Complexation with phenolic acids affect rheological properties and digestibility of potato starch and maize amylopectin

Abstract

As well-documented inhibitors of starch digestive enzymes, dietary phenolics are less known for the ability to modify starch structures and functionality. This study aimed to characterize changes in starch structures by complexing individual phenolic acids with maize amylopectin and potato starch respectively, and to determine pasting properties and digestibility of the resulting complexes. FTIR-ATR results confirmed (995/1022 and 1047/1022 cm−1/cm−1) reduced crystallinity in short-range order of both starches, which were likely caused by a decrease in moisture content and/or by attenuation of molecular interactions in both crystalline and amorphous lamellas. Measurements of apparent amylose content and amylose leaching discovered formation of amylose-like structures in amylopectin and V-type amylose in potato starch. These structural changes were negatively associated with pasting temperature, peak viscosity, hot paste viscosity and cold paste viscosity. Digestibility was modestly lower for starch-phenolic acid complexes than for native starch and starch-phenolic acids mixtures. More interestingly, a small fraction of phenolic acids remained bound to starch molecules after pasting of starch-phenolic acid complexes, suggesting bound phenolic acids as a potential factor inhibiting starch hydrolysis.