Abstract: The impacts of metal ions, cysteine, phosphate and ethanol on the browning and antioxidant activity of glycosylated whey protein isolate (WPI)-inulin conjugate were investigated in this study. With the increase in the concentrations of iron and zinc ions, the browning and antioxidant activity of glycosylated WPI-inulin conjugate increased initially and afterward decreased, whereas the content of free amino groups content firstly reduced and then increased. With increasing copper ion concentration from 0 to 150 mg/L, the browning and antioxidant activity increased whereas the content of free amino groups decreased. Cysteine could not only inhibit the browning, but also enhance the antioxidant activity of WPI-inulin conjugate. Phosphate buffer and ethanol could facilitate the glycosylation reaction, with the former being more effective. Therefore, the metal ions, phosphate and ethanol could promote the glycosylation reaction and enhance the antioxidant activity of WPI-inulin conjugate.

Key words: whey protein isolate, inulin, glycosylation, antioxidant activity