Frequency distributions of conjugated linoleic acid and trans fatty acid contents in European bovine milk fats

From a great number of European bovine milk fats (up to 2110 samples) frequ ency distributions of the contents of conjugated linoleic acid (c9t11-C18:2 ) as well as of the trans fatty acids (TFA) trans-C18:1, trans-C18:2, t11-C 18:1 (vaccenic acid), t11c15-C18:2 (main isomer of trans-C18:2) and of tota l TFA were established considering different normal feeding conditions (bar n feeding, pasture feeding and feeding in the transition periods in spring and late autumn). In addition to the average contents of c9t11 (0.76%), tra ns-C18:1 (3.67%), trans-C18:2 (1.12%) and total TFA (4.92%) the correspondi ng variation ranges of 0.13-1.89%, 1.29-7.17%, 0.30-2:04% and 1.71-8.70%, r espectively, were determined in these EU milk fats using a combination of A g-TLC and GC. High correlation coefficients (r) between the contents of the CLA isomer c9t11 and the contents of trans-C18:1, trans-C18:2, total TFA a nd C18:3 of 0.97, 0.91, 0.97 and 0.89, respectively, could be calculated. A nother high correlation with r=.89 between C18:3 and t11c15-C18:2 points at a probable metabolic pathway in the biohydrogenation of linolenic acid (c9 c12c15 --> c9t11c15 --> t11c15 --> t11).