Survival of pathogenic microorganisms in an egg-nog-like product containing 7% ethanol

A liquor consisting of whole egg, saccharose (25% w/v) and ethanol (7.0% w/v) was artificially contaminated with Salmonella enteritidis, S. typhimurium, Staphylococcus aureus (three different strains), Bacillus cereus and Listeria monocytogenes. After 3 weeks of incubation at 22 degrees C the numbers of Salmonella, S. aureus and L. monocytogenes decreased more than 3 log10 units. Under such conditions, however, the total number of microorganisms increased 3 log10 units. At 4 degrees C the decrease of pathogenic microorganisms was much slower and a decrease of 3 log10 units was observed only after 7 weeks of incubation. Egg-nog, without ethanol, incubated at 22 degrees C allowed growth of Salmonella and S. aureus, while the numbers of B. cereus spores remained unchanged. Vegetative cells of B. cereus as well as L. monocytogenes decreased in numbers. However, after prolonged incubation the numbers of L. monocytogenes increased significantly.