Pasting behaviors, gel rheological properties, and freeze-thaw stability of rice flour and starch modified by green tea polyphenols

Abstract

In order to interpret the mechanism underlying the changes in rice flour (RF), rice starch (RS), and their gels after green tea polyphenols (GTPs) addition, the pasting, thermodynamic, gel rheological attributes, and freeze-thaw stability of brown, refined RF, and RS were studied. GTPs reduced all pasting attributes of brown, refined RF, and RS mainly due to the building of the cross-linking between starch granule and GTPs. It also decreased the peak temperature and gelatinization enthalpy of RF and RS by facilitating the hydration of starch granules. The retrogradation degree after storage was reduced as well by GTPs, showing the inhibition on the long-term retrogradation of RF and RS. GTPs induced more reductions in G′ than in G″, and greater changes in RS than in RF. Moreover, GTPs improved the freeze-thaw stability of RF and RS gel. The addition of NaCl or sucrose showed certain impacts on these physical properties of rice flour or gel by interfering the cross-linking between GTPs and starch chain. Briefly, apart from starch, GTPs could remarkably influenced the pasting and thermodynamic attributes of brown and refined RF, it was proven a promising alternative in inhibiting the retrogradation and enhancing the freeze-thaw stability in rice-based products.