Eggs are packed with protein, 13 essential vitamins and minerals, all nine essential amino acids—and just 75 calories each. If you haven’t shopped for anything but the fake stuff for a while, you may need a refresher. Here are tips from the newly published Keys to Good Cooking: A Guide to Making the Best of Foods and Recipes, by Harold McKee.
Free-range or no? There’s virtually no difference among the various kinds of chicken eggs sold in supermarkets as far as flavor goes, although you may want to consider the price (small-farm varieties will be more expensive), whether it’s organic or not, and the size of the operation where it was produced (if animal welfare and sustainability are concerns).
What do the grades mean? The letter grade indicates the eggs’ quality when they were packed for shipping. Grade AA eggs start out with firmer yolks and whites than Grade A or B eggs (although this really matters only if you plan to cook the eggs whole—poached, fried, soft- or hard-cooked).
Does size matter? Eggs range in size from medium (1.75 oz.) to jumbo (2.5 oz). If you’re baking, the recipe often specifies the size (most often a large egg), but otherwise there’s not much reason to buy one over another. Though obviously the bigger an egg, the longer it takes to cook.
Should I buy pasteurized? If you’re worried about salmonella, pasteurized eggs are an option, but they don’t do quite as good a job as raw ones at foaming or emulsifying sauces. They can also have a pronounced cooked flavor. Bear in mind that the risk of exposure to salmonella is generally very small from one or two eggs cooked in a home kitchen and served right away. It’s more of an issue when dozens of eggs are combined in large food service operations, and prepared, held, and served over a period of hours.
Spoilage. Eggs seldom spoil but their contents do shrink and deteriorate. In old eggs, the normally thick white and yolk become runnier and the yolk membrane is more likely to break. To find out how old an egg is without cracking it open, place it in a bowl and add water. A fresh egg will lie flat, an older one will lift its blunt end toward the surface, and a very old egg will float.
Avoid boiling. Cook an egg in boiling water and you risk breaking the shell, toughening the proteins, intensifying the “cooked egg” flavor and turning the yolk surface green. Soft cook eggs for three minutes, just below the boiling point. Hard cook eggs at a much lower temperature—180-190 degrees F.