Monitoring lipid oxidation events at frying temperatures through radical scavenging assays

Abstract

This communication proposes an alternative approach for monitoring oils during thermal stress at frying temperatures through radical scavenging assays. Oxidation events for extra virgin olive, pomace, sesame, sunflower, soybean, corn and of a commercial blend of oils are followed through the DPPH assay during heating at 100, 150 and 190 °C. Radical scavenging activity decrease expressed as trolox equivalent antioxidant capacity (ΔATEAC, mmol trolox kg-1 oil) is found to be linearly related to increases in total oxidation (ΔTOTOX) values. This relationship is valid down to a certain -ΔTEAC value cutoff that is different for different oils. Considerable consumption of antioxidants demonstrated by high -ΔTEAC values renders the linear relationship invalid indicating that antioxidants cannot control late events of oxidative damage. Radical scavenging activity is found to increase upon sesame oil heating in contrast to all other oils. It is postulated that sesamolin, a phenolic antioxidant, decomposes during heating to the more potent antioxidant sesamol accounting for the increase of radical scavenging activity upon heating. This paper demonstrates prospects of radical scavenging activity assays as a tool for monitoring oxidation events during frying and warrants further research and evaluation.