Abstract: The Maillard reaction, also known as glycation, causes changes to the functional properties of proteins, but the impact of digests of the modified proteins on the immune status of normal mice has not been evaluated yet. In this study, glycated casein was prepared via the Maillard reaction between casein and lactose, and glycated and native casein were separately digested with trypsin. Normal mice were administered with either digest at doses of 100, 200, and 400 mg/kg mb for 28 days. At 24 h after the last administration, the mice in each group were sacrificed for measurement of immune indices such as spleen and thymus indices, hematological parameters, serum immunoglobulin (Ig) M, IgA, and IgG concentrations, lymphocyte proliferation, and natural killer (NK) cell activity. The results showed that the mice administered with the two digests had increased values of all evaluated indices compared with those mice administered with physiological saline (P < 0.05), indicating that the digests were able to improve the immune statue of the mice. Furthermore, the immuno-enhancing efficacy of native casein digest was higher than that of glycated casein digest. It is thus concluded that the Maillard reaction can weaken the enhancing effect of casein digest on the immune status of mice.

Key words: casein, Maillard reaction, glycation, mice, immuno-enhancing activities