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The Science of Eggnog
November 10, 2010 6:09 AM   Subscribe

Want to make eggnog weeks ahead of time? You might try this recipe, courtesy of The Rockefeller University's Dr. Rebecca Lancefield (PDF biographic article). In this 2008 video, her colleagues demonstrate how to make it; they suggest starting it now, tasting it at Thanksgiving, and drinking it at Christmas. In their 2009 follow-up video, they intentionally add Salmonella to the recipe as they make it, to see if the added liquor kills off the infection. Videos courtesy of Science Friday. (BONUS LINK: if you missed last year's Puerto Rican Nog celebration, get ready for the 9th annual NYC Coquito Contest!)
posted by Greg Nog (24 comments total) 21 users marked this as a favorite

 
Wow, Ira Flatow! I miss Newton's Apple. He never answered my question about lasers.
posted by Wolfdog at 6:12 AM on November 10, 2010


Not really being in a place to watch video right now, how well did the alcohol work against the Salmonella and at what percentage, temperature and time?
posted by caddis at 6:23 AM on November 10, 2010


The alcohol is about 20% of their eggnog (he didn't say if that was weight or volume, I assume the latter). It didn't kill the Salmonella, which is sad. (They called this "inconclusive" for some reason.) Even worse, it DID kill all the lactobacillus and so forth, which I guess means it also isn't any good if you prefer "live" eggnog.
posted by DU at 6:29 AM on November 10, 2010


Thanks for the reminder on the Coquito Contest. I now forgive you for last year.
posted by etc. at 6:29 AM on November 10, 2010


I just threw up a little bit in my mouth in anticipation. Great post!
posted by Blazecock Pileon at 6:31 AM on November 10, 2010


I know it sounds counterintuitive, but there is such a thing as aged eggnog. My friend makes the nog for his Christmas party a year in advance. It may not be live, but it is super delicious.
posted by dammitjim at 6:40 AM on November 10, 2010 [1 favorite]


Another way to avoid salmonella in your eggnog is to use pasteurized eggs (example). Then you can make a raw eggnog like Alton Brown's with as much or as little booze as you like. Mmm....so light and fluffy. I must sound like a shill for AB's eggnog, but it's really very different from other eggnog recipes; the whipped egg whites are the trick.

The alcohol is about 20% of their eggnog (he didn't say if that was weight or volume, I assume the latter). It didn't kill the Salmonella, which is sad.

Not surprising. "Cidal activity [of ethyl and isopropyl alcohols] drops sharply when diluted below 50% concentration, and the optimum bactericidal concentration is 60%–90% solutions in water (volume/volume)." (from the CDC). So anything capable of actually killing bacteria is going to be undrinkably strong unless you're the kind of person who enjoys a warm glass of Bacardi 151 neat.
posted by jedicus at 6:40 AM on November 10, 2010 [2 favorites]


epony-sterile-cle!
posted by lalochezia at 6:58 AM on November 10, 2010 [4 favorites]


Funny this. Yesterday I decided to make eggnog, which in these parts is some exotic North American drink. That is, for those who have even heard of it. I procured the neccessary ingredients, and the cream promptly ended up in the wife's chicken casserole. Oh well, I'll try again today. I'm in the enviable position of having a friend who keeps chickens, so I probably can't blame the ingredients if I fail.

More common in Norway is eggedosis, which is just whipped eggs and sugar. It's usually served with berries mixed in.
posted by Harald74 at 6:58 AM on November 10, 2010


It didn't kill the Salmonella, which is sad. (They called this "inconclusive" for some reason.)

The first video has them measuring the Salmonella content a day after innoculating the homemade nog with the bacteria. That day (with only 20% alcohol) wasn't enough to kill off the innoculation.

BUT: the second video clarifies this point; by letting the 20% alcohol nog sit for three weeks, the number of live bacteria drops to zero. So it does kill the live Salmonella, it just requires waiting for a bit.

Any toxins made by the Salmonella during their brief time on this earth will indeed still be present, but to say there's danger there requires two assumptions: A) you've got Salmonella-infected eggs to begin with, and B) the amount of toxins produced by those bacteria (in a not-particularly-conducive-to-growth environment of 20% alcohol) will be enough to harm you.
posted by Greg Nog at 7:15 AM on November 10, 2010


More common in Norway is eggedosis, which is just whipped eggs and sugar.

Man, that even sounds like a disease.
posted by electroboy at 7:25 AM on November 10, 2010 [3 favorites]


This is fascinating. I usually make Eggnog in Quantity, the recipe from the classic Joy of Cooking (the edition with the recipes for possum and potatoes in rosin). The recipe given above is fairly similar. I always believed the prodigious alcohol content took care of any bugs, but sounds like not so much. Shucks.

Anecdatally though, after many, many decades in and around the kitchen I personally know of no-one who has ever fallen ill licking the cookie dough off the mixer, or drinking raw egg nog. It makes me wonder if this is one of those situations where science knows simultaneously too much (there is salmonella in every egg!) and not enough (perhaps people become immune to their local salmonella cultures, as an arbitrary and probably false, example).
posted by Mei's lost sandal at 7:30 AM on November 10, 2010 [2 favorites]


Huh. Post-post, it looks like the alcohol does the trick, given enough time.
posted by Mei's lost sandal at 7:32 AM on November 10, 2010


Making eggnog with alcohol is basically a way of preserving eggs for the winter; chickens do tend to lay less in the winter (less light).
posted by thefool at 8:31 AM on November 10, 2010


Came for the eponysteria, stayed for the tips (and salmonella discussion).

And, of course, no discussion of this drink is complete without the obligatory Star Trek reference.
posted by Halloween Jack at 8:53 AM on November 10, 2010


Q: How are this post and a pig's tail alike?

A: They're both way twirly.

Though I will be referencing last year's post if I decide to do some Thanksgiving egg nog. After reading that post, simply throwing some coconut rum in with some store-bought pumpkin eggnog just seems too lame even for me. (And I drink that stuff straight out of the carton. I gargle with it. so goooood. So gooooood. sooooo. goooooooood.)
posted by not_on_display at 10:34 AM on November 10, 2010


I'm the Keeper of the Eggnog for my family, who's been making eggnog from the same recipe for at least 50 years. Raw eggs, and not an aged recipe, and not pasteurized or any other copout. Nobody's ever gotten sick from it. I'm always careful to use really fresh ingredients.
posted by Addlepated at 10:55 AM on November 10, 2010


I still have some of last year's aged eggnog, as do my parents. We've been using the chow.com recipe for a few years, and it really does improve after twelve months. It's great fresh, too, though.
posted by wzcx at 11:48 AM on November 10, 2010


I used to make eggnog from the Joy of Cooking (1964 ed.) recipe except I used all rum and honey instead of powdered sugar. After a few years I subsituted half and half for the cream. A few years later I cut it with milk. Then I quit altogether. But for fifteen years or so I had a crock full of eggnog on the back porch from about the 23rd of December until it was gone. I never worried about salmonella or anything else especially after I had a few cups.
posted by CCBC at 12:27 PM on November 10, 2010


They tell me in physiology class that whilst there is salmonella in almost every egg, our stomach acid is unbelievably awesome and protective and kills all but the strongest and meanest concentrations of bacteria.

So that may help to explain everyone's lack of post-nog stomach conditions.
posted by fizban at 12:54 PM on November 10, 2010 [1 favorite]


"Cidal activity [of ethyl and isopropyl alcohols] drops sharply when diluted below 50% concentration, and the optimum bactericidal concentration is 60%–90% solutions in water (volume/volume)." (from the CDC). So anything capable of actually killing bacteria is going to be undrinkably strong unless you're the kind of person who enjoys a warm glass of Bacardi 151 neat.

jedicus, the flaw in that statement is the omission of the time element. As Greg Nog pointed out, cidal activity is a (nonlinear) product of concentration and time (and temperature and oxygen content and...).

Washing your hands with bactericidal soap for a typical 3 seconds (guesstimate from public restroom observances) with typically cold to room-temp water won't kill all the germs, either. Applying some in weak solution to a bandage, and soaking a cut overnight, probably would, OTOH.

The CDC statement presumably refers to "nearly instantly cidal". You can't grow salmonella cultures in 40-proof schnapps (20% alcohol).

Beer and unsupplemented wine, both with ABW contents well below 20%, are plenty safe from salmonella (and other pathogenic bacteria). It takes days to weeks to develop their alcohol levels, so by then the germs are gone.
(Acidity helps.)
(Some hardy bacteria can survive, such as acetic bacteria, but they aren't typically pathogenic.)

The recipe is safe.
posted by IAmBroom at 1:22 PM on November 10, 2010 [1 favorite]


Some of those acetic bacteria (or their byproducts) are pretty yummy as well, as I know having just grown them in a batch of sauerkraut.
posted by Mei's lost sandal at 2:35 PM on November 10, 2010 [1 favorite]


The recipe is safe.

Fair enough, but I'd like to see a few more experiments with cultures done every couple of days instead of one experiment with cultures at day 1, day 7, and day 21. That's a big gap. If you can't let it sit the full 3 weeks, then is it still safe? Also, what about different strains of Salmonella? To what extent did refrigerator temperature play a role?

Other people's risk aversion may vary, but I'll stick to the pasteurized eggs and drink eggnog fresh until I see a couple more experiments.

Speaking of, this would actually make a great science fair experiment. It's got practical applications, teaches the student how to perform bacterial cultures, and gives the kid an opportunity to play with booze. What more could you want?
posted by jedicus at 3:45 PM on November 10, 2010


I'm always careful to use really fresh ingredients.

Addlepated, AFAIK the risk of salmonella infection is not much reduced by using fresh eggs. The risk is whether or not the eggs have been exposed to salmonella cultures - either coming from unvaccinated hens, or being washed in the fecal/feather/thousand-egg rinse water used in industrial egg farms.

If you have data that suggests fresh eggs are safe(r), I'd like to see it.

(Frankly, the risk of salmonella is much lower than most people think, anyway. I've never shied from raw eggs, always bought at stores, and never gotten it. FWIW.)
posted by IAmBroom at 4:54 PM on November 10, 2010


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