Effect Of Electron Beam Irradiation On The Nutritional Quality From Rice Bran And Rice Bran Oil

Rice bran contains important nutrients and essential elements of rice,which is a kind of valued by-product resource.Rice bran oil is the main nutrient component of rice bran with the characteristics of lowering cholesterol,lowering blood fat,anti-oxidation and anti-cancer,which is beneficial to human health.However,in the process of shedding of rice bran,the lipase contained in the rice bran easily combines with lipid,which could cause lipid oxidative rancidity and deterioration and reduce the utilization rate of rice bran.Therefore,in this paper,high-energy electron beam irradiation(EBI)technology was applied to treat rice bran to achieve the purpose of protecting the excellent characteristics of rice bran,reducing lipase activity effectively,prolonging the storage time of rice bran oil,and improving the comprehensive utilization rate of rice bran.The main research contents and results are as follows:The EBI treatment of the food-grade rice bran oil was carried out with different doses(2 kGy-10 kGy)to study the effect of EBI on the color change,saturated fatty acid content and unsaturated fatty acid content.With the increase of EBI dosage,the brightness of rice bran oil gradually brightened,and the content of saturated fatty acids and the content of unsaturated fatty acids,which above changes were not significant.The EBI treatment of fresh brown rice was carried out with different doses.The effects of EBI on the physical and chemical properties and quality of rice bran were studied by measuring the color change,main component content and lipase activity of rice bran.The results showed that with the increase of irradiation dose,the color of rice bran gradually darkened,and the contents of water,ash,protein,fat and reducing sugar of rice bran did not change significantly,and the activity of rice bran lipase decreased significantly.When the irradiation dose was 10 kGy,the EBI treated rice bran lipase activity was reduced to 54.84%of the untreated rice bran.Rice bran oil was extracted from EBI treated rice to study the effect of EBI on color change,saturated fatty acid content,unsaturated fatty acid content and acid value of rice bran oil.At the same time,the kinetic experiment was used to investigate the effect of prolongation rice bran shelf life by EBI treatment.The results showed that with the increase of EBI dosage,the brightness of rice bran oil increased,the content of saturated fatty acid such as stearic acid and palmitic acid decreased slightly,and the content of unsaturated fatty acids such as linolenic acid,oleic acid and linoleic acid increased slightly.Moreover,the acid value of the rice bran oil of EBI treated rice bran was significantly lower than the untreated rice bran,which caused the shelf life of rice bran extend by 37 days.The EBI treatment of solid and liquid lipase was carried out with different dose.The effects of different doses of EBI on the properties and structure of lipase were studied by measuring the hydrophobicity,carbonyl content,total sulfhydryl content,thermal stability,secondary structure relative content and lipase content and activity of lipase.The results showed that lipase activity showed good dose-effect relationship with EBI dose.With the increase of irradiation dose,the lipase content decreased significantly and the lipase activity decreased gradually.When the EBI dose was 10 kGy,the residual activity of solid lipase could be reduced to 59.43%of the original enzyme activity,while the residual activity of liquid lipase could be decreased to 66.58%.With the increase of irradiation dose,the total sulfhydryl content,surface hydrophobicity and thermal stability were significantly reduced,the carbonyl content was significantly increased,the number of a--helical structures and?-sheet structures decreased significantly,and the number of ?-turn structures and random coil structures increased significantly.Therefore,EBI could alter the secondary structure of lipase and disrupt the whole structure of lipase.With the same EBI dose,the effect of EBI on the liquid lipase was stronger than the solid lipase.The EBI treatment of the rice bran protein was carried out with different doses.The hydrophobicity,carbonyl content,total sulfhydryl content,thermal stability and secondary structure relative content changes of rice bran protein were determined to study the effects of EBI on the properties and structure of rice bran protein.The results showed that the properties and structure of rice bran protein were damaged,which were consistent with the changes of lipase.