Pan‐Frying Conditions Affect the Tocopherol Intake From Edible Oils: Results From Temperature Measurements and the Standardized Heating of an Edible Oil

Tocochromanols (vitamin E compounds) are essential ingredients in human nutrition. Their consumption via edible oils is considered the main source of dietary intake. However, these molecules are prone to degradation when heated, for example, during pan frying. Standardized measurements in five homes indicated that the temperature typically applied during heating is much higher than anticipated (Part 1 of the study). Subsequent heating experiments were carried out with a model rapeseed oil initially liberated from tocochromanols by countercurrent chromatography (CCC) and then supplemented with similar amounts of eight tocochromanols. Heating this oil in a miniature heating apparatus to 180°C resulted in an almost quantitative loss of tocochromanols within 15 min. At 160°C, the loss of tocochromanols was still ~70%–80%. The stability decreased in the order δ‐tocopherol > δ‐tocotrienol ~ β‐tocopherol ~ γ‐tocopherol > γ‐tocotrienol > α‐tocopherol > α‐tocomonoenol ≥ α‐tocotrienol (Part 2 of the study). A preliminary estimation indicated that the degradation of tocochromanols during heating in private households may lead to an overestimation of the daily vitamin E intake by about 1/3rd.