# Loss of Vitamin E While Baking and Heating French Fries
## 3 Results and Discussion
### Content of Tocochromanols in Frozen Pre-Fried French Fries and Factors Affecting It
These losses were independent of the baking method used (\(p<0.01\)) and averaged at 0.80 mg/kg (maximum 4.85) of the original pre-fried frozen products for \(\alpha\)-T, 0.44 (1.52) mg/kg for \(\alpha\)-T3, 1.11 (5.20) mg/kg for the sum of tocochromanols and 0.92 (4.92) mg/kg for the \(\alpha\)-TE content of vitamin E. These values represent an average of 9.1 (maximum 53.4)% of the original \(\alpha\)-T content, 36.6 (98.4)% of \(\alpha\)-T3, 12.7 (37.2)% of the sum of tocochromanols and 12.6 (51.4)% of the content of vitamin E expressed in \(\alpha\)-TE. Figure 1: The content of vitamin E in the analyzed pre-fried frozen French fries depending on the frying medium used. The results are presented as averages and spreads of the values for fries prepared using sunflower oil (four samples) and palm oil (five samples). The results from classic baking are comparable to those of an analogous study from 1965 [29] and also to the loss of tocochromanols and vitamin E found generally in studies about the loss of these analytes during the baking of different foods [25; 36; 37]. In these works, the losses of toochromanols and vitamin E during baking typically ranged from 0 to 30%. The only exception were the losses noted in the production of rye bread (30-50% of the original content), which also included growth time (18 h) [25] and wheat bread (47.6%), which has a low origin content of tocochromanols [37]. There is a relatively large number of studies about microwave heating that have studied the losses of tocochromanols and vitamin E in vegetable oils [38; 39; 40; 41]. Contrasting this study, the analytes typically lost 10% of the original content (compared to the heating time for baking French fries this study). These studies of vegetable oil and this study may differ in the temperatures achieved while microwave-heating the vegetable oils compared to other foods (due to the presence or absence of water in the material). Oils typically reach temperatures of 200-250 \({}^{\circ}\)C after 20 min of heating in the microwave oven [42; 43]; water-containing foods have significantly lower temperatures during and after microwave heating [44]. This, for instance, leads to low tocochromanol losses (up to 20% of the original content) which were observed when warming various plant seeds and seed oils in a microwave oven for 15 to 20 min [45; 46; 47]. Evaluation of French Fries, Prepared from Commercially Available Pre-Fried Frozen Products Baked in Conventional and Microwave Ovens, as a Source of Vitamin E  
Previous estimates of the biological activity among individual tocopherols and tocotrienols were obtained via experiments with laboratory animals. These estimates expressed the vitamin E activity in \(\alpha\)-tocopherol equivalents (\(\alpha\)-TE). \(\beta\)-tocopherol displayed approximately 50% activity of \(\alpha\)-T, \(\gamma\)-T 10% and \(\delta\)-T 3%. Tocotrienols have about two-thirds less biological activity than the corresponding tocopherols (i.e., \(\alpha\)-T3 30% \(\alpha\)-T activity and \(\beta\)-T3 5% \(\alpha\)-T activity; otherwise, T3 activity is not considered or is neglected) [44]. The recommended dietary allowance (RDA) of vitamin E has been identified as 12 mg \(\alpha\)-TE [48]. However, cotemporary research, based on the \(\alpha\)-tocopherol transfer protein, suggests that the human metabolism is only selective for 2R isomers of \(\alpha\)-tocopherol. Therefore, recent literature suggests that only 2R isomers of \(\alpha\)-tocopherol exhibit vitamin activity for humans. The other vitamin E vitamins (i.e., \(\beta\)-, \(\gamma\)- and \(\delta\)-tocopherol and tocotrienols) and 2S isomers of \(\alpha\)-tocopherol are absorbed from the human digestive system but not recognized in the liver by the \(\alpha\)-tocopherol transfer protein. They therefore do not contribute to the vitamin E requirement. These compounds are then excreted into the bile and only very small quantities enter the cells.