Abstract: In order to explore the effect of rice bran rancidity on the antioxidant activity of enzymatic hydrolysates of rice bran proteins (RBP), the oxidation degrees of crude rice bran oil (RBO) and RBP prepared from rice bran samples with different storage times were investigated as well as the antioxidant activity of alcalase hydrolysates of RBP. The results indicated that storage of rice bran could lead to hydrolysis and oxidation of RBO as well as oxidation of RBP, and the disulfide and non-disulfide covalent bonds participated in the formation of oxidation aggregates of RBP. As storage time of rice bran increased, the degree of hydrolysis (DH) of RBP firstly increased until reaching the maximum value on the third day of storage and then decreased. The free radical scavenging capacity against 2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radicals (ABTS+·), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, superoxide (O2-·), radicals hydroxyl (·OH), as well as metal-chelating capacity of RBP hydrolysates showed the same trend. These results indicated that shortterm storage of rice bran resulted in increased DH of RBP and antioxidant activity of their hydrolysates, whereas long-term storage reduced the DH of RBP and the antioxidant activity of their hydrolysates.

Key words: rice bran, rice bran protein, protein oxidation, hydrolysates, antioxidant activity