title: Identification and quantitative analysis of beta-sitosterol oxides in vegetable oils by capillary gas chromatography-mass spectrometry.
abstract: As vegetable oils and phytosterol-enriched spreads are marketed for frying food or cooking purposes, temperature is one of the most important factors leading to the formation of phytosterol oxides in food matrix. A methodology based on saponification, organic solvent extraction, solid-phase extraction (SPE), followed by mass spectrometric identification and quantitation of beta-sitosterol oxides using capillary gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode was developed and characterized. Relative response factors of six beta-sitosterol oxides, including 7alpha-hydroxy, 7beta-hydroxy, 5,6alpha-epoxy, 5,6beta-epoxy, 7-keto, and 5alpha,6beta-dihydroxysitosterol, were calculated against authentic standards of 19-hydroxycholesterol or cholestanol. Linear calibration data, limit of detection, and sample recoveries during analytical process. Recoveries of these oxidation compounds in spiked samples ranged from 88 to 115%, while relative standard derivation (R.S.D.) values were below 10% in most cases. The analytical method was applied to quantify beta-sitosterol oxides formed in thermal-oxidized vegetable oils which were heated at different temperatures and for varying time periods. Sitosterol oxidation is strikingly higher in sunflower oil relative to olive oil under all conditions of temperature and heating time.
authors.affiliation: Laboratoire de Chimie Analytique et Sciences de l'Aliment (UMR 7512), Faculté de Pharmacie, Université Louis Pasteur, 74 route du Rhin, 67400 Illkirch, France.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Diane
authors.initials: D
authors.lastname: Julien-David
authors.forename: Michel
authors.initials: M
authors.lastname: Miesch
authors.forename: Philippe
authors.initials: P
authors.lastname: Geoffroy
authors.forename: Francis
authors.initials: F
authors.lastname: Raul
authors.forename: Stamatiki
authors.initials: S
authors.lastname: Roussi
authors.forename: Dalal
authors.initials: D
authors.lastname: Aoudé-Werner
authors.forename: Eric
authors.initials: E
authors.lastname: Marchioni
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D000069463:Olive Oil; D010087:Oxides / Q000032:analysis*; D010840:Phytosterols / Q000032:analysis; D010938:Plant Oils / Q000737:chemistry*; D012855:Sitosterols / Q000032:analysis*; D000074242:Sunflower Oil
chemical_list: D000069463:Olive Oil; D010087:Oxides; D010840:Phytosterols; D010938:Plant Oils; D012855:Sitosterols; D000074242:Sunflower Oil; C025473:gamma-sitosterol