Soy protein isolate (SPI) is a protein product made from soybeans. It contains at least 90% protein. SPI is made through a process that involves solubilizing soy proteins using water and alkali, separating the solution from solids, and precipitating the proteins. The proteins are then separated, washed, and dried to produce a powder that is low in fat with a neutral taste. SPI is a complete protein that is used as an ingredient in foods like meat analogs, dairy products, baked goods and more due to its functional properties like emulsification.

2. Soy Protein Isolate or Isolated
Soy Protein(ISP) is the major
proteinaceous fraction of soybeans
prepared from dehulled,defatted
soyflakes by removing the majority of
non-protein components and must
contain not less than 90% protein on a
moisture-free basis.
Soy protein isolate is a complete
protein as it contains all the essential
amino acids.It has a neutral flavor and
taste.

3. COMPONENT WEIGHT %
PROTEIN 90
FAT 0.5
ASH 4.5
TOTAL CARB 0.3
Typical composition of ISP:
(Moisture-free basis)

4. The basic principle of ISP production is simple.
 SOLUBILIZATION:Using defatted soy flour or flakes
as the starting material, the protein is first solubilized
in water and alkali.
 SEPERATION:The solution is separated from the solid
residue.
 PRECIPITATION:Finally, the protein is precipitated
from the solution, separated and dried.

6. STARTING MATERIAL:
 Dehulled, defatted, edible grade soy
flakes or meal with the highest possible
protein solubility index are used.
 Although the rate of protein extraction
from finely ground flour would be faster,
flakes permit easier separation after
extraction.

7. (1)Protein extraction:
The flakes are mixed with the extraction
medium in agitated, heated vessels. The extraction medium is water
to which an alkali is added, so as to bring the pH to neutral to
slightly alkaline reaction(7.5-9.0). Under these conditions, the
majority of the proteins go into solution.
(2)Solid-liquid separation after extraction:
The extract contains considerable amount of fine
particles of extracted flour, the elimination of which, prior to
precipitation, is necessary in order to obtain a "curd" of acceptable
purity.

8. (3)Extract treatment:
The clarified extract can be treated so as to remove
certain impurities, thus improving the colour and nutritional quality
and modifying the functional properties of the final product. The use
of membrane processes for extract purification and
concentration is industrially applied in Europe and Japan.
(4) Precipitation:
The protein is precipitated from the extract by
bringing the pH down to the isoelectric region(around 4.5). The type
of acid used or the temperature of precipitation do not affect the
yield or purity of precipitated protein.

9. (5)Separation and washing of the curd:
The precipitated protein (curd) is separated from the
supernatant (whey) by filtration or centrifugation. Desludger or decanter
centrifuges can be used for this purpose. The curd must be washed with
water in order to remove residues of whey solubles.
(6)Drying:
The usual method for drying the washed curd is spray-drying and
the fine powder is packaged.

10.  a: Solubilization of the soy proteins in the salt solutions
(salting-in) followed by precipitation by dilution with
water.
 b: Precipitation from the extract at near-boiling
temperature, using calcium salts
 c: Ultrafiltration of the extract so as to remove the low
molecular weight components of the whey , leaving a
concentrated solution of protein
 d: Physical separation by floatation.
 e: Purification of the extract by ultrafiltration, filtration
through activated carbon and ion exchange, in order to
increase curd purity.

11. The product purity and yield depends on many different
parameters like,
 Alkalinity
 Extraction time
 Temperature
 Ratio of water to soy flakes
 Heat treatment
 Agitation

13.  Neutralised isolate :Mostly the isolate is neutralized
(Na or K proteinates ) to make it more soluble and
functional.
 Uses: Meat and dairy products and varied applications
requiring emulsification, emulsion stabilization, water
and fat absorption, adhesive or fiber-forming properties
etc.

14. Generally ISPs are used in,
dairy-type products such as beverage powders, infant
formulas, liquid nutritional meals, and some varieties of
liquid soymilk
bottled fruit drinks
power bars
soups and sauces
meat analogs that resemble conventional foods in color,
texture and taste
breads and baked goods
breakfast cereals
many weight and muscle gain products in the fitness
market

15. SOY PROTEIN WHEY PROTEIN
SOURCE Soy bean Cow’s milk
COST Not as expensive as whey protein. More expensive than soy protein.
COMPOSITION Mixture of globular proteins
immobilized in defatted flakes of flour
while allowing leaching off of soy
whey proteins, salts and carbohydrates.
Mixture of globular proteins which
have been isolated from whey, a
byproduct of cheese production. It is a
5% lactose solution in water.
HEALTH BENEFITS Reduce cholesterol, symptoms of
osteoporosis, hormonal diseases, heart
disease and increase in thyroid
metabolism.
Natural antibacterial and anti viral,
maintaining weight, improves immune
system functions and digestive system
functions.
HARMUL EFFECTS Can cause digestive disorders if allergic
to product.
Heat denatured whey can cause
allergies.
MARKET AVAILABILITY Tofu, soy milk, food bars, burgers, soy
flour, soy beans.
Infant formulas, nutrient special
products

16. REFERENCES
Cogan U., A. Yaron, Z. Berk and S. Mizrahi (1967)
Isolation of Soybean Protein: Effect of Processing Conditions on
Yield and Purity. J. Am. Oil Chem. Soc. 44: 321
Elias S. (1979)
Food Eng. 51(10), 81
Kolar C.W., S.H. Richert, C.D. Decker, F.H. Steinke and R.J. Van
der Zanden (1985)
Isolated Soy Protein in "New Protein Foods", A.M. Altschul and
H.L. Wilke eds. Academic Press Inc. Orlando, Florida.
"Soy Protein Products" Soy Protein Council, Washington, D.C.
Soya Bluebook (1990)
Soyatech Inc. Bar Harbor, ME.