Rice Bran Stabilization Using Natural Organic Acids and Optimization of Microwave Extraction on Free Fatty Acids and Protein

Rice bran is a by-product of rice milling industry and a rich source of vitamin, protein, essential fatty acids, dietary fiber and other sterols. It is increased applications in food, nutraceutical and pharmaceutical industries. However, potential applications are limited by its instability owing to hydrolytic rancidity. In this study, rice bran obtained from Klong Yong Rice Mill was stabilized with the natural organic acid mixture and a novel extraction technique. It was conducted to find the suitable ratio of rice bran (RB) with natural organic acids (vinegar and lime juice) for stabilization and to compare the conventional and microwave extraction method in controlling the lipase activity and retrieved the highest protein content. The response surface methodology as Box-Behnken Design (BBD) was used to optimize free fatty acid and protein contents from stabilized rice bran (SRB) using microwave extraction. The minimum value of free fatty acid was 1.93% free fatty acid as oleic acid for 30-days storage with the optimum conditions of microwave extraction as follows: 2 min, rice bran was treated with 48.49ml of natural organic acids mixture with the ratio of solid to 95%EtOH as 1:4 wt./lvol. at energy 750 W. The highest protein content was observed 85.33% at the microwave extraction conditions of 5.45 min, rice bran was treated with 49.18ml of natural organic acids mixture with the ratio of solid to solvent (70.92% EtOH) as 1:4 wt.lvol. at energy 750 W. Therefore, SRB with natural organic acid mixture and microwave extraction were the alternative effective method for rice bran stabilization and protein extraction.