Molecular Structure and Thermal Properties of the Starches from High Amylose Rice Cultivars and Their Amylose-lipid Complex Formation with Various Emulsifiers

Purpose: The present study assessed molecular structural and thermal properties of rice starches with high amylose content and their ability to form amylose-lipid complexes with various emulsifiers. Methods: Rice starches from four cultivars (Dodamssal, Bukkyoung, Saegoami, and Saemimyeon) were analyzed for amylose and amylopectin molecular structure using high performance liquid chromatography (HPLC), thermal properties, amylose-lipid complex formation with various emulsifiers using differential scanning calorimeter (DSC), and in vitro starch digestibility. Results: Among the four starches, Dodamssal, which has significantly higher amylose content and longer branched chains of amylopectin than the other three starches, showed significantly different thermal properties, amylose-lipid complex formation, starch digestibility based on high starch pasting and gelatinization temperature, high amylose-lipid complex dissociation enthalpy, and high resistant starch content. Bukkyoung and Saegoami were not significantly different molecular structure and exhibited similar thermal characteristics, amylose-lipid complex formation, and starch digestibility. Conclusion: Differences in the molecular structures of amylose and amylopectin for the four starches significantly influenced the starch pasting and gelatinization characteristics, the amylose-lipid complex formation by various emulsifiers, and the in vitro starch digestibility. Dodamssal could be a potential source for effective amylose-lipid complex formation, which may contribute to enhancing type 5 RS.