Determination of Cyclopropane Fatty Acids in Food of Animal Origin by¹H NMR

Abstract

Cyclopropane fatty acids (CPFAs) are unusual fatty acids of microbial origin, recently detected in milk and dairy products. CPFAs have been demonstrated to be interesting molecular markers for authentication of dairy products obtained without ensiled feeds. Moreover, they can also be recognized as a new secondary component of human diet. Information is lacking on the presence of cyclic fatty acids in other food sources. Cyclopropane fatty acids have been detected by GC-MS analysis in cheese and other animal fats in concentration ranging from 200 to 1000 mg/kg fat, but in some cases, the complex fatty acid profile and the possible presence of interfering peaks make the separation not straightforward and the quantification uneasy. Therefore, a new reliable 1H NMR method was developed to detect and measure CPFA content in different foods of animal origin, based on the detection of the characteristic signals of cyclopropane ring. The 1H NMR (600 MHz) method showed detection limits comparable with those of full scan GC-MS, and it allowed the identification and quantitation of the cyclopropane fatty acids in different foods.

Cyclic Fatty Acids in Food: An Under-Investigated Class of Fatty Acids

“…As suggested by Lolli et al [12], cyclopropane fatty acids (mainly dihydrosterculic acid) have also been detected in animal fat, especially in bovine meat fat. As results, CPFA were detected in the fatty profiles of commercial bovine meat samples but they were absent in the samples of certified meat from cows not fed with fermented forages, reflecting the same correlation observed in dairy products [10,11,43].…”

“…Cyclic fatty acids are generally secondary compounds in fatty acid profiles of food; however, due to the recent discovery, some gaps of knowledge must be fulfilled. In some cases, especially cyclopropane fatty acids, they could reach the g/ kg of total fat content in meat and dairy products [12,43] and their dietary intake may be not negligible.…”

“…Data reported on CPFA, mainly in dairy products, meat, and fish, were obtained in previous publications [10][11][12]. The content of cyclopropane fatty acids has also been evaluated in other food categories such as probiotic food supplements, vegetable edible oils (e.g., extra virgin olive, corn, soy, and peanuts oils) and cocoa butter, soy-derived products, and mushrooms (data not published).…”

“…Results showed that among all the analyzed food categories, the most important CPFA food source is Grana Padano cheese, reaching concentration levels of 1 g/ kg total fat ( Table 1). CPFA were detected not only in commercial bovine meat (200-400 mg/kg total fat) but also in some species of fish (eels and mullets) with concentrations between 400 and 800 mg/kg total fat [12], probiotics, and in mushrooms (data not published). On the contrary, poultry, pork meat, vegetable oils commonly consumed (e.g., extra virgin olive, corn, soy, and peanuts oils), and cocoa butter were all negative to CPFA (data not shown), indicating that CPFA presence in foodstuffs of animal origin is correlated with the use of silages in the animal feedings, whereas plant organisms generally do not produce CPFA.…”

“…CPFA, especially dihydrosterculic (9,10-methylene-octadecanoic acid) and lactobacillic (11,12-methylene-octadecanoic acid) acids, have been identified as minor component of lipid profile in a wide range of milk and dairy products [10,11] and, more recently, in meat and fish [12] representing important foodstuffs in human diet.…”