EFFECT OF GAMMA-IRRADIATION ON COMMERCIAL EGGS EXPERIMENTALLY INOCULATED WITH SALMONELLA-ENTERITIDIS

Using intact, fresh shell eggs, inoculated with 10(8) colony-forming u nits (cfu) of S. enteritidis, the effect of three doses of gamma irrad iation on bacteriologic population and physical characteristics (Haugh units and yolk color) of the eggs was determinated. Penetration test area was picked at random just off the air cell of each egg. Aluminum cylinders were attached to the egg surface with a rim of molten paraff in, and 10(8) S. enteritidis was then applied to inoculate the egg. Eg gs were then irradiated within 2 hours using a Cobalt-60 gamma source at either 1, 2, or 3 kGy. A second set of inoculated, nonirradiated wa s used as controls. Following irradiation, eggs were maintained at 4 d egrees C for 42 hours prior culture. Irradiation with 1 kGy resulted i n a significant (P less than or equal to .05), 3.9 log reduction in de tectable S. enteritidis in the shelf and a highly significant (P less than or equal to .025) 95 % reduction in detectable S. enteritidis in the internal shell membranes. Irradiation of eggs with either 2 or 3 k Gy reduced bacterial contamination to non-detectable levels in both th e shell and internal membranes. However, irradiation at either 1, 2 or 3 kGy resulted in a significant (P less than or equal to .05) decreas e (approximately 50 %) in Haugh units. Additionally, irradiation of in tact shell eggs at 2 or 3 Kgy significantly (P less than or equal to . 05) reduced yolk color regardless of the level of irradiation exposure implemented. This data indicates that gamma irradiation of intact raw eggs is effective in reducing (1 kGy) or eliminating (2 or more kGy) S. enteritidis contamination. However, each of the levels of irradiati on used in the present experiments caused marked reduction of selected measures of egg quality.