GPC Patterns of Tropical Starch Amylopectins Hydrolyzed by Isoamylase Reaction

Abstract

Four varieties of amylopectins isolated from tropical starches, i.e., edible canna, arrowroot, cassava and sago, were used to study their fine structure. Potato and corn amylopectins were used as references. The amylopectins were treated with isoamylase and the slow debranching process was monitored by gel permeation chromatography. The rates of these isoamylase α-1, 6 debranching reactions varied a little among six varieties of amylopectins, however, the respective retention times of peaks produced from each debranched amylopectin became longer as the debranching reaction proceeded, indicating that molecular weight of the isoamylase-treated amylopectin gradually became smaller. Conversely the retention time of the unit chain gradually became very slightly shorter. This shows that the molecular weight of the unit chain increases slightly as the debranching reaction proceeds. If the isoamylase debranching reaction proceeds predominantly at the outermost α-1, 6 linkage, the inside unit chain will be expected to be longer.