ABSTRACT
The amylopectin (AP) branching pattern is a fundamental feature of AP fine structure but a little-studied one. In this work, we followed enzyme digestion over time for AP from three maize genotypes (wx, du wx, and AP of ae VII). The objective was to describe differences in the progress of β-amylolysis and in subsequent debranching of β-limit dextrins (β-LD). During the progress of β-amylolysis, changes in the distribution of short residual chains show that the enzyme favors hydrolysis farthest from branch points. On treating β-LD with isoamylase (IA) alone, debranching was incomplete. Using IA and pullulanase (PUL) sequentially, a similar increase in the DP 5–7 region and the peak at DP 6 were observed for all samples, indicating a common element in the branching pattern. This similarity suggests that, despite differences in the proportion of short to long B chains, the most closely associated branch points may be arranged in a similar way for these AP. We suggest that the increase in DP 6 after PUL digestion would result from debranching of linear DP 6 residual B chains that originally had two branch points, consistent with interior segment length (ISL) of 1 or 2.
