EGGS
A. How soon do eggs become unsafe after the expiry date?
Q. First, let's stop using "expiry date" for foods other than baby formulae and baby foods, and special diet foods. The date on foods should be shown as are "best before dates", or perhaps "sell-by dates" or use-by dates", which are the manufacturer's estimate as to when the food will reached a peak quality, after which it might not retain all the desirable characteristics. Click here for more info about food-dates.
Eggs (whole, in-shell) are often given a 'best-before' or ‘sell-by’ date that is 3 to 5 weeks after packing, but refrigerated eggs can be used safely after that date. Longer storage is possible with little or no loss of taste or nutrients up to 90 days. The deterioration in a refrigerated egg is essentially in quality, texture, and appearance.
Here's what happens as an egg ages: Depending upon temperature and humidity in storage, the air sac at the rounded end of the egg will enlarge as moisture is lost by evaporation through the pores in the shell. The egg may even stand upright in water or even float, but this does not indicate anything detrimental. (This is yet another false belief!)
When older eggs are cracked and opened for use, the albumen (egg white) lies flatter on the plate or frypan, but provided the appearance and the smell is completely normal, the eggs are perfectly safe to cook and eat.
Any Salmonella organisms that entered through the pores in the shell at the time of laying are unable to multiply under refrigeration (and even experimentally up to 20 C /68 F which is close to room temperature*). Above 20C (68F), if any Salmonella are present, numbers begin to increase after 3 weeks storage. Sometimes, cells enter the yolk during formation (“trans-ovarian transmission”) and together these are estimated at between 1 in 10,000 to 1 in 20,000 eggs).
A true “bad egg”, on the other hand, is rare these days, but is instantly obvious. When encountering one, it is difficult to stay in the same room.
Some egg-producers in Canada and USA display both the packing date (when the washed, graded egg was placed in the carton) as a 3-digit day of the year from 001-365, together with the best-before date.
So the answer is..... Forget the best before date on eggs, and simply keep it refrigerated and make sure it looks and smells normal when you open it.
* Epidemiol Infect. 2007 Nov 8;136(9):1210–1216. doi: 10.1017/S0950268807009612
Q. Are eggs really dangerous when uncooked?
A. There are two ways in which an egg can carry Salmonella bacteria. the most common way is for these bacteria (from the gut of the hen) to be left on the shell of the egg. As the egg cools from the temperature of the hen (41C or 106F) the egg contents contract slightly, creating a slight vacuum which can pull bacteria through the pores in the shell to lie just under the surface against the membrane. These bacteria are prevented from multiplying by the lysozyme inside the egg for up to 20 days. After that, any bacteria inside the egg can begin to multiply unless the refrigerated storage is maintained.
The other route involves Salmonella cells finding their way onto the yolk before the white is laid down inside the hen. The is called trans-ovarian transmission. Together, the CDC estimates that live Salmonella cells occur in raw eggs at a rate between 1 in 10,000 and 1 in 20,000.
What does this mean for safety in egg consumption? Even though fairly uncommon, life, viable Salmonellae are sometimes ready to infect the food. The biggest danger here is the consumption of raw eggs or recipes containing uncooked eggs such as Hollandaise, home-made egg nog, Caesar's salad dressing. The elderly and immune-compromised should avoid these dishes. Cooking the egg to 71C (160F) for 3 minutes will render everything safe, but still be careful with 'runny' omelettes, or very soft-boiled eggs.
Q. Is it dangerous to keep eggs out of the refrigerator for more than 2 hours? When I was younger we never refrigerated eggs.
A. This is yet another bit of misinformation. It is certainly best to keep on the side of safety, especially knowing that eggs CAN carry live Salmonella inside them, but forget about two hours. Careful experimentation has shown that eggs retained even at 10C or 20C (50F or 68F) for two weeks will not grow Salmonella. After two weeks, if at 30C (86F) any Salmonella present will begin to grow to high numbers.
You may not know how long your eggs have been in storage, so it's best to store them in the refrigerator (at 4C or 40F). But please don't be persuaded to discard perfectly edible and safe eggs because someone forgot to refrigerate them overnight.
In Europe some eggs are not washed and retain the dried mucus from the hen ("bloom"). This is effective in preventing bacteria passing through the cell. For this reason many areas in Europe do not always refrigerate their eggs if they are destined to eat them fairly soon, and the temperatures are not excessive. In Canada and the USA, eggs are normally washed (which removed more surface contamination, but also removed the protective covering on the egg). The advice is to refrigerate eggs for extended storage.
Epidemiology & Infection , Volume 136 , Issue 9 , September 2008 , pp. 1210 - 1216 DOI: https://doi.org/10.1017/S0950268807009612
The rich creamy taste of Pi Daan
is excellent. But it's not a century egg! it's good for up to a year.
I can also appreciate the remarkable process that transforms a highly perishable food item - the fresh egg, into a form that remains quite safe and well preserved for many months, or even a year or so. This was devised in ancient times, long before refrigeration, using a simple technology that was carried out at village or neighbourhood level, and still today represents an effective way to preserve eggs.
Yes, it has been corrupted from time to time by larger food companies who have deliberately introduced a high level of lead compounds to produce the darker colour earlier than is normal. This prompted closer inspection and quality control, such that the labels now certify "lead-free".
If you haven't tried it, take yourself to the nearest Asian supermarket, and buy half a dozen. Scrape off the bran layer, and underneath will be a layer of firm grey clay. This can be softened in water and scraped off as well, until you reveal the egg shell. It's slightly larger than usual due to it usually being from a duck. Now crack the shell and remove it. The texture is the same as a hard boiled egg, but the "white" is a semi-transparent shining black colour. You will notice a slight hydrogen sulphide smell. This is normal, and it will dissipate in a few moments. Cut the egg with a sharp knife, and the solid yolk will be reveled as a dark greenish colour, a little softer and more creamy than usual. Then try it...... Yes, it's unusual, but so what? The taste is sweet and egg-like, but richer than a hard boiled egg.
The normal contents have been subject to an intense reduction (removal of oxygen) by components in the clay/ash mixture. The sulfur compounds when reduced, become much darker, but this has also removed all the available oxygen needed for growth and survival of any Salmonella that may have been present. And that's it. The only organisms likely to be present within the intact shell are aerobic, so cutting off all oxygen deactivates them, and voila! A preserved egg. The thick clay and bran also retain moisture for a long time, but after many months, the Pi Daan will begin to dry.
The closest the West has come to preserving egg without refrigeration is dried, pasteurized egg, which is fine for baking, but for eating - especially in congee - give me the Chinese preserved egg anytime!
