School of Graduate Study Department of Chemical Engineering

2.3.2 Full fat soy protein concentrates
Production of full fat soy protein concentrate (FF-SPC) can be produced by cracking and
dehulling the soybeans and adding the beans in to a hot water at a temperature range of
82-100 0 C and maintaining that temperature for 10-50 minutes. Then, removing the
soybean from the water, washing the soy bean with fresh hot water, and drying the
washed soybean to desired moisture content of preferably 8-15%. Such kind of SPC
production is used to get FF-SPC with a bland taste and light color, to provide SPC with
out significant loss of protein and oil, to destroy enzymes like lipoxidase activity (by
99%) which produce off- flavor with out producing any darkening in the color of soybean
material, to treat the soybean in such a manner as to destroy the anti-nutritional factors
such as trypsin inhibitor (by 95%) to remove flatulence producing factors such as
stachyose, rafinose etc…, to prepare an intermediate product that can be further
processed to get defatted SPC with protein content of 70% and with no oil (Daftary,
1976).
2.4 Extrusion cooking
Extrusion cooking is a thermodynamically efficient industrial method of cooking and
drying a wide range of foods based on cereals or vegetable proteins or mixtures of both
(Carl et al., 1986).
The extruder consists basically of a sturdy screw or worm rotating inside a cylindrical
barrel (Fig. 3.2). The barrel can be smooth or grooved. The screw configuration is such
that the free volume delimited by one screw flight and the inside surface of the barrel
decreases gradually as one goes from one end of the screw shaft to the other. As a result
of this configuration, the material is compressed as the rotating screw conveys it forward.
Screws having different compression ratios are used for different applications. The barrel
is usually equipped with a number of sections of steam-heated jackets or induction
heating elements or cooling jackets. A narrow orifice or "die" is fitted at the exit end of
the barrel. The shape of the die opening determines the shape of the extruded product
(Berk, 1992)
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