Structures of indica rice starches (IR48 and IR64) having intermediate affinities for iodine

Abstract

The amyloses of rice starches (IR48 and IR64) having intermediate affinities for iodine (i.a.) had number- and weight-average d.p. values of 930 and 1200, and 3300 and 3420, respectively, and average chain-lengths ( c.l. ) of 380 and 450. They comprised branched (∼6 chains on average) and unbranched molecules in the molar ratios 1:2 and 1:3, respectively, and the former appeared to be larger. The amylopectins had i.a. of 0.63 and 0.87 g/100 g and c.l. of 20 and 21, respectively, and were composed of long, medium, and short chains in the weight ratios 9:21:70. The amylose contents were 17.0 and 18.3%, respectively. The normal rice starches contained similar amounts of amyloses with similar structures, regardless of their i.a., but the amylopectin from the higher-i.a. starch had a higher i.a. and a larger proportion of long chains.