Abstract
The changes of physicochemical properties of protein in soybean milk affected by the preparation techniques and by the pH values were examined comparing with the results obtained from cow's milk. Results were as follows:
1. The contents of total solids, protein, ash, fat, nitrogen free extracts and minerals in the heatextracted soybean milk were higher than those in the unheated one. In heat-extracted soybean milk theincrease in nitrogen content was noted in the acid-insoluble fraction.
2. The shape of protein particle of unheated soybean milk was spherical under an electron micro-scope, having the diameter of about 50mμ.
3. The shape of protein particle of heat-extracted soybean milk was associated to form larger particles.
4. With decreasing of pH values of soybean milk protein particles tended to form larger particles, and at pH 2.4 they were present in somewhat swollen shape.
5. When the pH values of acidified soybean milks were readjusted to the original pH (6.6), it was found that the protein particles lost the original shape, showing that irreversible transformation had occured during the pH adjustments.
