HIGH-RESOLUTION NMR DETECTION OF CHOLESTEROL OXIDES IN SPRAY-DRIED EGG-YOLK

A new approach, alterative to currently available methods, for studying cholesterol oxidation in egg powder is reported. The quantitative analysis of cholesterol oxides was carried out by high-resolution proton nuclear magnetic resonance (H-1-NMR). The following oxides were isolated from spray-dried egg powder by rapid chromatographic procedures and detected by selecting "marker" H-1-NNR signals: 7-ketocholesterol, 7-alpha-hydroxy-cholesterol, 7-beta-hydroxy-cholesterol, cholesterol-alpha-epoxide and cholesterol-beta-epoxide. The quantified cholesterol derivatives ranged from 4.9 to 9.1 ppm with a detection limit of 0.3 ppm (5-mu-g from 16g of matrix). The main usefulness of the method should be in investigating intermediates and products due to chemical transformation of cholesterol during storage and heating of foodstuffs.