CHOLESTEROL OXIDES IN GAMMA-IRRADIATED SPRAY-DRIED EGG POWDER

Thin-layer chromatography was used to follow up the chemical changes of cholesterol in spray-dried egg powder gamma-irradiated under aerobic conditions with doses intended to eliminate Salmonella contamination. Chemical changes induced in cholesterol in egg powder by ionising radiation proved to be similar in nature to those known to occur during autoxidation. Formation of 7-hydroxy-cholesterol isomers (alpha and beta) could be observed even at 1 and 2 kGy. Doses of 4 and 6 kGy increased the quantity of these products and resulted in the appearance of cholesterol-5alpha,6alpha-epoxide. At 6 kGy 7-keto-cholesterol was also identified. Non-irradiated egg powder stored for 1 month contained approximately the same quantity of 7-hydroxycholesterols as a freshly produced egg powder irradiated at 1 kGy; freshly produced egg powder irradiated at 6 kGy corresponded to 3-month-old egg powder.