title: Determination of 10-hydroxystearic, 10-ketostearic, 8-hydroxypalmitic, and 8-ketopalmitic acids in milk fat by solid-phase extraction plus gas chromatography-mass spectrometry.
abstract: Fatty acids (FA) bearing oxygenated functions and present in esterified form in triacylglycerols are widespread in nature but very little is known about their occurrence in dairy products. A method based on gas chromatography (with flame ionization detector and mass spectrometry detectors), including the previous isolation of polar FA methyl esters by solid-phase extraction, was applied to quantify oxygenated FA in milk fat. Samples obtained from ewes and goats fed with a variety of oil sources were studied. Fatty acids identified were 8-ketopalmitic, 8-hydroxypalmitic, 10-ketostearic, and mainly 10-hydroxystearic acids. The highest levels of 10-ketostearic acid were obtained in milk from animals fed olive oil (up to 1.5%) and from those fed long-chain n-3 FA-enriched diets (0.5-1.0%). In all samples, 10-hydroxystearic acid, not reported so far in milk, was the second most abundant oxygenated FA (up to 0.8%). The high correlation obtained between contents of 10-ketostearic and 10-hydroxystearic acids would confirm the existence of a common pathway of formation in the rumen, whereas the presence of 8-ketopalmitate and 8-hydroxypalmitate could be putatively attributed to mechanisms of β-oxidation in the tissues. The influence of cis-9 C18:1 and trans-10 C18:1 as precursors of these compounds in milk and the metabolic pathways involved in their formation are discussed.
authors.affiliation: Instituto de Ciencia y Tecnología de Alimentos y Nutrición, CSIC, José Antonio Novais 10, 28040 Madrid, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Márquez-Ruiz
authors.forename: V
authors.initials: V
authors.lastname: Rodríguez-Pino
authors.forename: M A
authors.initials: MA
authors.lastname: de la Fuente
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006041:Goats; D008892:Milk / Q000737:chemistry*; D012756:Sheep; D013229:Stearic Acids / Q000032:analysis
chemical_list: C403718:10-ketostearic acid; D004041:Dietary Fats; D005227:Fatty Acids; D013229:Stearic Acids; C070376:10-hydroxystearic acid