Abstract
The effect of the addition of isolated soybean protein on gelatinization and retrogradation properties of starch during heating and storage was studied by measuring the enzymic susceptibility, swelling power, solubility and X-ray diffraction. The results are summarized as follows. (1)Swelling power and solubility of potato and sago starch decreased remarkably by adding isolated soybean protein. (2)During heat gelatinization of starch, the addition of isolated soybean protein caused a delay of gelatinization of all the starches examined. By the prolonged heating at 92.5°C, the degree of gelatinization reached the same level as the starch paste without isolated soybean protein. (3)During the cold storage of starch paste, the retrogradation of potato starch remarkably was accelerated by the addition of isolated soybean protein. Potato starch retrograded at the highest rate by the existence of isolated soybean protein among the examined starches. The rest of the starches were less affected by the addition of isolated soybean protein. (4)X-ray diffractogram obtained by the cold-stored starch paste with isolated soybean protein showed a much sharper pattern than the normal retrograded starch paste.
