Short communication: The nature of heptadecenoic acid in ruminant fats.

Heptadecenoic acid (17:1) is a minor constituent of ruminant fats and its isomeric definition remains undefined in most reports on ruminant milk and intramuscular fat. Samples of milk and intramuscular fat of bovine, ovine, and caprine origin were analyzed by gas chromatography (GC) using 3 capillary columns with and without addition of 17:1 cis-10. Additionally, cis isomers of ovine milk fat samples were isolated as methyl esters by preparative thin-layer chromatography and analyzed by GC. The structural analysis of 17:1 present in samples was achieved by chemical ionization tandem mass spectrometry techniques. The isomer 17:1 cis-9 is the overwhelming heptadecenoic isomer in ruminant milk and intramuscular fat; 17:1 cis-10 is virtually absent. Moreover, current GC methods were able to resolve cis-9 from cis-10 and cis-8 isomers, so reports on 17:1 contents in ruminant fat should define its isomeric composition.