Jane Says: Eggs Are Weird and Wonderful

From shell color to unlaid eggs, there's a lot to consider and understand when buying this kitchen essential.

(Photo: David Kiang/Getty Images)

Apr 9, 2014· 5 MIN READ
Jane Lear is a regular contributor to TakePart and the executive editor of CURED, a magazine devoted to the art and craft of food preservation. She was on staff at 'Gourmet' for almost 20 years.
“Thanks for last week’s lowdown on egg carton labels, but I still have a few questions. Does the color of the egg shell make a difference in the nutrition or flavor of the egg? What about size and grade? How can I tell if the eggs I’m eating are fertilized? And what’s the deal with pasteurized eggs and the ones that are ‘unlaid’?”
—Timothy James

I’m delighted to see all this interest in eggs, because really good-quality ones—eggs from happy hens raised on pasture—are among life’s most inexpensive luxuries. And having a dozen eggs in the fridge is like money in the bank: Once you think out of the (breakfast) box, they’re the secret to many a quick scratch lunch or dinner. Try a fried egg on wilted dandelion greens, hotted-up leftover pot greens, or nothing more complicated than steamed rice (cut up the egg on the rice and stir, so you coat the rice grains with yolk). Stracciatella soup was my antidote to last week’s window-rattling, biting-cold gusts, and an omelet topped with microgreens makes an easy, elegant (“oh, it was nothing!”) late-night supper after a movie.

A number of the commenters on last week’s column raise their own chickens, and if you’re in a position to do that, go for it. Check local ordinances first, though, and if you’re going to allow the birds to forage in a backyard, get the soil tested for lead—especially if you’ll be feeding those eggs to small children. For more information about raising chickens, check out BackyardChickens.com. You can indulge a specific interest in heritage breeds—that is, those from genetic populations established prior to the mid-20th century—at the Heritage Poultry Conservancy and Heritage Poultry Breeders Association of America. Another website I stumbled across, The Chicken Chick, gives a bird’s-eye view (sorry) of chicken anatomy, the genuinely marvelous egg production cycle, the whys and wherefores of double yolks, and more.

Speaking of egg production, let’s see if I can clarify matters from a biological perspective when it comes to equating the consumption of eggs (part of our diet since prehistoric times) with that of abortions or periods. Hens start to lay eggs once they reach maturity, whether or not there’s a rooster on the prowl (cue the one and only Sam Cooke). If there is no rooster involved, which is the case in most commercial egg production, the eggs aren’t fertile, so abortion doesn’t enter the picture. According to the experts at BackyardChickens.com, “Even with a virile rooster in residence, not all eggs will be fertile. Some hens just don’t interest a rooster....” The website also notes that “not all fertile eggs will develop into embryos. Some never develop due to egg deficiencies or temperature fluctuations.” Eggs collected daily and refrigerated will not develop even if they were fertilized. As for the comparison to a period, unlike a female human, a hen doesn’t go through a menstruation cycle (during which a woman ovulates about two weeks before her body sheds the lining of the uterus) or even an estrus cycle. A hen can mate and develop fertile eggs at any time.

About Color

In the beginning, all egg shells are white; the pigment for colored eggs is added to the shell at the end of its formation in the shell gland. Color is determined by the breed of chicken the eggs come from and has no effect on nutrition or flavor. Listed among the breeds that lay white eggs at the Murray McMurray Hatchery (“the World’s Rare Breed Poultry Headquarters,” and yes, juveniles are available now) are the Pearl-White Leghorn, the Ancona, and the Black Minorca. Layers of brown eggs include the Rhode Island Red, the Buff Orpington, and the Barred Rock. Eggs from the South American breed called Araucana come in interior-decorator shades that range from exquisite pale blue and green to taupe and are increasingly available at farmers markets and specialty markets.

About Size

Egg size is mostly a reflection of the hen’s age (the older the hen, the bigger the eggs), although breed and weight are also factors. The selection at your grocery store may encompass medium (minimum weight: 21 ounces per dozen), large (24 ounces per dozen), extra large (27 ounces per dozen), and jumbo (30 ounces per dozen) eggs. Large is the standard size called for in most recipes, and any size can be used for scrambling, poaching, frying, and hard cooking. Baking is a bit trickier and more precise: When a cake recipe calls for five large eggs, for instance, consult an egg conversion chart before substituting eggs of a different size.

About Grade

How eggs are graded depends in large part on how thick and firm the whites are: Grade AA eggs hold their shape in the skillet a little better than grade A eggs do. Grade B eggs are generally used in processed foods. The grades, as well as standards and weight classes, are spelled out in detail by the USDA.

About Fertilized Eggs

As I mentioned above, for an egg to be fertilized, the hen and rooster must mate prior to its formation, and even then fertilization isn’t guaranteed. A fertilized egg will not develop, however, once it is refrigerated, and it is safe to eat. Almost all commercial eggs are laid by hens that have not mated, so it’s highly unlikely that you’ll come across fertilized eggs at the supermarket. Contrary to the belief of some, the white, ropy strands found inside an egg aren’t an embryo or sperm; those are chalazae, which anchor the yolk at each end inside the white, and they’re found in all eggs. The tiny red “blood spot” you may occasionally see in the yolk is harmless; it’s simply a ruptured blood vessel that occurred when the hen was forming the egg, and if it bothers you, remove it with the tip of a knife or before cooking. Nutritionally, there is no difference between fertilized and unfertilized eggs.

Pasteurized Eggs

These eggs, which are primarily from conventional farms, are carefully heated for a specified time to a minimum required temperature (between 130° F and 140° F), which kills salmonella bacteria but does not cook the eggs. Most pasteurized eggs go to food service companies and caregiving environments such as hospitals and nursing homes, but you can also find them at the supermarket under the Davidson’s Safest Choice brand. And why would you want to use pasteurized eggs? Well, it takes the risk out of making lightly cooked eggs or something that has raw eggs in it (homemade mayo, for instance) for the very young, the very old, or anyone with a compromised immune system. As for flavor, a taste test conducted by the Chicago Tribune didn’t detect much of a difference, but some consumers still find it objectionable, and pasteurized eggs or egg whites do take up to three times as long to whip. Last month, Agricultural Research magazine published the news that Agricultural Research Service and Princeton scientists have developed a better, faster way to pasteurize eggs by heating them with energy from radio waves (aka radio frequency, or RF, heating).

Unlaid/Unborn/Immature Eggs

At any given time within her reproductive tract, a laying hen will have eggs in several stages—ranging from tiny, almost seedlike yolks just discharged from the ovary to progressively larger, more developed ones farther down the oviduct. They are discovered when a laying hen past her prime is slaughtered, and anyone who has grown up in a family that’s kept chickens knows that they are moist and tender, with deep, almost sweet, eggy flavor. Unlaid eggs are a secret farmhouse ingredient that you’ll find used in any number of recipes, from the chicken and noodles in the Mennonite More-with-Less Cookbook, by Doris Janzen Longacre (1976), to tagliatelle, as chef Dan Barber discovered on a trip to Italy.

About Food Safety

I’d be remiss if I didn’t add a quick note about food safety. Salmonella can be a problem in eggs, even those from organic and/or pastured hens (wildlife and their droppings often carry the bacteria). Minimize the risk by storing eggs in the refrigerator (to prevent the growth of any pathogens), on an inside shelf instead of a door compartment (so they stay as cold as possible). Keep them in the carton to help insulate them from any jostling that will cause cracks. Wash your hands and any utensils or prep surfaces that touch them. The Centers for Disease Control and Prevention has more safety tips on its "Salmonella" page; see also the section on pasteurized eggs above.