Supercritical Fluid Extraction Of Rice Bran Sterol Oil

China is the largest country of rice production and rice consumption in the world. The number of rice production was about180to200million tons. Rice bran is the main byproduct in rice processing process, as the most potential for development a high value-added resources has become increasingly subjected to the general concern of all countries in the world. However, the rancidity of rice bran not only limits its comprehensive utilization, but also restricts the storage system based on stabilization rice bran. Phytosterols are a natural steroidal.It has much aspects of physiological characteristics, the most striking is the effect of lowering cholesterol. Vegetable oil provide phytosterols accounting for40%of the total dietary intake. Rice bran is the phytosterols content of one of the most abundant oil crops. Supercritical CO2fluid extraction is a new separation and refining technology. Supercritical CO2fluid can provide a low temperature and anaerobic inert environment that has no solvent residue and is suitable especially for the extraction, separation and purification of the ingredients with heat-sensitive function.In this paper, stabilized treatment was conducted on rice bran through twin-screw extrusion, extracted rice bran sterol oil by supercritical CO2fluid extraction. In order to get green rice bran oil of high phytosterol content, natural, non-polluting, nutrition and health. The major findings of this paper is as followed:1. Rice bran of stabilizationStabilized treatment was conducted on rice bran through twin-screw extrusion. With residual peroxidase activity of rice bran as assessment indicators, analysis single-factor test results, screw rotation speed was33Hz; water consumption, extrusion temperature and feeding rate as variable factors, designed3-variable,3-level Box-Behnken experiment on optimize extrusion parameters. The results indicated that the optimal twin-screw extrusion conditions were water consumption of12%, extrusion temperature of143℃and feeding rate of220g/min. Under the optimal process conditions, the residual peroxidase activity was3.081%, which was less than5%of maximum permissible value.2. Research of rice bran storage stabilityThe effect of twin-screw extrusion on storage stability of stabilized rice bran was studied during the storage times. The results indicated whether25℃or0～4℃, the free fatty acid value (FFA) of stabilized rice bran were significantly lower than the unhandled rice bran with time prolonged. When stored in the0～4℃, FFA of stabilized rice bran were8.86KOH mg/g oil. FFA of the unhandled rice bran were69.59KOH mg/g oil. indicated that0～4℃storage did not significantly inhibit the lipase activity and prevent the rancidity of rice bran. Further verified the twin-screw extrusion treatment can effectively improve the storage stability of rice bran.3. Supercritical CO2extraction extracted rice bran sterol oilRice bran sterol oil was extracted from stabilized rice bran through supercritical CO2extraction. With the sterol content of rice bran oil as the key evaluation index, the extraction volume of rice bran oil as the reference index, designed5-variable,4-level L16(45) orthogonal experiment on optimize parameters. The optimized combination were extraction pressure of30MPa, extraction temperature of45℃, extraction time of120min and anhydrous alcohol addition of80mL. Under the optimal process conditions, the sterol content of rice bran oil was2.274%, the extraction volume of rice bran oil was18.43g/100g, significantly higher than the solvent extraction. The variance analysis shows that extraction pressure, extraction temperature, extraction time and anhydrous alcohol addition on the impact of SFE-CO2reached significant level. The primary and secondary order of influence factors was:extraction pressure> extraction temperature> anhydrous alcohol addition> extraction time.4. Deacidified of rice bran sterol oilThe effects of rectification pressure and rectification temperature on supercritical CO2extraction rectification deacidification were explored. Central Composite response surface methodology was applied to optimize deacidification processing, and optimal processing parameters were rectification pressure of15MPa and rectification temperature of20-33-43-53℃. Under the optimal process conditions, the rate of deacidification was83.64%, the rate of refined was75.32%, and the loss rate of sterol was24.03%. The comprehensive index reached to95.39.5. Oil quality analysisThe acid value of rice bran sterol oil was reduced significantly by Supercritical CO2extraction rectification deacidification process, dropped from16.37KOH mg/g to2.67KOH mg/g. At the same time, the other impurities were removed effectively, the moisture and volatile matter content dropped from4.75%to0.08%and the colloid and wax content dropped from1.06%to0.37%. After deacidification, the sterol content of rice bran oil still retained1.69%, significantly higher than the oil saled. Through the determination of physical and chemical indicators, the indicators have reached the national standar.