Contrasting starch digestion and physiochemical characteristics between japonica and indica rice varieties with comparable high-amylose content
Chengjing Liao, Jiana Chen, Fangbo Cao, Weiqin Wang, Min Huang, Huabin Zheng
Abstract
Limited information is available on the starch digestion properties in high-amylose japonica rice. This study compared starch digestion properties and physiochemical characteristics—including texture profiles, starch and protein composition, and pasting properties—between the high-amylose japonica rice variety Youtangdao 3 (Y3) and the high-amylose indica variety Guangluai 4 (G4). Y3 exhibited a 36% shorter active digestion duration, 24% faster glucose production rate, and 21% lower glucose production than G4. The faster starch digestion rate in Y3 was attributed to its lower cohesiveness, which was associated with its higher resistant starch content—driven by a higher amylose-to-amylopectin ratio and higher protein content, particularly albumin and glutelin. The lower glucose production in Y3 resulted from its lower total starch content—linked to higher protein content—and higher resistant starch content. This study clarifies varietal differences in starch digestion and related physiochemical traits between high-amylose japonica and indica rice. Additionally, this study highlights that a higher resistant starch content does not always correspond to slower starch digestion in rice.