Improving the techno-functional properties and glycemic index of Khai Mod Rin rice starch through...

Long-term food sustainability and security require the recognition and preservation of indigenous rice varieties and the exploration of their broader applications. Khai Mod Rin rice, a non-glutinous variety (Oryza sativa L.), is being conserved in the Nakhon Si Thammarat region of southern Thailand. This study aimed to develop modified starch from Khai Mod Rin rice a high-glycemic white rice using autoclaving-chilling (A/C) cycles. Starch was isolated and subjected to zero (C₀) and five (12C₅) cycles of 12-h chilling. The modified starches exhibited significantly improved functional properties, when compared to native rice flour and native starch. Resistant starch type III (RS3) content increased from 3.69 % (native) to 14.37 %, 18.26 %, and 49.71 % following A/C treatment. Additionally, swelling power and solubility were reduced, while water and oil holding capacities improved. Bile acid binding capacity increased from 1.67 % to 3.85 %, 4.83 %, and 14.68 %. The glycemic index was reduced from 73.93 to 70.16, 70.56, and 59.31, respectively. Thermal properties were enhanced, as evidenced by an increase in the gelatinization conclusion temperature (T_c) from 94.95 °C to 118.82 °C, 117.54 °C, and 119.25 °C. This enhancement was accompanied by a reduction in pasting temperatures from 79.60 °C to 80.90 °C, 62.85 °C, and 60.33 °C and an increase in enthalpy change, indicating greater energy required for gelatinization. Crystalline structure analysis revealed a transformation from A + V-types to V-type patterns. These findings suggest that the autoclaving-chilling process effectively enhances the physicochemical and functional properties of Khai Mod Rin rice starch, making it suitable for use in various functional food and non-food applications.