Degradation of Edible Oil During Deep‐Frying Process by Electron Spin Resonance Spectroscopy and Physicochemical Appreciation

Abstract

During frying process of edible oil, lipid oxidation occurs, which is a complex process and involves free radical chain reactions. The impacts of oil with different fatty acid composition on free radicals were evaluated. An ESR study was performed to identify and quantify the formed radicals, along with the assessment of physicochemical parameters including peroxide value, oxidative stability, fatty acid composition, and volatile profile. Results showed an increase of formed free radicals in frying oils over frying time. Besides, frying oils with higher content of unsaturated fatty acids were more prone to be oxidized, as well as physicochemical parameters evidencing this phenomenon. Volatile compounds produced by β‐scission homolytic cleavage of peroxide group during thermal oxidation in frying oils were detected by GC‐MS/MS. Results implied major aldehyde volatile compounds were derived from hydroperoxide and oil with higher proportions of unsaturated fatty acids are more likely to produce volatile oxidation products.In order to compare the degree of lipid oxidation in deep‐fried sunflower oil (high degree of unsaturation) and palm oil (high degree of saturation), the formed free radicals based on ESR, along with the assessment of physicochemical parameters including peroxide value, oxidative stability, fatty acid composition, and volatile profile to improve comprehensive assessment of degradation in oil with different fatty acid composition are investigated.