Effect of Fatty Acid Chain Length and Complexation Temperatures on Sorghum Starch-Fatty Acid Resistant Starch Nanoparticles

In this study, sorghum starch-fatty acid complex resistant starch nanoparticles were synthesized used sorghum starch and fatty acid with different chain length (lauric acid, palmitic acid, and stearic acid) at temperatures of 30°C, 60°C, and 90°C. The complex index (CI) was evaluated, then the in vitro digestibility and physicochemical properties of the prepared sorghum starch-fatty acid complex resistant starch nanoparticles were characterized to elucidate the effects of complexation temperature and fatty acid chain length. Results indicated that higher complexation temperatures and shorter fatty acid chain significantly increased the CI value. Correspondingly, rapidly digestible starch (RDS) content of sorghum starch-fatty acid complex nanoparticles showed a decreasing trend with decreasing fatty acid chain length at complexation temperature of 90°C, indicated that the molecular chain of starch could fully extend and it was conducive to the formation of the amylose-fatty acid single helix structure at 90°C. Additionally, the nanoparticles showed a V-type crystalline structure with enhanced thermal stability as the formation of complex. This finding is important for the study of sorghum starch-fatty acid complex, and laid the foundation for its application in low-glucose foods.