Can Spiking Eggnog Kill Bacteria From The Raw Eggs?

IRA FLATOW: For the rest of the hour, SciFi’s Charles Bergquist is here with an update on an important holiday story. Hey, Charles. What’s up?

CHARLES BERGQUIST: Hey, Ira. This is one you probably remember. So around 15 years ago, we made a couple of videos about eggnog.

IRA FLATOW: Eggnog. Yeah, I remember that, the question of whether or not the alcohol in the old-school, real creme, real egg drink, not that commercial stuff you buy at the grocery store, was the alcohol in the classic eggnog enough to protect you against germs, things like salmonella from the eggs?

CHARLES BERGQUIST: Yeah, it turns out there’s a lab at Rockefeller University that has this tradition of mixing up a big batch of old-fashioned eggnog around Thanksgiving, and then they serve it a couple weeks later at the lab holiday party. So years ago, we asked them about this whole food safety issue, and they tested their nog.

IRA FLATOW: Yeah, I remember that. And didn’t they follow up about a year later with an actual controlled study where they deliberately spiked samples of their eggnog with salmonella?

CHARLES BERGQUIST: Yeah, they were really good sports about this. But the take home is that, yes, if you mix the alcohol directly with the eggs and give it a while to age, the heavily spiked eggnog does seem to protect against bacteria, at least in their small, n equals 1 study.

But as we know, time marches on. Science progresses. So we wanted to check back in with them on whether there had been any updates in the field of eggnog allergy.

Dr. Vincent Fischetti is an American microbiologist and immunologist and head of the Laboratory of Bacterial Pathogenesis and Immunology at Rockefeller University in New York. Welcome back to Science Friday.

VINCENT FISCHETTI: Glad to be here.

CHARLES BERGQUIST: So it’s been a few years. Does the lab eggnog tradition continue?

VINCENT FISCHETTI: It does continue, yes. We had a lull over COVID, but it has continued.

CHARLES BERGQUIST: And have there been any follow-up experiments, advances in eggnogology?

VINCENT FISCHETTI: No. No. I mean, we’ve been doing it for so many years. It’s an ongoing experiment, basically.

CHARLES BERGQUIST: And still everybody has been healthy and fine? Nobody has succumbed to eggnog-related food poisoning?

VINCENT FISCHETTI: We’ve never had an issue except for intoxication.

CHARLES BERGQUIST: I mean, I should note that, as you just alluded to, this nog definitely qualifies as a potent potable.

VINCENT FISCHETTI: Yes, it’s a very high-alcoholic eggnog, but it’s very good. It’s very smooth, and it sort of sneaks up on you because it is so smooth.

CHARLES BERGQUIST: I think we can reveal the secret recipe. What’s the alcohol blend in there?

VINCENT FISCHETTI: Well, it’s eggs and cream, heavy cream, light cream. And then the alcohol is bourbon and rum, dark rum.

CHARLES BERGQUIST: So what is the alcohol actually doing, physically, to the bacteria? How does alcohol kill germs?

VINCENT FISCHETTI: Well, the way we make the– the way the recipe is designed is that the problem are the eggs. That’s where the contamination usually occurs. So when we crack the eggs and we put them into a bowl, then we add the alcohol directly to the eggs. So the concentration of alcohol in the egg concoction is sufficient to kill the organisms that are potentially in the eggs or on the eggs. It’s actually on the eggs.

CHARLES BERGQUIST: And how does it actually kill the organism? Is it breaking down the cell wall? Is it doing something else?

VINCENT FISCHETTI: The alcohol denatures the outer membrane or the membrane of the bacteria.

CHARLES BERGQUIST: Gotcha. Are some bacteria more resistant to this than others, or, given time, will a good bourbon-rum blend kill just about anything?

VINCENT FISCHETTI: Well, if it’s a high-enough concentration, it’ll kill pretty much most bacteria, yes. It’ll get into the cell membrane and denature the cell membrane.

CHARLES BERGQUIST: And if somebody didn’t want to, for some reason, make their nog quite so boozy, would the sterilization still work, just take longer, or do you really need a certain level of initial oomph for this to work?

VINCENT FISCHETTI: Well, we haven’t tested that directly, but it usually is the higher the concentration of alcohol, the more efficient the kill. So there’s probably a fine line where there’s not enough alcohol to really denature the outer membrane, and then you run into trouble. So I think this mixture of alcohol and eggs is sufficient to give enough alcohol for denaturation, but it doesn’t work immediately because we noticed in our experiment, the one that is on Science Friday, we made an experimental batch where we contaminated it with salmonella, which is usually the organism that causes the infection, and then we followed the concoction over time and found that we got better kill over a week. So it happened slowly. I think the initial interaction occurs when you mix the alcohol with the eggs, but then it continues to occur over a week’s time.

CHARLES BERGQUIST: You mentioned COVID earlier. We now live in a time where we’re thinking about things like COVID, bird flu as well. Does alcohol do anything to disrupt viruses?

VINCENT FISCHETTI: It would, to some degree, but you have to have a direct interaction with the virus itself. So you can’t constantly be drinking in order for it to occur, so it’s not going to– that’s not going to work.

CHARLES BERGQUIST: I see. So when you’re not celebrating, part of your lab work involves bacteriophages, viruses that hunt bacteria. Would it be possible to come up with a bacteriophage that targets salmonella or other food bacteria and dose your nog with that for protection?

VINCENT FISCHETTI: You could because bacteriophage are harmless to humans, and you could get a concoction of phage that you could add to the solution– to the eggnog– that would eventually kill the bacteria in there. That’s certainly possible. But the problem with phage and bacteria is that the bacteria become resistant to phage very rapidly.

Phage and bacteria have been battling for over a billion years, and nobody wants to win that battle because if bacteria win, then phage, then they don’t have a system by which they can acquire new genes so they can survive in the environment, and phage need bacteria in order to grow. So they’ve developed a balance where the bacteria sometimes become resistant, and the phage can still infect those resistant ones because the phage are modulating their genes during this time. So it’s a nice balance back and forth, and nobody wants to win. So phage will work for a limited period of time to control any organisms that are in eggnog, but it won’t work forever.

CHARLES BERGQUIST: I see. So you’ve pretty much optimized your lab’s eggnog situation. Is there any further exploration in this field, anything that you’d like to investigate?

VINCENT FISCHETTI: Eggnog research, not at the point. I think we’ve done it long enough and with confidence that we’ve never had an issue that I think the system does work quite well.

CHARLES BERGQUIST: Well, thank you so much for taking the time to talk with me today, and may all your beverages be safe.

VINCENT FISCHETTI: Thank you. Have a nice holiday.

CHARLES BERGQUIST: You too, Dr. Fischetti. Dr. Vincent Fischetti is an American microbiologist and immunologist and head of the Laboratory of Bacterial Pathogenesis and Immunology at Rockefeller University.

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