Conjugated linoleic acid in ewe milk fat.
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.
Luna
Pilar
P
Instituto del Frío (CSIC), José Antonio Novais 10, Ciudad Universitaria s/n, 28040 Madrid, Spain.
Fontecha
Javier
J
Juárez
Manuela
M
de la Fuente
Miguel Angel
MA
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
D044243:Linoleic Acids, Conjugated; D008055:Lipids; D012834:Silver