STEROLS AND STEROL OXIDES IN THE POTATO PRODUCTS, AND STEROLS IN THE VEGETABLE-OILS USED FOR INDUSTRIAL FRYING OPERATIONS

The objective of this study was to determine the composition of sterol s in vegetable oils used in industrial frying operations, and sterols and sterol oxides in the fried potato products. The sterols and sterol oxides were enriched by saponification of oils and by solid phase ext raction. Preparative thin layer chromatography, capillary gas chromato graphy, gas chromatography-mass spectrometry, and nuclear magnetic res onance spectroscopy were used to give qualitative and quantitative dat a. The results revealed that the content of desmethylsterols in palm o il, sunflower oil, high oleic sunflower oil, and rapeseed oil/palm oil blend were, 790, 4501, 3550, and 4497 ppm, respectively. Sitosterol w as the major desmethylsterol in all samples. Palm oil also contained t he lowest levels of total unsaponifiables. The sterols and unsaponifia ble contents in sunflower oil were, to some extent, higher than in hig h-oleic sunflower oil. The compositions of sterols after two days of f rying were neither markedly different in the oils nor in the potato pr oducts fried in these oils compared with the original oils. Isomerised sterols were tentatively quantified to account for 10 ppm, 50 ppm and 20 ppm, in rapeseed oil/palm oil blend, sunflower oil, and high-oleic sunflower oils, respectively. Lipids extracted from French fries prep ared in rapeseed oil/palm oil blend contained the highest levels of to tal sterol oxides, 191 ppm, and epoxides of both sitosterol and campes terol were the major contributors, together at a level of 172 ppm. On the other hand, lipids extracted from French fries prepared in sunflow er oil and high-oleic sunflower oil contained 7 alpha-hydroxy-, 7 beta -hydroxy-, 7-keto- and both epimers of epoxysitosterol, generally in e qual amounts. All samples also contained small amounts of different ox idation products of campesterol and stigmasterol.