The amylopectins from the apparent low-(japonica) and high-amylose (indica) varieties of rice showed, respectively, low (0.39-0.87 g/100 g) and high (1.62 2.57 g/100 g) affinities for iodine, average chain-lengths (a) of 19-20 and 21-22, and similar beta-amylolysis limits (5659%). Gel filtration of the isoamylase-debranched amylopectins indicated that the amylopectins showing a high aflinity for iodine contained lower proportions of short chains and higher proportions (up to 14.2%) of the long chains (x, 85-180). The long chains appeared to be derived from long B-chains with side chains widely spaced and located far from the nonreducing terminus. The apparent high-amylose (3&32%) rice starches had ordinary contents (15.~18.5%) of amylose.
lNTRODUCl'ION
Rice starches contain1 O-30% of amylose, and the content among varieties of rice varies with the ambient temperatures during development of the grain'-6. We found no significant differences in the structures of the amyloses from apparent low-and high-amylose starches7, but the corresponding amylopectins showed low and high affinities, respectively, for iodine. Similar finding&s have been reported, but the purities of the specimens were not examined. Some differences in the iodine-binding properties, chain lengths, and distributions of the amylopectins from various rice samples have been reported 4-6~9-12, but the experiments were carried out without pre-fractionation of the amylopectins from the rice starches.We now report on the amylopectins from apparent low-(M-22%, three japonica varieties) and high-amylose @O-32%, three indica varieties)13 rice starches.
BXPBRIMBNTAL.
iUateri4aL.v . -The japonica and indica starches, other than Koshihibari starch,