Isolation of soybean protein: Effect of processing conditions on yields and purity

The process of soybean-protein isolation, comprising extraction in dilute calcium hydroxide and precipitation with hydrochloric acid at pH 4.5, was evaluated from the viewpoint of the effect of processing conditions on yields and product purity. The course of extraction and the effect of particle size and agitation indicate that the process is quite rapid even when coarse meal is treated under mild agitation. The heattreatment history of the meal is the main factor governing the extraction and isolation yields. The precipitation yield is unaffected by temperature. Two steps of curd washing were found to suffice for maximum product purity. The purity is also improved considerably by preliminary sifting of the meal.