INFLUENCE OF PACKAGING ATMOSPHERE ON THE FORMATION OF CHOLESTEROL OXIDES IN GAMMA-IRRADIATED EGG POWDER

In a previous work the effect of ionising radiation on formation of ch olesterol oxidation products (COPs) under aerobic conditions was studi ed. In the present work the influence of aerobic and anoxic conditions have been comparatively investigated to study the chemical changes of cholesterol in gamma-irradiated egg powder. The irradiation treatment was carried out with powdered egg packed under air and also under vac uum in polyethylene (PE) bags and in laminated, oxygen impermeable thr ee-layer (polyester-aluminium-polyethylene) foil to dosage levels 2 an d 4 kGy at room temperature. The cholesterol oxidation is demonstrated by thin-layer chromatograms. In the egg powder wrapped in PE bags the predominant cholesterol derivatives-7-hydroxycholesterol isomers (alp ha and beta)-accumulated in significant amounts (increasing with dose) while vacuum-packaging in laminated foil considerably suppressed the quantity of these products and prevented the formation of cholesterol 5 alpha, 6 alpha-epoxide as well as 7-ketocholesterol. Little or no ch ange was observed in non-irradiated (control) vacuum-packed egg powder stored at approximately 22 degrees C for up to 5 months. Peroxide val ues showed changes parallel to the formation of COPs.