Structure and in vitro digestion of amylosucrase-modified waxy corn starch as affected by iterative retrogradation

Abstract

This study evaluated the effects of iterative retrogradation on the structure and in vitro digestion of amylosucrase-treated waxy corn starch. Iterative retrogradation was conducted by repeating the set of autoclaving and retrogradation (4°C for 5 d) up to three times. After amylosucrase treatment, the average branch chain length increased. With retrogradation cycle count, melting enthalpy and temperature of amylosucrase-treated starch increased from 3.2 to 9.2 J/g and from 89.5°C to 95.2°C, respectively, and its relative crystallinity increased from 33.1% to 40.4%. By iterative retrogradation, the internal structures of amylosucrase-treated starch crystallites were altered to exhibit increased heat stabilities and perfections. In regards to in vitro digestibility, iteratively retrograded amylosucrase-treated starches showed higher RS content and lower RDS content compared with amylosucrase-treated starch. However, the dramatic changes in thermal transition properties, relatively crystallinity, and in vitro digestibility occurred during the first cycle of retrogradation and further retrogradation cycle did not affect them.

Keywords

• modified starch
• iterative retrogradation
• in vitro digestibility
• amylosucrase