Studies on phytosterol oxides. II: Content in some vegetable oils and in French fries prepared in these oils

Abstract

Hydrogenated rapeseed oil/palm oil blend, sunflower oil and high-oleic sunflower oil, and French fries fried in these oils were assessed for contents of sterol oxidation products. Different oxidation products of phytosterols (7α-and 7βhydroxy-sito-and campesterol, 7-ketosito-and 7-ketocampesterol, 5α,6α-epoxy-sito-and campesterol, 5β,6β-epoxy-sitoand campesterol, dihydroxysitosterol and dihydroxycampesterol) were identified and quantitated by gas chromatography (GC) and GC-mass spectroscopy. Rapeseed oil/palm oil blend contained 41 ppm total sterol oxides before frying operations. After two days of frying, this level was increased to 60 ppm. Sunflower oil and high-oleic sunflower oil had 40 and 46 ppm sterol oxides, respectively, before frying operations. After two days of frying operations, these levels increased to 57 and 56 ppm, respectively. In addition to campesterol and sitosterol oxidation products, small amounts of 7α-and 7β-hydroxystigmasterol were detected in the oil samples. Total sterol oxides in the lipids of French fries fried at 200°C in rapeseed oil/palm oil blend, sunflower oil, and high-oleic sunflower oil were 32, 37, and 54 ppm, respectively. The levels of total oxidized sterols, calculated per g sample, ranged from 2.4 to 4.0 ppm. In addition to the content of phytosterol oxides, full scan mass spectra of several oxidation products of stigmasterol are reported for the first time. JAOCS 74, 659-666 (1997). FIG. 1. Mass spectrum of an authentic sample of trimethylsilyl-ether derivative of (A) 7α-hydroxystigmasterol showing the molecular ion at 572 and a base peak at 482 (M + − 90), and (B) 7β-hydroxystigmasterol showing the molecular ion at 572 and a base peak at 482 (M + − 90). Abbreviation: % FS, percentage full scale.

Oxidation of β-sitosterol and campesterol in sunflower oil upon deep- and pan-frying of French fries

“…However, comparisons between PS structures were difficult since the product profiles were quite different in SFO. In the case of refined oils, Dutta (1997) reported total POP contents of 41.0, 39.9, and 46.7 ppm in a palm/rapeseed oil blend, a sunflower oil, and a high-oleic sunflower oil, respectively. These values included also dihydroxy derivatives.…”

“…In the oils used to make French fries, the POP contents were 40-47 mg/kg of lipids before frying and 56-59 mg/kg of lipids after 48 h of frying (Dutta 1997). Yet, less information on the effect of pan-frying can be found.…”

Validation of a gas chromatography–mass spectrometry method for the analysis of sterol oxidation products in serum

“…There are only a few reports regarding the cytotoxic effects of POPs, which seem to be less severe [23][24][25]. Some research works attending to find out a proper methodology for the identification and quantification of POPs in vegetable oils, potato chips and French fries [26][27][28], milks [29], enriched spreads [30,31] have been performed. Recently, it has been tried to optimize the analytical method for the determination of POPs in foods using a method based on saponification transesterification of the lipid extract, in combination with solid phase extraction (SPE) [32].…”

Les oxystérols dans l’alimentation

“…Des quantités très faibles de ces composés ont été trouvées dans de la farine [27], du café [28] et des laits infantiles [29]. Les pommes de terre frites sont le seul aliment où des quantités notables d'oxyphytostérols ont été décelées [30]. Le tableau 5, extrait de ce travail, montre, par exemple, que c'est le 7-cétositostérol qui est le principal oxyphytostérol présent.…”