality is a term which refers, in a general 
sense, to the property or properties of a food ingredient or additive that 
defines or influences the character of any processed food containing the 
ingredient or additive. For example, the milk protein or soy protein 
stabilizes emulsified fat in a whipped topping, and also stabilizes the 
foam structure when air is incorporated through whipping. The newer soy 
proteins have been selected and characterized for functional use in 
processed food items. 
The functional character of soy proteins includes properties such as 
solubility, water adsorption and holding capacity, fat absorption and 
holding, emulsification, viscosity, gelation, cohesion-adhesion, foaming, 
flavor binding, and the like. The development of soy protein products with 
new or, particularly, improved functional properties, has been an 
ever-increasing challenge. 
Soy protein concentrates have been defined as products prepared from 
defatted soybean source material by removing a preponderance of soluble 
non-proteinaceous material, and containing a minimum of 70 percent protein 
(N.times.6.25) on a moisture-free basis. These products have been 
commercially available since about 1960. 
Prior to the commercial introduction of soy protein concentrates, the only 
soy protein products available for food use were soy flours and grits 
(about 50% protein). Concentrates were designed to offer improved 
nutritional value (higher protein content) and improved functional values, 
including flavor and odor. 
Three basic commercial processes were developed during the late 1950's and 
early 1960's to provide these concentrates. The common element in these 
processes is the immobilization of the major protein fraction of the 
defatted soybean source material in aqueous suspension to permit the 
removal of soluble low molecular weight materials including sugars, 
non-protein nitrogenous matter, some minerals, and the like. 
In one process, as described in U.S. Pat. No. 2,881,076, acidification of 
the aqueous solution to the average isoelectric pH of the protein is 
utilized to immobilize the protein. The low molecular weight materials are 
then removed by aqueous leaching. In this process, the wet acidic 
concentrate may be neutralized with food-grade alkali prior to drying. 
This improves the solubility of the protein. 
In another process, the defatted soybean source material is leached with 
aqueous ethanol to remove the low molecular weight materials (Mustakas, 
Kirk, and Griffin, J. Am. Oil Chem. Soc. 39, 222, 1962; U.S. Pat. No. 
3,365,440). In the third basic process, the protein of the defatted source 
material is immobilized by steaming prior to the leaching with water (U.S. 
Pat. No. 3,142,571). Since the early 1960's, modifications of several of 
these processes have been proposed or commercialized. 
The soy protein concentrates possess, in some degree, a number of the 
functional properties recited above. The kind and degree of these 
functional properties are dictated by the processing parameters. For 
example, the aqueous-alcohol process concentrates possess low protein 
solubility in spite of the fact that their aqueous suspensions are almost 
neutral in pH. This is a result of protein denaturation by aqueous alcohol 
and heat in desolventizing. In contrast, the acid-leach concentrates which 
are neutralized with alkali possess a higher protein solubility. 
Although the functional properties of soy protein concentrates are useful 
in the production of certain processed or manufactured foods, this is a 
limiting factor in the broader application of these concentrates in the 
food field. They suffer by comparison to the soy protein isolates as to 
kind, range, and degree of functional activity. Thus, there has existed a 
distinct challenge to improve the functional properties of the 
concentrates to allow replacement of the more expensive isolates in 
processed foods. All soy protein products have been increasing in cost 
because of inflationary economic factors, yet it is expected that the 
differential between concentrates and isolates will continue to widen due 
to the inherent complexities of isolate processing. 
It is apparent that there is a need for soy protein concentrates with 
greater functionality produced at lower cost relative to the cost of 
producing soy protein isolates. 
SUMMARY OF THE INVENTION 
We have found that the acid leach process mentioned earlier can be made to 
produce a very functional soy protein concentrate if certain 
newly-discovered critical parameters are adhered to. Further, we have 
discovered that the combination of these parameters is a critical factor 
in producing the novel soy protein concentrate. This was unexpected since 
the process is at least twenty years old with certain antecedents in older 
art, and undoubtedly, has been examined many times in the intervening 
years. 
In order to define the critical parameters, it is necessary to describe the 
general elements of the acid-leach process in some detail. Defatted 
soybean source material, either flour, grits, or flakes, is intimately 
mixed with acidified water at about pH 4.4 to 4.6 and allowed to leach in 
order to dissolve soluble matter present in the source material. A 
significant portion of the aqueous fraction is separated by settling and 
decantation, filtration, or centrifugation. This step may be repeated one 
or more times to remove most of the soluble matter. The final step or 
steps may comprise washing with water which has not been acidified. A 
variety of acids has been used in the acid-leach step as described in the 
prior art. These include hydrochloric acid, orthophosphoric acid, sulfur 
dioxide, and the like. Sulfur dioxide has anti-microbial properties, and 
materially alters the functionality and properties of the protein. As an 
alternative to sulfur dioxide, the use of sulfites or bisulfites at some 
stage of the process has been described in the prior art. Also, mention is 
made of other additives, presumably oxidizing agents, to reduce or bleach 
the color of the soy protein concentrate. 
The dewatered, moist soy protein concentrate cake may be dried as such or 
neutralized and dried. The acidic product has a lower protein solubility 
and a lower functionality in food systems as compared to the neutralized 
product. The prior art indicates that a diversity of alkalies and alkaline 
salts can be employed in the neutralization step prior to drying. Sodium 
and potassium derivatives are to be preferred for higher solubility soy 
protein concentrate. A variety of dryers has been employed to dry the 
acid-leach soy protein concentrates. These include oven dryers (moving 
belt), flash dryers, spray dryers, and fluid bed dryers. Obviously, the 
physical form of the wet material is an important factor in the choice of 
a dryer. 
We have discovered that a certain combination of parameters or conditions 
results in a highly functional soy protein concentrate having high protein 
solubility, high viscosity, good gelling character, excellent 
fat-emulsification and holding, and high water holding properties. The 
combination of the discovered parameters includes: 
(a) the use of defatted soy flour with high nitrogen solubility, 
(b) the rapid wetting and aqueous leaching at pH 4.4 to 4.6 under mild 
temperature conditions, 
(c) use of hydrochloric acid or phosphoric acid as acidifying agents, 
(d) avoidance of the use of sulfur dioxide, sulfite, bisulfite, or 
oxidizing agents, 
(e) limited time exposure at acidic conditions, 
(f) neutralization with either sodium or potassium hydroxides, 
(g) pasteurization at relatively low temperatures, and 
(h) drying at restricted temperatures. 
The details of this novel process combination, and the characterization of 
the resulting soy protein concentrate are described in conjunction with a 
schematic flow diagram constituting the drawing hereof. 
DETAILED DESCRIPTION OF THE INVENTION 
The source material for the preparation of the novel concentrate of this 
invention is a defatted soybean flour with a Nitrogen Solubility Index 
(NSI) (American Oil Chemists' Offical Method Ba 11-65) of at least 65, and 
preferably in the range of 65 to 75. In other words, 65 to 75 percent of 
the nitrogen present in the flour should be soluble under the conditions 
of the standard method. Further, a soy flour with a particle size wherein 
90 to 95 percent passes through a 200 mesh U.S. Standard screen is 
preferred. 
The defatted soy flour of this type is the source material of choice for 
several reasons. Because of the fine particle size and the high degree of 
cell fracturing, the soluble materials of this defatted soy flour leach 
out very rapidly when the flour is placed in aqueous suspension. In 
addition, the fine particle size of the flour results in a more 
finely-divided and uniform end-product, as compared to that derived from 
defatted grits or defatted flakes as described in prior art. 
We have discovered that aqueous acid leaching under mild temperature 
conditions is necessary and critical for the production of a highly 
functional concentrate having food-use properties similar to that of a soy 
protein isolate. Water at a temperature of less than 90.degree. F., and 
preferably in the range of 60.degree. to 80.degree. F., is employed. Water 
at higher temperatures results in a diminution of water solubility of the 
finished concentrate. This is related to a general degradation of all 
functional values. Water at lower temperatures is not desirable since the 
diffusion of water-soluble components into the aqueous phase is 
diminished. 
For the necessary rapid aqueous leaching of the defatted soy flour, the 
flour is mixed with water in any one of several continuous liquid-solid 
mixing devices. The Waukesha DTL blending unit is but one example of such 
a device. The ratio of water to defatted soy flour is in the range of 5 to 
1 and 10 to 1 on a weight-to-weight basis. The preferred ratio is 8 to 1. 
After almost instantaneous and continuous blending of flour and water, the 
effluent, a suspension of soy flour in water, is acidified on a continuous 
basis to a pH of about 4.4 to 4.6. Food-grade hydrochloric acid is the 
acid of choice for lowering the pH of the flour-water suspension. 
Phosphoric acid may also be used. It is imperative that no sulfur dioxide 
or salts of sulfurous acid be used in this or subsequent processing steps 
because of their deleterious impact on protein properties, presumably 
through cleavage of disulfide bonds and re-establishment of new unnatural 
ones. However, the novelty and scope of this invention is not constrained 
by any hypothetical theorizing. Acidification is continuously controlled 
by a pH sensor with a feedback mechanism regulating the flow of acid. 
To produce the unique soy protein concentrate of this invention, it is 
mandatory to restrict the time exposure of the source material to the 
acidic leaching conditions. It was discovered that with increasing 
exposure of the defatted soy material to the acidic (pH 4.4 to pH 4.6) 
conditions, the solubility of the protein at neutral pH declined markedly. 
Such a decline is detrimental to overall functional properties necessary 
for use in a wide variety of food systems. 
Rapid water washing of the acid-leached defatted soy flour may be 
accomplished in several ways. One useful way is to separate the leached 
solids from acidic solution and water wash the leached soy source material 
in a countercurrent fashion employing two or three stages of separation as 
exemplified in the drawing and as described below. Although any of several 
different types of centrifuges may be used for separation of acid-leached 
cake at the stages, scroll-type centrifuges are eminently satisfactory for 
this type of operation. 
It is to be understood that this invention is not restricted to this mode 
of rapid separation of acid-treated defatted soy flour from the acidic 
environment and the washing of the leached defatted soy flour. However, 
the described countercurrent system offers economy of wash-water volume, 
and, hence, lower volume of sewer loading or recovery, and, also, 
conservation of costly energy. 
As recited above, the residence time of the defatted soy flour under the 
acidic conditions, about pH 4.4 to about 4.6 is a critical parameter in 
the practice of this invention. We have discovered that the time, starting 
with the blending of the soy flour with the water system to the time that 
the washed leached cake exits the last of the washing stages, should be no 
longer than one hour, and preferably thirty to forty-five minutes. 
Obviously, if a low number of washing stages are employed, the residence 
time of the leached cake will be shorter, but removal of mineral acid will 
be less. 
We have found in the practice of our discovery that three stages of leached 
soy flour separation and washing are satisfactory in producing a product 
with unique properties. This is not to say that other modes of washing are 
not within the scope of this invention.

A useful system of acid-leaching of defatted soy flour is shown in the 
drawing and described as follows. 
The defatted soy flour enters the system as shown in the lower left. At 
station 10, it is blended, in continuous manner, with water at about 
80.degree. F. and/or wash liquor. These are previously blended in the 
mixing tank 11. The slurry proceeds to tank 12 where the pH is adjusted 
from pH 4.4 to about pH 4.6 by an automatic pH control system with 
hydrochloric acid. It should be pointed out that all tanks in the system 
are equipped with mixing devices to provide for the blending of all 
in-coming and out-going liquors. 
The acidic slurry from tank 12 is then pumped to the first separator such 
as a centrifuge wherein the separated liquor is continuously discharged to 
tank 13, and then to recovery or sewer. The cake is discharged to a tank 
14 where it is blended with wash liquor from the last stage of the 
process. This wash liquor is described below. 
The blended slurry from Tank 14 is then pumped to a second separator 
(centrifuge preferably) for continuous separation with the liquid phase 
(Tank 15) and/or water at about 80.degree. F. directed to Tank 11 and 
being used for the wetting of the starting defatted soy flour. The 
dewatered cake from the second separator is mixed with water at about 
90.degree. F. and blended in Tank 16. This slurry is continuously pumped 
to the third centrifuge or separator where it is separated into liquor and 
cake. The liquor is mixed with a very small quantity of hydrochloric acid 
in Tank 17. This is used to dilute the cake from the first stage of 
separation as in Tank 14. The small amount of acid is useful at this stage 
to prevent the leached cake pH rising into ranges wherein the protein of 
the cake becomes sufficiently soluble, leading to unacceptable losses in 
exiting liquors. The final leached cake issuing from the third separator 
has a pH over 5.0, but no higher than 6.0. the pH may range from 5.3 up to 
5.9. pH's over 6.0 indicate that unnecessary protein losses are occurring 
through solubilization in "waste" liquors. 
The cake from the third separator is slurried with water at about 
80.degree. F., and blended in Tank 18 to provide a slurry having more 
managable viscosity characteristics for further processing. Additional 
dilution with water may be done in Tank 19 if needed. The solids-liquid 
slurry issuing from Tank 19 is then ready for further processing. 
The solids of the leached slurry are primarily composed of the major 
soybean protein globulins and the polysaccharides of the soybean. The 
leaching process removes the soluble sugars, natural mineral matter, 
soluble nitrogenous constituents, among other minor materials. 
The leached slurry exiting at the lower right in the drawing is further 
processed by neutralization, pasteurization, and spray drying to provide 
the unique protein concentrate of this invention. 
The solids content of the protein concentrate slurry for further processing 
should be in the range of from about 10 percent to about 16 percent. Low 
solids content results in excessive drying energy input and a low rate of 
production. A high solids content results in unwanted protein-protein 
interactions which detract from functional values. 
Neuralization of the slurry is done with an aqueous solution of sodium or 
potassium hydroxide. Polyvalent alkaline earth hydroxides such as calcium 
hydroxide result in an unwanted insolubilization of the soy protein. The 
pH of the slurry is adjusted to be within a range of about 6.5 to about 
7.5, and preferably in the range 6.8 to about 7.2. 
Pasteurization of the neutralized soy protein concentrate slurry may be 
carried out by indirect heat or direct steam injection in any one of a 
number of commercially available devices. Devices with low-shear agitation 
are preferred since without agitation, protein "bank-on" can occur, 
seriously reducing the efficiency and effectiveness of the pasteurization 
process. In one type of unit, automatically controlled neutralization and 
subsequent pasteurization by direct steam injection are accomplished in a 
single unit fitted with zones of agitation through which the fluid under 
process advances. 
Pasteurization temperatures to achieve an acceptable microbial profile in 
the finished soy protein concentrate are dictated by the nature of the 
equipment employed. In the unit described above, pasteurization was 
accomplished by direct steam injection with a temperature of 
175.degree..+-.2.5.degree. F. after mixing. This temperature was 
maintained for 15 minutes prior to delivery of the fluid feed to a spray 
dryer through a high pressure pump for adequate spray pattern development. 
Other time-temperature relationships, as influenced by pasteurization, can 
be readily determined. Time-temperature should not be such that a 
significant decrease in protein solubility occurs. 
After pasteurization, the neutral soy protein concentrate slurry is then 
pumped to a spray dryer under high pressure to effect atomization through 
appropriately-sized spray nozzles. The particular type of drying equipment 
is not a part of this invention, yet the temperature-residence conditions 
of drying are critical. It is important that the drying equipment be 
designed for dry powder removal as dried. Vertical spray driers are 
preferred, but this discovery is not limited thereto. 
For obtaining a dry powdered soy protein concentrate with unique functional 
properties of value in processed foods as described below, we have found 
that the outlet exhaust temperature of the dryer should preferably be in 
the range of about 180.degree. F. to about 190.degree. F. to maximize the 
balance of product functional value and energy conservation. 
The spray-dried powdered product may be coated with commercial lecithin or 
other food-grade surfactants, such as mono- and mono-diglycerides, in a 
spray blending-mixing device to improve water dispersibility. Such 
coating-addition should be in the range of about 0.25 to about 0.5 percent 
and should not exceed about 0.7 percent, because of a deleterious impact 
upon flavor, a prime requisite for food utilization. 
In the foregoing detailed description of the invention process, a 
three-stage separation process is described. It is obvious that with these 
teachings of the invention, persons skilled in the art can devise 
processes wherein more or fewer stages of separation are utilized. 
The product produced according to the above described parameters, and newly 
discovered constraints therein, has unique functional properties of 
importance in food use, properties not possessed by soy protein 
concentrates in current marketing channels. 
There are a number of tests which characterize the functional properties of 
food proteins. These are concerned with physico-chemical behaviorisms 
which have an impact on the character of the food item in which these 
proteins are incorporated. 
A fundamental character of all functional proteins is solubility. Although 
insoluble proteins demonstrate water-absorption, fat-absorption and the 
like, the range of functional value is limited. Soluble proteins 
demonstrate a much broader range of use properties. A critical test of the 
protein solubility of a protein-containing product is the Nitrogen 
Solubility Index (American Oil Chemists' Society Official Method, 
Ba-11-65). 
The product of this invention possesses a Nitrogen Solubility Index of 70 
or better, as produced, meaning that at least 70 percent of the protein in 
the soy protein concentrate is soluble in water as determined by the 
Official Method of the American Oil Chemists' Society (Ba-11-65). The 
extent of this solubility has a bearing on other functional values 
described in the following. 
Another functional property of soy proteins of value in various food 
systems is their ability in aqueous dispersion to form gel structures when 
heated. These structures are three-dimensional networks which entrap 
moisture, fat, and other food constituents. A critical test for the heat 
gelation ability of a protein is described by Circle, Meyer, and Whitney 
in "Rheology of Soy Protein Dispersions. Effect of Heat and Other Factors 
on Gelation", Cereal Chemistry, 41 157-172 (1964). Therein it was 
demonstrated that gel formation and gel strength are concentration and 
temperature dependent. Upon until the present discovery, among all soy 
protein products for food, only certain commercial neutral soy protein 
isolates possessed this unique heat-gelling character. Ten percent protein 
product dispersions were specified as critical for isolates. We have 
discovered that soy protein concentrates prepared according to this 
invention forms gels when thirteen percent protein product (N.times.6.25) 
dispersions are heated at 100.degree. C. and higher as described in the 
above cited assay procedure. These gels have viscosities above 5000 poises 
(Brookfield Viscometer, Helipath device). 
Viscosity alone, as recited in the Circle et al reference, is not 
sufficient to distinguish gels from heavy pastes even when the specified 
Helipath device is used. Gels possess characteristics which heavy pastes 
do not. These are: 
(a) translucency in varying degrees, 
(b) retention of imprint on container features when carefully removed from 
container, 
(c) cuts or slices cleanly, and 
(d) tears when pulled apart. 
The soy protein concentrates of this invention have these characteristics, 
whereas conventional or currently produced soy protein concentrates do 
not. 
Moreover, the heat-formed gels of the soy protein concentrates of this 
invention maintain high viscosity in the presence of salt (NaCl) up to 
three percent weight per volume. This is important in that salt is a 
common additive in processed foods, such as chopped, ground, and 
comminuted meat foods wherein protein additives are used to control fat 
separation and cooking or frying losses. 
High viscosity of dispersions in salt solutions is another important 
attribute of the soy protein concentrates of this invention. This is 
demonstrated by the viscosity of twenty percent solids dispersion in two 
and one half percent salt solution. Viscosities in excess of 20,000 poises 
are often achieved. High viscosity in salt-containing dispersions is 
useful in the preparation of finely-chopped meat emulsions for sausage, 
meatloaf products, and the like, where heavy consistency is desired for 
ease of handling and processing. In the past, such viscosity has been 
attained only with certain heated soy protein isolates. 
Another valuable functional attribute of protein additives for processed 
food is their ability to bind water. This ability varies considerably 
among the various food-grade protein products. This variance applies 
equally to commercially available soy protein concentrates. A very useful 
method for measuring water-binding or water holding capacity of protein 
products was described by Quinn and Patton, "A Practical Measurement of 
Water Hydration Capacity", Cereal Chemistry, 56, 38-40 (1979). This method 
is considered superior to older methods which do not account for protein 
solubility. 
We have discovered that the soy protein concentrates produced by the 
described invention have superior water-binding and water holding 
characteristics. Utilizing the Quinn and Patton method, which produces 
results in terms of grams of water bound per gram of sample, we found that 
our soy protein concentrates had hydration characteristics approaching 
that of soy protein isolates. For example, currently available soy protein 
concentrates had holding values ranging from about 2.0 to about 4.0 grams 
of water bound per gram of sample. The insoluble concentrates had the 
lowest values, whereas the commercially-available neutral soluble 
concentrates were at the upper end of the range. In contrast, commercial 
neutral soy protein isolates had holding values ranging from about 5.5 to 
6.5 grams of water bound per gram of sample. We were surprised to discover 
that the soluble neutral soy protein concentrates demonstrated hydration 
capacity values in the range of about 5.7 to about 6.0 grams of water 
bound per gram of sample. 
Many processed foods contain protein additives to aid in fat emulsification 
and emulsion stabilization. A prime example of these processed foods are 
ground and chopped meat foods including meat patties, coarse and finely 
chopped sausages, and non-specific meat loaves. 
A number of model systems and test food systems have been employed to 
determine the fat emulsifying capacity and fat emulsion stabilizing 
activity of protein additives, including soy protein products. See Inklaar 
and Fourtuin, "Determining and Emulsifying and Emulsion Stabilizing 
Capacity of Protein Meat Additives", Food Technology, 23, 103-108 (1969). 
We have found that a particular model fat emulsion is eminently suitable 
for rating protein additives as to their emulsifying and emulsion 
stabilizating activities. This emulsion contains 1 part of the protein 
product under test, 4 parts of water, and 4 parts of cod (flair or leaf) 
fat. A small chopper or silent cutter is used to prepare the emulsion. 
This emulsion test method, as described in detail later herein, on frying 
sustains a fat or fry-loss which is indicative of the relative ability of 
the protein products to hold fat in fat-containing ground, chopped, 
comminuted, or flanked meat systems which are fried before consumption; 
for example, meat patties, meat balls, ground meat fillings, and the like. 
Concentrates prepared according to the present invention demonstrated 
frying losses in fat emulsions ranging from about 6.5 percent to 10.5 
percent, whereas concentrates made by the aqueous or aqueous alcohol 
processes recited earlier, in comparative emulsions, had frying losses 
ranging from about 14.0 percent to 19.5 percent. This is very significant 
in the yield of fried meat foods. 
Cold water (28.degree.-40.degree. F.) thickening is another protein-product 
functional attribute which is important in certain food systems, such as 
fortified pancake and waffle batters, cookie doughs for depositing, sheet 
cake doughs, and others. In ten percent aqueous suspensions, the 
concentrates of this invention possessed viscosities ranging from about 
390 to 420 centipoises (Brookfield). Other representative concentrates had 
viscosities no higher than 100 cps, and ranging to as low as 15 cps. 
The following examples illustrate the practice of this invention, and the 
characterization of products resulting therefrom. 
EXAMPLE 1 
This example describes a typical process for preparing the unique soy 
protein concentrate of this invention. 
This trial run was carried out in a process equipment set-up such as 
depicted in the drawing. The process is a continuous one through the 
acid-leaching and solids washing stages. 
A combination of water and/or aqueous effluent from the second stage (tank 
15) of aqueous washing was pumped at a rate of 45 gallons per minute (GPM) 
to a Waukesha DTL liquid-solids blender 10. Simultaneously, defatted 
untoasted soy flour, SOYAFLUFF-200W (Central Soya Company, Inc.) with a 
71% NSI was fed to the Waukesha blender by an Acrison feeder at a rate of 
60 pounds per minute. The flour-aqueous mixture weight ratio was 
calculated to be 1:6. The rapidly blended slurry was then fed to a surge 
tank 12 equipped with an automatic pH controller with feedback control for 
the addition of food-grade hydrochloric acid at 35 percent concentration. 
The pH of the blended slurry was continuously adjusted to a pH of 4.5 in 
this particular trial. The acidic slurry was then continuously pumped to a 
P-5400 Sharples scroll centrifuge wherein it was separated into leach 
liquor in tank 13 and leached cake in tank 14. The liquor was sewered. The 
rate of pumping to the centrifuge was 55 to 64 GPM. 
The leached cake of (solids about 20 to 25 percent) the first separator or 
stage was diluted continuously in tank 14 with wash liquor from tank 17 
associated with the third stage of cake separation. These aqueous washings 
are slightly acidified with a small amount of hydrochloric acid to a pH of 
4.9 to 5.2 in tank 17 to prevent protein solubilization. The slurry was 
then pumped to the second stage scroll centrifuge and separated into 
aqueous liquor in tank 15 and cake in tank 16. As indicated above, this 
aqueous liquor from tank 11 was used in the preparation of the initial 
flour slurry. 
The cake from the second centrifuge stage (tank 16) was slurried therein 
with 80.degree. F. water added at a rate of 65 to 80 GPM and pumped to the 
third stage of scroll centrifugation. The wash liquor from this stage was 
delivered to tank 17 and the cake to tank 18 along with 80.degree. F. 
water to result in a more managable viscosity. The resulting slurry was 
then pumped to a 10,000 gallon holding tank 19 for further processing. 
Since the process is a continuous one to this point, when balanced, the 
tanks can be sized to meet the flow requirement. 
In this particular trial, the water make-up tank 11 was 10,000 gallons in 
size, the surge tank 12 for pH adjustment was 3,000 gallons, the six tanks 
in the centrifuging stages were each 1,000 gallons, and the final holding 
tank 19 was a 10,000 gallon tank. All thanks and all other equipment in 
the process were constructed of stainless steel. Each tank was equipped 
with an efficient, effective agitator. 
The device used for the neutralization and pasteurization of the slightly 
acidic, leached, wet soy protein was a mixing column (Lightnin Mixer 
Company) constructed with five mixing compartments, each equipped with a 
zone agitator, all driven by a central shaft. Fluid flow is directed 
upward. Both the concentrate slurry and food-grade sodium hydroxide (50 
percent) were pumped into the bottom chamber at about the same point 
(about 1 foot from the bottom). The sodium hydroxide was fed by a 
vari-stroke positive displacement pump, the feed rate of which was 
controlled by a pH controller whose pH probe was positioned about six 
inches higher than the hydroxide feed inlet. The set point of the 
controller was placed to pH 7.1. Steam at about 90 to 100 pounds per 
square inch (gauge) was injected at the top of the first or bottom chamber 
for pasteurization. The rate of steam injection was controlled to give a 
neutral concentrate dispersion of about 175.degree. F. at the top exit of 
the mixing column. It was estimated that residence time in the mixing 
column was 15 minutes. 
The concentrate dispersion from the top of the mixing column was pumped by 
a Manton-Gaulin high pressure pump at 7,500 to 8,000 pounds per square 
inch to a twelve foot diameter vertical spray dryer (De Laval) equipped 
with a Delevan Swirl SH nozzle with a 0.075 inch orifice. The outlet 
temperature of the dryer was controlled at 180.degree. F. The dry powder 
was then spray-blended with fluid lecithin at a calculated level of 0.3 to 
0.5 percent, weight basis, and then packed. 
Six thousand five hundred pounds were produced in this trial, a yield of 60 
percent based on weight of the initial defatted soy flour. Some line 
losses were experienced in this run. 
EXAMPLE 2 
The product prepared in Example 1 was analyzed with the following results: 
______________________________________ 
Percent 
Weight Basis 
______________________________________ 
Moisture 4.4 
Protein (N .times. 6.25), as is 
69.6 
Protein (N .times. 6.25), mfb 
72.8 
Crude Fiber 4.9 
Ash 3.65 
pH (1:10 aq. dispersion) 
7.0 
Nitrogen Solubility Index 
82.0 
Chloroform Extract 0.42 
______________________________________ 
Several competitive soy protein concentrates and a soy protein isolate were 
analyzed for comparison. The results of this survey are presented in the 
table below. It should be noted that the product of this invention 
possesses a Nitrogen Solubility Index approaching that of a soy protein 
isolate. 
__________________________________________________________________________ 
% % AS IS % 
PRODUCT SOURCE MOISTURE 
PROTEIN 
NSI 
ASH 
pH 
__________________________________________________________________________ 
PROMOSOY-100.sup.1 
Central Soya 
4.91 66.4 2.77 
6.42 
6.9 
GL-301.sup.1 
Griffith Lab 
4.70 69.5 23.30 
3.85 
6.6 
PROMAX.sup.1 
Griffith Lab 
4.50 70.1 13.70 
3.64 
6.3 
PROMINE-D.sup.2 
Central Soya 
4.76 90.4 88.60 
3.55 
7.0 
__________________________________________________________________________ 
.sup.1 Commercial Soy Protein Concentrates. 
.sup.2 Commercial Soy Protein Isolate. 
EXAMPLE 3 
As noted in the foregoing exposition, the water-holding capacity of protein 
products is an important attribute for food systems. The earlier cited 
method was applied to a product of this invention and to certain other 
representative concentrates and isolates. The results are recorded below. 
______________________________________ 
PRODUCT TYPE.sup.1 
SOURCE WHC.sup.2 
______________________________________ 
Present Invention 
SPC -- 5.7 
Present Invention 
SPC -- 5.8 
PROMOSOY 100 SPC Central Soya 
2.2 
GL-301 SPC Griffith Lab 
3.8 
PROMAX SPC Griffith Lab 
3.9 
PROMINE-D SPI Central Soya 
6.3 
SUPRO 620T SPI Ralston Purina 
6.4 
______________________________________ 
.sup.1 SPC -- soy protein concentrate; 
SPI -- soy protein isolate. 
.sup.2 Water holding capacity in grams of water bound per gram of sample 
(as is). 
As is evident from this examination, the product of this invention is 
superior in water holding capacity to several representative commercial 
soy protein concentrates, and approaches the functional capability of 
several soy protein isolates. 
EXAMPLE 4 
Thirteen percent soy protein concentrate dispersions in water were prepared 
as described by Circle et al. (reference cited earlier). These were canned 
in No. 1 C-lined cans and heated at 70.degree. C. for one hour and then at 
100.degree. C. for thirty minutes. After cooling to room temperature, the 
viscosities were determined as described in the cited reference. The cans 
were then resealed and heated at 120.degree. C. for thirty minutes. 
Viscosities were again determined after the contents of the can came to 
room temperature (75.degree. to 78.degree. F.). 
Similar aqueous dispersions containing three percent salt were prepared and 
treated in the same fashion. 
The results of this examination are listed below: 
______________________________________ 
VISCOSITIES OF 13% PRODUCT DISPERSIONS.sup.1 
PRODUCT SOURCE NO SALT.sup.2 
3% SALT.sup.2 
______________________________________ 
SPC Present Invention 
12,200.sup.3 
14,800.sup.3 
23,000.sup.3 
22,000.sup.3 
PROMOSOY-100 
Central Soya 14.9 2.3 
-- 
GL-301 Griffith Lab 2,130 6,800 
-- 
PROMAX Griffith Lab 7,500 3,900 
-- 8,400 
______________________________________ 
.sup.1 Viscosities are given in poises. 
.sup.2 The first figure is that of the dispersion after heating to 
100.degree. C.; the second is that after heating to 120.degree. C. 
.sup.3 These dispersions exhibited the characteristics expected of a gel 
rather than a heavy paste; (a) translucence, (b) slices cleanly, (c) tear 
when pulled apart, and (d) retains the imprint of the container in which 
it was heated. 
These results indicate that the soy protein concentrate of this invention 
exhibited gel structures far superior to three other 
commercially-available concentrates. It is important to note that these 
were equally strong in the presence of salt, an ingredient in many food 
systems. 
EXAMPLE 5 
1:4:4 fat emulsions were prepared from the protein concentrate of this 
invention and from several commercial soy protein concentrates. The 
purpose of this was to compare fat emulsification and stabilization 
characteristics. 
To prepare the emulsion, 350 grams of protein product, 1,400 grams of 
water, and 1,400 grams of beef cod fat (flair or leaf fat) were employed. 
The fat and water were placed in the bowl of a small Hely-Joly chopper or 
silent cutter. These ingredients were chopped for sixty revolutions and 
the bowl was scraped down. After another sixty revolutions, the protein 
was added and chopping was continued for sixty revolutions. The bowl was 
scraped down again, and the contents were chopped for another sixty 
revolutions. Additional emulsions were prepared with two percent salt in 
the water. 
The fat emulsion was then immediately stuffed into No. 1 C-lined cans which 
were then sealed. The sealed cans were then placed at 4.degree. C. and 
held for twenty-four hours. The cold emulsions were removed carefully from 
the opened can so as to preserve the cylindrical shape. For the 
frying-loss or cook-out test, the cold fat emulsion was cut 
longitudinally. After weighing one half portion, it was placed sliced 
surface down on an electric skillet heated to 175.degree. C., with no 
turning. The emulsion section was fired for ten minutes, carefully 
separated from fry-out liquid, and reweighed. The percentage of fry-loss 
of cook-out was then calculated. 
______________________________________ 
FRY TEST 
% COOK-OUT 
PRODUCT SOURCE NO SALT 2% SALT 
______________________________________ 
SPC-1.sup.1 Present Invention 
9.4 10.4 
SPC-2.sup.1 Present Invention 
10.4 11.6 
PSC-3.sup.1 Present Invention 
6.5 -- 
PROMOSOY-100.sup.1 
Central Soya 18.1 20.8 
PROMAX.sup.1 
Griffith Lab 19.4 20.9 
GL-301.sup.1 
Griffith Lab 14.0 15.0 
PROMINE-D.sup.2 
Central Soya 7.2 10.2 
______________________________________ 
.sup.1 Soy Protein Concentrate. 
.sup.2 Soy Protein Isolate. 
This work demonstrates that the product of this invention is uniquely 
superior to available commercial soy protein concentrates in fat holding 
capacity, and, indeed, is similar in this functional property to an 
isolate. 
It was noted that the fat emulsions prepared from the concentrates of this 
invention and that of the isolate, PROMINE-D, were different in character 
than those of the commercial concentrates. The emulsions of the former 
were moist on the surface, with a gelatinous structured character which 
tended to tear when pulled apart. This may suggest an oil-in-water system. 
In contrast, the emulsions of the commercial concentrates were greasy on 
the surface, suggesting a water-in-oil system. 
In addition to the experiment described above, sealed cans of each fat 
emulsion were heated at 70.degree. F. for one hour and at 100.degree. C. 
for thirty minutes. The cans were then held overnight at 10.degree. C. 
Each emulsion was then examined visually for fat separation or 
fat-capping. No fat-capping occurred in the emulsions containing the 
concentrates of this invention or the isolate. In contrast, moderate to 
severe separation occurred in the PROMOSOY-100, PROMAX, and GL-301 
emulsions. Even heating at 120.degree. C. for thirty minutes of the fat 
emulsions containing the herein described novel concentrates resulted in 
only trace amounts of fat separation. 
EXAMPLE 6 
In order to test out the functional value of the soy protein concentrate of 
the present invention, it was used in the preparation of canned chili. For 
comparison, several commercial soy protein concentrates and soy protein 
isolates were also used. 
The ingredients of the chili were as follows: 
______________________________________ 
WEIGHT 
INGREDIENTS GRAMS PERCENT 
______________________________________ 
Beef Trimmings 908.00 40.00 
(45% fat) 
RESPONSE 4320.sup.1 
68.10 3.00 
Water 1122.30 49.44 
Soy Protein.sup.2 
9.08 4.00 
Spice 8.08 3.56 
2115.56 g. 
100.00% 
______________________________________ 
.sup.1 A textured soy protein concentrate from Central Soya Company. 
.sup.2 Either a soy protein concentrate or a soy protein isolate, as the 
later recitation of variables indicates. 
The meat was ground through a 3/8 inch plate and placed in a steam jacketed 
Hobart kettle equipped with a scraper-type agitator. The meat was browned 
until the fat was liquified. The spice was then added, and the mixture was 
mixed well. The soy protein product was slurried in a minimal amount of 
water and held for later addition. The remainder of the water was added 
with continued mixing. The textured concentrate was then added. The 
mixture was mixed well. Finally, the slurry of soy protein product was 
added with additional mixing to insure a uniform composition. After this 
mixing, the chili preparation was heated to 180.degree. F. and held at 
this temperature for ten minutes with continued mixing. The food product 
was then canned in No. 1 C-lined cans and retorted at 255.degree. F. for 
fifty-five minutes. The product was then cooled and refrigerated for up to 
twenty-four hours. 
The thorougly chilled cans were then opened and weighed. The hardended fat 
on the surface of each can was carefully scraped off and weighed. The 
percent of fat-cap was then calculated as follows: 
##EQU1## 
The results of this testing are summarized in the following table: 
______________________________________ 
CANNED CHILI SURFACE FAT 
PERCENT 
PROTEIN PRODUCT 
SOURCE SURFACE FAT 
______________________________________ 
SPC.sup.1 Present Invention 
5.22 (4.98-5.92).sup.3 
PROMOSOY-100.sup.1 
Central Soya 15.25 (13.69-18.17) 
GL-301.sup.1 Griffith Lab 11.73 (11.33-12.18) 
SUPRO-620T.sup.2 
Ralston Purina 
5.65 (5.37-5.95) 
CENPRO-DHV.sup.2 
Central Soya 9.94 (9.48-10.38) 
______________________________________ 
.sup.1 Soy Protein Concentrate. 
.sup.2 Soy Protein Isolate. 
.sup.3 Average and range of three cans per variable. 
The results summarized above indicate that the concentrate of this 
invention is superior to two commercial concentrates and one commercial 
isolate in stabilizing fat in an actual food system. Indeed, it is equal 
to another commercial isolate, SUPRO-620T, in this functional capability. 
In general, the novel product of the invention can be characterized by 
having a Nitrogen Solubility Index of at least about 70%, a heat 
gelability to provide a viscosity of at least about 5,000 poise, a 
viscosity maintenance in the presence of 3% sodium chloride, a water 
holding capacity of at least about 5 grams of water per gram of bound 
sample, and a frying loss of below about 12%. 
Whereas in the foregoing specification we have set forth a detailed 
description of the embodiments of this invention for a thorough 
explanation thereof, those skilled in the art will perceive many 
variations in the details given herein without departing from the spirit 
and scope of this invention.