Physicochemical interactions between rice starch and different polyphenols and structural characterization of their complexes

Polyphenols are widely present in diverse foods and have great health benefits. The objective of this study was to investigate the physicochemical and structural properties of rice starch (RS) in the presence of ferulic acid (FA), gallic acid (GA), and quercetin (QC). FA and GA significantly increased the water solubility index and decreased the swelling power of RS. Differential scanning calorimetry analysis revealed that FA and GA facilitated the gelatinization of RS, while QC increased the gelatinization temperatures and decreased the melting enthalpy. FA and GA decreased the peak viscosity, hot paste viscosity, and final viscosity, whereas QC increased the viscosity of RS paste. Compared to the mixture of RS and GA, new signals appeared at 1685 and 1447 cm(-1) in the Fourier transform infrared spectroscopy of GA-RS complexes. However, these new peaks were not observed in the spectra of FA-RS or QC-RS complexes. X-ray diffraction results demonstrated that GA inhibited the retrogradation of RS and formed a new minor crystalline region at 2 theta = 13 degrees in the complexes. Scanning electron microscope suggested that polyphenols could cause looser gel structure of RS. This study may provide a basis for the application of polyphenols in starch-based functional food formulations.