Quality Evaluation Of Peanut Oils Prepared By Different Processes And Its Effect On Lipid Metabolism And Oxidative Stress In SD Rats

Peanut oil is one of the main edible oils in China.It is rich in unsaturated fatty acids and minor bioactive compounds.However,the present peanut oil extraction processes can easily cause the loss of micronutrients and the increasing of harmful substances,affecting the quality of peanut oil.In this paper,qualities of peanut oils prepared by cold pressing and enzyme-assisted aqueous extraction methods and traditional hot pressing technology were compared to investigate the effects of different peanut oil preparation technologies on the basic physicochemical indicators,minor bioactive compounds and harmful factors.Meanwhile,the impacts of different peanut oils on lipid metabolism and oxidative stress were studied by a high-fat experimental animal model of SD rats,evaluating the relationship between peanut oils'nutrition and oil extraction methods.The main contents and results of this research are as follows:(1)With peanut as raw material,the peanut oils were prepared by cold pressing(temperature was 60~oC),hot pressing(temperature was 150~oC),and enzyme-assisted aqueous extraction methods,and the quality difference of peanut oils prepared by different processes was compared and analyzed.The results showed that both of the color index(Y19.5R1.0)and peroxide value(2.05±0.00 mmol/kg)in enzyme-assisted aqueous extracted peanut oil(EAO)were the lowest compared to cold pressed peanut oil(CPO)and hot pressed peanut oil(HPO).While,its acid value(0.66±0.05 mg KOH/g),and oleic acid content(50.73%±0.43%)were the highest;the contents of total tocopherols(206.61±3.24 mg/kg)and polyphenols(44.27±2.60 mg GAE/kg)in HPO were the highest;whereas the squalene(477.20±10.31 mg/kg)and sterols(730.87±3.26 mg/kg)in CPO were the highest,compared with HPO and EAO;and the benzo(a)pyrene was not detected.The physicochemical properties and contents of minor bioactive compounds and harmful substances were different among the peanut oils.(2)The antioxidant capacity of peanut oils prepared by the three extraction methods in vitro were studied by measuring oxidative stability index(OSI),DPPH and ABTS free radical scavenging capacity.The results showed that the OSI of EAO was highest,the ability of scavenging free radicals(DPPH and ABTS)of HPO was the strongest.Polyphenols and tocopherols in the peanut oils may be the main cause of the differences in their antioxidant capacity.(3)SD rats fed high-fat diet model was established to study the effects of the peanut oils extracted with different methods on lipid metabolism and oxidative stress.The results illustrated that the three peanut oils could improve the lipid metabolism disorder and oxidative stress injuries in SD rats induced by HFD,compared with the lard oil control group.Among the peanut oil groups,CPO could have better effects on ameliorating lipid metabolism and oxidative stress injuries,while,there was no significant difference between HPO and EAO;Moreover,hepatic histopathological examination showed that CPO could also reduce liver lipid deposition and improve hepatic steatosis damage in SD rats fed HFD;There was no difference in fatty acid composition and content in liver tissues in all peanut oil groups;The peanut oils could affect expression of genes related to liver lipid metabolism in SD rats fed HFD,that is,up-regulating the expression of PPAR?,Acox1 and CYP7A1,and down-regulating the expression of SCD-1 in SD rats to improve the lipid metabolism disorder induced by HFD,compared with the lard control group.However,there was no significant difference in the regulation of the above genes expression among the peanut oil groups.The basic physicochemical indicators,bioactive components,hazardous substances,and antioxidant capacity of peanut oils prepared by the three different processes were different.And the effects of these peanut oils on lipid metabolism in SD rats were also different.Compared with EAO,the contents of bioactive substance in pressed peanut oils were higher,showing stronger antioxidant capacity.Among them,CPO contained lesser harmful substances and could have better effects on improving lipid metabolism disorder and regulating oxidative stress damage in animals fed HFD.This study can provide some theoretical references for peanut oil processing technology and product control in China.