In supermarkets across the United States, Australia, and Japan, eggs can be found in
the refrigerated section alongside other cold items such as milk and cheese.
However, in most other countries of the world, eggs can be found stored at room temperature
alongside nonperishable food items.
People eat both kinds of eggs every day, usually without any ill effects.
So why do some people refrigerate eggs and others don’t?
The answer lies in the bacteria group known as salmonella and how a particular country
chooses to make sure their eggs don’t get contaminated with it.
Salmonella enters eggs through one of two ways- via contaminating the egg internally
before the hen lays it (when a hen’s ovaries have been infected); or via the porous egg
shell (when an egg comes in contact with contaminated matter such as chicken manure).
Egg producers in the United States address the salmonella problem with eggs by concentrating
on preventing the bacteria from entering through the shell.
Towards this end, the United States Department of Agriculture (USDA) mandates that all eggs
be washed with water at a minimum temperature of 90 degrees Fahrenheit and at least 20 degrees
warmer than the internal temperature of the egg at the time of washing.
(If it were colder than the egg, this could result in a very slight contraction, sucking
in contaminated water through the shell’s pores).
The eggs will also be washed with some form of detergent and chemical sanitizer like chlorine,
then are rinsed again and thoroughly dried- the latter further helping make sure pathogens
can’t easily find their way through the egg’s thousands of pores.
After this, the eggs are often sprayed with some form of protective coating like mineral
oil.
Finally, the eggs are taken into a room where they are stored at temperatures at or below
45 degrees Fahrenheit.
This effectively deals with the external sources of salmonella (and helps ensure you won’t
accidentally contaminate other foods with salmonella from touching a contaminated egg
shell then touching other items as you prepare food).
However, this does nothing to destroy any salmonella potentially already present within
the egg.
This is where the refrigeration comes in.
By keeping the eggs sufficiently cold, it mostly makes sure any salmonella present will
not multiply sufficiently to cause problems given a couple month shelf life, keeping the
eggs safe to eat so long as they are cooked.
Even for those eggs not internally contaminated with salmonella, it’s still best to keep
them refrigerated if they have previously been.
As scientific adviser to the International Egg Commission Vincent Guyonnet notes, “Once
you start refrigeration, you have to have it through the whole value chain, from farm
to store.
Because if you stop — if the eggs are cold and you put them in a warm environment — they’re
going to start sweating.”
The United Egg Producers Association further notes that condensation on egg shells “facilitates
the growth of bacteria that could contaminate the egg.”
So why aren’t Europeans and others who don’t refrigerate their eggs getting food poisoning
left and right from eating contaminated eggs?
They rely on other methods to keep the salmonella problem in check and don’t refrigerate them
at any point, though because of the sweating and contraction issues with significant temperature
changes, they do recommend eggs be stored in transport and by supermarkets at specific
temperatures- in the winter between 66.2 – 69.8 degrees Fahrenheit (19 – 21 degrees Celsius)
and in the summer between 69.8 – 73.4 degrees Fahrenheit (21 – 23 degrees Celsius).
For starters, the European Union prohibits egg producers from washing their eggs.
You see, shells have natural protection from salmonella and other contaminants via a waxy
substance known as the cuticle.
The cuticle coats the shell initially as a liquid when a hen lays the egg and then dries
within minutes of being exposed to the air.
Egg washing, when done properly, may eliminate surface contaminants, but it also washes away
the cuticle and its natural protection, potentially allowing bacteria to get into the egg via
its pores or hairline cracks.
Both methods of eliminating external contaminants are quite effective, but the washing strategy
requires that the eggs are processed in a very precise way to be effective.
If, for instance, eggs are allowed to sit in dirty washing water too long after losing
the cuticle, this would be an ideal situation for microbes to quickly infect the inside
of the eggs.
Thus, the EU and others deem it safer to cut out the potentially error-prone middle man
and simply leave the cuticle on.
Of course, by not washing the eggs at all, the occasional egg with feces and other such
things will pop up (the egg being laid via the same hole the chicken poops through and
the laying area potentially not being perfectly clean).
But the fact that visibly dirty eggs will most definitely turn off some customers and
that European Union egg farmers aren’t allowed to wash the eggs is actually seen as a net-positive
by some.
For instance, Britain’s Egg Industry Council’s Chief Executive Mark Williams states of this,
“In Europe, the understanding is that [prohibiting the washing and cleaning of eggs] actually
encourages good husbandry on farms.
It’s in the farmer’s best interests then to produce the cleanest eggs possible, as
no one is going to buy their eggs if they’re dirty.”
Unfortunately, in this scenario you’ll still get the occasional egg with fecal matter or
the like on it.
This also increases the chances of cross contamination with handling the potentially contaminated
egg shells and then perhaps touching other food items without washing your hands.
But both of these problems are easily solved by simply washing the eggs (and your hands)
directly before using them.
This “do nothing” method also saves an amazing amount of effort and cost in the processing
of the eggs.
It’s also a superior method of keeping eggs as safe as possible in areas where end customers
don’t necessarily have refrigerators, as well as helps minimize the risk of egg contamination
if a customer has a long drive home from the supermarket, which potentially allows the
cold egg shells to form condensation giving pathogens easier access to the inside.
So, the cuticle solves the problem of external sources contaminating the inside of the egg,
but how does the EU and other countries that don’t refrigerate their eggs deal with eggs
that were contaminated while being formed inside the chicken?
They mandate that their egg laying chickens must be vaccinated against salmonella, among
other requirements, if they are to receive the Lion Quality Code of Practice seal.
The result of this is that approximately 90% of chicken eggs sold in Britain come from
vaccinated hens, with the other 10% coming from small farmers who don’t typically sell
eggs through major retailers.
So which way of storing eggs produces fewer cases of salmonella induced food poisoning?
As the aforementioned Vincent Guyonnet notes: “They’re different approaches to basically
achieve the same result…
We don’t have massive [food safety] issues on either side of the Atlantic.
Both methods seem to work.”
But what about the numbers?
In that, there seems to have never been any definitive studies (at least that I could
find), but it would seem on the surface that the European method is the winner.
(Though there are uncontrolled factors that could potentially be skewing the numbers,
so take this with a very large grain of salt.)
On average, there are approximately 142,000 cases of egg-related salmonella poisoning
in the United States every year according to the U.S. Department of Agriculture.
This is approximately 1 in 2,200 people infected every year (give or take depending on whether
an individual is a repeat offender in a given year).
In contrast, in England and Wales in 2009, there were just 581 cases of egg-related salmonella
poisoning, or about 1 in 95,000.
Notably, before the British started vaccinating their chickens in the late 1990s in response
to a major egg-induced salmonella outbreak, in 1997 there were 14,771 cases of egg related
salmonella poisoning in England and Wales, or 1 in 3,700.
You might then be wondering why it simply isn’t mandated that United States egg producers
vaccinate their chickens.
This is primarily because when the last batch of rules concerning this very thing were put
together, the limited number of large sample-size studies available indicated vaccination wasn’t
an effective way to stop the internal contamination of salmonella in eggs.
More recent vaccination methods and studies have produced entirely different results.
Because of this, and the fact that henhouses and eggs are now being continually tested
for salmonella contamination (with a positive result meaning the egg farmer must break all
the eggs open from a batch and pasteurize them, leading to significant profit loss),
approximately one-third to one-half of all egg producers in the United States have voluntarily
begun vaccinating their chickens.
This voluntary adoption of vaccinations was also spurred on in response to a 2010 egg-related
salmonella poisoning outbreak in the United States resulting in half a billion eggs needing
recalled.
To avoid such problems, more and more U.S. egg farmers are jumping on board the hen vaccination
train every year.
In the end, while there are pros and cons of each method of keeping eggs contaminate
free, both have proven extremely effective when properly executed, though seemingly the
European method has a large edge in terms of keeping people from getting sick.
However, if you’ve got a refrigerator handy, it is superior in one regard- eggs that are
not refrigerated have a shelf life of about three weeks.
Those stored in a typical consumer’s refrigerator are generally good for about two months, and
drastically longer given better regulated temperatures, something that used to be key
to keeping eggs on the supermarket shelves year round.
You see, naturally most chickens will stop laying eggs in the winter as a response to
shorter daylight hours.
(There is a photo-receptive gland in a chicken’s eye that, when exposed to sufficient light,
ultimately triggers the release of the hormone that in turn spurs egg production when present
in sufficient quantities in the hen.)
This created an egg supply problem that used to be solved by egg farmers in the United
States via keeping the eggs at the perfect, constant chilled temperature not found in
your normal consumer refrigerator which is regularly being opened and closed.
This allowed egg producers to store eggs for as much as a year according to United Egg
Producers’ Vice President of Government Relations, Howard Magwire.
Today, of course, the problem is somewhat controversially solved with artificial light
and strictly controlled egg production environments with the egg finding its way from hen to customer
generally in under a couple weeks, regardless of what time of year it is.
Bonus Fact: Ever wonder what the difference between brown
eggs and white eggs are?
Well, wonder no more.
While some people say that brown eggs are better for you and contain more nutrients;
or that brown eggs taste better; or brown eggs are better for cooking things like quiches,
while white eggs are better for baking cakes, etc. etc., the truth is the difference between
brown eggs and white eggs are that brown eggs are brown and white eggs are white.
How the rumours started about brown eggs being “better” is thought to be because they
are often more expensive at supermarkets.
This is, in part, because the hens that lay them usually eat more, which means the hens
cost more to keep per egg.
You see, white eggs are most often laid by white or light coloured hens with white ear
lobes, while brown eggs are most often laid by red-feathered or brown / dark-feathered
chickens with red ear lobes.
(This is not a universal truth, just a general rule.
Further, the chicken's ear lobes are really the indicator here, not the feathers, but
there is a very strong correlation between ear lobe colour and feather colour, so feather
colour can be a decent indicator too.
Ultimately, egg colour is determined by genetics, but the ear-lobe / feather colour thing is
a good, though slightly flawed indicator.)
In the end, red-lobed chickens tend to be larger than their white-lobed counterparts,
which is why they eat more.
The farmers need to get reimbursed for the extra feed somehow, so they up the price of
the brown eggs.
This also explains why white eggs tend to be more popular in supermarkets.
White-lobed chickens cost less for farmers to keep, which leads to cheaper eggs, which
leads to grocers buying more white eggs to put on the shelves to offer this product cheaper
to customers.
White eggs are simply more cost-effective.
As for the supposed difference in taste and nutritional content, there isn’t one, with
one caveat, though it isn’t anything to do with the colour of the egg—rather, it
has to do with the chicken’s diet.
Many chickens raised at home are brown-egg layers, while most of the chickens raised
for commercial use are white-egg layers.
The different diets affect the taste of the eggs and even the colour of the yolk, similar
to how diet can drastically affect the taste of the meat of some animal.
However, if you were to take one of those brown egg-laying chickens and raise it on
the same food as a white egg laying chicken, their eggs would taste the same and be otherwise
indistinguishable aside from the colour of the shell.
If their diets are the same, the yolks will even be identical in colour.
Today, chickens raised for commercial purposes, whether layers of white eggs or brown, are
all getting fed the same thing, with perhaps just a slight variance from company to company.
If you've had some brown eggs from a neighbor or a chicken of your own that's fed a different
diet than commercially fed chickens eat, then there may be a difference in taste.
It just doesn't have anything to do with the colour of the egg.
Of course, these days some of the most hotly debated arguments aren’t over white vs.
brown eggs, but over the superior quality of organic vs. not organic eggs, or free range
vs. cage eggs.
While differences in diet can affect the taste, if you're wondering about quality of the egg
or nutritional value, a study done by D.R. Jones et al. through the Agricultural Research
Service and published in Poultry Science in 2010 found that, ultimately, there is very
little difference in the quality of eggs produced in these different ways.
The small differences they did find "varied without one egg type consistently maintaining
the highest or lowest values."