The Effects of Starch Molecular Fine Structure on Thermal and Digestion Properties of Rice Starch

Whole white rice is a major staple food for human consumption, with its starch digestion rate and location in the gastrointestinal tract having a critical role for human health. Starch has a multi-scale structure, which undergoes order-disorder transitions during rice cooking, and this structure is a major determinant of its digestibility. The length distributions of amylose and amylopectin chains are important determinants of rice starch gelatinization properties. Starch chain-length and molecular-size distributions are important determinants of nucleation and crystal growth rates, as well as of intra- and intermolecular interactions during retrogradation. A number of first-order kinetics models have been developed to fit starch digestograms, producing new information on the structural basis for starch digestive characteristics of cooked whole rice. Different starch digestible fractions with distinct digestion patterns have been found for the digestion of rice starch in fully gelatinized and retrograded states, the digestion kinetics of which are largely determined by starch fine molecular structures. Current insights and future directions to better understand digestibility of starch in whole cooked rice are summarized, pointing to ways of developing whole rice into a healthier food by way of having slower starch digestibility.

Automated summary

Whole white rice is an important staple food, and its starch digestion rate and location in the gastrointestinal tract play a crucial role in human health. The structure of starch undergoes order-disorder transitions during cooking, which determines its digestibility. The length distributions of amylose and amylopectin chains influence the gelatinization properties of rice starch. The chain-length and molecular-size distributions of starch affect nucleation, crystal growth rates, and interactions during retrogradation. Various kinetics models have been developed to study starch digestibility, providing new insights into the structural basis of cooked whole rice. Different digestible fractions of starch with distinct digestion patterns have been discovered, and their kinetics are largely determined by fine molecular structures. This review summarizes current insights and future directions for understanding starch digestibility in whole cooked rice, with the aim of developing a healthier rice with slower starch digestibility.