Some recipes call for egg yolks, others for egg whites. Still others call for both, but the eggs still need to be separated because they're used at different stages. Separating an egg sounds like a very simple task, but even some experienced cooks find it intimidating.
The egg shell must be cracked near the center, where the diameter is largest. Holding it in one hand, either sharply tap the egg on the rim of a measuring cup or small bowl, or strike it with the blade of a knife. The goal is to break the shell only partway through.
At this point there are at least three ways to proceed:
* Holding the egg over a measuring cup or small bowl, pull the shells apart and catch the yolk in one half, allowing the white to spill over into the bowl (Method 1). Carefully transfer the yolk back and forth between the shell halves two or three times until the yolk and white are separated.
* Holding the egg over a measuring cup or small bowl, pull the shells apart and catch the egg yolk near the place where your fingers meet the palm of your hand. Spread your fingers slightly and the white will slip through into the bowl (Method 2), but the yolk will stay in your hand.
* Place one of the numerous egg-separating gadgets on the market over a measuring cup or small bowl. Open the egg over the place designed to catch the yolk (Method 3) and the white will flow over into the receptacle.
When separating more than one egg, it's wise to have one bowl for breaking them over and two others to transfer the yolks and whites to as they're separated. That way, if a yolk accidentally breaks, it won't affect the entire batch. Even a speck of yolk will prevent an egg white from whipping.
If a bit of yolk does get into the white, scoop it up with a piece of shell or paper towel. Shell fragments can also be scooped out of the white with a piece of shell.
Some classic recipes, such as cold souffles, contain uncooked eggs. In recent years, outbreaks of food-borne illness caused by raw eggs contaminated with Salmonella enteritidis have prompted the U.S. Department of Agriculture to recommend consumers avoid eating raw eggs and foods containing raw eggs. This is particularly true for the elderly, the very young, the chronically ill, pregnant women or others with a weakened immune system.
Newer cookbooks may have updated recipes that either omit or call for thoroughly boiling the eggs to destroy the harmful bacteria.
Most recipes, including those printed in The Times' Food Section, use large eggs. If you have jumbo or medium, here is what the USDA has to say in its "Home and Garden Bulletin No. 103," "Eggs in Family Meals--A Guide for Consumers": "Substitution of another size often makes little difference in results. In some recipes, however (sponge and angel food cakes, for example), the proportion of egg to other ingredients is of special importance. For these recipes, it may be necessary to increase the number of eggs if you are using a smaller size."
Common market sizes and their minimum weights per dozen (in the shell) are: Jumbo--30 ounces. Extra-large--27 ounces. Large--24 ounces. Medium--21 ounces. Small--18 ounces. Peewee--15 ounces.
One large egg equals approximately three tablespoons volume. Substitute the same number of extra-large, medium or small eggs.
Two large eggs equals approximately one-quarter cup plus two tablespoons volume. Substitute the same number of extra-large or medium eggs or three small eggs.
Three large eggs equals approximately one-half cup plus two tablespoons volume. Substitute three extra-large eggs, four medium eggs or four small eggs.
Four large eggs equal approximately three-fourths cup plus one tablespoon volume. Substitute three extra-large, five medium or six small eggs.
Five large eggs equals approximately one cup volume. Substitute four extra-large eggs, six medium eggs or seven small eggs.
Six large eggs equals approximately one cup plus three tablespoons volume. Substitute five extra-large eggs, seven medium eggs or eight small eggs.
Eight large eggs equals approximately 1 1/2 cups plus two tablespoons volume. Substitute six extra-large eggs, 10 medium eggs or 11 small eggs.
Ten large eggs equals approximately two cups volume. Substitute eight extra-large eggs, 12 medium eggs or 14 small eggs.
Twelve large eggs equals approximately 2 1/4 cups plus two tablespoons volume. Substitute 10 extra-large eggs, 14 medium eggs or 17 small eggs.
Once in a while a recipe will call for a specific amount rather than a number of eggs, yolks or whites. It takes the following number of whole eggs to make one cup:
Small--seven. Medium--six. Large--five. Extra-large--four.
This number of whites or yolks makes one cup:
Small--10 whites; 18 yolks. Medium--eight whites; 16 yolks. Large--seven whites; 14 yolks. Extra-large--six whites; 12 yolks.
Publications from the American Egg Board state that the freshness of eggs is determined by how recently an egg was laid, the temperature and humidity at which it is stored and how it is handled. "These variables are so important that an egg 1 week old, held under ideal conditions, can be fresher than an egg left at room temperature for one day."
According to the board, "The ideal conditions (for egg storage) are temperatures that don't go above 40 degrees and a relative humidity of 70% to 80%. Fresh shell eggs can be stored in their carton in the refrigerator for at least four to five weeks. Grade quality losses should be insignificant if the eggs are refrigerated as soon as possible after purchase from a refrigerated case. "As an egg ages, the white becomes thinner and the yolk becomes flatter. These changes do not have any great effect on the nutritional quality of the egg or its functional cooking properties in recipes. Appearance may be affected, though. When poached or fried, the fresher the egg, the more it will hold its shape rather than spread out in the pan."