Study On Extraction And Oxidation Stability Of Pumpkin Seed Oil

In recent 20 years,the output of pumpkin in China has increased year by year,and pumpkin seeds,as the most important by-product of pumpkin,have gradually received attention.Pumpkin seeds are rich in fat,minerals and a variety of bioactive ingredients,making them a kind of oilseed with great potential.In this paper,the optimal process parameters of extracting pumpkin seed oil by pressing with microwave pretreatment and the effect of microwave pretreatment on the physicochemical properties of and the content of oil accompanying substances were studied.The optimum conditions of extracting pumpkin seed oil by supercritical carbon dioxide were optimized by response surface design,compared the quality difference of pumpkin seed oil produced by three extraction methods and during storage.The following results have been achieved:Taking the extraction rate of pumpkin seed oil as an index,the extraction conditions of pumpkin seed oil by squeeze with microwave pretreatment were optimized by single factor experiment and orthogonal experiment.Under the optimal conditions,the oil extraction rate of pumpkin seed oil was 69.5%.The effects of microwave conditions on the physicochemical properties of pumpkin seed oil and the content of oil accompanying substances were also investigated.The results showed that proper microwave pretreatment not only increased the oil extraction rate of pumpkin seed oil,but also increased the content of oil accompanying substances.With the index of extraction rate of pumpkin seed oil for reference,the process conditions of supercritical CO₂ extraction method was optimized through single factor,PB experimental design,steepest climbing test and BB response surface.The highest extraction rate of 74.9%was achieved under the optimum extraction conditions.The effects of 3 different processes,including cold-pressing,microwave-assisted pressing,and supercritical CO₂ extraction method on the oil extraction rate,physicochemical properties,content of accompanying substances of and free radical scavenging ability of pumpkin seed oil were compared.The results showed that the pumpkin seed oil prepared by supercritical CO₂ extraction method had higher moisture content,peroxide value and iodine value,and had advantages in total tocopherol and squalene content;The acid value of pumpkin seed oil by pressed with microwave pretreatment was higher and had advantages in total phenol content and total sterol content;Pearson bivariate correlation analysis showed that total phenol played a major role in antioxidant capacity of pumpkin seed oil,and other oil accompanying substances such asα-tocopherol andβ-sitosterol also exerted antioxidant effects.In the process of storage at room temperature,the acid value and peroxide value of pumpkin seed oil gradually increased with the increase of storage time,but the p-anisidine value had little change,although the content of oil accompanying substances and free radical scavenging ability decreased but did not change much,this indicates that the quality of pumpkin seed oil is relatively stable under normal temperature storage.The acid value,peroxide value and p-anisidine value of pumpkin seed oil increased gradually when the oil was accelerated oxidation by Schaal oven,while the content of oil accompanying substances and free radical scavenging ability decreased,it showed that high temperature could reduce the storage stability of pumpkin seed oil.At the early stage of storage,the contents of total phenol and tocopherol decreased rapidly,indicating that the total phenol and tocopherol had the main antioxidant effect in the early storage period;According to Pearson bivariate correlation analysis,polyphenols and tocopherols played an important role in the accelerated oxidation process of pumpkin seed oil,while squalene was not the main component to inhibit the oxidation of pumpkin seed oil.In this study,the effects of different processing methods and storage on the quality of pumpkin seed oil were explored.Pearson bivariate correlation analysis was used to explore the oil accompanying substances that played a major antioxidant role in the storage process.These results can lay a foundation for the research on the preparation and storage of pumpkin seed oil.