Particulate structure of phytoglycogen studied using β-amylolysis

Phytoglycogen (PG), a dendrimer-like glucan particulate, has a much higher dispersed molecular density than amylopectin (AP). In this study, β-amylase was used to investigate the effect of high molecular density of PG on its susceptibility to enzymatic hydrolysis. AP and PG reached the limit of β-amylolysis at 20 and 480 min, respectively, suggesting a much higher resistance of PG to β-amylase. The majority of PG β-amylolysis occurred in the initial 2 min, followed by a slow progression that implied low accessibility of internal particulate portion to enzyme. The chain length profile of PG β-limit dextrin showed only one population of long chains, indicating the absence of branch clusters with PG. At the limit of β-amylolysis, a substantial decrease in the molar mass was observed for both PG and AP, whereas only a slight reduction in the Z-average root mean square radius was observed for PG (from 24.5 to 23.1 nm) compared to that of AP (from 91.1 to 69.6 nm).