Formation of oxidative and cytotoxic products of tocopherols and their adsorption onto the surface of French fries when fried with rapeseed oil

This work examines the impact of frying (180 °C) French fries on the degradation of fatty acids and tocopherols in rapeseed oil, with a particular focus on the formation and adsorption of gamma-tocopheryl quinone on the surface of French fries. Gamma-tocopheryl quinone has a cytotoxic effect, and long-term exposure may alter DNA. It was found that gamma-tocopheryl quinone formed 1.2 times faster than alpha-tocopheryl quinone during pan-frying French fries. Addition of French fries also accelerated the hydrolysis of fatty acids, leading to a 1.3-fold increase in the rate of tocopherol degradation compared to heating pure oil. A new finding of this study is that gamma-tocopheryl quinone is the dominant oxidation product adsorbed onto the surface of French fries during frying, with its content being 1.5 times higher than that of alpha-tocopheryl quinone. The study highlights the need to reconsider using oils rich in gamma-tocopherol for frying to minimise health risks.