Comparative Effects of Fatty Acids and Emulsifiers on Amylose–Lipid Complexation and In Vitro Digestibility of High-Amylose Rice Starch

High-amylose rice starch (HARS) complexation with fatty acids and emulsifiers was evaluated using differential scanning calorimetry (DSC), Rapid Visco Analyzer (RVA) pasting, X-ray diffraction (XRD), and in vitro digestibility. DSC confirmed amylose–lipid complex formation for both additive types, with emulsifiers more effective than fatty acids. Lysolecithin produced the largest amylose–lipid complex endotherm with no detectable uncomplexed melting peak. Complexation increased up to 2.5% (w/w) and then plateaued, accompanied by a reduced gelatinization endotherm. Fatty-acid effects depended on chain length and included overlapping melting from uncomplexed lipids; higher additive levels generally increased complex stability. RVA results indicated that emulsifiers, but not fatty acids, increased pasting temperature by approximately 10 °C and delayed pasting. Lysolecithin markedly reduced viscosity breakdown, suggesting restricted granule swelling due to stabilized complexes. Myristic acid and lysolecithin caused the greatest changes in thermal and pasting parameters. XRD patterns shifted from mixed A + V to predominantly V-type reflections, confirming V-amylose complex formation. In vitro digestion showed decreases of 7.5–15.8% in rapidly digestible starch and increases of 4.7–12.3% in slowly digestible starch and 2.4–39.5% in resistant starch, with the strongest effects for lysolecithin (and myristic acid). These results support emulsifier-assisted production of RS5 from HARS, enhancing its utilization.