[Quantitative analysis of auto-oxidation products of cholesterol in food of animal origin].

After extraction with methylene chloride, isolation of the unsaponifiable lipid fraction and enrichment by two-step column chromatography, the oxycholesterols were gas chromatographically separated in the form of their trimethylsilyl ethers on a thin film capillary and identified by mass spectrometry. The three major products of cholesterol autoxidation were cholest-5-en-3 beta, 7 alpha-diol(I) its 7 beta-epimer(II) and 5,6-epoxy-cholestan-3 beta-ol(III). In addition, traces of cholestan-3 beta, 5 alpha, 6 beta-triol and cholest-5-en-3 beta,25-diol were detected in some samples. Quantitative analysis was performed with cholest-5-en-3 beta,19-diol as internal standard. The highest concentrations of I-III were found in spray dried egg powders (total amount 15-60 micrograms/g). Parmesan cheese, butter oil and sausages contained significantly lower levels of I-III (total amount 0.1-2.6 micrograms/g). The concentrations of I-III increased strongly when butter oil and beef tallow were heated at 170 degrees C in the presence of air for a longer period.