Dependence of tocopherol stability on different cooking procedures of food.
The influence of the kind of treatment during the preparation of hot meals (roasting, baking, stewing) on the stability of the tocopherols, which were added to the food through the margarines used, were examined in different food matrices. All preparation methods resulted in a loss of tocopherols. They could be divided into a group of only small loss of tocopherols (lower than 20%) and into a second group with nearly 70% loss of tocopherols (roasting of meat, steaming of peas). In the first group losses of tocopherols were directly associated with the fatty acid patterns of the used margarines, especially with the share of polyunsaturated fatty acids. On the other hand, during the roasting of meat nearly 70% of the tocopherols were destroyed by direct oxidation without a prohibitive effect on the lipid oxidation. The extreme high loss of tocopherols during the steaming of peas may be caused by the catalytic effect of the metal surface of the used pot. There were no losses of tocopherols observed when the experiments were repeated under identical conditions in an inert glass pot. Only tocopherol losses during baking may have a nutritional importance because of the great fat amount which are taken in with cookies.