Trans octadecenoic fatty acid (TFA) isomers in German foods and bakery goods

Abstract

In the present study, 122 food samples from the German food market were analysed for their C18:1 trans fatty acid (TFA) content and profile. A particular focus of the survey were baked and fried foods. TFA analysis was performed by means of silver ion SPE (Ag+-SPE) in combination with high-resolution GC (HRGC-FID). Overall, 51 bakery product samples were analysed of which 25 samples were prepacked bakery products purchased from local retail stores and 26 samples of unpacked bakery products purchased from local bakery shops. In addition, 14 French fries samples obtained from small local fast food restaurants as well as from internationally operating fast food chains, 27 potato and tortillas chips, 15 instant soups as well as 15 dry culinary sauces were analysed. The highest amounts of C18:1 TFA isomers were found in deep-fried bakery products. Prepacked branded cookies and biscuits on the other hand contained only negligible C18:1 TFA amounts. Regarding their C18:1 trans isomer profile most deep-fried bakery products exhibited a Gaussian-distributed isomer profile. The analysed prepacked croissants, cookies and biscuits contained predominantly ruminant TFA (TFA) as suggested by the presence of vaccenic acid (C18:1 trans 11), which was the major C18:1 TFA isomer in these products. All non-bakery samples (n = 71) contained less than 3 g C18:1 TFA per 100 g fat. In conclusion, TFA still occur in considerable amounts in a few German food products, especially in some deep-fried bakery products (‘Berliner’ type of doughnuts). Practical applications: Trans fatty acids, in particular the trans octadecenoic fatty acid isomers (C18:1), are generally considered from the nutritional point of view as undesirable food components due to their negative health effects. Tremendous efforts have been made by major food processors in order to decrease or even eliminate the presence of TFA in some foodstuffs (e.g. in margarines in European countries). However, some food processors of other food sectors are still applying oils and fats containing partially hydrogenated vegetable oils, whereas others within the same food category have already switched their processing conditions and/or raw materials towards TFA alternatives. Therefore, actual TFA data of foodstuffs determined by means of state-of-the-art analytical procedures (Ag+-SPE in combination with GC-FID) is necessary to detect areas of further improvement in the food supply chain and to provide data for an update of dietary TFA intake.