In 2008, National Public Radio’s Science Friday searched the scientific literature to find answers to an important holiday question: does the alcohol in eggnog kill Salmonella? When the team couldn’t find the answers in the literature, they instead found a lab that routinely makes eggnog each year.
Forays into eggnog science
Vincent Fischetti, a microbiologist at Rockefeller University, helped Science Friday with their experiment. The lab made alcoholic eggnog according to a recipe from Rebecca Lancefield, a microbiologist who was best known for her serological classification of ß-hemolytic streptococcal bacteria. The lab compared their concoction with store-bought non-alcoholic eggnog.
After culturing samples of each type of eggnog on agar plates and incubating them for 24 hrs at 37 °C, they found that the store-bought samples contained many different bacteria while the homemade version seemed free of bacteria. However, what grew from the store-bought eggnog were likely harmless bacteria naturally found in most dairy products.
They tried the experiment again, this time adding a hefty dose of Salmonella, about 1,000 times more Salmonella than in one contaminated egg. The results were inconclusive. “In order to authoritatively say that spiked eggnog is either safe or unsafe, we’d have to repeat the experiment under a range of more realistic conditions. We’d probably need a grant,” Fischetti says.
Spike your eggnog, and do so early to ward off Salmonella
A year later, the lab and Science Friday revisited the eggnog/Salmonella question. Lancefield usually made eggnog before Thanksgiving each year for over 40 years. She would let it sit in the fridge for weeks until Christmas time to drink it. One month, twelve dozen raw eggs. No one has gotten sick to date, according to Fischetti.
Lancefield’s recipe contains a lot of alcohol. About 14 percent alcohol, according to Ben Chapman, a food safety researcher at NC state. Is this enough to prevent Salmonella growth in eggnog?
To Lancefield’s recipe, the lab added Salmonella equivalent to one to ten bad eggs. The team plated samples of the eggnog at different timepoints. As expected, the eggnog, upon mixing was full of bacteria. After 24 hours in the fridge, it contained fewer bacteria than before. After one week in the fridge, the eggnog contained even fewer bacteria, but was still not drinkable. After three weeks in the fridge, the eggnog was finally free of bacteria.
The conclusion (from a sample size of one): spike that eggnog and let it sit in the fridge.
If you’re still not sure about using raw eggs in your eggnog there are a few things you can try. You can use pasteurized eggs or bring the base of the eggnog before adding alcohol to 160 °F.
Happy holidays!
