Taking a crack at cooking eggs

Preparation: Boiling over with questions about how to do the job? We've come up with some answers.

April 19, 2000|By Shirley Corriher | Shirley Corriher,Los Angeles Times Syndicate

What could possibly be involved in simply hard-cooking a couple of innocent eggs?

Well, should they be started in tap water or boiling water? How long should they cook? How can you prevent that yucky green on the surface of the yolk? How can you cook them so that they will peel smoothly and not leave you with pitiful, pitted whites? How can you get the yolk in the center and not off to one side?

Oh, dear! There's more to this simple egg than meets the eye.

Egg experts use the term hard-cook instead of hard-boil to indicate that eggs should not be boiled. They are brought to a boil, but then the heat is turned down or off so that they will be tender and not rubbery. The secret of tenderness is gentle cooking.

There are two schools of thought about how to prepare hard-cooked eggs. In the boiling-water start, the eggs are gently lowered into boiling water, then heat is turned down to a low simmer. The eggs must be at room temperature or warm for the boiling start. An egg straight from the refrigerator will crack when it hits boiling water.

The other way is the cold-water start.

Hard-cooked eggs can be cooked gently with either technique.. I prefer a cold-water start because I don't always have time to warm the eggs before cooking.

The American Egg Board's recommended procedure for hard-cooked eggs is to start them in regular tap water (they can come straight from the refrigerator), cover them by at least an inch with tap water and set them on medium heat. Cover and bring to a full boil. Turn off the heat and let stand 15 minutes.

Pour off the hot water and rinse with cold running water for five minutes. Pour off the water, shake the pan vigorously to bang the cooked eggs against each other and the sides of the pan. Shells will crack all over. The eggs are then easy to peel under running water. Some people prefer to roll each egg on the counter to crack it all over. Because it saves time, I find the shaking method wonderful, especially if you're cooking a large number of eggs.

Older eggs (one week to 10 days old) are easier to peel. Egg researchers have found that ease of peeling is related to pH, a measure of acid/alkaline levels. Acidity/alkalinity determines how tightly the membranes between the white and the shell are bonded together. Older eggs, which have lost some of their carbon dioxide on standing, are more alkaline, with a pH of 8.7 to 8.9 or higher, and are much easier to peel.

Yolks of fresh eggs don't discolor readily. Although older eggs are easier to peel, they are more prone to the ugly discoloration around the yolk. This greenish-gray layer on the surface of the yolk is caused by the combining of iron in the yolk with sulfur in the white.

Heat, which speeds up many chemical reactions, is the primary cause. The longer the heat is on the egg, the greater the opportunity for these two chemicals to combine. Careful timing and the cold-water rinse to stop the cooking are excellent techniques to combat the green surface.

Alkalinity is also a factor. This reaction is slowed or prevented by acidic surroundings. Older eggs that are more alkaline (less acidic) and easier to peel are, unfortunately, more susceptible to discoloration. Using the recommended 15-minute standing time and an immediate cold-water rinse, you should not have any discoloration, even with older eggs.

An acidic sauce can repair some of the damage. Acids react with this green iron sulfide, changing it back to egg-colored substances. So even if you have overcooked eggs with badly discolored yolks, mixing them with acidic ingredients like mayonnaise with a little lemon juice will greatly reduce the discoloration.

Deviled eggs or sliced eggs are more appealing if the yolk is centered or at least not off to one edge. Researchers have found that eggs stored on their sides have the most consistently centered yolks (eggs stored large end down came in second). Some recommend cooking eggs in an upright position; you may have seen little wire holders or racks designed to hold an egg or several eggs upright in the pot.

At the Cordon Bleu Cooking School in London, students are instructed to twirl the eggs for several minutes at the beginning of cooking. Researchers have confirmed the validity of this technique and rollers are used to hard-cook eggs commercially. Few of us at home have the patience for twirling eggs. You can do only one at a time, which makes it out of the question for a large batch.

I prefer another technique. The night before hard-cooking eggs, I turn the carton -- tightly closed -- on its side. If you have an egg rack, cooking them standing up is effective, too.

Starting the eggs in tap water reduces the chance of the shells' cracking, but inevitably some do. Adding vinegar to the cooking water will speed up coagulation and seal any cracks fast, but it also will make the eggs more difficult to peel. Adding salt, which speeds up coagulation, is a much better solution (1 teaspoon for small batches, or 1 tablespoon for big batches).

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