August 2, 2010
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How to Cook Eggs
Nest by Tilly Woodward, courtesy Olson-Larsen Gallery
Eggs have three extraordinary characteristics. 1.) They thicken liquids into solids; 2.) They create the texture of foam with their whipped whites and 3.) They can stabilize oil and liquid with the emulsifiers in their yolks.
Most egg cookery has the same purpose – to bond liquids (the egg’s own, or others) into a moist, soft solid. Egg proteins coagulate when heated, so overcooking causes the proteins to overbond and squeeze out liquids, turning your dish rubbery or curdling it. Eggs whites begin to set at 145 degrees F and are completely set at 160 degrees F. After that, there’s trouble – fried eggs get rubbery and scarambled eggs separate into solids and liquids. Diluting eggs with other liquids raises the temperature at which coagulation occurs. Addind sugar does the same thing, though for different reasons. Salt and acids (crème of tartar, juice of any kind) have the reverse effect.
Boiling
Three to five minutes will solidify the white. To solidify the yolk, you can cook it five times as long. Tender whites will result from simmering the eggs instead of boiling them, no more than 185 degrees F, for 25 to 30 minutes. You can tell a raw egg from a cooked one by the way it spins, raw eggs spin reluctantly and will start moving again if stopped and then released. Fresh eggs are hard to peel, because their lower pH count makes the albumen adhere to the shell. The green color that occasionally forms in a hard boiled egg yolk is the result of gas formed by heating albumen’s high sulfur and then exerting pressure on the yolk’s high iron content. You can avoid this by only cooking the eggs long enough to solidfy the yolk and then plunging them in cold water, or peeling them instantly.
Poaching
Only use AA grade eggs, as they have a higher proportion of thick to thin albumen and will form more nicely in hot water. Do not boil the water, start at about 200 degrees and then reduce to simmering. Adding salt, or acid will speed the coagulation but it will also add flavors.
Frying
The trick is to not let the white spread out too thin. Scientists believe the best temperature for frying eggs is 255 – 280 degrees F – that’s the same temperature at which butter will melt without turning brown.
Scrambled eggs and omelets
The amount of liquid that is added is key. Omelets are cooked faster at higher heat than scrambled eggs, so they can’t hold as much liquid. Scientists recommend 2 to 5 teaspoons per egg in scrambled eggs but only 2 to 3 teaspoons in omelets. If you add no liquid at all, be extra careful the eggs do not dry out. In any case, remove the eggs from the frying pan immediately as they will continue to cook even if the heat source is turned off.
Custards
Custards are sweetened gels of tender egg protein. Quiche is unsweetened custard. The basic custard combines an egg with a cup of whole milk and two teaspoons of sugar. Extra yolks can be added for richness. The bonding of proteins that makes the custard set will occur between 180 and 190 degrees F and the custard will curdle when it reaches just 5 more degrees. So slow cooking in an oven that never reaches 212 degrees F is essential.
Foam
Egg whites increase in volume by up to 8 times when beaten. In technical terms, egg foams are gas dispersed in liquid. In common talk, they are stable bubble masses of protein. Meringues can be beaten too little ( poor volume) or too much (premature collapse). Most cooks advise beating until the foam can stand up in a defined peak and not a second longer. A single drop of yolk, or any fat, will reduce the foam’s volume by as much as two thirds. Once the foam has formed though, it can be folded into the yolks or other fatty mixes and still leaven appropriately. That is how soufflés and sponge cakes are made. Acids (cream of tartar or lemon juice) are added to stabilize the foam. Sugar is added, after the foam forms, to improve the flavor. Since the 1771 French Encyclopedia was published, copper pans have been preferred for meringues. Copper pans create a creamier yellowish foam that is harder to overbeat than those made in ceramic and glass pans. If you don’t have copper pans, you can achieve similar results with cream of tartar. Scientists have been trying to analyze and explain the copper phenomenon for decades. Whatever the cause, they think it may hold the biochemical key to understanding how proteins interact during destabilization.
As soon as meringues are formed, they are baked to stabilize the structure, by coagulating the proteins and drying out the sugar syrups. Soft meringues are baked at 350 F for about 15 minutes. Hard meringues are baked at 225 F for an hour to two hours.
Angel cakes and sponge cakes derive their lightness from egg white foam but flour and milk give them their strength. Sponge cake batter includes egg yolks and sugar, where as angel cakes just add sugar. Souffles are light sponge cakes, with about half as much flour. Beaten egg whites are folded into a sauce rather than a batter. They can be made into savory or sweet versions, with purees of meat and cheese in the former and fruits, sugar, chocolate and liqueurs in the latter. The trick is to bake them hot enough for the proteins to set before the foam has fully expanded and begins to fall – yet at low enough heat to cook the center before the outside burns.
Whipped yolks
Egg yolks have too many fats to foam easily and their proteins are not suited to denature easily either. Still, the classic dish zabaglione manages the tricks with its mix of Marsala wine, frothy yolks and sugar.
The miracle of egg yolks is their emulsification properties, particularly in bonding oils and liquids, as in mayonnaise and béarnaise sauce. In the mid 17th century, Pierre Francois de la Varenne discovered the whipped egg yolks could bond proteins into new sauces, his “Fragrant Sauce for asparagus” is the original hollandaise. It was named about 100 years later when Louis 14’s courtiers discovered it among Huguenots exiled in Holland. It‘s still made the same way, with clarified butter, egg yolks, lemon juice or vinegar. Mousseline is a hollandaise sauce made with whipped cream. Bearnaise sauce has the same base but also uses reduced white wine, shallots, chervil and tarragon. The trick is to not use more oil than your egg yolks can emulsify. Julia Child insists the proper ratio is 3/8th cup of butter per large egg yolk. Always make these sauces in stainless steel, enameled or coated pans, as metal oxides in iron and aluminum will discolor them.
Similarly mayonnaise was imported from the Minorcan port city Mahon. Its made by emulsifying olive or vegetable oil with eggs, vinegar or lemon juice. Unlike Hollandaise sauce, it’s made at room temperature. Mrs. Clark’s distinctive recipe in Des Moines has always added mustard seed. Remoulade sauce is a mayonnaise base with gherkins pickles, capers, mustard and anchovy paste. In the development of sauces, French writers used the word “liaison” likening the thickening agents of sauce to facilitators in romance and warfare. When you make mayo in a blender, you can use whole eggs, as the albumen breaks down enough to weave between oil droplets.
Hundred/Thousand Year Eggs
A 100O year old, or hundred-year-old egg,, is preserved by coating an egg in a mixture of clay, ash, salt, lime, and straw for several weeks to several months, depending on the method. The yolk becomes a dark green, cream-like substance with a strong odor of sulfur and ammonia, while the white becomes a dark brown, transparent jelly with a comparatively mild, distinct flavor. The transforming agent is its alkaline material, which gradually raises the pH of the egg from around 9 to 12 or more. This chemical process breaks down some of the complex, flavorless proteins and fats of the yolk into simpler, flavorful ones, which in some way may be thought of as an “inorganic version” of fermentation.
