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by ofalkaed·3y ago·view on hn ↗
Freshly laid eggs have no salmonella in them. Despite what many think egg shells are permeable, stuff gets through them, and eggs when laid generally have a fair amount of blood and shit on them which do have salmonella in them. If kept dry and at a reasonably even temperature than this is no problem. But say you stick those fresh unwashed eggs in the fridge, when you take them out moisture will condense on them and absorb into the shell along with anything on the shell, so general wisdom has always been to never refrigerate unwashed eggs.

Problem with not refrigerating eggs is that they start change after a few weeks, going bad is not the proper term, less fresh would be more apt, another few weeks and things start turning green (Dr Seuss did not invent those green eggs) and are still not bad in the sense of not being able to eat them but they are far from appetizing in anyway. Modern world requires eggs to last longer, could be 3 months before an egg hits the shelf at the grocery store, so we wash them and keep them refrigerated.

Salmonella is still on the shell of washed eggs, most comes off with the bloom (the coating on a fresh egg) but the bloom is not perfect. So we keep our washed eggs in the fridge to slow growth and store the eggs in a carton which can absorb anything which condenses on them when you take them out of the fridge.

The best by date on an egg carton mostly refers to raw consumption, moisture in the fridge and moisture that condenses on the shell when you take them out will slowly seep into the egg and carry the salmonella into the part we eat and where the salmonella can grow and multiply to dangerous levels for raw. If you have gone past the use by date you may want to skip those soft boiled or sunny side up eggs but they are fine for more firmly cooked eggs and probably fine for soft boiled and sunny side up unless you are well past the use by date.

13 comments
Your first statement is not true. Eggs can absolutely have salmonella in them if the chicken ovary is infected as the egg is forming.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC173326/

Unless the rules changed within the last six years, if a hen house returns a positive environmental Salmonella Enteritidis test and the farm is large enough they must undergo an egg break test to show that the eggs themselves are not infected with SE before they can be sold to consumers. If the egg test is positive the eggs can only be sold as some form of pasteurized egg product until testing shows negative.

Page 47 if you're bored. https://www.govinfo.gov/content/pkg/FR-2009-07-09/pdf/E9-161...

From the practical consumer standpoint, it is essentially true. Getting an egg with salmonella in it is like winning the lottery. But good information either way since some people do get their eggs from small farms which are exempt from testing.
Thats interesting because the egg white is rich in avidin which binds biotin which inhibits many bacterial pathogens, but not viruses because flu vaccines are grown in sterile eggs. The BBC broadcasted this with cross rail plague pits when they got a bod from porton down in to explain some of this stuff.

I can find these studies suggesting salmonella inhibits biotin in the gut[1], and this link suggesting a biotin deficiency can increase susceptibility to salmonella [2].

However one thing that can not be disputed is the reduction in choline intake from the egg yolk would have dumbed down the nation much like covid has dumbed down the world aka brain fog.

Maybe we need a law to sue political parties out of existence if they screw the nation.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504957 [2] https://academic.oup.com/nutritionreviews/article-abstract/4...

I’m not sure if this is regionalisms, or an industry jargon I’m not familiar with, but I couldn’t make head or tails of “BBC broadcasted this with cross rail plague pits when they got a bod from porton down in to explain some of this stuff”. Could you help me understand?
Cross-rail is a new underground metro line in London. During digging of the tunnels, they discovered interesting archeological remains, which included plague pits (where plague victims were disposed of).

Portion Down is the site of a UK military facility specialising in research into chemical and biological hazards.

/Brit

> Despite what many think egg shells are permeable, stuff gets through them, and eggs when laid generally have a fair amount of blood and shit on them which do have salmonella in them.

In Europe eggs are sold unwashed and I can assure you there is nothing on them except for a white or brownish shell. Occasionally a down gets lost in the packaging - that's it. The shell gets permeable when the protective layers are removed by washing it and that's why eggs are sold refrigerated in the US. In Europe eggs are neither washed nor refrigerated.

They're cleaning the eggs somehow. Maybe they're not washing them, and I don't know about the rest of the comment, but having chickens myself and getting eggs from others all my life, chicken eggs are not clean besides an occasional feather by any stretch of the imagination. Poop is plentiful.

Maybe they're getting a thorough wipe? That's about the only way I could imagine this happening, unless you have 24/7 surveillance to clean as soon as they poop and snatch up the eggs. Even then, both sometimes happen simultaneously.

They aren't washing them. More commercial operations might brush them with a dry brush (to remove dirt and chicken poop), while others are just collecting them more immediately, but it's illegal in Europe to wash eggs -- which is required by law in America. Washing eggs removes the bloom, which coats them and protects the permable egg from infection. The trade-off is that European eggs should be washed just before use.

In America, we mandate that eggs are washed in a chemical bath. This diminishes the bloom and replaces it with a chemical wash.

Both mechanisms are ostensibly intended to prevent Salmonella, but I don't have data on which is more effective.

As this piqued my interest I tried to find data but it is complicated mainly by the fact that vaccination rates are vastly different. If we go by raw, reported Salmonella cases the American approach seems to be significantly safer, but then again we seem not to have a good idea about the unreported cases. It probably doesn't help that it is a politically charged topic too - see "Eggwina" in the UK [1].

[1] https://en.m.wikipedia.org/wiki/Salmonella-in-eggs_controver...

Regular changing of the nest bedding can work wonders. -have raised many chickens.
That's true. Even then, every once in a while you end up with a blood covered one.
The whole point is to preserve the protective coating and I don't see how this can happen when you clean the eggs. I'm not a chicken farmer though and maybe the dirt is removed somehow.
> Modern world requires eggs to last longer, could be 3 months before an egg hits the shelf at the grocery store, so we wash them and keep them refrigerated

Far from true everywhere, including in the UK which the article is about.

Here in Ireland, it would even be illegal to sell washed eggs in a supermarket.

But everyone lives in the United States, didn't you know?
> Modern world requires eggs to last longer, could be 3 months before an egg hits the shelf at the grocery store.

Here in EU eggs have printed on them the date they were laid, I never seen eggs in a supermarket more than a few days older.

I haven't checked the dates. But going by varying best-by dates, some of them must be older than few days. Ofc, I use so few I always go with the longest available date as such the freshest.
> But say you stick those fresh unwashed eggs in the fridge, when you take them out moisture will condense on them and absorb into the shell along with anything on the shell, so general wisdom has always been to never refrigerate unwashed eggs.

Do you have a source on this? I'm having trouble finding anything that says refrigerating unwashed eggs has any effect other than simply helping them last longer.

Maybe the general wisdom refers to taking eggs from the fridge and storing them on the counter, rather than using them?

They will last longer in the fridge, but there is little sense in leaving them unwashed if you are going to refrigerate them, you just increase the risk of salmonella getting into the eggs for the reasons I explained. The conventional wisdom I mentioned probably dates back to the days of the ice box which have rather high humidity levels due to the massive block of ice slowly melting, in a modern fridge this is not as big of an issue but humidity levels in the fridge can be quite high, depends on what food you have in there.

I can not provide a source off the top of my head, been a few years since I went through my egg curiosity phase. But it is a simple experiment, take an egg out of the fridge on a hot humid day, you will see water condense on them, and if you let it sit you will see that water absorb in, it will disappear faster than evaporation could explain. This will be easiest to see on a washed egg since the bloom on an unwashed egg helps some, but the bloom is never perfect and each time water condenses on the egg it damages the bloom.

I know fridges certainly used to have those egg compartment things in the doors, but never saw anyone actually use them - tends to be the cardboard egg box is in the fridge, this would probably absorb any extra moisture.
Going off heresay here, but I believe in the US, "washing" the eggs involves a high-acid solution that removes many of the layers that would otherwise keep bacteria and other bugs out. It's also the reason eggs are a such uniform-white colour, whereas elsewhere (at least here in Australia) eggs are mostly various shades of tan.

I usually store eggs outside a fridge. A pack of 18 eggs will last me about 3 weeks and I've not had one spoil yet.

Egg color has to do with breed and diet, the dominant hen type in the US produces white eggs but brown are fairly common. At the co-op I can get eggs that are blue and green, just different breed of hen. Washing does not affect color in the slightest.
I'm guessing that a co-op wouldn't use the same industrial corrosive washing that larger agri-corps do; it'd be a lot closer to how the rest of the world washes their eggs.
I would presume "co-op" here is a market, not a farm. The co-op near where I live is one if not the oldest example and is part of a giant network of co-ops... they certainly don't wash their own eggs: they source them from distributors much like any other market, and it isn't even inherent to the premise that they are using local sources (though mine does care a bit more, as it is a natural foods co-op, the goal of being a co-op is mostly about having a fair and equitable ownership model of the company that enables both employees and customers to have equity).
The reason eggs are refrigerated in the USA and not in the EU is all about different methods of salmonella prevention.

USA regulations have eggs externally washed and disinfected, and require they be kept at a low temperature for storage and transportation. The point of washing is to remove external salmonella contamination from the outside of the egg. The washing process removes some of the natural barrier from the egg and leaves it much more susceptible to bacteria penetrating through the shell and contaminating the egg, so they must be kept cool or refrigerated to help limit and slow the bacteria penetration process.

Eggs are not refrigerated in Europe and are still generally healthy to eat. In most of the EU washing eggs is actually illegal, because it removes the protective coat that helps prevent bacteria from entering eggs. To prevent salmonella there have been some vaccination campaigns where EU chickens are mass vaccinated against salmonella (which is not a requirement in the US). I think in the UK you must have vaccinated all your egg producing chickens to be certified, but other countries are less strict.

Refrigerating with or without the protective coat extends the shelf life.

In the UK all eggs are unwashed and we mostly keep our eggs in the fridge.

I've heard the idea that it's temperature change which causes things to cross the barrier, and the fridge is the place in your kitchen with the most stable temperature.

>I've heard the idea that it's temperature change which causes things to cross the barrier, and the fridge is the place in your kitchen with the most stable temperature.

Correct, but it is not temperature change in general, it is when that change is great enough to cause condensation. Everytime you take something out of the fridge it generally will cause water to condense on the surface because of that temperature change from cold fridge to warm kitchen, same reason you glass of cold water sweats on a hot summer day.

The conventional wisdom here probably changes with region (as conventional wisdom often does) since everywhere does not have the same climate. UK is a rather damp place so fridge is probably safer for much of the year. On reflection I did not think that part through completely, did not take into account everyone having a different local climate.

I have chickens and as long as I keep their nesting boxes clean, the eggs will be there with no blood or shit on them. In my limited experience I have never seen blood on eggs.
What if an egg floats when placed in a bowl of water? I've always taken this as an indication something inside has transitioned to a gas, and that such eggs are spoiled and will not longer be good to eat.
Yep, that's a freshness test. It does not, as far as I know, indicate anything about salmonella.
It's not that something inside has transitioned to a gas, it's that water has evaporated, shrinking the white and enlarging the air bubble (the shell is permeable to air). The egg is probably still safe to eat until it actually starts smelling bad.
I feel like this comment should have been read out loud to me somewhere back at school. That's the most comprehensive guide to "how to interpret best by date on an egg carton" I've ever seen. Thanks.
bacteria may enter through pores or cracks (very common during transport) on shell of eggs