Enrichment of Olive Oil with Polyphenols from Oleaster Leaves Using Central Composite Design for the Experimental Measurements

There is a growing need to develop an effective process for improving the oxidative stability of edible oils using natural antioxidants. Central composite design of experimental measurements was used to investigate the effects of three process variables (weight of dried powdered oleaster leaves, volume of olive oil, and maceration time) on olive oil enrichment with oleaster (wild olive trees) leaves. By solving the regression model equations and analyzing three-dimensional response surface plots, the optimum conditions were determined for the polyphenol, chlorophyll and carotenoid contents and for the antioxidant activity using 2, 2 diphenyil-1-picrylhydrazyl (DPPH) and 2, 2’‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS) assays. The optimal conditions were 7.76 g of dried powdered oleaster leaves, 116.44 mL of olive oil and 41.82 h for the maceration time. High polyphenols (354.95 mg/kg), chlorophylls (8.13 mg/kg) and carotenoids (1.51 mg/kg) were determined to be optimism. High-performance liquid chromatography analysis showed that the enrichment process improved the phenolic profile of the enriched olive oil. Furthermore, the DPPH and ABTS activities were 427.30 and 738.50 mg TEAC/kg oil, respectively. The experimental measurements agreed with the predicted values. Oleaster leaves have great potential to be applied as natural sources of bioactive molecules for edible oil processing.