In vitro enzymatic hydrolysis of amylopectins from rice starches

The effects of the molecular structures of amylopectins on the enzymatic hydrolysis of waxy-rice amylopectin (WRA) and normal-rice amylopectin (NRA) were investigated. The results indicated that compared to NRA, WRA possessed larger chain length, number of chains, internal chain length, degree of polymerisation, interblock chain length, and lower degree of branching and short:long B-chains, which caused WRA was much less susceptible to enzymatic hydrolysis than NRA. The digestibility curves for WRA and NRA were well fitted by the first-order kinetic equation. WRA and NRA were hydrolyzed in two separates phases in the LOS plots. Whether using α-amylase alone, or together with amyloglucosidase, WRA and NRA exhibited different digestibility rates due to different chain structure of amylopectin. The low C_1∞ values predicted that WRA and NRA would have little impact on blood glucose concentrations in the early digestion stage. HPLC results showed that G1∼G5 from WRA using α-amylase were lower than that from NRA, whereas from WRA were higher than that from NRA. There was the synergism between α-amylase and amyloglucosidase in glucose released from WRA and NRA.