Study On The Influence Of Perilla Seed Oil Refining Process On Its Quality

The study is one of the subjects of the key scientific and technological project of the Science and Technology Department of Jilin Province(20190301058NY)and the core technical projects of “double tenth engineering”(18SS030)supported by Jilin Province science and technology bureau.Perilla seed oil in different refining stages were regarded as the research object in the paper,to analyze the effect of different refining stages on physicochemical indexes,oxidation indexes,biological active compounds and antioxidant activities,and the correlation of each other was analyzed using the Pearson method;then the key refining processes affecting the quality of perilla seed oil were determined.And physicochemical indexes during the oxidation process and the shelf-life of refined oil were determined,in addition,cluster analysis was performed based on perilla seed oil quality.The oxidation induction time was measured at last,and the shelf-life prediction was performed using an oxidation kinetic model.(1)Physicochemical indexes of perilla seed oil in different refining stages were measured,and results indicated that acid value,iodine value,saponification value,and refractive index differed depending on the refining stage.GC-MS and normalized area method were used to determine the fatty acid composition,a total of 11 fatty acids were detected.The higher content was linolenic acid,linoleic acid,palmitic acid,and stearic acid.Results of the oxidation index showed that there is a significant difference in the peroxide value during different refining stages of perilla seed oil,and the crude oil has a higher peroxide value.Anisidine value,thiobarbituric acid,conjugated triene have significant differences in the refining process,and they increase firstly and then decrease.Overall,neutralization,bleaching and deodorization stages have significant effects on the physicochemical and oxidation indexes of perilla seed oil.(2)HPLC was used to determine bioactive compounds in perilla seed oil at different refining stages,and the correlation analysis was performed in combinationwith the in vitro antioxidant activity to determine the key processes affecting the oxidation stability.Degumming and neutralization led to a large decrease in total phenol content,with a loss rate of 19.4%.Bleaching resulted in a significant decrease in the content of ?-tocopherol,?-tocopherol,and the loss rate of total tocopherol was7.0%.In addition,bleaching also caused a significant decrease in carotenoid content,with a reduction rate of 73.6%.Neutralization and bleaching are the main stages leading to the loss of phytosterols,with loss rates of 11.3% and 1.9%,respectively.Neutralization reduced the DPPH value of perilla seed oil significantly;bleaching caused a slight decrease in ABTS value;FRAP value was the lowest during bleaching additionally;the most obvious stage of ORAC value reduction occurred in deodorization,followed by degumming and neutralization,respectively.Comprehensive analysis shows that the key processes affecting the content of bioactive substances in perilla seed oil are ranked from high to low in order of bleaching,neutralization,and deodorization.(3)The Schaal oven method was used to study the oxidation stability.Acid value,peroxide value and conjugated diene showed an upward trend with increasing storage time.After analysis,the most severe primary oxidation was crude oil,followed by degummed oil,while the refined oil was relatively stable.The thiobarbituric acid and conjugated triene showed an overall upward trend during the oxidation process,and the winterization and refined oils were relatively low.Anisidine values of winterization and refined oils remained low during acceleration.The order of oxidative stability determined by research is: refined oil ? dewaxing oil >neutralization oil > bleaching oil ? deodorized oil > degummed oil ? crude oil.(4)The Rancimat method was used to observe the change in oxidation induction time(IP),furthermore,the oxidation kinetic model and the Arrhenius equation were performed to predict the shlf-life.The IP is positively correlated with the degree of refining and negatively correlated with temperature.The shelf-life of perilla seed oil at room temperature was inferred by using the Arrhenius equation.Results showed that the shelf-life of winterization and refined oils was significantly extended,and the refined oil is 1.6 times longer than the crude oil.