Effects of storage temperatures on the starch digestibility of whole rice with distinct starch fine molecular structure

Abstract

starch digestibility of 3 rice varieties kept under 5 different storage temperature programs (room temperature (RT), 4 °C, -18 °C, 4 °C/RT (4 °C for 24 h and then RT for 24 h), -18 °C/RT (-18 °C for 24 h and then RT for 24 h)) were investigated. As expected, a significant variance in starch digestibility was observed for samples after storage at different temperatures. Overall, storage at 4 °C could most effectively decrease the starch digestibility of retrograded rice. The digestion rate constant was for the first time found to be determined by short-range amylopectin intermolecular interactions rather than long-range starch molecular interactions, for all different storage conditions. Furthermore, the digestion extent was determined by both inter- and intramolecular interactions among starch molecules as well as by the long-range order of the retrograded double helices. These results could prove useful to devise storage regimes which use retrogradation to produce cooked rice with lower glycemic index.