Fine Structure of Amylopectin in Relation to Gelatinization and Retrogradation Behavior of Maize Starches from Three wx-Containing Genotypes in Two Inbred Lines

Maize starches from three wx-containing genotypes (wx, du wx, and ae wx) in two inbred lines (W64A and IaS125) were examined to evaluate the effect of mutant genotype on amylopectin fine structure and thermal behavior of starch granules. The amylopectin chain length distribution and A:B chain ratio were investigated by enzymatic treatments followed by high-performance size-exclusion chromatographic separation. Gelatinization and retrogradation behavior at 10 and 30% starch concentrations were studied by differential scanning calorimetry. Chain length distribution profiles of the isoamylase-debranched amylopectins showed distinct patterns according to genotypes. Starch from the ae wx genotype in both lines had a greater proportion of longer chains (degree of polymerization > 30) than the other genotypes. The A:B chain ratios were calculated from the high-performance size-exclusion chromatograms of the debranched l3-limit dextrins. Except starch from the ae wx genotype of the W64A line, which had an A:B chain ratio of 1.5, all of the samples