title: Conjugated linoleic acid in ewe milk fat.
abstract: Ewe milk fat from five different herds was studied to determine the content of conjugated linoleic acid (CLA) isomers. Research was carried out by combining gas chromatography-mass spectrometry (GC-MS) of fatty acid methyl esters (FAME) and 4,4-dimethyloxazolyne derivatives (DMOX) with silver ion-high performance liquid chromatography (Ag+-HPLC). Reconstructed mass spectral profiles of CLA characteristic ions from DMOX were used to identify positional isomers and Ag+-HPLC to quantify them. Total CLA content varied from 0.57 to 0.97 g/100 g of total fatty acids. FAME and DMOX were separated into a complex mixture of minor isomers and major rumenic acid (9-cis 11-trans C18:2) by GC-MS using a 100-m polar capillary column. Rumenic acid would represent more than 75% of total CLA. 11-trans 13-trans, 11-13 cis/trans plus trans/cis and 7-9 cis/trans plus trans/cis were the main CLA isomers after rumenic acid. Minor amounts of 8-10 and 10-12 C18:2 isomers were also found. Although most of the isomers were present in each herd's milk, differences in content were observed for some CLA species.
authors.affiliation: Instituto del Frío (CSIC), José Antonio Novais 10, Ciudad Universitaria s/n, 28040 Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Luna
authors.forename: Javier
authors.initials: J
authors.lastname: Fontecha
authors.forename: Manuela
authors.initials: M
authors.lastname: Juárez
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: de la Fuente
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000662:veterinary*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods / Q000662:veterinary*; D007536:Isomerism; D044243:Linoleic Acids, Conjugated / Q000032:analysis* / Q000737:chemistry; D008055:Lipids / Q000032:analysis / Q000737:chemistry; D008892:Milk / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012756:Sheep; D012834:Silver
chemical_list: D044243:Linoleic Acids, Conjugated; D008055:Lipids; D012834:Silver