Cyclic fatty acids in foods: origin, role in food authentication, relevance in the human diet, and health aspects

Cyclic fatty acids are an unusual class of minor fatty acids generally produced by bacteria and less frequently by plants. Bacteria (e.g. lactic acid bacteria) synthetize cyclopropane fatty acids, as dihycrosterculic acid (9, 10-methylene octadecanoic acid) and lactobacillic acid (11, 12 methylene octadecanoic acid), to strength their membrane, improving their resistance to environmental stress. Another class of cyclic fatty acids is omega-cyclohexyl fatty acids, present in milk and probably produced by rumen bacteria. Cyclopropane and omega-cyclohexyl fatty acids have been recently found in bovine meat and dairy products, representing important foodstuffs in human diet. The doctoral research project principally focused on the application of GC-MS and 1H NMR techniques to study cyclic fatty acids as molecular markers for food authenticity and their role in human nutrition. The occurrence and content of cyclopropane fatty acids in dairy and meat products were mainly correlated with the feeding system (use of silages in ration), whereas omega-cyclohexyl fatty acids have been proposed as markers for ruminant species. From a nutritional point of view, the origin and the presence of cyclic fatty acids (especially cyclopropane fatty acids) in several food sources, their bioavailability and potential bioactivity in humans have been investigated. Data presented in this PhD thesis represent a promising starting point for future studies on their potential healthy aspects.