Research On The Extraction, Purification And Antioxidant Activity Of Oryzanol From Rice Bran Oil Soapstock

Oryzanol is a mixture of ferulic acid esters of triterpene alcohols and sterols. Owing to its safety, nutritional functions and stable physicochemical properties, oryzanol is increasingly used in food, pharmaceutical and cosmetic products, and other fields. Oryzanol is rich in crude rice bran oil, and large amounts of oryzanol go into rice bran oil soapstock in the process of chemical refinning. So oryzanol is mainly extracted from rice bran oil soapstock in industry currently. In this paper, with crude rice bran oil as raw materials, after enzymatic degumming, the process of crude rice bran oil deacidification was optimized combined with molecular distillation process and alkali refining process; The conditions of column chromatography was optimized with recovery rate and purity of oryzanol as index; Oryzanol products storage stability, thermal stability, oil solubility and chemical structural characterization was analysed; The ability of oryzanol to affect oxidative stability of kinds of vegetable oil and scavenge free radical was studied on. This paper provides a reference for the depth of the development and application of rice bran oil and oryzanol, and the main research results are as follows.1. The first process was mechanical impurity and enzymatic degumming of crude rice bran oil. Then the first step of deacidification was molecular distillation deacidification, which removed most of the fatty acid. The second step of deacidification neutralized the remaining fatty acid by alkali and oryzanol enriched to the rice bran oil soapstock. On the basis of single factor experiment, the optimum molecular distillation conditions were obtained as follows:feed rate 3 mL/min, scarping film speed 320 r/min, distillation temperature 115℃. Function model was established about temperature and reserved acid value. With soapstock absorption of oryzanol as an index, the reserved acid value after molecular distillation deacidification was determined to 8 mgKOH/g.2. The crude extract rich in oryzanol was obtained from rice bran oil soapstock by soxhlet extraction process with ethyl acetate as main solvent, the extraction rate of oryzanol was 93.4% in this process. Then oryzanol was isolated and purified from the crude extract by column chromatography process. TLC chromatography technology was used for eluent preliminary screening, and eluent was determined trichloromethane/ ethyl acetate (97:3, v/v) mixed solvent. On the basis of single factor experiment, with recovery and purity of oryzanol products as index, response surface analysis was used to determine the optimum technology conditions what were obtained as follows:sample concentration 4.00%, sample volume 8.70 g,60.00 g amount of silica gel.88.5% pure oryzanol were obtained in this conditions and the recovery reached 62.9%, the total extraction rate of oryzanol from soapstock could reach 58.7%.3. Investigation results of oil-soluble displayed that solubility of oryzanol product in rice bran oil, rapeseed oil, soybean oil, peanut oil, tea seed oil were 8.61 g/100g, 7.11 g/100g,6.49 g/100g,5.90 g/100g,7.05 g/100g. The results showed that oryzanol product had good solubility in kinds of vegetable oil. The research results of storage stability showed that oryzanol product had good storage stability when it was dissolved in n-heptane.0.2% and 0.5% oryzanol/n-heptane solutions were well-sealed stored at room temperature for 12 days under dark and light conditions respectively. Oryzanols in solutions had few losses and each retention rate of oryzanols was more than 99%. The results of thermal stability showed that the oryzanol in rice bran oil had good thermal stability habit. Rice bran oil was heated at 200 ℃ for 8 h and oryzanol in it was at less than 15% loss. Thermal performance measurement results showed that the main ferulic acid easters of oryzanol was ferulic acid esters of triterpene alcohols. Oryzanol product melting point was at range of 160-170℃, and its crystallization temperature was at about 80 ℃.4. In the research, oryzanol was added to several kinds of common vegetable oils (soybean oil, rapeseed oil and tea seed oil) in different proportions. The results showed that oryzanol improved antioxidant of soybean oil and tea seed oil and extended their oxidation induction period and shelf life. And oryzanol can slow down the PUFA oxidation process in oils. In particular, the antioxidant effect on tea seed oil was the most significant. The results of free radical scavenging capacity of oryzanol showed that oryzanol had some degree of free radical scavenging. Under the experimental conditions, oryzanol EC50 value of DPPH radical and ABTS radical were 0.06 mg/mL and 0.006 mg/mL.