   #copyright

Egg (food)

2007 Schools Wikipedia Selection. Related subjects: Food and agriculture

   An egg is an ovum produced by a female animal for reproduction, often
   prepared as food.

   Most edible eggs, including bird eggs and turtle eggs consist of a
   hard, oval outer eggshell, the "egg white," or albumen, the egg yolk,
   and various thin membranes. Every part of these eggs is edible,
   although the eggshell is generally discarded.

   Roe and caviar are edible eggs produced by fish.

Egg uses as food ingredients

   A carton of free-range chicken eggs
   Enlarge
   A carton of free-range chicken eggs
   Ostrich egg
   Enlarge
   Ostrich egg

   Bird eggs are a common food source. The most commonly used bird eggs
   are those from the chicken, duck, and goose, but smaller eggs such as
   quail eggs are occasionally used as a gourmet ingredient, as are the
   largest bird eggs, from ostriches. Most commercially produced chicken
   eggs intended for human consumption are unfertilized, since the laying
   hens are kept without any 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.

   Chicken eggs are widely used in many types of cooking. Dishes that use
   eggs range from both sweet to savoury dishes. Eggs may be pickled;
   hard-boiled and refrigerated; or eaten raw, though the latter is not
   recommended for people who may be susceptible to salmonella, such as
   the elderly, the infirm, or pregnant women.

Separated eggs

   Eggs are easily separated by cracking the shell and pouring off the egg
   white while carefully holding the egg yolk in the shell. The egg yolk
   and the albumen behave quite differently when cooked, so recipes often
   require separating the egg white from the yolk.

Yolk

   Egg yolks are used to make mayonnaise and other dishes high in fat. Egg
   yolks are important as binding agents in many preparations in European
   cooking due to the emulsifying action of lecithin. This property is
   crucial for sauces such as mayonnaise and Hollandaise; custards such as
   crème anglaise, crème brûlée, flan, and lemon custard; and meat dishes
   such as sausages and pâté.

White

   The albumen, or egg white contains protein but little or no fat. It is
   used in cooking separately from the yolk, and can be aerated or whipped
   to a light, fluffy consistency known as soft peaks and stiff peaks.
   Beaten egg whites are used in desserts such as meringues and mousse.

Eggshell

   Ground egg shells are sometimes used as a food additive to deliver
   calcium.

Problems when cooking eggs

   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.

   When eggs become rotten, the yolk will turn green, and the egg will
   emit a pungent sulfurous odour when broken.

Egg substitutes for baking

   For those who choose not to or are unable to consume eggs, alternatives
   used in baking include other rising agents, such as "Ener-G" egg
   replacer; or binding materials, such as ground flax seeds. Tofu can
   also act as a partial binding agent, since it is high in lecithin due
   to its soy content. Extracted soybean lecithin, in turn, is often used
   in packaged foods as a cheap substitute for egg-derived lecithin.

Egg characteristics

   The shape of an egg is an oval with one end larger than the other end.
   The egg has cylindrical symmetry along the long axis.

   An egg is surrounded by a thin, hard shell. Inside, the egg yolk is
   suspended in the egg white by one or two spiral bands of tissue called
   the chalazae (from the Greek word khalazi, meaning hailstone or hard
   lump.)

Air cell

   The larger end of the egg contains the air cell that forms when the
   contents of the egg cool and contract after it is laid. Chicken eggs
   are graded according to the size of this air cell, measured during
   candling. A very fresh egg has a small air cell and receives a grade of
   AA. As the size of the air cell increases, and the quality of the egg
   decreases, the grade moves from AA to A to B.

Shell and its colour

   Egg shell colour is caused by pigment deposition during egg formation
   in the oviduct and can vary according to breed, from the more common
   white or brown to pink or speckled blue-green. Although there is no
   significant link between shell color and nutritional value, there is
   often a cultural preference for one colour over another. For example,
   in most regions of the United States, eggs are generally white; while
   in the northeast of that country and in the United Kingdom, eggs are
   generally light-brown. Regarding chicken eggs, the color of the egg
   depends on the color of the bird. According to the Egg Nutrition
   Centre, hens with white feathers and earlobes will lay white eggs, and
   chickens with red feathers and earlobes will lay brown eggs (see also [
   ])

White (Albumen)

Yolk

   The yolk in a newly laid egg is round and firm. As the yolk ages it
   absorbs water from the albumen which increases its size and causes it
   to stretch and weaken the vitelline membrane (the clear casing
   enclosing the yolk). The resulting effect is a flattened and enlarged
   yolk shape.

   Yolk colour is dependent on the diet of the hen; if the diet contains
   yellow/orange plant pigments known as xanthophylls, then they are
   deposited in the yolk, coloring it. A colorless diet can produce an
   almost colorless yolk. Farmers may enhance yolk colour with artificial
   pigments, but in most locations, this activity is forbidden.

Abnormalities

   Three eggs frying, two of which are double-yolked eggs.
   Enlarge
   Three eggs frying, two of which are double-yolked eggs.

   Some hens will lay double-yolked eggs as the result of unsynchronized
   production cycles; although heredity causes some hens to have a higher
   propensity to lay double-yolked eggs, these occur more frequently as
   occasional abnormalities in young hens beginning to lay. Usually a
   double-yolked egg will be longer and thinner than an ordinary
   single-yolk egg. Double-yolked eggs only rarely, and even then only
   with human intervention, lead to the successful development of two
   embryos .

   It is also possible for a young hen to produce an egg with no yolk at
   all. Yolkless eggs are usually formed about a bit of tissue that is
   sloughed off the ovary or oviduct. This tissue stimulates the secreting
   glands of the oviduct and a yolkless egg results.

Nutritional value

   Eggs provide a significant amount of protein to one's diet, as well as
   various nutrients.

   Chicken eggs are the most commonly eaten eggs, and are highly
   nutritious. They supply a large amount of complete, high-quality
   protein (which contains all essential amino acids for humans), and
   provide significant amounts of several vitamins and minerals, including
   vitamin A, riboflavin, folic acid, vitamin B6, vitamin B12, choline,
   iron, calcium, phosphorous and potassium. They are also one of the
   least expensive single-food sources of complete protein. One large
   chicken egg contains approximately 7 grams of protein.
   3 egg yolks in a glass
   Enlarge
   3 egg yolks in a glass

   All of the egg's vitamin A, D and E is in the yolk. The egg is one of
   the few foods which naturally contain vitamin D (although this nutrient
   is naturally produced in humans when their skin is exposed to
   sunlight). A large egg yolk contains approximately 60 calories (250
   kilojoules); the egg white contains about 15 calories (60 kilojoules).
   A large yolk contains more than two-thirds of the recommended daily
   intake of 300 mg of cholesterol (although one study shows that your
   body does not absorb much cholesterol from eggs ). The yolk makes up
   about 33% of the liquid weight of the egg. It contains all of the fat
   in the egg and slightly less than half of the protein. It also contains
   all of the choline, and one yolk contains approximately half of the
   recommended daily intake. Choline is an important nutrient for
   development of the brain, and is said to be important for pregnant and
   nursing women to ensure healthy fetal brain development .

   Recently, chicken eggs that are especially high in Omega 3 fatty acids
   have come on the market. These eggs are made by feeding laying hens a
   diet containing polyunsaturated fats and kelp meal. Two brands
   available in the UK are "Columbus Eggs" and "The Hearty Egg" .
   Nutrition information on the packaging is different for each of the
   brands.

Health issues of eating chicken eggs

Cholesterol and fat

   Chicken egg yolks contain a small amount of fat. People on a low-
   cholesterol diet may need to cut down on egg consumption, although most
   of the fat in egg is unsaturated fat and may not be harmful. The egg
   white consists primarily of water (87%) and protein (13%) and contains
   no cholesterol and little, if any, fat.

   Some people try to avoid eggs in their diet because they are high in
   cholesterol, which is concentrated in the yolk. This issue is sometimes
   addressed by eating only some or none of the yolk. People sometimes
   remove the yolk themselves, or may use prepared egg substitutes such as
   Egg Beaters.

   There is debate over whether egg yolk presents a health risk. Some
   research suggests it may lower total Low density lipoprotein ("bad"
   cholesterol) while raising High density lipoprotein ("good"
   cholesterol) levels. Some people advocate the eating of raw eggs and
   egg yolks for this reason, claiming that uncooked cholesterol in the
   yolk is healthier than when it is cooked.

   The United States egg industry launched its continuing "Incredible
   Edible Egg" campaign, which touts eggs as a healthy part of a balanced
   diet. The American Egg Board publicizes modern research which shows
   that dietary cholesterol has less effect on blood cholesterol than
   previously thought.

Contamination

   A health issue associated with eggs is contamination by pathogenic
   bacteria like Salmonella enteritidis. Contamination of eggs exiting a
   female bird via the cloaca may also occur with other members of the
   Salmonella group, so care must be taken to avoid the egg shell becoming
   contaminated with fecal matter. In commercial practice, eggs are
   quickly washed with a sanitizing solution within minutes of being laid.

   Most health experts advise people to cook their eggs thoroughly before
   eating them, as the heat is necessary to kill any infectious
   micro-organisms that may be present. Raw and undercooked eggs have been
   associated with salmonella infection. As with meat, containers and
   surfaces that have been used to process raw eggs should not come in
   contact with ready-to-eat food.

   The risk of infection from raw or undercooked eggs is dependent in part
   upon the sanitary conditions under which the hens are kept. Some
   smaller egg producers make a point of keeping their hens in cleaner
   (and, in their view, more humane) conditions, and observe few or no
   cases of salmonella in the birds themselves.

   Recent evidence suggests the problem is not as prevalent as once
   thought. A study by the U.S. Department of Agriculture earlier this
   year (Risk Analysis April 2002 22(2):203-18) showed that of the 69
   billion eggs produced annually, only 2.3 million of them are
   contaminated with salmonella - equivalent to just one in every 30,000
   eggs.

   Egg shells act as Hermetic seals which guard against bacteria entering,
   but this seal can be broken through improper handling or if laid by
   unhealthy chickens. Most forms of contamination enter through such
   weaknesses in the shell.

Food allergy

   One of the most common food allergies is eggs. Infants usually have the
   opportunity to grow out of this allergy during childhood, if exposure
   is minimized. Generally, physicians will recommend feeding only the
   yolk to infants because of the higher risk of allergic reaction to the
   egg white.

Edwina Currie, Salmonella and the UK Lion Mark

   The Lion Mark was introduced to the UK by the British Egg Information
   Council (the equivalent of the American Egg Board) in 1998. British
   Health Minister Edwina Currie sparked a controversy in 1988 after she
   issued a warning about salmonella in British eggs that was criticised
   for being hysterical and over-cautious. The amount of eggs infected by
   salmonella was a minority and Currie resigned after the then UK Prime
   Minister Margaret Thatcher stated, "I had eggs for breakfast".

   The Lion Mark was launched as an attempt to restore UK public
   confidence in eggs, which had been smashed by Currie's claims. The Lion
   Quality Code of Practice includes compulsory vaccination against
   Salmonella Enteritidis of all pullets destined for Lion egg-producing
   flocks, independent auditing improved traceability of eggs and a
   "best-before" date stamped on the shell and pack which shows that they
   are fresher than required by law, as well as on-farm and packing
   station hygiene controls.

   Since its introduction in 1998, the Lion Mark has been extremely
   successful so much so that, in 2001 a UK Government committee (the
   Advisory Committee on the Microbiological Safety of Food) produced a
   report highlighting the effectiveness of poultry vaccination in
   reducing human salmonella cases by half.

   This has since been reinforced by the Food Standards Agency which has
   confirmed the success of the UK egg industry in overcoming salmonella
   in eggs. In its survey, published in 2004, it tested more than 28,000
   UK-produced eggs and no salmonella was found inside any of them.

   Approximately 85% of UK eggs are now produced to Lion Quality
   Standards.

   The Lion Mark was itself well known in the UK from the 1950s, which was
   one reason why it helped to restore public confidence. The British Egg
   Industry also brought back the popular advertising strapline from the
   1950s, Go To Work On An Egg.

Chicken egg sizes

   Chicken eggs are graded by size, for the purpose of sales. The United
   States Department of Agriculture grades them by weight per dozen. The
   following egg masses have been calculated on the basis of the USDA
   grades:

   CAPTION: Modern Sizes

                Size                      Mass per egg
               Jumbo              Greater than 2.5 oz. or 71 g
   Very Large or Extra Large (XL) Greater than 2.25 oz. or 64g
             Large (L)             Greater than 2 oz. or 57g
             Medium (M)           Greater than 1.75 oz. or 50g
             Small (S)            Greater than 1.5 oz. or 43g
               Peewee             Greater than 1.25 oz. or 35g

   CAPTION: Traditional Sizes

    Size        Mass
   Size 0 Greater than 75 g
   Size 1      70g-75g
   Size 2      65g-70g
   Size 3      60g-65g
   Size 4      55g-60g
   Size 5      50g-55g
   Size 6      45g-50g
   Size 7   less than 45g

   The most common size of chicken egg is 'Large' and is the egg size
   commonly referred to for recipes.

Issues in mass production

   Commercial factory farming operations often involve raising the hens in
   small crowded cages, preventing the chickens from engaging in
   activities such as wing-flapping, dust-bathing, scratching, pecking,
   perching and nest-building. Laying hens are often slaughtered after
   twelve months when their egg productivity starts to decline. All hens
   confined to battery cages, and many raised in cage-free conditions, are
   de-beaked, typically with a hot laser, to prevent cannibalistic
   pecking. According to critics of the practice, this can cause hens
   severe pain to the point where some may refuse to eat and prefer to
   starve to death. Some hens may be force molted to increase egg quality
   and production level after the molting . Due to modern selective
   breeding, laying hen strains differ from meat production strains. As
   male birds of the laying strain do not lay eggs and are not suitable
   for meat production, they are generally killed at one to three days old
   .

   Many animal welfare advocates object to the industrial agriculture
   conditions, such as those stated above, under which laying hens are
   raised. Animal welfare advocates claim that the resulting frustration
   and stress on the hens can lead to aggressive behaviour such as
   feather-pecking and cannibalism.

   Free-range eggs are considered by some advocates to be an acceptable
   substitute to factory farmed eggs. Free range laying hens are given
   outdoor access instead of being contained in crowded cages. Questions
   on the actual living conditions of free range hens have been raised as
   there is no legal definition or regulations for eggs labeled as free
   range in the US .

Trivia

     * If a raw egg is spun, abruptly stopped and then quickly released,
       it will start to spin again as the liquid inside continues to
       rotate. This technique can be used to reliably determine whether an
       egg is raw or already boiled — a solid egg will remain stationary
       once halted. Additionally, if a cooked egg and a raw egg are spun
       with the same force, the cooked egg will spin much faster. Another
       way of determining if an egg is raw or already boiled is to spin it
       quickly. An already boiled egg will spin into an upright position
       after a few seconds, but the raw egg will continue to spin on its
       wide side.
     * It is more difficult to break a chicken egg by squeezing it from
       end-to-end than on its long axis.
     * An ostrich egg can make omelets for ten people, and takes
       forty-five minutes of boiling to harden through.
     * An egg that floats in water is likely to have been spoiled by
       bacteria that entered through the pores in the shell and created
       gas inside it. The increased pressure due to the gas production may
       push some of the white through the shell, which may also signify a
       bad egg.
     * An alternative theory to the floating egg is that because the shell
       is porous, liquid can slowly evaporate out. Thus an older egg has
       more evaporated liquid and therefore a bigger air gap. This is used
       as a test of the freshness of an egg, as a very fresh egg will sink
       in a bowl of water, and lie on its side. An older egg with a bigger
       air gap will tilt up slightly, as the air acts as a float. A very
       old egg will point straight up or may even float to the surface.
     * The world's fastest egg thrower is American Brandon L. Shellhorn,
       who holds the world record of throwing 136 eggs per minute for 30
       minutes in 2001.
     * The world's fastest omelette maker is American Howard Helmer who
       rustled up 427 omelettes in 30 minutes in 1990.
     * The longest throw of a fresh egg — without breaking it — is
       98.51 metres. The record was achieved in Texas, USA in 1978.
     * The world's largest omelette was made in Madrid from 5,000 eggs by
       chef Carlos Fernandez. It weighed 1,320 lbs.
     * An egg will age more in 24 hours at room temperature than it would
       in a week under refrigeration.
     * Eggs contain naturally occurring Vitamin D, a rarity with foods.
     * It takes a hen 24–26 hours to lay an egg, with the cycle repeating
       30 minutes later.
     * A large egg contains 75 calories and 5 grams of fat.
     * A typical egg shell contains up to 17,000 pores, through which
       odors and flavours can pass.
     * Keeping eggs stored in their cartons keep eggs fresher by isolating
       them from the rest of the refrigerator.
     * The colour of a yolk varies with a hen's diet; although artificial
       colors are not allowed in chicken feed, naturally occurring items
       such as yellow-orange marigold petals may be used.

Culture

   A popular Easter tradition in some parts of the world is the decoration
   of hard-boiled eggs (usually by dyeing). Adults often hide the eggs for
   children to find, an activity known as an Easter egg hunt.

Egging

   Although a food item, eggs are sometimes thrown at people or things
   such as houses and cars. This act, known commonly as egging in the
   United States, is a minor form of vandalism and therefore usually a
   criminal offence. On Halloween, for example, trick or treaters have
   been known to throw eggs (and sometimes flour) at property or people
   from whom they received nothing. Furthermore, egg white can degrade
   (and sometimes remove) certain kinds of automotive paint. Eggs are also
   often thrown in protests, as they are cheap, nonlethal and, at the same
   time, very messy when broken. There is also an element of humiliation
   associated with being covered in an egg's contents, referenced by the
   phrase "egg on one's face". The act is often used on October 30,
   sometimes referred to as Mischief night, or on March 31 on the day
   before April fools day.

   Retrieved from " http://en.wikipedia.org/wiki/Egg_%28food%29"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
