Thermal and rheological properties of granular waxy maize mutant starches after β-amylase modification

The objective of this work was to investigate the impact of β-amylolysis on the physicochemical properties of two granular waxy maize mutant starches. The β-amylolysis progressed rapidly at the beginning and then gradually leveled at approximately 5% for wxwx and 8.5% for duwx. With increasing β-amylolysis, both starches showed a decrease in the proportion of long B chains, average chain length, molar mass, and z-averaged radius of gyration, but an increase in the proportion of short B and A chains, and chains with 2–5 glucose units. The onset gelatinization temperature and pasting viscosity of hydrolyzed samples did not decrease until reaching the hydrolysis degree of 5% for the wxwx and 8.5% for the duwx. Moreover, both wxwx and duwx retained their respective characteristics in molecular size distribution and rheological properties during β-amylolysis. The rheological properties of waxy maize starch were more affected by the crystalline structure and the proportion of long chains in amylopectin.