Anyone can break open an eggshell, but if you aspire to be a better cook you'll want to know all about eggs. Here's a registered dietician who will tell you.
There are no two ways about it: The egg is a marvel of nature, and one of the most valuable, versatile foods around! Low in cost and high in nutrition, the common egg can perform more different functions in cooking than almost any other food. It serves to bind ingredients together (as in meat loaves and croquettes); to leaven soufflés and sponge cakes; to thicken custards and sauces; to emulsify mayonnaise and hollandaise sauce; to glaze or coat breads and cookies; to clarify soups and coffee; and to retard crystallization in candies and frostings. Furthermore, eggs can be used in many types of dishes, from fancy crepes, quiches, and soufflés to simple French toast and western omelets. In fact, legend says the pleats around the top of a fine chef's hat are all about eggs; each represents his or her mastery of a different method of preparing this food!
Nutritionally, the little ovoids are a bargain, too. They contain every vitamin except C, many important minerals, and a goodly amount of protein. In fact, two large eggs (totaling only 160 calories) supply approximately 13 grams of protein, which is 30% of the U.S. recommended daily allowance for adults. Of course, eggs are also a source of cholesterol (a large one contains about 260 milligrams), which can be a concern for folks with high levels of blood cholesterol: If you're such a person, you should consult with your physician about the use of eggs in your diet. [EDITORS NOTE: The regular ingestion of soy lecithin is reputed to prevent a buildup of cholesterol in the body. Lecithin is available in granule, liquid, or capsule form from many health food outlets.]
Eggs are classified according to grade and size standards established by the U.S. Department of Agriculture (or the equivalent state agency). Check the carton for the USDA shield, which shows that the eggs have been inspected and graded.
Grade (AA, A, B, or C) refers to the quality of the egg and shell at the time of packing. A grade AA egg has a firm, tall yolk, the area covered by the white is small, and there's much more thick white than thin white. A grade A specimen typically has a yolk that has begun to spread a little but is still round and upstanding, and the thick white is still large in proportion to the thin white. As you'd expect, a grade B egg spreads out much more, the yolk is flattened, and there's about as much — or even more — of the thin white as there is thick white. (Grade B and C eggs are usually processed into dried egg products and the like. Egg grade does not have any direct relation to nutritional value.)
The to-be-graded eggs pass on rollers over high-intensity lights which shine through the shells and reveal their interiors. The eggs are also rotated, so that all of the internal components can be seen and evaluated. (For example, the size of the air cell and the distinctness of the yolk outline are disclosed.) Imperfections, such as blood spots, will also show up in the process. (These spots, incidentally, do not necessarily indicate a fertile egg, and do not affect the nutritional or chemical content of the food in any way: They're typically caused by the rupture of a small blood vessel on the yolk surface during its formation. Simply remove the spot with the tip of a knife before using the egg.)
Sizing is established according to the net weight per dozen. There are five size categories: jumbo, 30 ounces ... extra large, 27 ounces ... large, 24 ounces ... medium, 21 ounces ... small, 18 ounces ... and pee wee, 15 ounces. Most recipes for baked dishes — such as custards and cakes — are based on the use of large eggs.
When buying eggs, there are several guidelines that are worth remembering. First of all, keep in mind how you plan to use the eggs. The lower grades are best suited for scrambled eggs or combination dishes where a firm yolk isn't important. If you're going to be frying or poaching, however, grade AA is the preferred choice. Once you've decided which grade is most suitable for your purpose, follow this hint: When there's less than a 7¢ price difference between one size and the next smaller size in the same grade, it's generally more economical to buy the larger size.
The only other factor that might influence your choice is color. Well, it may come as a surprise to some folks, but the hue of the eggshell is determined by the breed of hen and has nothing to do with nutritional value, flavor, keeping quality, or cooking characteristics. Unless you have a special reason for purchasing eggs of a particular color, you might as well just buy whichever is less expensive!
In order to maintain quality, it's important to store eggs in a refrigerator set between 35°F and 45°F (3° and 7°C). In fact, they'll age more in one day at room temperature than in one week in the fridge. [EDITOR'S NOTE: For a comparison of other egg storage techniques, see How to Store Fresh Eggs] If possible, keep them in their cartons, since eggs can absorb odors through their shells. Unbroken raw yolks can be stored, covered with water, in a tightly covered container in the refrigerator for two or three days. Raw egg whites will keep for a week to ten days in the refrigerator if they're in a tight-lidded container. Hard-cooked eggs—if in their shells—will keep for a week in the refrigerator.
Raw eggs can be frozen whole (but out of the shell) or with the yolks and whites separated (be sure no yolk gets in with the whites when you're breaking the eggs, or the whites won't beat properly later on). However, to-be-frozen egg yolks require special treatment in order not to become too gelatinous for use. To prevent — or at least retard — this process, add either salt or such sweeteners as sugar, honey, or corn syrup to the yolks or whole eggs before freezing them. It's best to use salt if you intend to serve the eggs as main dishes, and add the sweeteners if you'll be using them for desserts. Whole eggs should be forked together lightly (without beating in air) before being frozen. The following chart shows the proportions to use when adding retardants:
Whole Eggs (2)
- salt: 1/8 tsp.
- sugar, honey, or corn syrup: 1 1/2 tsp.
Whole Eggs (1 cup)
- salt: 1/2 tsp.
- sugar, honey, or corn syrup: 3 tsp.
Yolks (4, or 1/4 cup)
- salt: 1/8 tsp.
- sugar, honey, or corn syrup: 1 1/2 tsp.
Remember to label the containers with the date, the number of whole eggs or yolks, and the type of retardant you put in!
Egg whites can simply be poured into containers, sealed tightly, and labeled — or you can freeze each one in an ice cube tray and later transfer the cubes to a plastic bag.
It's a good idea to take frozen whites from the freezer the night before you plan to use them and let them thaw in the refrigerator. If time is short, they can be thawed more quickly by holding the covered container under cold running water. These whites are used in the same way as fresh ones, but if you plan to beat them you'll get better results if you first let them sit at room temperature for about 30 minutes. When reconstituting thawed eggs, remember that two tablespoons of white can be substituted for one large fresh egg white; one tablespoon of yolk will equal one large fresh yolk; and three tablespoons of whole egg will be the equivalent of one large fresh whole egg.