Effect Of Refining Technology On The Content And Color Of Oryzanol In High Acid Value Rice Bran Oil

The development of rice bran oil is restricted to some extent by the problems of high acid value,deep color and nutrient loss during refining.In this paper,the refining process of rice bran oil was studied to keep the oryzanol in the oil efficiently during deacidification.In the process of decolorization,the effective adsorbent was introduced to assist the bleaching of clay.At the same time,the dewaxing and degumming links in the refining process of rice bran oil with high acid value were well pretreated.Because the oryzanol in rice bran oil did not form salt when its acid value was high in the early stage of alkali refining,it had strong oil affinity,high molecular polarity,and was not adsorbed by the soap foot.When the acid value of rice bran oil decreased to a certain value,the oryzanol was saponified,and the polarity changed after salt formation,which was easy to be adsorbed by the alkaline soap foot,so a two-stage deacidification process was constructed.That is to say,the acid value is reduced to a certain value by the first alkali refining and deacidification,and then the remaining fatty acids are removed by the distillation deacidification process.At the same time,the effect of acid value retention on the retention rate of oryzanol is studied when the rice bran crude oil with different acid value is deacidified by alkali refining.The results show that for crude oil with acid value of 22 mg/g-25 mg/g,the best acid value is 5 mg/g in alkali refining and deacidification;for crude oil with acid value of 25 mg/g-35 mg/g,the best acid value is 6 mg/g;for crude oil with acid value of 35 mg/g-37 mg/g,the best acid value is 7 mg/g.Taking the content of oryzanol as the main index,response surface optimization experiment was designed on the basis of single factor experiment.The best conditions of deacidification by alkali refining are 25 ?,22 min and 16.91% of alkali solution.Under these conditions,the content of oryzanol in rice bran oil is 2.05%,the deacidification rate is 77.78%,and the refining rate is 80.05%.The best conditions of deacidification by distillation are225 ?,86 min.Under these conditions,the content of oryzanol in rice bran oil is2.16%,the deacidification rate is 90.83%,and the refining rate is 92.42%.The color of rice bran oil is deep,and the effect of adsorption and decolorization of conventional clay and activated carbon is not ideal.Silica gel is a kind of highly active porous adsorption material because of its abundant porous structure.In view of the weak adsorption capacity of silica gel for natural pigments and the low efficiency and practicability of chromatography decolorization,activated clay combined with silica gel can reduce the color of rice bran oil to a large extent.Taking decolorization rate as the main index,response surface optimization experiment was designed on the basis of single factor experiment.The results showed that the best decolorization conditions were 5%,93 ? and 27 min.Under these conditions,the decolorization rate of rice bran oil is 74.63%,the content of oryzanol is 2.02%,the refining rate is 90.05%,and the color indexes are yellow 20,red 1.7 and blue 0.The optimum technological conditions of silica gel decolorization were as follows: silica gel 4.22%,temperature 81 ?,time 30 min.under these conditions,the decolorization rate of rice bran oil was 47%,the content of oryzanol was 2.01%,the refining rate was 89.36%,and the color indexes were yellow 5,red 0.3 and blue 0.