Formation of cholesterol oxidation products in marinated foods during heating

The objectives of this study were to develop a gas chromatography-mass spectrometry (GC-MS) method to analyze the contents of cholesterol oxidation products (COPs) in marinated eggs, pork, and juice and to compare the effect of heating time and soy sauce or sugar on the formation of COPs. By using a silica cartridge for purification and GC-MS with selected ion monitoring for detection, seven COPs, including 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 5,6alpha-epoxycholesterol, 5,6beta-epoxycholesterol, 5alpha-cholestane-3beta, 5,6beta-triol, 5-cholesten-3beta-25-diol, and 7-ketocholesterol, as well as internal standard 5alpha-cholestane, were resolved within 16 min by using a HP-5MS capillary column. During marinating, the levels of most COPs followed an increasing trend with increasing heating time. However, a higher amount of COPs was generated for ground pork as compared to eggs. The incorporation of soy sauce or sugar (1 and 10%) was effective in inhibiting COPs formation, with the latter being more pronounced than the former in both marinated eggs and pork.