Study on difference of multi-scale structure of japonica rice starch with different glycemic index

<bold>Objective</bold> The characteristics of multi-scale structure of japonica rice starch with different glycemic index were analyzed to provide theoretical basis for breeding and cultivation management of rice varieties with low glycemic index. <bold>Method</bold> Using ion chromatography，gel chromatography，¹H nuclear magnetic resonance，and X-ray diffraction analysis methods，low glycemic index <italic>japonica</italic> rice ‘Youtangdao 2’（High resistant starch content），middle glycemic index <italic>japonica</italic> rice ‘Shenyou 28’（High quality <italic>japonica</italic>），and high glycemic index <italic>japonica</italic> rice ‘Hulan 1212’（<italic>japonica</italic> soft rice） were selected to analyze the differences in the multi-scale structural characteristics of rice starch. <bold>Result</bold> Compared with the Huruan 1212，which had a high glycemic index，the amylose content of the Shenyou 28 and Youtangdao2 increased significantly by 107.2% and 262.7%，respectively.Conversely，the amylopectin content decreased significantly by 9.9% and 28.0%.Notably，the total starch and protein contents did not exhibit significant differences among the varieties.Additionally，the resistant starch content of ‘Youtangdao 2’ was 15.7% higher than that of both ‘Hulan 1212’ and ‘Shenyou 28’.The results of the starch chain length distribution and branching indicated that the fb₂ chain，fb₃ chain，and amylopectin average chain length in ‘Shenyou 28’ and ‘Youtangdao 2’ were significantly reduced by 5.3%~13.6%，8.5%~37.8%，and 2.7%~15.2%，respectively，compared with ‘Huruan 1212’.Additionally，the fa chain，the ratio of（fa + fb₁）/（fb₂ + fb₃），and the starch branching degree were significantly decreased by 1.6%~34.8%，10.0%~30.0%，and 19.7%~44.7%，respectively.The results of the starch crystal configuration and granule size distribution indicated that the ‘Huruan 1212’ and ‘Shenyou 28’ exhibited an A-type crystal configuration with high relative crystallinity.In contrast，‘Youtangdao 2’ displayed a B-type crystal configuration characterized by low relative crystallinity and a smaller granule size. <bold>Conclusion</bold> Low glycemic index <italic>japonica</italic> rice ‘Youtangdao’ 2 exhibits a high content of amylose，resistant starch，long chain ratio of amylose，long chain ratio of amylopectin and average chain length.Additionally，it demonstrates the low short chain ratio of amylopectin and low starch branching ratio，characterized by a B-type crystalline configuration.