What could be more festive than a dozen raw eggs, a quart of rum and a pint of bourbon getting friendly in a pot in the fridge for six weeks?
Conventional wisdom would suggest eggnog should bring about a spike in salmonella cases every December, but it doesn't happen. Call it a holiday miracle -- or just call it science.
"Actually, it happens very, very, very, very infrequently," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University Medical Center in Nashville, Tenn. "We do not record an increase in salmonellosis due to eggnog. Otherwise, there would be a CDC health advisory."
Unlike raw chicken, store-bought eggs rarely have salmonella on their shells because they are cleaned before they're packaged, Schaffner said. On the rare occasion that the salmonella bacteria enters an egg, it's likely one of the 800 salmonella species that needs to be present in large quantities to make someone sick. (On the other hand, up to 20 percent of store-bought chicken contains salmonella, and they have a lot more diarrhea-causing bacteria than eggs do, Schaffner said.)
At Rockefeller University, the Laboratory of Bacterial Pathogenesis and Immunology has been making a raw-eggs-and-alcohol eggnog for at least 60 years. It calls for leaving the egg, sugar, cream, spices and alcohol mixture in the fridge for about six weeks. Yes, really.
"I've been here almost 50 years, and we've made it every year," said professor and lab head Vincent Fischetti. "We usually make it about a week or so before Thanksgiving, sip it to cheer Thanksgiving, and finish it at the Christmas party."
The recipe comes from Dr. Rebecca Lancefield, a microbiologist who was born in 1895, and Fischetti says it may have been a recipe from her family. Although the original recipe calls for leaving the mixture in the refrigerator at least overnight, it says it will be "better" after three or four weeks. Fischetti said the added time makes it smoother.
A few years ago, Fischetti's lab made an extra batch – for the sake of science – spiked with an extra ingredient: salmonella. Within the first five days of sitting in the cold with the alcohol, the batch still tested positive for salmonella, but it was sterile not long after, Fischetti said. They even tried to culture the aged eggnog on a petri dish, but no bacteria would grow on it.
"There's enough alcohol in there to kill a horse," he said, laughing. "It's a standard recipe. We're not spiking it any more than it should be."
Indeed, raw eggs and alcohol are a long-standing winter tradition, said Dale DeGroff, the legendary bartender made famous for his gourmet cocktails at New York's Rainbow Room during the 1980s
"Nogs go back to merry old England," DeGroff said. "The idea of mixing egg with beer or rum and spices is a very old world thing."
Although the original varieties were hot drinks involving beer and raw eggs, chilled eggnog became popular in Baltimore in the mid-19th century, DeGroff said. In New York, Tom and Jerrys were popular egg drinks that involved making a "batter" of raw eggs, ground clove, cinnamon, nutmeg, rum and cream, DeGroff said. The batter then went into a big crockery bowl over ice, and when someone ordered the drink, the bartenders would dollop a tablespoon of batter into a mug and add brandy, hot water and milk.
In the 1950s, Degroff's Uncle Angelo submitted his homemade eggnog recipe to a Four Roses Whiskey contest and won. The six-egg recipe appeared on whiskey bottles for years, he said.
Today, popular drinks that involve raw, emulsified eggs include traditional flips, sours and daiquiris. In many cities, restaurants are required to note that food contains raw egg and carries a risk of salmonella.
Food safety expert Dave Arnold said it's true that salmonella does not grow in refrigerator temperatures or in 5 percent alcohol or more, but that doesn't mean the bacteria is gone.
"The issue isn't growth, it's how long is salmonella that's already there take to die," said Arnold, the directory of culinary technology at the International Culinary Center, which has campuses in New York, California and Italy.
Although the risk of getting salmonella from a cocktail is small, the customer should be able to make his or her own decision about taking it on.
"In my bar, if I was going to serve eggnog – even if I had aged it in the fridge and even if I knew for certain it had zero chance of giving salmonella to a customer -- I would still put a label for raw eggs. Why? Because," he said. "Why would I open myself to that risk?"
Fischetti sent along his eggnog recipe, but if you'd rather avoid eggs and alcohol completely, here's a recipe for you.
Original Dr. Rebecca Lancefield recipe:
1 dozen eggs 1 quart heavy cream 1 quart light Cream 1 quart bourbon 1 pint rum nutmeg (1/3 3/4 box) sugar to taste (1/2 to 3/4 Lb)
Modifications: (This is the one Fischetti uses.) 1 quart rum 1 pint bourbon
1. Beat eggs, add bourbon and rum slowly with stirring to prevent precipitation of egg proteins. 2. Add the light cream with mixing using a large spoon. Add the sugar to taste with mixing (about ½-1 pound / batch ) then nutmeg last. 3. Beat heavy cream separately 'till peaks and add to the egg/bourbon/rum - mix into rest. 4. Leave standing at least overnight in refrigerator. Better after 3-4 weeks in the refrigerator.