Improvement of Refined Soybean Oil by Enrichment with Phenolic Extracts from Wild and Cultivated Olive Leaves

Abstract

Background:: Several researches have focused on the antioxidant capacity of natural components extracted from plants. Their properties are determined by the presence of phenolic compounds that extend the shelf life of food and protect fats from autoxidation. Olive leaves, an abundant raw material, are a significant source of bioactive phenolic compounds, which can be used to enrich a widely used edible oil. Objective:: The goal of this study was to improve the properties and stability of soybean oil by adding phenolic compounds extracted from the leaves of wild and cultivated olive trees. Methods:: Leaf polyphenolic extracts obtained from Chemlal cultivar and wild olive were used to enrich refined soybean oil. The antioxidant activity was evaluated for the chain-breaking antioxidant effect using DPPH and FRAP assay. The oxidative stability was estimated using a rancimat apparatus. The effect of the frying conditions was studied by determining the rate of the polar fraction. Results:: Total phenol contents from cultivated and wild olive leaves were important: 1047.19mg EAG /100g and 1424.59mg EAG/100g, respectively. Oil extracts enriched with Chemlal and wild olive leaves extracts at 25ppm presented 93.29% and 93.20% inhibition percent of DPPH radical, respectively. An improvement of 75 and 73% was observed for oils enriched with Chemlal and wild olive leaves respectively, for the antiradical activity against DPPH radical. The stability of the enriched oils is proportional to the concentrations of phenolic extracts and higher than that shown for the non-enriched ones. The frying test showed that the enrichment is causing a complete absence of polar compounds in the fries. Conclusion:: The results of this study show the efficacy of adding polyphenols to olive leaves to increase the quality and oxidative stability of refined soybean oil.