corn and
marigold petals.
[Shell eggs from farm to table](_blank)
. USDA Food Safety and Inspection Service, (2011). In the US, the use of artificial color additives is forbidden.
Abnormalities
Abnormalities that have been found in eggs purchased for human consumption include:
*
Double-yolk eggs, when an egg contains two or more yolks, occurs when ovulation occurs too rapidly, or when one yolk becomes joined with another yolk.
*
Yolkless eggs, which contain whites but no yolk, usually occurs during a pullet's first effort, produced before her laying mechanism is fully ready.
* Double-shelled eggs, where an egg may have two or more outer shells, is caused by a counter-peristalsis contraction and occurs when a second oocyte is released by the ovary before the first egg has completely traveled through the oviduct and been laid.
* Shell-less or thin-shelled eggs may be caused by
egg drop syndrome
Egg drop syndrome '76 (EDS '76) is a viral disease that affects birds, notably chickens, ducks, geese and swans. It is characterised by a sudden drop in production of eggs as well as its eggshell quality in apparent healthy laying birds.
Previou ...
.
Culinary properties
Types of dishes
Chicken eggs are widely used in many types of dishes, both sweet and savory, including many
baked goods
Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most common baked item is bread but many other types of foods can be baked. Heat is gradually transferred ...
. Some of the most common preparation methods include
scrambled,
fried,
poached,
hard-boiled
Hardboiled (or hard-boiled) fiction is a literary genre that shares some of its characters and settings with crime fiction (especially detective fiction and noir fiction). The genre's typical protagonist is a detective who battles the violence ...
, soft-boiled,
omelettes
In cuisine, an omelette (also spelled omelet) is a dish made from beaten eggs, fried with butter or oil in a frying pan (without stirring as in scrambled egg). It is quite common for the omelette to be folded around fillings such as chives ...
, and
pickled
Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called ...
. They also may be eaten raw, although this is not recommended for people who may be especially susceptible to
salmonellosis
Salmonellosis, more commonly known as food poisoning is a symptomatic infection caused by bacteria of the ''Salmonella'' type. It is also a food-borne disease and are defined as diseases, usually either infectious or toxic in nature, caused
by a ...
, such as the elderly, the infirm, or pregnant women. In addition, the protein in raw eggs is only 51 percent
bioavailable
In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation.
By definition, when a medication is administered intravenously, its bioavailability is 100%. Ho ...
, whereas that of a cooked egg is nearer 91 percent bioavailable, meaning the protein of cooked eggs is nearly twice as absorbable as the protein from raw eggs.
As a cooking ingredient, egg yolks are an important
emulsifier in the kitchen, and are also used as a thickener, as in
custards.
The
albumen
Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms aro ...
(egg white) contains protein, but little or no
fat
In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.
The term often refers specifically to triglycerides (triple est ...
, and may be used in cooking separately from the yolk. The proteins in egg white allow it to form foams and aerated dishes. Egg whites may be aerated or whipped to a light, fluffy consistency, and often are used in desserts such as
meringue
Meringue (, ; ) is a type of dessert or candy, often associated with Swiss, French, Polish and Italian cuisines, traditionally made from whipped egg whites and sugar, and occasionally an acidic ingredient such as lemon, vinegar, or cream o ...
s and
mousse.
Ground eggshells sometimes are used as a
food additive to deliver
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
. Every part of an egg is edible, although the eggshell is generally discarded. Some recipes call for immature or unlaid eggs, which are harvested after the hen is slaughtered or cooked, while still inside the chicken.
Cooking
Eggs contain multiple proteins that gel at different temperatures within the yolk and the white, and the temperature determines the gelling time. Egg yolk becomes a
gel
A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still dif ...
, or solidifies, between . Egg white gels at different temperatures: . The white contains exterior albumen which sets at the highest temperature. In practice, in many cooking processes the white gels first because it is exposed to higher temperatures for longer.
Salmonella is killed instantly at , but also is killed from , if held at that temperature for sufficiently long time periods. To avoid the issue of salmonella,
eggs may be pasteurized in-shell at for an hour and 15 minutes. Although the white then is slightly milkier, the eggs may be used in normal ways. Whipping for meringue takes significantly longer, but the final volume is virtually the same.
If a boiled egg is overcooked, a greenish ring sometimes appears around egg yolk due to changes to the
iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
and
sulfur compounds in the egg. It also may occur with an abundance of iron in the cooking water. Overcooking harms the quality of the protein. Chilling an overcooked egg for a few minutes in cold water until it is completely cooled may prevent the greenish ring from forming on the surface of the yolk.
Peeling a cooked egg is easiest when the egg was put into boiling water as opposed to slowly heating the egg from a start in cold water.
Flavor variations
Although the age of the egg and the conditions of its storage have a greater influence, the bird's diet affects the flavor of the egg.
For example, when a brown-egg chicken breed eats
rapeseed
Rapeseed (''Brassica napus ''subsp.'' napus''), also known as rape, or oilseed rape, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturally contains a ...
(canola) or soy meals, its intestinal microbes metabolize them into fishy-smelling
triethylamine
Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...
, which ends up in the egg.
The unpredictable diet of free-range hens will produce likewise, unpredictable egg flavors.
Duck eggs tend to have a flavor distinct from, but still resembling, chicken eggs.
Eggs may be soaked in mixtures to absorb flavor.
Tea egg
Tea egg is a typical Chinese savory food commonly sold as a snack, in which a boiled egg is cracked slightly and then boiled again in tea, and sauce or spices. It is also known as marble egg because cracks in the egg shell create darkened ...
s, a common snack sold from street-side carts in China, are steeped in a brew from a mixture of various spices, soy sauce, and black tea leaves to give flavor.
Storage
Careful storage of edible eggs is extremely important, as an improperly handled egg may contain elevated levels of ''
Salmonella''
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
that may cause severe
food poisoning. In the US, eggs are washed. This cleans the shell, but erodes its
cuticle.
The USDA thus recommends refrigerating eggs to prevent the growth of ''Salmonella''.
Refrigeration also preserves the taste and texture, however, intact eggs (unwashed and unbroken) may be left unrefrigerated for several months without spoiling. In Europe, eggs are not usually washed, and the shells are dirtier, however the cuticle is undamaged, and they do not require refrigeration.
[ In the UK in particular, hens are immunized against salmonella and generally, their eggs are safe for 21 days.][
]
Preservation
The simplest method to preserve an egg is to treat it with salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
. Salt draws water out of bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
and mold
A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not ...
s, which prevents their growth. The Chinese salted duck egg
A salted duck egg is an East Asian preserved food product made by soaking duck eggs in brine, or packing each egg in damp, salted charcoal. In Asian supermarkets across the Western world, these eggs are sometimes sold covered in a thick layer ...
is made by immersing duck eggs in brine, or coating them individually with a paste of salt and mud or clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
. The eggs stop absorbing salt after approximately a month, having reached osmotic equilibrium
Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane.
It is also defined as the measure of the tendency of a solution to take in a pure s ...
. Their yolks take on an orange-red color and solidify, but the white remains somewhat liquid. These often are boiled before consumption and are served with rice congee.
Another method is to make pickled egg
Pickled eggs are typically hard boiled eggs that are cured in vinegar or brine. As with many foods, this was originally a way to preserve the food so that it could be eaten months later. Pickled eggs have since become a favorite among many ...
s, by boiling them first and immersing them in a mixture of vinegar
Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...
, salt, and spices, such as 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 may 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
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...
enough to inhibit the growth of bacteria and molds. Pickled eggs made this way generally keep for a year or more without refrigeration.
A century egg or hundred-year-old egg is preserved by coating an egg in a mixture of clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
, wood ash
Wood ash is the powdery residue remaining after the combustion of wood, such as burning wood in a fireplace, bonfire, or an industrial power plant. It is largely composed of calcium compounds along with other non-combustible trace elements presen ...
, salt, lime
Lime commonly refers to:
* Lime (fruit), a green citrus fruit
* Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide
* Lime (color), a color between yellow and green
Lime may also refer to:
Botany ...
, and rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
straw for several weeks to several months, depending on the method of processing. After the process is completed, 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 in a century egg is its alkaline material, which gradually raises the pH of the egg from approximately 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.
Nutrition
Egg sizes
Nutritional value
A medium/large chicken egg provides approximately 70 kilocalories (290 kJ) of food energy and 6 grams of protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
.["Full Report (All Nutrients): 01129, Egg, whole, cooked, hard-boiled"]
USDA Branded Food Products Database["Full Report (All Nutrients): 45174951, EGGS"]
USDA Branded Food Products Database
Eggs (boiled) supply several vitamins and minerals as significant amounts of the Daily Value
The Reference Daily Intake (RDI) used in nutrition labeling on food and dietary supplement products in the U.S. and Canada is the daily intake level of a nutrient that is considered to be sufficient to meet the requirements of 97–98% of healthy ...
(DV), including (per 100g) vitamin A
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably ...
(19 percent DV), riboflavin (42 percent DV), pantothenic acid
Pantothenic acid, also called vitamin B5 is a water-soluble B vitamin and therefore an essential nutrient. All animals require pantothenic acid in order to synthesize coenzyme A (CoA) – essential for fatty acid metabolism – as well as to, ...
(28 percent DV), vitamin B12 (46 percent DV), choline Choline is an essential nutrient for humans and many other animals. Choline occurs as a cation that forms various salts (X− in the depicted formula is an undefined counteranion). Humans are capable of some ''de novo synthesis'' of choline but r ...
(60 percent DV), phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
(25 percent DV), zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
(11 percent DV) and vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
(15 percent DV).
The diet of laying hens also may affect the nutritional quality of eggs. For instance, chicken eggs that are especially high in omega-3
Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chem ...
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
s are produced by feeding hens a diet containing polyunsaturated
In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.
The term often refers specifically to triglycerides (triple es ...
fats from sources such as fish oil
Fish oil is oil derived from the tissues of oily fish. Fish oils contain the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), precursors of certain eicosanoids that are known to reduce inflammation in the b ...
, chia seeds, or flaxseeds. Pasture-raised free-range hens, which forage for their own food, also produce eggs that are relatively enriched in omega-3 fatty acids when compared to those of cage-raised chickens.
A 2010 USDA study determined there were no significant differences of macronutrients
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...
in various chicken eggs.
Cooked eggs are easier to digest than raw eggs, as well as having a lower risk of salmonellosis
Salmonellosis, more commonly known as food poisoning is a symptomatic infection caused by bacteria of the ''Salmonella'' type. It is also a food-borne disease and are defined as diseases, usually either infectious or toxic in nature, caused
by a ...
.
Health effects
Cholesterol and fat
More than half the calories found in eggs come from the fat in the yolk; 50 grams of chicken egg (the contents of an egg just large enough to be classified as "large" in the US, but "medium" in Europe) contains approximately five grams of fat. Saturated fat ( palmitic, stearic, and myristic acid
Myristic acid (IUPAC name: tetradecanoic acid) is a common saturated fatty acid with the molecular formula CH3(CH2)12COOH. Its salts and esters are commonly referred to as myristates or tetradecanoates. It is named after the binomial name for nut ...
s) makes up 27 percent of the fat in egg. The egg white consists primarily of water (around 90 percent) and protein (around 10 percent) and contains no cholesterol and little, if any, fat.
There is debate over whether egg yolk presents a health risk. Some research suggests dietary cholesterol
Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...
increases the ratio of total to HDL cholesterol
High-density lipoprotein (HDL) is one of the five major groups of lipoproteins. Lipoproteins are complex particles composed of multiple proteins which transport all fat molecules (lipids) around the body within the water outside cells. They are t ...
and, therefore, adversely affects the body's cholesterol profile; whereas other studies show that moderate consumption of eggs, up to one a day, does not appear to increase heart disease risk in healthy individuals. Harold McGee
Harold James McGee (born October 3, 1951) is an American author who writes about the chemistry and history of food science and cooking. He is best known for his seminal book '' On Food and Cooking: The Science and Lore of the Kitchen'' first pu ...
argues that the cholesterol in the egg yolk is not what causes a problem, because fat (particularly saturated fat) is much more likely to raise cholesterol levels than the consumption of cholesterol.
Type 2 diabetes
Studies have shown conflicting results about a possible connection between egg consumption and type 2 diabetes
Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urinatio ...
.
A meta-analysis from 2013 found that eating four eggs per week was associated with a 29 percent increase in the relative risk of developing diabetes. Another meta-analysis from 2013 also supported the idea that egg consumption may lead to an increased incidence of type two diabetes. A 2016 meta-analysis suggested that association of egg consumption with increased risk of incident type 2 diabetes may be restricted to cohort studies from the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
.
A 2020 meta-analysis found that there was no overall association between moderate egg consumption and risk of type 2 diabetes and that the risk found in US studies was not found in European or Asian studies.
Cancer
A 2015 meta-analysis found an association between higher egg consumption (5 a week) with increased risk of breast cancer
Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a r ...
compared to no egg consumption. Another meta-analysis found that egg consumption may increase ovarian cancer
Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...
risk.
A 2019 meta-analysis found an association between high egg consumption and risk of upper aero-digestive tract cancers in hospital-based case-control studies.
A 2021 review did not find a significant association between egg consumption and breast cancer. A 2021 umbrella review found that egg consumption significantly increases the risk of ovarian cancer.
Cardiovascular health
One systematic review and meta-analysis of egg consumption found that higher consumption of eggs (more than 1 egg/day) was associated with a significant reduction in risk of coronary artery disease. Another systematic review and meta-analysis of Dietary Cholesterol and Egg Consumption found that egg consumption was associated with an increased all-cause mortality and CVD mortality. These contrary results may be due to somewhat different methods of study selection and the use primarily of observational studies
In fields such as epidemiology, social sciences, psychology and statistics, an observational study draws inferences from a sample to a population where the independent variable is not under the control of the researcher because of ethical concern ...
, where confounding factors are not controlled.
A 2018 meta-analysis of randomized clinical trials found that consumption of eggs increases total cholesterol (TC), LDL-C
Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall densit ...
and HDL-C compared to no egg-consumption but not to low-egg control diets. In 2020, two meta-analyses found that moderate egg consumption (up to one egg a day) is not associated with an increased cardiovascular disease risk. A 2020 umbrella review concluded that increased egg consumption is not associated with cardiovascular disease risk in the general population. Another umbrella review found no association between egg consumption and cardiovascular disorders.
A 2013 meta-analysis found no association between egg consumption and heart disease or stroke. A 2013 systematic review and meta-analysis found no association between egg consumption and cardiovascular disease or cardiovascular disease mortality, but did find egg consumption of more than once daily increased cardiovascular disease risk 1.69-fold in those with type 2 diabetes mellitus when compared to type 2 diabetics who ate less than one egg per week. Another 2013 meta-analysis found that eating four eggs per week increased the risk of cardiovascular disease by six percent.
Eggs are one of the largest sources of phosphatidylcholine
Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup.
They are a major component of biological membranes and can be easily obtained from a variety of readily available sources, such as egg yolk or soybea ...
( lecithin) in the human diet. A study published in the scientific journal, ''Nature
Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
'', showed that dietary phosphatidylcholine is digested by bacteria in the gut and eventually converted into the compound TMAO
Trimethylamine ''N''-oxide (TMAO) is an organic compound with the formula (CH3)3NO. It is in the class of amine oxides. Although the anhydrous compound is known, trimethylamine ''N''-oxide is usually encountered as the dihydrate. Both the anhyd ...
, a compound linked with increased heart disease. Another study found that type 2 diabetes mellitus and kidney disease also increase TMAO levels and that evidence for a link between TMAO and cardiovascular diseases may be due to confounding or reverse causality.
Other
Egg consumption does not increase hypertension risk. A 2016 meta-analysis found that consumption of up to one egg a day may contribute to a decreased risk of total stroke. Two recent meta-analyses found no association between egg intake and risk of stroke.
A 2019 meta-analysis revealed that egg consumption has no significant effect on serum biomarkers of inflammation
Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...
. A 2021 review of clinical trials found that egg consumption has beneficial effects on macular pigment optical density and serum lutein.
Contamination
A health issue associated with eggs is contamination by pathogenic bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
, such as ''Salmonella enteritidis
''Salmonella enterica'' subsp. ''enterica'' is a subspecies of ''Salmonella enterica'', the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the ''S. enterica'' species are in this subspecies, inclu ...
''. Contamination of eggs with other members of the genus ''Salmonella'' while exiting a female bird via the cloaca may occur, so care must be taken to prevent the egg shell from becoming contaminated with fecal
Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
matter. In commercial practice in the US, eggs are quickly washed with a sanitizing solution within minutes of being laid. The risk of infection from raw or undercooked eggs is dependent in part upon the sanitary conditions under which the hens are kept.
Health experts advise people to refrigerate washed eggs, use them within two weeks, cook them thoroughly, and never consume raw eggs.[Eggs – No Yolking Matter]
." ''Nutrition Action Health Letter,'' July/August 1997. As with meat, containers and surfaces that have been used to process raw eggs should not come in contact with ready-to-eat food.
A study by the U.S. Department of Agriculture in 2002 (Risk Analysis April 2002 22(2):203-18) suggests the problem is not so prevalent in the U.S. as once thought. It showed that of the 69 billion eggs produced annually, only 2.3 million are contaminated with ''Salmonella''—equivalent to just one in every 30,000 eggs—thus showing ''Salmonella'' infection is quite rarely induced by eggs. This has not been the case in other countries, however, where ''Salmonella enteritidis'' and ''Salmonella typhimurium
''Salmonella enterica'' subsp. ''enterica'' is a subspecies of ''Salmonella enterica'', the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the ''S. enterica'' species are in this subspecies, includin ...
'' infections due to egg consumption are major concerns.
Egg shells act as hermetic seal
A hermetic seal is any type of sealing that makes a given object airtight (preventing the passage of air, oxygen, or other gases). The term originally applied to airtight glass containers, but as technology advanced it applied to a larger categor ...
s that 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. In the UK, the British Egg Industry Council
The British Egg Industry Council is an organisation set up in 1986 to represent the British egg industry. It currently has 11 member organisations including the British Egg Products Association, the National Farmers Union and the British Free R ...
awards the lions stamp to eggs that, among other things, come from hens that have been vaccinated against '' Salmonella''.
In 2017, authorities blocked millions of eggs from sale in the Netherlands, Belgium, and Germany because of contamination with the insecticide fipronil.
Food allergy
One of the most common food allergies
A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressur ...
in infants is eggs.[Egg Allergy Brochure](_blank)
, distributed by Royal Prince Alfred Hospital
The Royal Prince Alfred Hospital (abbreviated RPAH or RPA) is a major public teaching hospital in Sydney, Australia, located on Missenden Road in Camperdown. It is a teaching hospital of the Central Clinical School of the Sydney Medical School a ...
Infants usually have the opportunity to grow out of this allergy during childhood, if exposure is minimized. Allergic reaction
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...
s against egg white are more common than reactions against egg yolks. In addition to true allergic reactions, some people experience a food intolerance
Food intolerance is a detrimental reaction, often delayed, to a food, beverage, food additive, or compound found in foods that produces symptoms in one or more body organs and systems, but generally refers to reactions other than food allergy. Fo ...
to egg whites. Food labeling practices in most developed countries now include eggs, egg products, and the processing of foods on equipment that also process foods containing eggs in a special allergen alert section of the ingredients on the labels.
Farming
Most commercially farmed chicken eggs intended for human consumption are unfertilized, since the laying hens are kept without rooster
The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult m ...
s. Fertile eggs may be eaten, with little nutritional difference when compared to the unfertilized. Fertile eggs will not contain a developed embryo, as refrigeration temperatures inhibit cellular growth for an extended period of time. Sometimes an embryo is allowed to develop, but eaten before hatching as with balut.
Grading by quality and size
The U.S. Department of Agriculture grades eggs by the interior quality of the egg (see Haugh unit) and the appearance and condition of the egg shell. Eggs of any quality grade may differ in weight (size).
*U.S. Grade AA
**Eggs have whites that are thick and firm; have yolks that are high, round, and practically free from defects; and have clean, unbroken shells.
**Grade AA and Grade A eggs are best for frying and poaching, where appearance is important.
*U.S. Grade A
**Eggs have characteristics of Grade AA eggs except the whites are "reasonably" firm.
**This is the quality most often sold in stores.
*U.S. Grade B
**Eggs have whites that may be thinner and yolks that may be wider and flatter than eggs of higher grades. The shells must be unbroken, but may show slight stains.
**This quality is seldom found in retail stores because usually they are used to make liquid, frozen, and dried egg products, as well as other egg-containing products.
In Australia and the European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...
, eggs are graded by the hen raising method, free range
Free range denotes a method of farming husbandry where the animals, for at least part of the day, can roam freely outdoors, rather than being confined in an enclosure for 24 hours each day.
On many farms, the outdoors ranging area is fenced, ...
, battery cage
Battery cages are a housing system used for various animal production methods, but primarily for egg-laying hens. The name arises from the arrangement of rows and columns of identical cages connected together, in a unit, as in an artillery batt ...
d, etc.
Chicken eggs are graded by size for the purpose of sales. Some maxi eggs may have double-yolks and some farms separate out double-yolk eggs for special sale.
File:Egg and maxi egg 1.jpg,
File:Egg and maxi egg 2.jpg,
File:Egg with two yellows.jpg,
Color of eggshell
Although eggshell color is a largely cosmetic issue, with no effect on egg quality or taste, it is a major issue in production due to regional and national preferences for specific colors, and the results of such preferences on demand. For example, in most regions of the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, chicken eggs generally are white. However, brown eggs are more common in some parts of the Northeastern United States, particularly New England
New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the Can ...
, where a television jingle for years proclaimed "brown eggs are local eggs, and local eggs are fresh!". Local chicken breeds, including the Rhode Island Red
The Rhode Island Red is an American breed of domestic chicken. It is the state bird of Rhode Island. It was developed there and in Massachusetts in the late nineteenth century, by cross-breeding birds of Oriental origin such as the Malay wit ...
, lay brown eggs. Brown eggs are preferred in China, Costa Rica, Ireland
Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
, France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
, and the United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
. In Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
and Poland
Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...
, white chicken eggs are generally regarded as industrial, and brown or reddish ones are preferred. Small farms and smallholdings, particularly in economically advanced nations, may sell eggs of widely varying colors and sizes, with combinations of white, brown, speckled (red), green, and blue (as laid by certain breeds, including araucanas, heritage skyline, and cream leg bar) eggs in the same box or carton, while the supermarkets at the same time sell mostly eggs from the larger producers, of the color preferred in that nation or region.
These cultural trends have been observed for many years. ''The New York Times'' reported during the Second World War that housewives in Boston preferred brown eggs and those in New York preferred white eggs. In February 1976, the ''New Scientist
''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publish ...
'' magazine, in discussing issues of chicken egg color, stated "Housewives are particularly fussy about the colour of their eggs, preferring even to pay more for brown eggs although white eggs are just as good". As a result of these trends, brown eggs are usually more expensive to purchase in regions where white eggs are considered "normal", due to lower production. In France and the United Kingdom, it is very difficult to buy white eggs, with most supermarkets supplying only the more popular brown eggs. By direct contrast, in Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...
it is very hard to source brown eggs, as demand is almost entirely for white ones, with the country's largest supplier describing white eggs as "table eggs" and packaging brown eggs for export.
Research conducted by a French institute in the 1970s demonstrated blue chicken eggs from the Chilean araucana
The Araucana ( es, Gallina Mapuche, italic=no) is a breed of domestic chicken from Chile. Its name derives from the Araucanía region of Chile where it is believed to have originated. It lays blue-shelled eggs, one of very few breeds that do so. ...
fowl may be stronger and more resilient to breakage.[
Research at ]Nihon University
, abbreviated as , is a private university, private research university in Japan. Its predecessor, Nihon Law School (currently the Department of Law), was founded by Yamada Akiyoshi, the Minister of Justice (Japan), Minister of Justice, in 1889. ...
, Japan in 1990 revealed a number of different issues were important to Japanese housewives when deciding which eggs to buy and that color was a distinct factor, with most Japanese housewives preferring the white color.
Egg producers carefully consider cultural issues, as well as commercial ones, when selecting the breed or breeds of chickens used for production, as egg color varies between breeds. Among producers and breeders, brown eggs often are referred to as "tinted", while the speckled eggs preferred by some consumers often are referred to as being "red" in color.
Living conditions of birds
Commercial factory farming 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. Such restrictions may lead to pacing and escape behavior.
Many hens confined to battery cages, and some raised in cage-free conditions, are debeaked to prevent them from harming each other and engaging in cannibalism. According to critics of the practice, this can cause hens severe pain to the point where some may refuse to eat and starve to death. Some hens may be forced to molt to increase egg quality and production level after the molting
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
. Molting can be induced by extended food withdrawal, water withdrawal, or controlled lighting programs.
Laying hens often are slaughtered when reaching 100 to 130 weeks of age, when their egg productivity starts to decline. Due to modern selective breeding
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...
, laying hen strain
Strain may refer to:
Science and technology
* Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes
* Strain (chemistry), a chemical stress of a molecule
* Strain (injury), an injury to a mu ...
s differ from meat production strains. As male birds of the laying strain do not lay eggs and are not suitable for meat production, they generally are killed soon after they hatch.
Free-range eggs
Free-range eggs are eggs produced from birds that may be permitted outdoors. The term "free-range" may be used differently depending on the country and the relevant laws, and is not regulated in many areas.
Eggs from hens that are only indoors ...
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 regarding the living conditions of free-range hens have been raised in the United States of America, as there is no legal definition or regulations for eggs labeled as free-range in that country.
In the United States, increased public concern for animal welfare has pushed various egg producers to promote eggs under a variety of standards. The most widespread standard in use is determined by United Egg Producers United Egg Producers (UEP) is a Capper–Volstead agricultural cooperative in the United States which represents the interests of American egg producers.
History
Egg producer's concern over the volatility of prices due to overproduction during th ...
through their voluntary program of certification. The United Egg Producers program includes guidelines regarding housing, food, water, air, living space, beak trimming, molting, handling, and transportation, however, opponents such as The Humane Society have alleged UEP certification is misleading and allows a significant amount of unchecked animal cruelty. Other standards include "Cage Free", "Natural", "Certified Humane", and "Certified Organic
Organic certification is a certification process for producers of organic food and other organic agricultural products, in the European Union more commonly known as ecological or biological products.Labelling, article 30 o''Regulation (EU) 2018/ ...
". Of these standards, "Certified Humane", which carries requirements for stocking density and cage-free keeping and so on, and "Certified Organic", which requires hens to have outdoor access and to be fed only organic vegetarian feed and so on, are the most stringent.
Effective 1 January 2012, the European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...
banned conventional battery cages for egg-laying hens, as outlined in EU Directive 1999/74/EC. The EU permits the use of "enriched" furnished cages
A furnished cage, sometimes called enriched cage, colony cage or modified cage, is a type of cage used in poultry farming for egg laying hens. Furnished cages have been designed to overcome some of the welfare concerns of battery cages (also cal ...
that must meet certain space and amenity requirements. Egg producers in many member states have objected to the new quality standards while in some countries, even furnished cages and family cages are subject to be banned as well. The production standard of the eggs is visible on a mandatory egg marking categorization where the EU egg code begins with 3 for caged chicken to 1 for free-range eggs and 0 for organic egg production.
Killing of male chicks
In battery cage and free-range egg production, unwanted male chicks are killed at birth during the process of securing a further generation of egg-laying hens. In Germany in June 2019, a court decided that culling chicks "violates the country's laws against killing animals without a justifiable reason". However, the court permitted an exemption for hatcheries until a viable alternative is possible.
Cultural significance
A popular Easter
Easter,Traditional names for the feast in English are "Easter Day", as in the '' Book of Common Prayer''; "Easter Sunday", used by James Ussher''The Whole Works of the Most Rev. James Ussher, Volume 4'') and Samuel Pepys''The Diary of Samuel ...
tradition in some parts of the world is a decoration of hard-boiled eggs (usually by dyeing, but often by spray-painting). A similar tradition of egg painting exists in areas of the world influenced by the culture of Persia
Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
. Before the spring equinox
A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and se ...
in the Persian New Year tradition (called '' Norouz''), each family member decorates a hard-boiled egg and they set them together in a bowl.
In Northern Europe and North America, Easter eggs may be hidden by adults for children to find in an Easter egg hunt
An egg hunt is an Eastertide game during which decorated eggs or Easter eggs are hidden for children to find. Real hard-boiled eggs, which are typically dyed or painted, artificial eggs made of plastic filled with chocolate or candies, or foil- ...
. They may be rolled
Rolling is a Motion (physics)#Types of motion, type of motion that combines rotation (commonly, of an Axial symmetry, axially symmetric object) and Translation (geometry), translation of that object with respect to a surface (either one or the ot ...
in some traditions.
In Eastern and Central Europe, and parts of England, Easter eggs may be tapped against each other to see whose egg breaks first.
Since the sixteenth century, the tradition of a dancing egg
The dancing egg (''L'ou com balla'' in Catalan) is an old tradition that takes place in several towns in Catalonia, Spain, during the feast of Corpus Christi, when an egg is suspended in the vertical jet of a water fountain. The tradition proba ...
is held during the feast of Corpus Christi in Barcelona and other Catalan
Catalan may refer to:
Catalonia
From, or related to Catalonia:
* Catalan language, a Romance language
* Catalans, an ethnic group formed by the people from, or with origins in, Northern or southern Catalonia
Places
* 13178 Catalan, asteroid #1 ...
cities. It consists of a hollow eggshell, positioned over the water jet from a fountain, which causes the eggshell to revolve without falling.
See also
* Fish eggs
* Cock egg
A yolkless egg is a small egg with no yolk, sometimes produced by a pullet that has only just started laying. These eggs are common and usually pose no harm.
The eggs can also be called fart eggs, cock eggs, fairy eggs, dwarf eggs, and witch eggs. ...
* Ham and eggs
Ham and eggs is a dish combining various preparations of its main ingredients, ham and eggs. It has been described as a staple of "an old-fashioned American breakfast". It is also served as a lunch and dinner dish. Some notable people have prof ...
* List of foods
This is a categorically-organized list of foods. Food is any substance consumed to provide nutritional support for the body. It is produced either by Plants or Animals, and contains essential nutrients, such as carbohydrates, fats, proteins, vit ...
References
External links
British Egg Industry and the Lion Mark
* ttps://www.fda.gov/food/guidanceregulation/guidancedocumentsregulatoryinformation/eggs/default.htm Egg InformationU.S. Food and Drug Administration (2011)
Egg Basics for the Consumer: Packaging, Storage, and Nutritional Information
. (2007) University of California Agriculture and Natural Resources. Accessed 23 May 2014.
{{DEFAULTSORT:Egg (Food)
Egg (food)
Types of food
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