Nwh. Cheetham et Lp. Tao, THE EFFECTS OF AMYLOSE CONTENT ON THE MOLECULAR-SIZE OF AMYLOSE, AND ON THE DISTRIBUTION OF AMYLOPECTIN CHAIN-LENGTH IN MAIZE STARCHES, Carbohydrate polymers, 33(4), 1997, pp. 251-261
The amylose to amylopectin ratios in six maize starch samples of diffe
ring amylose contents were measured by enzymatic debranching, followed
by high performance size exclusion chromatography (HPSEC). The molecu
lar size of amyloses, estimated by -logK(wav), shows progressive decre
ase with the increase in amylose content in maize starches. The gel pe
rmeation chromatographs of the corresponding amylopectins, debranched
with isoamylase, showed bimodal distributions containing long and shor
t chains. The average chain length of amylopectin has a correlation wi
th amylose content. The correlation coefficients between amylose conte
nt and average chain length, long chain length, weight ratio and the m
ole ratio of long and short chain length, were 0.97, 0.92, 0.96, 0.94
respectively. The maize starch with the highest amylose content has th
e lowest amylose molecular size and the longest chains, with a high ra
tio of long to short chains in its amylopectin fraction. Comparing the
values of amylose content determined by HPSEC of starch or debranched
starch with those of the iodine-complex method, we conclude that long
chains of amylopectin in high amylose starches contribute significant
ly to apparent amylose content. Copyright (C) 1997 Elsevier Science Lt
d. All rights reserved.