Structural Changes of Starch–Lipid Complexes during Postprocessing and Their Effect on In Vitro Enzymatic Digestibility

The effects of cooking and storage on the structure and in vitro enzymatic digestibility of complexes formed between fatty acids and debranched high-amylose starch (DHA7-FA) were investigated for the first time. Cooking greatly decreased the crystallinities of DHA7-lauric acid (LA) and DHA7-myristic acid (MA) complexes but had little effect on the crystallinities of DHA7-palmitic acid (PA) and DHA7-stearic acid (SA) complexes. Cooking increased the enthalpy-change (Δ H) values and short-range molecular orders of DHA7-FA complexes. Cooking decreased the in vitro enzymatic digestibility of DHA7-FA complexes, with the extent of the effect decreasing with increasing fatty acid chain length. Holding the samples at 4 °C for 24 h after cooking did not greatly affect the long- and short-range molecular orders nor the in vitro enzymatic digestibility of DHA7-FA complexes. From this study, we conclude that cooking disrupted the long-range crystalline structures of DHA7-LA and DHA7-MA complexes but enhanced the short-range molecular orders of all of the DHA7-FA complexes. The latter effect accounted mainly for the reduced in vitro enzymatic digestibility of DHA7-FA complexes.