Testing the Freshness of Eggs

You're a Really Good Egg ... or Are You?

You kind of have to wonder about the first human being who, upon observing a hard, brown (or maybe white) ovoid object dropping from the nether regions of a chicken, decided to pick it up and eat it. At least he knew it was fresh….whatever it was.

Although a lot of country folk still keep a few chickens around to produce eggs for the household, most of us townies and city dwellers depend upon our local grocery store to supply us with fresh, wholesome eggs. But since we aren’t actually present when the egg makes its debut, how do we know how fresh that egg really is?

Freshness of an egg is not only determined by the date when the egg was laid, but also by the way the egg has been stored. Thanks to modern processing and transportation, most eggs reach stores within a few days after the hens lay them. They are packaged in cartons designed to protect and preserve them, and these cartons themselves give the first indication of the freshness of the eggs they contain. Egg cartons with the USDA (United States Department of Agriculture) grade shield on them, indicating that they came from a USDA-inspected plant, must display the “pack date.” This is the day that the eggs were washed, graded, and placed in the carton. Look for a three-digit code (the “Julian date”) that represents the consecutive day of the year, with January 1 being represented as 001 and December 31 coded as 365. (Do we really have to mention leap year?) Most egg cartons also display a “sell by” date beyond which they should not be sold. According to the USDA, this date can’t exceed 30 days beyond the pack date. Always purchase eggs before their “sell by” date. This is sometimes expressed as an “expiration” date, although the eggs do not truly “expire” on the date indicated.

Proper handling and storage is perhaps the most important factor in determining an egg’s freshness. If a freshly laid egg is left at room temperature for a full day, it will not be as fresh as a week old egg that has been refrigerated between 33° and 40°F from the time it was laid. Refrigerated eggs will keep without significant quality loss for about 4 or 5 weeks beyond the pack date, or for about 3 or 4 weeks after you bring them home. Buy your eggs refrigerated and store them in the refrigerator, in their original carton, as soon as you get home. Store them in the coldest part of the refrigerator, not in the door.

Why the original carton and why not the door? It’s all about air.

The air cell within a very fresh egg is very small. However, even under refrigeration, eggs slowly lose carbon dioxide, which enlarges the size of the air cell, causing the yolk to flatten and the white to spread. It is because of this air cell that eggs are packaged pointy side down. Egg shells are also very porous. Egg cartons are designed not only to protect their fragile little inhabitants, but to preserve them against air, light, temperature variations, and odors, all of which adversely affect the freshness of the egg. And that’s also why you don’t store them in the door, even if your refrigerator has a nifty egg carton-shaped storage shelf. Every time you open the door, you’re changing the temperature and rattling the eggs around. Being very sedentary creatures, eggs really don’t appreciate all that stimulation and exercise.

So how do you tell if an egg is still fresh? Well, the obvious way is to break it. If an egg has gone bad, your nose will be the first to know. And there are physical and visual cues, as well. A fresh egg is generally heavy and compact. Small air cell, remember? A bad egg, because of a big, bad air cell, will usually feel very light in weight.

Visually, the yolk of a very fresh egg will have a round and compact appearance and it will sit positioned high up in the middle of the egg. The white that surrounds it will be thick and will stay close to the yolk. A cloudy character to the egg white indicates extra freshness, as this cloudiness is actually the aforementioned carbon dioxide. The clearer the egg white, the more the carbon dioxide has dissipated. A less fresh egg will also contain a flatter yolk that may break easily and a thinner white that spreads out quickly. It’s perfectly okay to use these eggs. They’re just not quite as fresh. Very fresh eggs are ideal for frying or poaching, but less fresh eggs can be used in sauces, cake mixtures or omelets, where the shape and texture of the egg is not as noticeable.

An egg that has a pinkish tint to the white has definitely gone round the bend and should be discarded immediately.

It is for all of these reasons that most cooks crack an egg into a separate bowl before incorporating it into other ingredients. If you’ve got a bad egg, you really want to know it before you dump it into your cake mix, soufflé or whatever.

If you just want to know if those eggs that you’ve had in the fridge for a few days are still okay to use without having to break them all open, there is a popular and time-tested method for determining freshness that involves a bowl of water. The USDA tends to frown on it, but people have been doing it for generations.

Here, too, there are variations depending on whether your grandmother used salt in the water and whether she used warm water or cold, etc. The easiest and most popular method involves filling a fairly deep bowl with plain, unsalted cool water and carefully lowering the egg into the water.
A very fresh egg will immediately sink to the bottom and lie flat on its side. This goes back to that small air cell we discussed.

As an egg starts to lose its freshness and as more air enters the egg, it will begin to float and stand upright. The smaller, pointy end will lie on the bottom of the bowl, while the broader, rounder end will point towards the surface. Such an egg is still good enough to use. However, if the egg fully floats in the water and does not touch the bottom of the bowl at all, toss it, as it is probably bad. Big, bad air cell, remember?

Finally, through the marvels of modern science, you can freeze eggs. But not in the shell, please. That follows the same logic as not cooking a whole egg in the shell in the microwave. Unpleasant things happen.

It's best to freeze eggs in small quantities so you can thaw only what you need. An easy way to do this is to store them in an ice cube tray. Once frozen, transfer them to a freezer container and label with the date and number of eggs contained. But don’t just crack them into the tray and stick them in the freezer. There’s a little prep work involved. Crack the egg into a bowl first and gently stir to break up the yolk a little. Don’t whip it up and incorporate a lot of air. Just a gentle stir will do. Then do the ice cube tray trick or store them in some other appropriate container. Eggs can be kept frozen for up to a year and should be thawed in the refrigerator a day or so before you intend to use them. Only use thawed eggs in dishes that will be thoroughly cooked. And be aware that the freezing process will somewhat degrade the taste and texture of the egg.

Egg yolks and egg whites can be frozen separately. To keep yolks from getting lumpy during storage, stir in 1/2 teaspoon of salt per 1 cup of egg. If you’re planning to use the frozen egg yolks for desserts, use a tablespoon of sugar or corn syrup per cup of egg instead of the salt.

Raw egg whites do not suffer from freezing. No salt or sugar is needed. Just be careful when separating that no yolk mixes in with the white.

You can freeze hard-cooked egg yolks if you want to use them later for toppings or garnishes. Just don’t try to freeze a whole hard-cooked egg. Cooked egg whites are very rubbery to begin with and freezing will only make them more so and they’ll be watery to boot. Not, as Alton Brown would say, “good eats.”

Now that we’ve cracked and unscrambled the mysteries of egg freshness, I wish you, as always, buon appetito.