The covalent binding of rice bran protein with gallic acid was studied by alkali induced.Comparing the effects of different addition amounts of gallic acid on the enhancement of covalent reactions,with the aim of improving the bioavailability of polyphenols in protein modification.Experiments have shown that as the addition amounts of gallic acid increases,the water holding capacity,oil holding capacity,emulsifying capacity,DPPH radical scavenging rate,reducing power,and free thiol groups of the covalent complex significantly increase.When the addition amounts of gallic acid is 12.5%,compared with rice bran protein,the water holding capacity,emulsifying capacity,DPPH radical scavenging rate,reducing power,and free thiol groups of the complex increase separately by 0.95 times,4.45 times,8.10 times,19.31 times and 1.82 times.Compared with rice bran protein,the surface hydrophobicity of the complex significantly reduces.The results of endogenous fluorescence spectroscopy show that the intrinsic fluorescence intensity of the complex is lower than that of rice bran protein.As the addition amounts of gallic acid increase,the maximum fluorescence emission peak wavelength of the complex shifts red from 325 nm to 355 nm.The occurrence of the red shift indicates that the protein's tertiary structure tends to loosen,which changes the group distribution on the molecular surface and improves the water solubility of protein.Therefore,under alkaline induction,the functional properties of covalent complex such as water holding capacity,oil holding capacity,and emulsifying capacity significantly improve,and the antioxidant capacity significantly enhance.
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