Free-radical-induced grafting of rice starch with gallic acid and evaluation of the reaction products' ability to stabilize Pickering emulsions.

Pickering emulsions can be stabilized with native rice starch (NRS), but their hydrophobicity is low. Gallic acid (GA) has a simple molecular structure and a rich variety of functional groups. Pickering emulsions can be made more stable by hydrophobically modifying the esterification reaction of NRS with GA to improve its dual wetting properties. In this study, the free radical-induced grafting method was used to prepare rice starch-GA graft copolymer (NRS-g-GA). The addition of GA could improve the crystallinity and orderliness of NRS. The results of Fourier transform infrared spectroscopy and H NMR indicated that GA was successfully grafted onto NRS. After modification, the contact angle of NRS increased from 18.2° to 60.2° (NRS-g-GA; 1:1). The emulsion prepared from NRS-g-GA showed better stability than NRS, improving the emulsification of NRS. Its stable emulsion exhibited an emulsion system dominated by elasticity. Thus, GA could be grafted onto NRS to enhance its emulsifying properties, opening up new applications for GA and NRS and promoting the development of starch-based Pickering emulsions in the future.