STUDIES ON PHYTOSTEROL OXIDES .1. EFFECT OF STORAGE ON THE CONTENT INPOTATO-CHIPS PREPARED IN DIFFERENT VEGETABLE-OILS

Potato chips fried in palm oil, sunflower oil, and high-oleic sunflowe r oil were studied for the content of different phytosterol oxides dur ing 0 to 25 weeks of storage in the dark. Oxidation products of sitost erol (24 alpha-ethyl-5-cholesten-3 beta-ol) and campesterol (24 alpha- methyl-5-cholesten-3 beta-ol) were synthesized to help identify the ph ytosterol oxides. The oxides of phytosterols were analyzed by preparat ive thin-layer chromatography, solid-phase extraction, capillary colum n gas chromatography (GC), and GC-mass spectrometry. Epimers of 7-hydr oxysitosterol and 7-hydroxycampesterol; 7-ketositosterol and 7-ketocam pesterol; epimers of 5,6-epoxy-sitosterol and 5,6-epoxy-campesterol; 2 4 alpha-ethylcholestane-3 beta,5,6 beta-triol (dihydroxysitosterol) an d 24 alpha-methylcholestane-3 beta,5,6 beta-triol (dihydroxycampestero l) were detected and quantitated in the samples of chips fried in diff erent vegetable oils. Potato chips fried in palm oil had the lowest le vel of total sterol oxides, ranging from 5 to ca. 9 ppm in the lipids from time 0 to 25 wk of storage. The level of total sterol oxides in c hip samples fried in sunflower oil ranged from 46 to 47 ppm, and the l ipids in samples fried in high-oleic sunflower oil ranged from 35 to 5 8 ppm from 0 time to 25 wk of storage. During 25 wk of storage no cons iderable increase in sterol oxides was observed in the samples of chip s fried in palm oil and sunflower oil. The chip samples fried in high- oleic sunflower oil had slightly higher levels of sterol oxides after 10 and 25 weeks of storage. In addition to the levels of individual st erol oxides, a new method for enrichment of phytosterol oxides from th e unsaponifiables and Cull-scan mass spectra of various oxidation prod ucts of sitosterol and campesterol are reported in this paper.