Abstract

The aim of present study was to compare the effects of ultrasound‐assisted and microwave‐assisted extraction with solvent extraction method on antioxidant activities of jujube ( Ziziphus mauritiana Lam.) leaf extracts in stability of sunflower oil during deep frying. The antioxidant activities of the extracts were evaluated by using 2, 2‐diphenyl‐1‐picrylhydrazyl ( DPPH ˙) radical scavenging and β ‐carotene bleaching assays. Ultrasound‐assisted extraction was the most effective method on antioxidant activities of extracts and extraction yield of phenolic compounds compared to other extraction techniques. Protective effect of methanol–water extract of jujube leaf obtained with ultrasound‐assisted extraction ( ULMW ) at 500 and 700 ppm in stability of sunflower oil was compared to synthetic antioxidants by measuring total polar compounds ( TPC ), carbonyl value ( CV ), peroxide value ( PV ), free fatty acids ( FFA ), oxidative stability index ( OSI ), conjugated dienes ( CD ), and trienes values ( CT ). Results showed ULMW at 700 ppm had higher stabilization efficiency than synthetic antioxidants.

Oil oxidative stabiliy during frying conditions.