抄録
Degradation of starch, amylopectin and amylose in DMSO was investigated at 20 kHz sonication. Concentration was 0.1 wt% for all samples and ultrasonic irradiation was carried out at 10 W which was estimated by calorimetry. Corn starch used in this work consists of 19 % amylose and 81 % amylopectin. Viscosity of starch solution decreases with sonication time. The time dependence of viscosity in amylopectin solution was coincident with that of starch solution, since the average molecular weight of corn starch is nearly equals to that of amylopectin (10^7) and the latter may contribute the viscosity of starch solution. Viscosity of amylose solution gently decreases in comparison with that of other two samples, since the molecular weight of amylose is low. Analysis of gel permeation curves was carried out. In the case of starch and amylopectin, the main peak decreased with sonication time and a strong peak around the molecular weight of 10^5 appeared. Branched parts of amylopectin consist of ca. 25 glucose residues. The species with the molecular weight of 10^5 also has branched parts. This suggests that degradation of amylopectin mainly occurs at the backbone.
