Abstract: This study aimed to investigate the effect of heat moisture treatment (HMT) on the granular morphology, crystalline structure, short-range ordered structure and digestibility of waxy rice flour (WRF), and the potential mechanism by which HMT influences its digestibility was also revealed. Results indicated that HMT induced significant aggregation of WRF particles, with the average particle size increasing from 13.38 to 23.27 μm as the temperature rose to 120 ℃. Additionally, the relative crystallinity (RC) of WRF decreased from 38.9% to 34.4%, accompanied by a reduction in the short-range order index from 0.97 to 0.81. Although HMT disrupted the ordered molecular structures of WRF, the synergistic action of thermal energy and moisture strengthened the interactions between molecular chains, thereby promoting the formation of V-type starch-lipid complexes. Moreover, the RC of V-type complexes increased from 1.5% to 2.9%, and the gelatinization temperature of WRF also increased. The aggregation of WRF particles, enhanced formation of V-type complexes and higher gelatinization temperature, together impeded adsorption and specific binding of enzymes to WRF and consequently inhibited its hydrolysis, thereby slowing down the digestion rate of WRF and increasing the proportion of slowly digestible and resistant starch, which reached a maximum of 39.4% at 110 ℃. In conclusion, HMT could effectively reduce the digestibility of WRF by modulating its multi-scale structural features, which provides a theoretical basis for the development of low glycemic index products.

Key words: waxy rice flour; heat moisture treatment; starch digestibility; structure