The interaction between tea polyphenols and rice starch during gelatinization

The interaction between tea polyphenols (TPLs) and rice starch (RS) during gelatinization has been studied. In the RVA analysis, TPLs-fortified RS exhibited no clearly defined peak viscosity and hot paste viscosity. After excluding other factors, irregular viscosity changes were attributed to the strong interactions between RS and TPLs during pasting/gelatinization. Subsequently, the coupling constants of samples A (the gelatinized sample of the blend of 16% TPLs and RS) and B (the blend of 16% TPLs and gelatinized RS sample) in (1)H-NMR measurements were found to be the difference. Sample A had two coupling constants, (26h)J(HH) = 82.08, 100.77 Hz and (6h)J(HH) = 35.57 Hz, whereas Sample B had one larger coupling constant, (9h)J(HH) = 140.24 Hz. This implied that these two samples differed in H-H interaction and interaction strength of sample A may be stronger than that of sample B. More important is, sample A had clearly broadened O-H stretching and frequency red-shifts of C-O-H bending as compared with sample B in quantitative FT-IR analysis. The overall results indicate that TPLs and RS can have hydrogen bonding interaction during gelatinization.