Abstract: Maillard reaction products (MRPs)were prepared from whey protein isolate (WPI) and its hydrolysate (WPH)
with galactose (Ga), respectively. Changes in the degree of browning, degree of glycation and fluorescence spectrum of
MRPs were investigated during reaction periods. The antioxidant activity of MRPs was evaluated by comparing with that of
WPI and WPH. The results showed that the degree of browning (DB), degree of glycation (DG), and antioxidant capacity of
MRPs from WPI and WPH reached the maximum values at 4 h of reaction. The maximum DB and DG values of MRPs from
WPI and WPH with Ga were 1.114, 18.431%, and 1.413, 28.273%, respectively, and the reducing power, 2,2’-azinobis-
(3-ethylbenzthiazoline-6-sulphonate) (ABTS+) radical scavenging percentages and 1,1-diphenyl-2-picrylhydrazyl (DPPH)
radical scavenging percentages of both MRPs were 0.605, 46.29%, 61.77%, and 0.923, 69.81%, 78.43%, respectively, which
were significantly higher than those of the controls (P < 0.05). Meanwhile, the intrinsic fluorescence spectra indicated that
the structure of WPI and WPH became loose after Maillard reaction.

Key words: whey protein isolate (WPI), whey protein isolate hydrolysate (WPH), Maillard reaction, antioxidant activity