Eggs have been eaten by humans for thousands of years.  They can be cooked in a variety of ways and are commonly eaten for breakfast, are healthy additions to soups, salads, sandwiches, entrees, and are essential for baking.

Eggs are laid by females of many different species, including birds, amphibians, reptiles and fish. The most commonly consumed egg is from the chicken, although duck, goose and quail eggs are prominent as well. The largest bird eggs, from ostriches tend to be used only as special luxury food. Gull eggs are considered a delicacy in England and Norway and guinea fowl eggs are commonly seen in African marketplaces. Although pheasant and emu eggs are just as edible, they are not as widely available. Most laying hens in the U.S. are Single-Comb White Leghorns.

History

There is evidence of eggs eaten in Southeast Asia and India as far back as 7500 BCE and Egyptian and Chinese records show domesticated birds producing eggs for human consumption as in 1400 BC. In ancient Rome, meals often began with a preserved egg course. During the Middle Ages, eggs were forbidden during lent because of their richness. The word mayonnaise may have been derived from moyeu, the medieval French word for the yolk, meaning center or hub.

Before the invention of the egg carton, eggs were gathered and carried in egg baskets. A predecessor to the modern egg box was invented by Thomas Peter Bethell of Liverpool in 1906 and marketed as the Raylite Egg Box. He created frames of interlocking strips of cardboard. These frames were themselves packed in cardboard or wooden boxes for transport by road or rail. In 1911, the egg carton was invented by Joseph Coyle in British Columbia to solve a dispute about broken eggs between a farmer and the owner of a hotel that he supplied. Early egg cartons were made of paper.

Grading

Eggs are composed of the shell, albumin or white, and the yolk.  An egg is a prolate spheroid, with one end larger than the other. The air cell is on the larger end of the egg and its size is used in grading the eggs. A very fresh egg has a small air cell and receives a grade of AA. Its “spread” is compact, the albumen is clear, thick and firm, the yolk stands round and high. Grade A eggs have a slight spread, clear and reasonably firm albumen and a yolk that stands fairly high and practically free from defects.  A grade B egg spreads over a wide area, has a clear, weak or watery albumen and an flattened yolk. As an egg gets older, the larger end of the egg will rise to increasingly shallower depths when the egg is placed in a bowl of water. A very old egg will actually float in the water and should not be eaten. Eggs come in sizes of jumbo, extra large, large, medium, small and peewee.

Health

Eggs contain significant amounts of protein, vitamins, antioxidants and are about 70 calories each.   More than half the calories found in eggs come from the fat in the yolk. Thus, people on a low-cholesterol diet may need to reduce egg consumption. The egg white, however, consists primarily of water (87%) and protein (13%) and contains no cholesterol and little, if any, fat. Despite their nutritional value, however, there are health concerns involving allergy, storage and preparation. To prevent salmonella poisoning, always cook eggs thoroughly.

Culinary Uses

An egg can be boiled, scrambled, fried, poached, made into an omelet or pickled. It is used as an emulsifier (help suspend one liquid in another, as in salad dressings) and as a thickener. The proteins in egg white allow it to form foams and aerated dishes. Egg whites, which contain the protein and very little fat,  may be aerated or whipped to a light, fluffy consistency, and are often used in desserts such as meringues and mousse. Eggs can also be soaked in mixtures to absorb flavor. Tea eggs are steeped in a brew from a mixture of various spices, soy sauce, and black tea leaves to give flavor.

Pidan (also known as hundred year or thousand year eggs) is a Chinese method of preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, lime and rice hulls for several weeks to several months. In the process, the yolk becomes dark green to gray in color and develops a creamy consistency with an odor of sulphur and ammonia.  The egg white becomes a dark brown, translucent jelly with a salty flavor. Century eggs are often eaten without further preparation, on their own or are used as a side dish, sometimes with ginger root or tofu.

A Balut is a developing duck embryo (fertilized duck egg) that is boiled and eaten in the shell. It is commonly sold in the Philippines, Laos, Cambodia and Vietnam. The broth surrounding the embryo is first sipped and then the undeveloped chick inside is eaten, often with salt and/or a chili, garlic and vinegar (white or coconut sap) mixture as seasoning.

Storage

Uncooked eggs can be kept refrigerated for up to 4-5 weeks, while hard-boiled eggs left in their shells should be used within a week.

Commercial Production vs. Cage Free

Commercial factory farm operations often involve raising the hens in small, crowded cages, preventing the chickens from engaging in natural behaviors, such as wing-flapping, dust-bathing, scratching, pecking, perching and nest-building. Many hens have their beaks removed to prevent harming each other and to prevent cannibalism. In the United States, increased public concern for animal welfare has resulted in the United Egg Producers program which includes guidelines regarding housing, food, water, air, living space, beak trimming, molting, handling, and transportation. However, some organizations such as the Humane Society, claim that the UEP certification is misleading. “Certified Organic” labeling, which requires hens to have outdoor access and be fed only organic vegetarian feed and so on, is considered the most humane.

Cultural Traditions

During Easter in many countries, eggs are dyed, decorated and hidden for children to find. Before the spring equinox in the Persian New Year tradition, each family member decorates a hard-boiled egg and sets them together in a bowl. The tradition of a dancing egg is held during the feast  Corpus Christi in Barcelona and other Catalan cities since the 16th century, which consists of an emptied egg, positioned over the water jet from a fountain, which starts turning without falling.

Resources

Labensky, Sarah R., and Alan M. Hause. On Cooking: A Textbook of Culinary Fundamentals.

Wikipedia

http://www.eggnutritioncenter.org

http://www.incredibleegg.org