Study On Oxidative Stability Of Acer Truncatum Oil During Storage

Acer truncatum oil is a kind of high quality edible oil with high nutritional value.However,due to its high content of unsaturated fatty acids,it is susceptible to oxidative rancidity affected by external environmental factors.Therefore,it is necessary to explore the storage stability of Acer truncatum oil to delay the process of oxidative rancidity.In this thesis,the quality changes of Acer truncatum oils prepared by three extraction technologies during the storage process and the effects of storage conditions and additive antioxidants on the oxidation stability of Acer truncatum oil were studied,and the oxidation kinetics model was established to predict the shelf life of Acer truncatum oil under different storage conditions.This study aims to provide a theoretical basis for well-informed storage of Acer truncatum oil.The main research contents and results are as follows:(1)Taking Acer truncatum seed oils prepared by the pressing method,organic solvent extraction and supercritical CO₂ extraction as the research object,the effects of three oil extraction processes on the physicochemical properties,composition and content of fatty acids,and oxidation stability during storage were studied.The results showed that:a)The refractive index,moisture and volatile matter,acid value(AV),peroxide value(POV)and iodine value of the three types of Acer truncatum oil are quite different,while the saponification value and 2-thiobarbituric acid(TBA)value have little difference.The moisture and volatile matter,saponification value and iodine value decrease during storage,while refractive index,AV,POV and TBA value increase.b)The effect of extraction process and storage time on the composition and content of fatty acids is marginal.The initial unsaturated fatty acid content follows a descending order of organic solvent extracted oil(92.36%)>pressed oil(92.29%)>supercritical CO₂ extracted oil(91.86%).The content of unsaturated fatty acids in the three kinds of Acer truncatum oil decreased slightly with the storage time(the saturated fatty acid content increased slightly),but remained above 90%.c)The POV,AV and TBA values of the supercritical CO₂ extracted oil are larger than those of the pressed oil and the organic solvent extracted oil,and the growth rate is higher during storage,indicating that its oxidation stability is poor.(2)Taking pressed Acer truncatum seed oil as the raw material and the POV,AV and TBA value as indicators for its oxidation stability,the effect of storage conditions such as temperature,light,air,bottle material and color on the oxidation stability of Acer truncatum seed oil was studied.The oxidation kinetic model was further established to predict the shelf life of Acer truncatum seed oils.The results showed that:a)Under the storage conditions of low-temperature,dark,oxygen-free and with packaging materials of stainless steel,ceramics,or glass tinted in blue/green,the POV,AV,and TBA values only grow very slowly,showing strong oxidation stability of the Acer truncatum seed oil.b)The oxidation process follows zero-order reaction kinetics,and the POVs at 30°C well matched the predicted values according to the kinetic model.c)The shelf life of Acer truncatum seed oil under sealed and dark storage conditions at 20°C and 25°C was calculated to be 17 months and 11 months,respectively.(3)Taking pressed Acer truncatum seed oil as the raw material,using the Schaal oven method and the POV as an indicator of oxidation stability,the effects of natural and synthetic antioxidants and synergists on the oxidation stability of Acer truncatum oil were studied.The results showed that:a)By adding the same amount(mass based)within the permissible limits,9 single natural and chemical antioxidants presented oxidation inhibition effects on the Acer truncatum oil,with TBHQ,rosemary and tea polyphenols being the most prominent.b)Ascorbic acid(Vc)and citric acid(CA)are effective synergists of compound antioxidants,and the synergistic effect of Vc is better than CA.c)The oxidation inhibitory effect of compound antioxidants is significantly better than a single antioxidant at the same additive levels.0.01%TBHQ+0.01%rosemary+0.01%Vc is the optimal combination of antioxidants,which can significantly slow down the oxidation rate of Acer truncatum oil.The predicted storage period under 20°C is extended from 4 months to 19 months.