Different effects of tocopherol natural extract on sunflower oil stability under frying and accelerated storage conditions: A comprehensive study on the fate of major and minor components of oil, and added tocopherols

The effect of adding a tocopherol-rich natural extract (TNE) at 0.1 % and 0.5 % on sunflower oil stability under frying and accelerated storage conditions was studied using ¹H NMR and DI-SPME-GC/MS. The impact was more pronounced at the higher enrichment level under both conditions. During frying conditions, oil stability significantly decreased due to accelerated degradation of linoleate and minor components (tocopherols, squalene and sterols), along with a marked increase in oil viscosity. Additionally, the selective generation of aldehydes occurred, with the formation of alkanals, E-2-alkenals and toxic oxygenated α,β-unsaturated aldehydes being lagged. Under storage, TNE initially promoted linoleate degradation and the formation of monohydroperoxy-octadecadienoates but delayed their transformation into secondary or further compounds. Similarly, the degradation of oil minor components occurred more slowly. Tocopherol-derived metabolites varied depending on processing conditions. Pristane was the most abundant during frying, while 4,8,12,16-tetramethylheptadecan-4-olide predominated under storage conditions. Formyl derivatives were identified for the first time.