Retarding sunflower oil oxidation during the deep-fat frying of potato chips using micro-encapsulated Convolvulus arvensis Linn leaf phenolic extract

In this research, the extraction of polyphenols from Convolvulus arvensis (CA) leaves was optimized using ethanol (80%) at plant/solvent ratios and extraction times which varied between 1/10 to 1/30 (w/v) and 20 to 120 min, respectively. The extract with the highest polyphenol content was obtained at a ratio of 1/30 and 90 min. At 120 ppm, the preceding extract in either lyophilized (LyCAE) or encapsulated (EnCAE) form was evaluated as an antioxidant during the frying process using sunflower oil in comparison to TBHQ. Frying oil quality indices including refractive index, smoke point, acid value, anisidine value, polar and polymer compounds were monitored throughout frying times. FTIR spectroscopy was used to investigate the changes in trans-fatty acids, hydroperoxides and aldehyde contents. The results showed that the phenolic extract, especially in EnCAE form, exhibited superior antioxidant activity over TBHQ, which consequently led to the utilization of this phenolic extract as an antioxidant in frying oils.