Total Phenolic Content and Antioxidant Activity of Extruded Brown Rice

Abstract

Three paddy cultivars varying in l/b ratio (2.67–4.59) were dehusked to obtain brown rice. The brown rice was germinated for 24 and 48 h, dried, and milled into grit. The grit from controlled (un-germinated) and germinated brown rice was extruded at 100 and 120°C and the total phenolic content and antioxidant activity of the extrudates was determined. The total phenolic content of the control and germinated brown rice varied from 0.803–0.992 mg/g ferulic acid equivalent and germination increased total phenolic content by 8.8–12.0%. The antioxidant activity varied from 6.96–15.86% (decrease in absorbance of 2,2-diphenyl-1-picrylhydrazyl) and germination increased the antioxidant activity by 18.2–37.2%. Upon extrusion at 100°C, the total phenolic content decreased by over 50%. A further decrease of 6–15% in total phenolic content was observed when the extrusion temperature was increased from 100 to 120°C. Similar decrease in the antioxidant activity was observed upon extrusion and rise in extrusion temperature. Significant increase in water solubility, water absorption capacity, and percent expansion of extrudates was observed upon extrusion. The extrudates from germinated brown rice were used to make an instant pudding, which upon evaluation scored higher as compared to the pudding from control brown rice.

Keywords:

• Total phenolic content
• Antioxidant activity
• Germinated brown rice
• Extrusion