Studies On Rice Bran Microwave Stabilization And Extraction Of Oil And Protein From Rice Bran

Quality deterioration of rice bran during storage is largely due to rancidity and other metamorphism, therefore, stabilization is required to improve the storage quality of rice bran. Extrusion has been widely accepted in industry, however, extrusion method is of high cost, inflexibility processing, and is bad for the nutrition and function properties of rice bran.Microwave shows considerable potential for rice bran stabilization due to its efficient inactivation effect on lipase in rice bran. In this study, the effects of microwave on rice bran stability and the optimum condition of microwave were studied. And characteristics of rice bran oil and rice bran protein extracted by solvent and enzymatic extraction were investigated. The main results were as follows:1. Studies on the conditions of microwave stabilization of rice bran. Optimum condition for microwave stabilization was that rice bran was treated by microwave for 2.5 min at dose of 4.5 Kw/kg. Fatty acid value of rice bran was less than 15mg KOH/g during storage at 25℃and 37℃for 90 days.Microwave stabilization could increase the solubility, emulsifying and water holding capacity of rice bran protein. Compare with other heat treatments, acid value of rice bran oil treated by microwave was low, but peroxide value was high. The change of acid value and brightness of rice bran oil treated with microwave was small, and peroxide value decreased significantly during storage. The quality of rice bran oil treat with microwave was best.2.Solvent Extraction of rice bran oil. Rice bran was stabilized by microwave under its optimum conditions following extraction with hexane. Optimum extraction conditions were that rice bran to hexane at the ratio of 1:5 (w/v) extracted at 50℃for 20min, the extraction rate was 94.1%.Exponential kinetic equation of rice bran oil extraction was established by spherical model, and the fitting precision was high. Oil diffusion coefficient was 0.0038mm2/min, diffusion energy was 1109 J/mol.Microwave was good for extraction of rice bran oil and protein. The extraction rate of rice bran oil extracted by isopropanol was highest.3.Enzymatic extraction of rice bran oil and protein. Protease enzyme dosage, reaction temperature and time had significant effects on the extraction rate of rice bran oil and protein. Optimum conditions of rice bran oil and protein extraction was protease concentration was 1.0%, and digested at 55℃for 5 h. Under this condition, rice bran oil and protein extraction rates were 72.85% and 83.62%, which were lower than those of the solvent extraction.4.The quality characteristics of rice bran oil.The content of unsaturated fatty acids of rice bran oil was high. The content of oleic acid, linoleic acid content decreased after microwave stabilization treatment. Rice bran oil prepared by enzymatic extraction had high peroxide value than solvent extraction, but had lighe color.the quality of rice bran oil prepared by enzymatic extraction meet the standard of GB19112-2003 third level rice bran oil.