ULTRASONIC DEGRADATION OF WAXY RICE STARCH

Sonication behavior of waxy rice starch in water has been investigated in terms of number average molecular weight and molecular weight dist ribution evaluated by gel permeation chromatography. Observed results on decreases in number average molecular weight indicated the ultrason ic degradation of waxy rice starch. The rate of degradation was accele rated at or above the temperature where gelatinization started. High s onopower also accelerated the degradation rate. After long sonication, the value of number average molecular weight tended to an limiting co nstant value, and the molecular weight distribution tended to be fairl y narrow. Observing degradation curves of other water soluble alpha-gl ucans, dextran, and pullulan, in addition, it was found that branched alpha-glucans have larger limiting molecular size than the unbranched one has, and an universal degradation curve can be obtained by plottin g the ratio of the molecular size of the degraded alpha-glucan to the correspondent limiting one against time.