School of Graduate Study Department of Chemical Engineering

In general concentrates involve counter current extraction. The three defatted soy protein
concentrate extraction methods are discussed as follows.
a) Aqueous alcohol Process
The preferred alcohol concentration is 60% by weight. Soy proteins appear to be least
soluble in about 50% aqueous alcohol; their solubility increases on either side of that
concentration. Excess water in the extraction solvent is to be avoided because of
additional energy costs for removal and because an extremely wet soy protein cake tends
to agglomerate, clogging the process system. The aqueous alcohol removed by
evaporation from the alcohol water soy soluble is recycled to the extraction step
(Antonio, 2007).
b) Acid wash process
The acid wash process yields soy protein concentrate products with a relatively high NSI
(about 65-75%) because severe denaturation steps are not introduced in the process and
the proteins are neutralized before drying (Smith and Circle,1972).
Figure 2.1: Soybean Proteins; Effect of pH on Solubility
(Based on Smith and Circle, 1972)
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