Effects of storage temperatures on the starch digestibility of whole rice with distinct starch fine molecular structure
Xueer Yi, Shuaibo Shao, Xiaowei Zhang, Wenwen Yu, Bin Zhang, Hongsheng Liu, Robert G. Gilbert, Cheng Li
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.