IDENTIFICATION OF THE UNSATURATED OXO FATTY-ACIDS IN CHEESE

The nature and composition of the unsaturated (monoenoic) oxo fatty ac ids in Cheddar cheese have been re-evaluated. Following isolation by c olumn chromatography and silver ion HPLC, the fatty acids were identif ied in the form of their picolinyl ester derivatives by gas chromatogr aphy-mass spectrometry. For confirmation, they were analysed similarly following deuteration of the double bonds with deuterium and Wilkinso n's catalyst. Fifteen fatty acids were identified fully, only five of which corresponded to those reported in an earlier study. Isomers with double bonds in positions 5, 7, 9 and 11-15 were identified, with oxo groups in positions 8, 9, 10, 13, 16 and 17, and with chain-lengths v arying from C-14 to C-18; but with C-18 predominating.