Effects of tea polyphenols on the structural and physicochemical properties of high-hydrostatic-pressure-gelatinized rice starch

Effects of tea polyphenols (TP) on the structural and physicochemical properties of rice starch were evaluated under a 30 min high hydrostatic pressure (HHP) treatment (200-600 MPa). The results of differential scanning calorimetry (DSC) indicated a reduction in the gelatinization temperatures and the gelatinization enthalpy of rice starch/tea polyphenols (RS/TP) mixtures with increasing pressure levels. At 400 MPa, RS/TP mixtures (30% TP addition, starch basis) were entirely gelatinized in 30 min, and the rice starch gelatinization was enhanced with increasing TP concentration. The results of X-ray diffraction (XRD) and NMR (solid-state C-13 CP/MAS NMRs) revealed a reduction in crystallinity and peak intensity of RS/TP mixtures with increasing TP concentration at 400 MPa, which resulted from the increasing starch disruption extent induced by TP. Polarized light microscopy (PLM) and scanning electron microscopy (SEM) showed that the surface and interior structures of starch granules were destroyed depending on the pressure level and TP concentrations. In summary, the overall results suggested that the TP accelerate HHP-induced gelatinization and changed the structural and physicochemical properties of rice starch under sufficiently high pressure (>= 400 MPa) at room temperature.