Eggs a detailed overview

W.J.Pais Food Information - Health Issues
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eggsMost commercially produced chicken eggs intended for human consumption are unfertilized, since the laying hens are kept without roosters. Fertile eggs can be purchased and eaten as well, with little nutritional difference. Fertile eggs will not contain a developed embryo, as refrigeration prohibits cellular growth for an extended amount of time (although sometimes the embryo is allowed to develop on purpose, as in balut).
 
 

Chicken eggs are widely used in many types of dishes, both sweet and savory. Eggs can be pickled, hard-boiled, soft-boiled, scrambled, fried and refrigerated. They can also be eaten raw, though this is not recommended for people who may be especially susceptible to salmonella, such as the elderly, the infirm, or pregnant women. In addition, the protein in raw eggs is only 51% bio-available, whereas that of a cooked egg is nearer 91% bio-available, meaning the protein of cooked eggs is nearly twice as absorbable as the protein from raw eggs.[6] As an ingredient, egg yolks are an important emulsifier in the kitchen, and the proteins in egg white allow it to form foams and aerated dishes.


Soft-boiled quail eggs, with potato galettes

The albumen, or egg white, contains protein but little or no fat. It can be used in cooking separately from the yolk, and can be aerated or whipped to a light, fluffy consistency. Beaten egg whites are used in desserts such as meringues and mousse. Ground egg shells are sometimes used as a food additive to deliver calcium.

Every part of an egg is edible,although the eggshell is generally discarded.

Egg white coagulates, or solidifies, when it reaches temperatures between 144 °F and 149 °F (62.2 °C-65 °C) Egg yolk coagulates at slightly higher temperatures, between 149 °F and 158 °F (65 °C-70 °C).

If a boiled egg is overcooked, a greenish ring sometimes appears around egg yolk. This is a manifestation of the iron and sulfur compounds in the egg. It can also occur when there is an abundance of iron in the cooking water. The green ring does not affect the egg's taste; overcooking, however, harms the quality of the protein (chilling the egg for a few minutes in cold water until the egg is completely cooled prevents the greenish "ring” from forming on the surface of the yolk).

Cooking also increases the risk of atherosclerosis due to increased oxidization of the cholesterol contained in the egg yolk
 
 Preservation

Salted duck egg

Preservation of edible eggs is extremely important, as an improperly handled egg can contain elevated levels of Salmonella, bacteria that can cause severe food poisoning. The simplest method to preserve an egg is to treat it with salt. Salt draws water out of bacteria and molds, which prevents their growth.The Chinese salted duck egg is made by immersing duck eggs in brine, or coating them individually with a paste of salt and mud or clay. The eggs stop absorbing salt after about a month, having reached chemical equilibrium. Their yolks take on an orange-red color and solidify, but the white remains liquid. They are boiled before consumption and often served with rice congee.


Pickled egg, colored with beetroot juice

Another method is to make pickled eggs, by boiling them first and immersing them in a mixture of vinegar, salt, and spices like ginger or allspice. Frequently, beetroot juice is added to impart a red color to the eggs. If the eggs are immersed in it for a few hours, the distinct red, white, and yellow colors can be seen when the eggs are sliced  If marinated for several days or more, the red color will reach the yolk. If the eggs are marinated in the mixture for several weeks or more, the vinegar will dissolve much of the shell's calcium carbonate and penetrate the egg, making it acidic enough to inhibit the growth of bacteria and molds.Pickled eggs made this way will generally keep for a year or more without refrigeration.



 

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