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Rice bran is an abundant renewable and cheap sources of edible oil,which can be pressed or extracted or through other methods to obtain crude rice bran oil. Rice bran oil contains complete, reasonable fatty acids and, and is rich of oryzanol, vitamin E, squalene, and other natural active nutrients. However, crude rice bran oil contains higher phospholipids, free fatty acids, wax, pigments and other impurities, compared to normal vegetable oil. In order to take full advantage of the provincial rice bran resources, and to obtain high oryzanol content and high quality rice bran oil, the processes of degumming, deacidification, bleaching and other processes were systematically studied and improved in this article.The chief study content and results are as follows:(1) The degumming process:The methods of simultaneous degumming and dewaxing, citric acid, oxalic acid and double-ethanolamine are tested and compared, the results show that the oxalic acid method is best suited for degumming of rice bran oil. Single factor and orthogonal experimental designs are used to optimize the process of degumming, the optimal acidic degumming parameters are:the amount of oxalate added 1.20%(of crude oil weight), water addiction 4%, temperature 40℃, stirring time 40min, phosphorus content of degummed oil is decreased from 681.5mg/kg to 20.32mg/kg.(2) The decolorization process:Mixture of activated carbon and activated clay are used as a bleaching agent for rice bran oil. Single factor and orthogonal tests indicate the best bleaching process of rice bran oil, which are:bleaching agent dosage 4.0%(of oil weight), activated carbon proportion of mixture 10%, bleaching time 25min, bleaching temperature 60℃, the final decolorization rate is 90.81%.(3) The deacidification process:The extraction efficiency of ethanol and isopropanol are tested, the results show that the combination of ethanol and isopropanol gets the best extraction efficiency. Then the proportion of ethanol and isopropanol, the dosage of mixed extraction solvent, extraction temperature and extraction time are Respectively studied for extraction efficiency in single factor design. Response surface methodology is used to optimize the deacidification process, the optimum process parameters deacidification are:the volume rate of ethanol and isopropanol 1:1, solvent oil ratio (v/m) 2.0, extraction time 40min, extraction temperature 19.3℃, the acid value of rice bran oil is reduced from 18.6mgKOH/g down to 1.97mgKOH/g, and it can be further reduced to less than 1.OmgKOH/g for another extraction.(4) The comparison of oryzanol content before and after refining, the determination of physical and chemical indicators and gas chromatography-mass spectrometry are tested. Two-step (firstly use acid, secondly use alkali) method of methyl ester treatment is adopted. Then the rice bran oil fatty acid composition is tested through gas chromatography-mass spectrometry analysis. The results show that:the final oryzanol content of rice bran oil is 1.52 percent (crude oil content is 1.70 percent), oleic acid content is 48.81%, linoleic acid content is 32.05%, other physical and chemical indicators all meet the national standards for edible rice bran oil.
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