Effects of high oryzanol rice bran oil on free radical formation and oxidation of whole milk powder

Abstract

The purpose of this study was to assess the influence of high oryzanol rice bran oil (RBO) on the oxidation of whole milk powder (WMP). Whole milk powder was manufactured from whole milk, which had been fortified with RBO at 0.1% and 0.2% w/w, while control WMP was made from milk without added RBO. The WMP samples were stored at 45°C and aw of 0.31 for 35 days. Free radicals were determined by electron spin resonance (ESR)spectroscopy while lipid oxidation was determined by thiobarbituric acid reactive substances(TBARS) at 0, 10, 20, 25, 30 and 35 days of storage. The free radicals were significantly lower (P<0.05) for WMP fortified with 0.2 RBO than for control WMP. RBO fortified WMP had a lower rate of oxidation than control WMP during storage. The TBARS for control reached a peak at 25 days and decreased on further storage while that for RBO fortified WMP did not peak during storage for 35 days and was lower than RBO fortified WMP. The RBO at 0.1%level did not significantly influence the organoleptic properties of WMP. The RBO reduced free radical concentration and oxidation of WMP and therefore has the potential for use as an antioxidant in the manufacture of WMP.

Keywords: whole milk powder, rice bran oil, oxidation, TBARS electron spin resonance spectroscopy

International Journal of Agriculture and Rural Development Vol. 5 2004: 134-139