What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (11 page)

How, then, does butter homogenize and thicken a pan sauce? In two ways. First, butter’s fat content can absorb the fat in the pan while its water content can absorb the wine or stock, thus bringing them into a sort of matrimonial harmony. But the marriage wouldn’t last very long if the butter didn’t contain a small amount (about 0.24 percent) of lecithin, an emulsifier. An emulsifier’s molecules stabilize an emulsion by latching onto both fat molecules and water molecules at the same time, effectively keeping them together. (See p. 380.) When the entire contents of the pan have thus become a fat-and-water emulsion, the contents will obviously be thicker, glossier, and more unctuous than the watery wine or stock alone. French chefs ever since Escoffier have been finishing their pan sauces with
une noisette
of butter.

There are so many kinds of eggs in my supermarket, I don’t know which to buy. They all seem to be Grade A, which I suppose is good, but what about size and freshness?

....

T
he USDA grades eggs according to quality—not according to freshness—as AA, A, or B. To earn a grade of AA, an egg must have an air cell within the wide end that is less than an eighth of an inch (3 millimeters) deep; a shell that is well shaped and clean, with very few ridges or rough spots; and when the egg is broken onto a flat surface, a yolk that stands up high and domelike in the center of a clear, thick, and firm white.

Grades A and B fit these criteria slightly less rigorously. They may not look as pretty when fried or poached, because the yolks may be a bit flat and the whites a bit more runny, but they are perfectly fine for uses in which they won’t be served whole.

Submitting eggs for federal grading, however, is optional for the producers (the human ones, that is, not the hens). Eggs sold in cartons without the USDA shield will have been graded according to state laws, which vary all over the lot.

If you find some eggs in a carton that don’t appear to be the same size, curb your suspicions. The USDA determines their average size by the weight of a whole dozen. The standard egg sizes are jumbo, extra-large, large, medium, small, and peewee. By the dozen, they weigh 30, 27, 24, 21, 18, and 15 ounces, respectively.

Unless they state otherwise, you can assume that all recipes, including those in this book, have been tested using large eggs. But if you have only mediums, here’s how to substitute: If the recipe calls for one, two, or three large eggs, use the same number of mediums. For four, five, or six large eggs, add one medium. Have only extra-large eggs? For one, two, three, or four large eggs, use the same number of extra-large. For five or six large eggs, use one fewer extra-large. Or, just forget the whole thing and use
1
/
4
cup of beaten egg for every egg specified in the recipe.

But are they fresh? Like so many other things we’d rather not think about, an egg’s yolk tends to sag with age. Its white thins (like our hair) and grows cloudy (like our eyes), while its air cell increases in size (like . . . well, you know). But we don’t know that until we’ve bought and broken the eggs.

Cartons of eggs from USDA-inspected plants and from most state-regulated plants must display the date on which the eggs were packed, which is almost always the same day they were laid. Although not required to by law, the packer or the supermarket chain may also choose to specify a “sell by” date, not to exceed thirty days from packing.

Eggs should be stored on an inside shelf of your refrigerator, not in those cute little depressions in the door rack. Refrigerator engineers apparently consider the rack an efficient use of space, but it’s a poor preserver of eggs because of its higher and varying temperature. Refrigerated eggs will keep, with slightly deteriorating flavor and texture, for four to five weeks beyond the packing date. Keep them in their cartons to protect them from refrigerator odors; eggshells are porous and can absorb unpleasant smells. Most commercial eggs, however, have been coated with a thin film of oil to seal the pores and extend their shelf life by reducing moisture loss and preventing bacteria from invading the shell.

A well-known organic restaurant says it uses fertilized brown eggs, claiming that they are the “most nutritious eggs available.” Are there any scientific facts to back this up?

....

U
nfortunately, no.

I hereby join forces with every other printed dissertation on eggs to assure you that no differences in flavor or nutrition have been found between brown eggs and white eggs. Just as brown-skinned people produce brown-skinned children, brown-feathered chickens lay brown-shelled eggs. Among the brown-egg layers are the Barred Plymouth Rock and the Red Rock Cross, while the white-feathered White Leghorn lays white eggs. The Columbian Rock, which sports both black and white feathers, is one of several exceptions. It must have flipped a genetic coin at some time in the past and decided to lay brown eggs.

The color of the yolk, incidentally, depends on the hen’s diet; wheat-based diets produce lemon-yellow yolks, while alfalfa-based diets produce orange-yellow yolks.

Then why do brown eggs cost more? They are generally produced by species of larger hens that consume more feed and lay bigger eggs. One might also speculate that people who think brown eggs are superior are willing to pay more for them.

Some people believe that fertilized eggs are more healthful to eat because they contain a “life force” not present in “dead” foods. I shall not express my opinion of that idea because I am a very tolerant, open-minded, and nonjudgmental person who believes that people have the right to think whatever they choose.

No matter how absurd.

While making breakfast the other day, I broke an egg and found a red spot, looking like blood, on the yolk. I threw it away, but was it okay to eat? And what caused it?

....

I
t doesn’t mean that the egg was fertilized, and it will not hatch no matter how long you sit on it. Hens that lay eggs for commercial distribution have never even seen, much less “dated,” a rooster. Layers just aren’t breeders.

The red spots are indeed blood, from the rupture of a blood vessel on the yolk’s surface that occurred during formation of the egg, or by a similar mishap in the wall of the oviduct. Less than one percent of all eggs laid have blood spots.

The routine inspection process of candling—turning the eggs on rollers in front of high-intensity lights (originally they were held up to a candle) to reveal their interior qualities—catches most eggs with blood spots, and they are removed. But a few inevitably sneak though and reach the market. They are perfectly fit to eat, although Jewish dietary law rejects them as not kosher.