Optimization of Ethanol Extraction of Rapeseed (Brasica napus L.) by Response Surface Methodology and Comparison of Antioxidant Effect of Extract on Oxidative Stability of Soybean Oil

Natural antioxidants are nowadays used to replace synthetic antioxidants to delay or prevent the oxidation of edible oils. In this study, Rapeseed (Brasica napus L.) was used as a natural compound to improve oxidative stability and increase shelf life of soybean oil. In this study, the extract was extracted under the influence of three variables at three levels: concentration (200, 500 and 800 ppm), time (10-30 minutes) and temperature (35-55°C). After extraction optimization, extracts with the highest antioxidant activity and total phenolic compounds were added to soybean oil with three concentrations (800, 500 and 200 ppm) and then oil samples at three levels temperature (72, 48 and 24 hours) and temperature (65, 55 and 45°C) were maintained. After various experiments on the extracts, the best extraction conditions for the extracts were determined using response surface methodology and extraction at optimum conditions. The results of the extract extraction optimization process showed that in the hydroethanolic extract, the optimal concentration was 200 ppm, the optimal time was 30 minutes and the optimum temperature was 47.028°C, which was used to evaluate the optimal amount of inhibitory free radical activity and total phenolic compounds in hydroethanol extraction were 43.885% and 39.852 mg GA/g, respectively. The time obtained from the oxidative stability of the oil showed that the time was 72 hours, the concentration was 200 ppm, and the temperature was 45°C. The results of oxidative stability of oil showed that the peroxide and thiobarbiotic acid indices in hydroethanolic extraction were 2.388 meq O2/kg and 0.329 mg/kg, respectively. The results of this study showed that natural antioxidants can be used as an alternative to synthetic antioxidants in edible oil formulations.