Abstract
Several polyunsaturated fatty acids are considered to have beneficial health effects, while saturated fatty acids and industrial trans fatty acids (TFAs) are linked to negative health consequences. Given the increased formation of TFAs during heating, many studies already investigated compositional changes in oils after prolonged heating or at extremely high temperatures. In contrast, our aim was to measure changes in fatty acid composition and in some health-related indices in edible oils after short-time heating that resembles the conventional household use. Potatoes were fried in palm, rapeseed, soybean, sunflower and extra virgin olive oils at 180 °C for 5 min, and samples were collected from fresh oils and after 1, 5 and 10 consecutive heating sequences. Regardless of the type of oil, the highest linoleic acid and alpha-linolenic acid values were measured in the fresh samples, whereas significantly lower values were detected in almost all samples following the heating sequences. In contrast, the lowest levels of TFAs were detected in the fresh oils, while their values significantly increased in almost all samples during heating. Indices of atherogenicity and thrombogenicity were also significantly higher in these oils after heating. The present data indicate that prolonged or repeated heating of vegetable oils should be avoided; however, the type of oil has a greater effect on the changes of health-related indices than the number of heating sequences.
Highlights
The fatty acid (FA) composition of edible oils plays an important role in human nutrition
Because they use the same enzymes during their metabolism, trans isomeric fatty acids (TFAs) can disturb the metabolism of n–3 and n–6 fatty acids
In the present study we focused on the total fatty acid composition of commonly used plant-based oils and fats and found significant changes in the availability of important dietary fatty acids during the frying process
Summary
The fatty acid (FA) composition of edible oils plays an important role in human nutrition. Essential fatty acids (EFAs) cannot be synthesized in the human body and should be taken up with our diet Both the omega–6 (n–6) EFA, linoleic acid (C18:2n–6, LA) and the omega–3 (n–3) EFA, alpha-linolenic acid (C18:3n–3, ALA) as well as their most important, longer chain derivates, arachidonic acid (C20:4n–6, AA), eicosapentaenoic acid (C20:5n–3, EPA) and docosahexaenoic acid (C22:6n–3, DHA) are considered to have beneficial health effects that can influence several areas of human physiology [1,2,3,4]. The physiologically important unsaturated fatty acids contain double bonds in cis configuration causing a bend of the molecule, while trans isomeric fatty acids (TFAs), to saturated fatty acids (SFAs), exhibit linear spatial configuration. Because they use the same enzymes during their metabolism, TFAs can disturb the metabolism of n–3 and n–6 fatty acids. The unfavorable health effects of TFAs in the human body can be caused by both their more rigid structure in lipid membranes and by their disturbing effect on fatty acid metabolism [5,6]
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