Study The Antioxidation Effect Of Lycopene On Walnut Oil

At present,walnut is widely distributed in China,Xinjiang plays the most important role in walnut production(mainly in Kahi,Hetian,Akesu).The fat content of the walnut kernel is up to 60%.However,walnut oil is prone to oxidative rancidity during the storage process.Lycopene which is a natural functional pigment with the ability to remove free radical and quench singlet oxygen.Since lycopene is a fat-soluble substance,it can be dissolved in walnut oil to provide an antioxidant effect and better promote the absorption and utilization of lycopene.Suggesting that the adding lycopene to the walnut oil has practical significance.The main research contents and results are as presented follows:(1)In this study,walnut oil was extracted by cold pressing method.Five different levels of lycopene(i.e.0.0010%,0.0025%,0.0030%,0.0050%,0.0100%,0.0150%)were added to walnut oil and the Schaal oven accelarated oxidation was carried out at(60±1)?.The peroxide value,acid value,total phenol content,fatty acid composition and FRAP reduction ability of walnut oil was determined.This study suggested that the optimal addition of lycopene to be added to walnut oil was 0.0050%.(2)This study investigated the effect of temperature on the antioxidant activity of lycopene on walnut oil.The Schaal oven accelarated oxidation was conducted for oil at 40?,60?and 80?.The peroxide value,anisidine value and total oxidation value were determined.A good linear relationship was observed between the logarithm of oxidation rate constant of walnut oil and the reciprocal of temperature(R~2>0.987),which was consistent to Arrhenius law.Under the condition of 80?,60?and 40?,the optimal addition of lycopene on walnut oil was 0.0150%,0.0050%and 0.0050%respectively.(3)The walnut oil was subjected to an accelerated oxidation process in Schaal oven at(60±1)?by adding antioxidant including the same amout(0.0050%)of lycopene,TBHQ,BHA,BHT,?-tocopherol.The peroxide value,acid value,total phenol content,fatty acid composition and FRAP reduction ability of walnut oil were determined.After the enhanced oxidation at(60±1)?for 45 d,lycopene had better antioxidant activity than synthetic antioxidant BHA,BHT and natural antioxidant?-tocopherol.(4)This study also evaluated the effect of lycopene on the antioxidant effect of walnut oil during the storage period.Walnut oil was kept in the dark at 25?for 150 days with 0.005%lycopene.The contents of tocopherol,total phenol content and squalene content were decreased to 33.76 mg/kg,200.54 mgGAE/kg,14.03 mg/kg,respectively in the walnut oil with.0.005%lycopene while the figure was 30.98 mg/kg,110.75 mgGAE/kg and 13.83 mg/kg in the walnut oil without lycopene.The contents of five fatty acids were also changed in varying degrees.In a conclusion,this study showed that adding 0.005%lycopene to the walnut oil could effectively retard the oxidative rancidity of the oil and improved the preservation rate of the active ingredients in the oil.Thus,this would help to prolong the storage and shelf life of walnut oil.