46C-35 |
Effect of water washing on the reduction of total lipid, free fatty acids, and conjugated dienes content of milled rice |
M. A. MONSOOR, Department of Food Science, University of Arkansas, 2650 N Young Avenue, Fayetteville, AR 72704 and A. Proctor. Degradation of milled rice lipid is related to the quality deterioration during storage. Milled rice surface lipid is mainly composed of triacylglycerides from residual bran that degrade to free fatty acids (FFA) through lipase action. The FFA content is an indicator for future off flavor development as FFA are more prone to oxidation than triacylglycerides. Milled rice FFA are determined as an index of quality by brewing industry. The objective of this research was to determine the effect of water washing milled rice on the total lipid, free fatty acids (FFA), and conjugated dienes (CD) content. Milled rice (long grain, 1st break) was washed with de-ionized water, the ratios of milled rice and water were maintained to 1:1 and 1:2 (W/V) respectively. The duration of water washing was 5 and 10 min, respectively. The water washed and unwashed control was incubated at 37 C and 70% relative humidity for 7 days to evaluate the tendency for FFA formation and oxidation. Total surface lipid content, FFA, and CD content of water washed and unwashed stored milled rice were determined. Approximately 60% - 70% of total surface lipid was removed by water washing milled rice samples. After incubation FFA levels of water washed rice rose to 0.04 - 0.05 % compared to 0.20 % in unwashed controls. Conjugated dienes of the washed rice samples was 11.11 - 11.43 mmol/100 g rice compared to 16.56 mmol/100 g rice in the unwashed controls. With the exception of control there was little change in FFA levels during incubation. The reduction in oil and FFA was due to the removal of residual bran. Water washing would be a simple practical and acceptable way to reduce FFA formation and oxidation in milled rice at the brewery prior to processing.
Session 46C, Food Chemistry: Lipids, antioxidants and emulsifiers
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