Microstructural, physicochemical properties and starch digestibility of brown rice flour treated with extrusion and heat moisture

Effects of heat moisture treatment (HMT), extrusion treatment (ET), and the combination treatment (HMT-ET) on microstructural, physicochemical properties, and starch digestibility of brown rice flour (BRF) were investigated. With a rise in resistant starch (RS), melting temperature, and a decrease in swelling capacity (SC), peak viscosity, and apparent amylose content (AAC), the HMT-ET BRF showed a significant lower expected glycemic index (eGI) than HMT and ET. XRD and FTIR results showed ET, HMT-ET caused the transition of starch crystals from amorphous to crystalline region, suggesting the formation of the starch-lipid complex. The analysis of DSC and RVA proved HMT-ET flours induced starch gelatinization and inhibited the starch retrogradation of BRF compared with the other three flours. Correlation analysis suggested that the combined effect of HMT and ET was response for the changes in physicochemical properties and reduction of in vitro starch digestibility. Overall, the BRF after HMT-ET with improved physicochemical properties and starch digestibility could be better utilized as a good substitute for carbohydrate sources.

Automated summary

This study investigates the effects of heat moisture treatment (HMT), extrusion treatment (ET), and the combination treatment (HMT-ET) on the microstructural, physicochemical properties, and starch digestibility of brown rice flour (BRF). Results show that the HMT-ET BRF has lower expected glycemic index (eGI) compared to HMT and ET, due to the increase in resistant starch (RS) and melting temperature, as well as the decrease in swelling capacity (SC), peak viscosity, and apparent amylose content (AAC). XRD and FTIR analysis suggest the formation of starch-lipid complex in ET and HMT-ET flours. DSC and RVA analysis confirm that HMT-ET flours induce starch gelatinization and inhibit starch retrogradation. Overall, the HMT-ET BRF with improved physicochemical properties and starch digestibility could be a good substitute for carbohydrate sources.