Behavior of water in gelatinized glutinous rice starch, nonglutinous rice starch and nonglutinous rice in course of retrogradation at 3°C was studied by pulsed NMR measuring spin relaxation times of water molecules. Changes of
T1 and
T2, and hence, changes of the correlation time (τ
b) and the fraction of bound water (
P) in retrogradation process of nonglutinous rice starch and rice were both small and closely similar in each other. On the contrary, remarkable change of water behavior was observed in retrogradation process of gelatinized glutinous rice starch. The most remarkable changes observed around the water content of 1 g/DM g, were as follows;
P increased from 0.1 to 0.23 and τ
b from 5 × 10
-8 to 12 × 10
-8 sec at 3 days after gelatinization. In cases of more or less water content than 1 g/DM g, the changes of
P and τ
b in retrogradation were smaller. As water content was decreased, changes of
P and τ
b occurred fast, namely, on the first day and little change was observed thereafter. Retrogradation proceeded gradually as the water content become larger, and finally no change of
P and τ
b was observable for samples containing larger water content than 3 g/DM g.
抄録全体を表示