High-Resolution NMR Detection of Cholesterol Oxides in Spray-Dried Egg Yolk

A new approach, alternative 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 (¹H-NMR). The following oxides were isolated from spray-dried egg powder by rapid chromatographic procedures and detected by selecting “marker”¹H-NMR signals: 7-ke-tocholesterol, 7α-hydroxy-cholesterol, 7β-hydroxy-cholesterol, cholesterol-α-epoxide and cholesterol-β-epoxide. The quantified cholesterol derivatives ranged from 4.9 to 9.1 ppm with a detection limit of 0.3 ppm (5 μ.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.