Effect of extrusion on the antioxidant ability of brown rice in vitro

Extrusion was employed for the process of the brown rice in the present study. Free and bound phenolics were respectively extracted from processed and unprocessed brown rice. The content of total phenols, scavenging ability of ABTS radicals, and ferric reducing antioxidant potential (FRAP) of the extracts was determined for both free and bound extracts. The relationship between phenols and their antioxidant properties was analyzed. Degree of brown rice starch gelatinization of extruded brown rice was also determined.Results showed that the free and bound phenol contents ranged from 210.48 to 747.70μg/g (GAE/DW) and260.77 to 470.94μg/g (GAE/DW) , respectively. The scavenging ability on ABTS+radicals and FRAP value of the free and bound extracts ranged from 1.15 to 4.52μmol/g (Trolox/DW) and 3.09 to 4.97μmol/g (Trolox/DW) , 2.57to 9.86μmol/g (FeSO4/DW) and 4.53 to 7.03μmol/g (FeSO4/DW) , respectively. Degree of brown rice starch gelatinization increased with the temperature of extrusion, when the temperature was higher than 130℃, no significant change was observed. The correlation analysis indicated that no significant correlation was observed between free phenolics and antioxidant ability, whereas a significant correlation was observed between bound phenolics and antioxidant ability.