The tea polyphenol-milk protein complex was used as raw material, the effect of tea polyphenols on the structure of protein was analysed by measuring the degree of binding, turbidity, protein secondary and tertiary structure and free sulfhydryl content. The results showed that the protein turbidity decreased with the increase of tea polyphenol concentration when the temperature was less than 65 ℃. At 65 ℃, the degree of binding was higher, and the free sulfhydryl content increased from 17.61 μmol/g to 19.11 μmol/g. Moreover, at 95 ℃, the free thiol content of protein decreased from 19.89 μmol/g to 16.58 μmol/g with the increase of the tea polyphenol concentration. Meanwhile, the turbidity increased. Under the three temperature treatments, protein secondary and tertiary structure changed in a similar trend. Taking 65 ℃ as an example, the β-turn content in the secondary structure increased from 23.13% to 32.87% with the increase of tea polyphenol concentration. While the random curl increased from 9.36% to 20.31% and the α-helix decreased from 49.15% to 25.86%. In addition, both the endogenous fluorescence and the exogenous fluorescence intensity of the protein decreased with the increase of tea polyphenol concentration. At the same time the surface hydrophobicity decreased. The effect of tea polyphenols on the structure of milk protein is different under different temperature treatments. These results provide a theoretical basis for the development of tea polyphenols.
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