| Rapeseed oil has high nutritive value with rational fatty acid composition and abundant micronutrients, but the extracted and refined methods in China could result in the loss of micronutrients and decrease the antioxidant activity and nutritional value in rapeseed oil. Therefore, rapeseed oil processing methods on physiochemical, oxidative stability and biological evaluation in rats was studied to provide the foundation for appropriate processing of domestic rapeseed oil.Firstly, cold pressed, hot pressed, aqueous enzymatic extraction, hexane extraction and refined rapeseed oils were studied on physiochemical properties. The result showed: the content of C18:3ω3 fatty acid, triglyceride OOLn and LLL decreased and C18:3ω6 fatty acid, triglyceride OLL increased in refined rapeseed oil, but the other four processed rapeseed oils showed no difference on fatty acid and triglyceride composition. The order of tocopherols’ content was hexane extraction, aqueous enzymatic extraction, cold pressed, hot pressed and refined rapeseed oil with 833.74, 756.10, 723.94, 678.93 and 500.96 mg/kg. The order of β-carotene’s content was aqueous enzymatic extraction, hot pressed, hexane extraction, cold pressed and refined rapeseed oil with 5.39, 3.72, 3.60 and 2.59 mg/kg. The order of polyphenol’s content was aqueous enzymatic extraction, hexane extraction, hot pressed, cold pressed and refined rapeseed oil with 152.08, 144.77, 71.66, 54.08 and 47.33 mg GAE/kg. The content of sterol was the highest with 6607.35 mg/kg in hexane extraction rapeseed oil, but there was no significant difference among other four processing rapeseed oils.Secondly, based on the Rancimat method, Schaal oven method and scavenging capacity for DPPH radicals in different processed rapeseed oil, the trend of oxidative induction time and scavenging DPPH capacity was same with the following order: aqueous enzymatic extraction rapeseed oil, hexane extraction rapeseed oil, hot pressed rapeseed oil, cold pressed rapeseed oil and refined rapeseed oil. Furthermore,the oxidative stability was significantly related to the polyphenol content in different processed rapeseed oil. And the correlation coefficient was 0.949 and 0.920 respectively.Finally, to study the lipid-lowering effects of different processing methods in SD rats, the high-fat model was established. After feeding for thirteen weeks, SD rats were analyzed for their weight growth status, serum lipid biochemical parameters, serum and hepatic redox indicators, tissue histopathological examination and hepatic fatty acid composition. The results showed that the the lipid-lowering effects in aqueous enzymatic rapeseed oil was better than the other processed rapeseed oil. Compared with the high-fat group, the aqueous enzymatic rapeseed oil could significantly reduce body and organ weight, improve lipid metabolism, and decrease liver lipid metabolism disorder caused by high-fat diet. The serum TC, TG and LDL-C content were decreased by 27.09%, 11.81% and 35.52%. The levels of ALT and AST were decreased by 31.02% and 27.61%, improving the hepatic function in SD rats. At the same time, SOD and CAT levels increased and the MDA content decreased, improving the antioxidant ability. Histopathological examination indicated that aqueous enzymatic extraction rapeseed oil could protect liver cell damage induced by high-fat diet and reduce hepatic fat deposition. Cold-pressed rapeseed oil and hot-pressed rapeseed oil could also decrease lipid metabolism disorders, but there was no significant difference between the two groups; refined rapeseed oil group like high-fat group could cause lipid metabolism in SD rats. |
