Zuzana Réblová

Vitamin E, as the most important lipophilic antioxidant of eukaryotic cells, plays an important role in human nutrition. So far, information has focused on the content of vitamin E in raw food materials or foods, and its losses under various processes and culinary treatments. However, the different degradation rates of its eight different forms, four tocopherols and four tocotrienols, during the preparation of oven-ready products have not been clearly and in detail described. Therefore, the aim of our research was to determine the changes in the content of tocochromanols and to evaluate the risks of the loss of these substances while preparing frozen French fries baked in classic and microwave ovens. The tocochromanols were determined using reverse-phase high-performance liquid chromatography with an amperometric detector. The results showed a statistically insignificant loss of γ-tocopherol (γ-T), δ-tocopherol (δ-T), γ-tocotrienol (γ-T3) and δ-tocotrienol (δ-T3). Conversely, the losses of α-tocopherol (α-T), α-tocotrienol (α-T3), the total content of tocochromanols and the vitamin E content in α-tocopherol equivalents (α-TE) were statistically significant (p < 0.01). These losses were independent of the type of baking (conventional heating, heating with air circulation, grill, microwave heating, microwave and grill heating) and averaged at 0.80 mg/kg of the original fries (9.1% of the original content) for α-T, 0.44 mg/kg (36.6%) for α-T3, 1.11 mg/kg (12.7%) for the sum of the tocochromanols and 0.92 mg/kg (12.6%) for the vitamin E content expressed as α-TE. These dishes contained 0.4% to 26% of the daily requirement of vitamin E, based on a 100 g portion, depending on the fat used in the manufacture of the products. The choice of the right frying medium on the part of the manufacturer can increase the content of vitamin E both in the semi-finished product and in the final food, and consequently also its dietary intake.