Chicken egg

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White chicken egg
An egg without an egg shell
Hortus sanitatis , Mainz 1491. Illustration to the chapter Ova - eggs

The egg is avian egg of Henne and serves the production of biologically their progeny. As an agricultural product, it is used as food by humans .


Chicken eggs at various stages of development found in a slaughtered hen

Laying hens usually only have one functioning ovary , the other is not fully developed. There are numerous egg cells in the ovary that are formed during the hen’s embryonic development . They are surrounded by auxiliary cells and together with them form so-called follicles or follicles. During sexual maturity , a small part of these (originally several million) follicles grow into so-called preovulatory follicles, from which eggs will later develop; the rest is receding.

It does this as follows. In sexually mature laying hens, individual follicles that are less than 0.5 mm in size are selected in order to transition into a growth phase during which they grow to a size of 6-8 mm. Most of these in turn die off (in a form of programmed cell death ); only a few grow into mature follicles. The young egg is formed in them, which initially consists of alternating layers of white and yellow yolk surrounded by a membrane. The surrounding wall of the largest follicle in the ovary, which is permeated by blood vessels, bursts at regular intervals in a designated area free of blood vessels, the so-called stigma (or crack scar), and the egg leaves the ovary and migrates into the fallopian tube . This process is known as ovulation or ovulation; the time from first selection of the follicle to ovulation takes about 2-3 weeks.

Fallopian tubes of a chicken
1. Infundibulum
2. Magnum
3. Isthmus
4. Uterus
5. Vagina with egg

By the time the egg passes from the ovary to the fallopian tube, it only has the yolk. The formation of the albumen, the eggshell membranes and the shell takes place in the fallopian tube over a period of approximately 24 hours. The fallopian tube can be divided into several sections: The first section, immediately adjacent to the ovary, is the infundibulum , in which the egg cell is fertilized if the hen has been mated beforehand . In addition, the chalaciferous egg white layer forms here around the yolk, from which the hailstones originate. The egg stays in the infundibulum for about half an hour. The second, longest section of the fallopian tube is the magnum, in which most of the albumen forms; the egg spends about 2–3 hours here. The next section is the isthmus , where the inner layer of egg white is formed and the calcification of the egg shell begins; this takes about 1–5 hours. In the subsequent section, the uterus, the shell formation is completed, pigments are stored in the shell and the outer shell skin (cuticula) is formed; here the egg spends most of the remaining time until it is laid; in the last section of the fallopian tube, the vagina, the egg stays only briefly.

The laying performance of hens is calculated as the number of eggs per day per chicken and expressed as a fraction of 1. In Germany it is 0.8 on average.

Whether hens hatch the eggs in a nest depends on the breed, length of daylight and ambient temperature. The breeding instinct (= increased level of the hormone prolactin ) is promoted by 12-hour days, as well as by the pressure of many eggs (up to 30) against the lower abdomen of the hen, it ends after 21 days or with the beeping of the first chicks.

Chicken eggs commercially available today are usually unfertilized.

Multiple yolks

A chicken egg can contain several yolks - up to four. Theoretically, a chick could develop from any yolk, but no such case is known due to the lack of space.


The shell of the chicken egg is usually less than 0.5  mm thick and consists of 90% calcium carbonate . If the eggshell thickness is less than 0.3 mm, the egg is at risk of breaking. The eggshell thickness is highest at the pointed end and lowest at the blunt end.


Different colored chicken eggs
Candle lamp for
candling eggs, as found in some grocery stores

The color of the lime shell of the chicken egg is genetic and depends solely on the breed of chicken from which the egg comes. Purebred chickens with white ear discs usually lay white eggs, whereas those with red ear flaps usually lay brown- skinned ones . A special feature Araucana are chickens, the ear lobes in different colors, but have always put greenish-bluish eggs. There is hardly any correlation between the color of the plumage and that of the eggs . In non-purebred chickens, the color of the ear flap and disc color does not allow any conclusions to be drawn about the color of the egg. All possible combinations occur.

In the acquisition of free-range white hens in are farmers less popular: The breeding direction are said to be less robust, a stronger disease pressure ( salmonella , Atypical avian = Newcastle disease suspended and will often prey of u a..) Raptors . With the increase in free-range farming since the 1980s, the market share of brown eggs has also risen to over 60%. One reason is the widespread association of the consumer of brown eggs with organic farming . In commercial breeding, the plumage color of the animals or the egg color play no role, but it is genetically more difficult to keep the white egg color if the main goals are egg number and feed conversion.

On the other hand, around 15% of brown eggs have clots, such as blood or meat stains, compared to less than 1% of white eggs. White eggs of this kind can easily be sorted out by fluoroscopy .

Egg weight

Most eggs of modern chicken breeds, and especially those of conventional laying hens, weigh 50–60 g. This is significantly higher than that of the great chicken (G. gallus bankiva), which is around 23 g. The heaviest known egg of a chicken was laid in 1956 and weighed 454 g.

industrial production

For the production of eggs in are factory farming egg layers used. These breeds are optimized for the laying of eggs through hybrid breeding (crossing of two inbred lines ) and have a laying capacity of more than 300 eggs per year. However, male chicks are also hatched - but their fattening is not economical (fattening hybrids are used for this). The day-old male chicks are therefore sorted out after hatching and gasified with CO 2 or shredded . Worldwide this happens to around 2.5 billion chicks (in Germany it is around 40 million) per year. In West Berlin , which was limited in area by the Berlin Wall and isolated from agriculture in the surrounding area , an attempt at industrial egg production in the chicken tower failed .

Economical meaning

The greatest producers

According to the Food and Agriculture Organization FAO, 76.7 million tons of chicken eggs (with shell) were produced worldwide in 2018 . This corresponded to about 1.378 trillion pieces. The following table gives an overview of the 20 largest producers of chicken eggs worldwide, which produced a total of 79.0% of the total. This table also contains the figures for Austria and Switzerland for comparison:

The largest chicken egg producers worldwide (2018)
rank country Quantity
(in t )
rank country Quantity
(in t)
1 China People's RepublicPeople's Republic of China People's Republic of China 26,590,000 13 PakistanPakistan Pakistan 847.739
2 United StatesUnited States United States 6,466,263 14th GermanyGermany Germany 846,000
3 IndiaIndia India 5,236,935 15th SpainSpain Spain 839,347
4th MexicoMexico Mexico 2,871,918 16 ArgentinaArgentina Argentina 829,000
5 BrazilBrazil Brazil 2,665,613 17th ColombiaColombia Colombia 780,000
6th JapanJapan Japan 2,627,764 18th United KingdomUnited Kingdom United Kingdom 777,000
7th RussiaRussia Russia 2,486,288 19th Korea SouthSouth Korea South Korea 772.898
8th IndonesiaIndonesia Indonesia 1,644,460 20th ItalyItaly Italy 736,400
9 TurkeyTurkey Turkey 962,542 ...
10 UkraineUkraine Ukraine 922,300 52 AustriaAustria Austria 127,585
11 MalaysiaMalaysia Malaysia 856.767 78 SwitzerlandSwitzerland Switzerland 60,648
12 FranceFrance France 847,868
world 76,700,529

In 2018, 11 million tons of chicken eggs were produced in Europe. The largest producers were Ukraine, France and Germany.


In 2016, the largest exporters worldwide (chicken eggs, with shell) were: the Netherlands (470,149 t), Turkey (281,370 t) and Poland (213,561 t).

In the same period, Germany was the world's largest importer of chicken eggs (440,776 t), followed by Iraq (263,878 t) and the Netherlands (190,319 t).

Switzerland's imports come mainly from the Netherlands, Germany and France.

Per capita consumption

For 2013 the FAO registered an average worldwide consumption of eggs of 9.19 kg per capita and year. The largest consumers were Japan with 19.15 kg, Paraguay with 18.83 kg and the People's Republic of China with 18.76 kg per capita per year. (The FAO does not provide more recent figures.) This year the Austrians consumed 14.68 kg, the Germans 12.20 kg and the Swiss 10.53 kg of eggs per capita per year.

In 2017, 239 eggs were consumed per capita in Austria, 230 in Germany and 179 in Switzerland. Since the eggs imported into processed foods have been included in Switzerland since 2018, the number of eggs consumed rose to 196 that year.

Use as a food

Egg production in Germany from 2008-2018 (in pieces)
The annual laying performance of a hen in Germany between 2000 and 2011 was around 290 to 300 pieces.

In 1950, a chicken in Germany laid an average of 120 eggs per year; in 2015 it was around 300.
In Germany, an average of 11.9 billion eggs were produced every year between 2008 and 2018 and around 2.8 billion eggs were exported. The import of eggs is increasing rapidly and is around 8 billion eggs per year. The per capita consumption has increased slightly since 2005 to 211 so-called shell eggs per year. Around 50% of this is consumed by private households, 30% in the food processing industry and 20% in local canteen kitchens and bakeries.

Chicken eggs may be stored unrefrigerated for the first 18 days from the laying date, as the egg has its own immune protection on the shell and inside in the form of enzymes . For this reason, the eggs must not be washed, but only mechanically cleaned before they are sold, because otherwise the cuticle would be destroyed. However, after strong temperature fluctuations or cooling, this immune protection can be impaired in its function due to condensation. Therefore, all eggs that have been refrigerated must continue to be refrigerated continuously. From the 18th day, all eggs must be chilled continuously. Eggs that have been subject to refrigeration for more than three days - i.e. after 21 days at the latest - may no longer be sold commercially to end consumers. The 28th day from the laying day is defined as the maximum best before date. However, the producer or trader is free to specify earlier times for the best before date and compulsory refrigeration, which has to be done if, in particular in the case of floor or free-range eggs, the bacterial load in the freshly laid egg is already increased due to pecking of feces .

The so-called Tier-LMHV (Tierische-Lebensmittel-Hygieneverordnung) regulates the food law regulations for the food egg. The regulation writes u. a. suggest that chicken eggs must be given to the consumer within 21 days of being laid. This ordinance serves consumer protection, as raw hen's eggs are one of the most productive breeding grounds for bacteria and therefore a very sensitive food. In particular, there is a high risk of salmonella transmission .

When making products from raw eggs ( e.g. egg whites , mayonnaise , ice cream or desserts ), there is a risk that bacteria from the shell surface will get into the egg mixture when the eggs are opened. In addition, bacteria from the hands of the person preparing the meal can be introduced into the egg mass. When stored, these bacteria can multiply quickly in the ice cream and cause food poisoning . By briefly immersing in boiling water for a few seconds, the bacteria on or directly under the bowl can be killed. Without special conservation measures, uncooked dishes with fresh eggs should best be consumed on the day of production. Particularly strict requirements apply to commercial processing.

When heating the eggs increased egg white from a temperature of about 62 ° C and from about 68 ° C, the yolk . Therefore, when preparing freshly whipped ice creams such as hollandaise sauce or zabaglione, the egg yolk is slowly heated to just below this temperature with the help of a metal bowl in a water bath .

It is seldom eaten raw by humans; the egg is usually boiled or added to a dough. When cooking, a further distinction is made between cooking as a whole in the bowl and cooking in an open form without a bowl. It is usually cooked in a pot with normal tap water, often with a little salt or vinegar added. The salt or vinegar does not prevent the egg from breaking, but it accelerates the denaturation of the albumen if the egg breaks. The vinegar also dissolves lime from the skin. Whole eggs are punctured at their blunt end, where there is usually an air bubble; this can usually prevent overpressure and the bursting of the eggshell. A general warning should be given before heating in a microwave , as this leads to hardening from the outside to the inside with very strong gas formation from water vapor, which usually leads to the ice bursting explosively. Whipped eggs are fried in the pan as fried or scrambled eggs . There are no particular restrictions on the preparation of pasta if it contains egg. Individual special forms of pasta, mostly Easter biscuits , but also meat dough, make it possible to integrate boiled eggs as a whole and thus combine them into a food design . Whipped eggs with a few added items can also be whisked cold ( e.g. egg whites ), whereby the egg white and yolk must be separated when the eggs are opened. It is possible to bake the mass (for example meringue ).

Eggshells, on the other hand, are usually thrown away, but can also serve as fertilizer for ornamental and useful plants by placing them in a water bath. A certain disruptive gas formation is to be expected from the fermentation process. When feeding turtles (e.g. Greek tortoises ) in pet ownership , (boiled) crushed eggshells can represent an additional source of calcium.

When cooking with the shell on, the cooking time and the temperature determine how much the substances in the egg change from their initially rather liquid form to a viscous to sliceable or crumbly state. The transparency of the liquid is also lost. The egg white hardens faster than the egg yolk. An irreversible chemical change takes place ( denaturation of proteins ). If the egg is cooked too long, the sulfur-containing amino acids in the proteins will produce hydrogen sulfide , which is responsible for the typical rotten egg smell. In addition, the bound iron contained in the egg reacts with the hydrogen sulfide and iron sulfide is formed , which gives the "boiled over" egg yolk its green-blue color. The eggshell is removed after cooking, for example at the table when serving the egg in an egg cup . However, the breakfast egg should not be eaten with a silver spoon, as the sulfur contained in the egg reacts with the silver to form silver sulfide and the spoon turns black. When cooking without a shell, the same thing takes place, whereby a distinction must be made between the preparation forms with whole yolk ( fried egg , bouillon ) and those in which the egg is whisked ( pasta , scrambled eggs , enema soup ). When used in pasta, the slightly sticky characteristics of the substances in the egg also have a helping effect.

Transport and Storage

Eggs used to be stored in racks (here a model from a doll's kitchen)

Eggs are a fragile and perishable food. In the case of hard eggs, the thickness of the chalky eggshell is usually less than half a millimeter and also slightly brittle, so that even a fall over a few centimeters or the application of pressure with a hard edge can damage or destroy the egg. Damaged or broken eggs, however, spoil quickly because bacteria and molds spread quickly through them, and these are usually also harmful to health. A small crack in the shell may be enough for such spoilage.

In the past, eggs were stored in racks or shelf-like egg boxes. Egg cartons have been in use for transport and storage since around 1960 ; they contain and buffer the eggs individually in hollows. Egg cartons protect eggs from rolling away, point pressure and are stackable. Packs of 6 and 10 that can be folded up can also be made of hard plastic film or plastic foam, but single-shell packs for 10 × 10 pieces consist entirely of wood pulp , can be stacked in an offset manner and also serve as simple sound absorbers.

Intact eggs can be stored at room temperature for several weeks, although a cool storage can be useful. In Europe, eggs are labeled with production codes to identify their origin and age. For this purpose, gentle, contactless processes such as inkjet technology are usually used.

To eggs for times higher demand (Christmas, Easter) and offer eggs to make durable , they were until the advent of refrigerators to 1955/1960 sometimes in wide-mouthed glass bottles of typically 3 to 6 liters into dilute sodium silicate (solution closure with cellophane + String) cold, individually inserted with a spoon and thus made more durable at cellar temperature. The process closes the pores in the lime shell, which prevents putrefactive bacteria from entering, prevents them from drying out and reduces the supply of oxygen. In Ireland, freshly laid eggs are rubbed with butter in a similar process . Sealed in this way, buttered eggs can be kept for up to six months.

Egg products

Chicken eggs are used for the production of countless foods (for example for cakes and pastries , pasta, mousse au chocolat , ...). However, the natural egg, which is also called fresh egg in the food industry, is not always processed, but often so-called egg products:

“Products made from eggs, their various components or mixtures thereof; the products can be liquid , concentrated, dried , crystallized , frozen, deep-frozen or fermented . They may only have been made from eggs from chickens. Other foods or additives can be added to these products. In deviation from the EU standard, the egg products are always documented within the KAT system, as long as they also have to be mentioned in the declaration of the respective mixture of the respective food. "

- KAT - Association for controlled alternative forms of animal husbandry : Guidelines for egg products from the KAT system (Version 3.0, January 2014)

Average composition

Total content

Chicken eggs contain almost all vitamins except vitamin C . An average-sized chicken egg covers up to 38% of the daily requirement of vitamin B 12 . The missing vitamin C is only formed during the brood, mainly by the membrane of the yolk sac. All of the nutrients are in egg yolks and white whites, but a greater proportion of them are in the yolk. In general, in terms of nutrients, it doesn't matter whether the egg is eaten raw or cooked. The exception is biotin , which is only available from cooked hen's eggs, and whose reserves can even be flushed out of the body by eating raw hen's eggs.

It should be noted that the diet of the laying chicken drastically affects the nutritional value of the egg. Eggs from chickens, which eat fresh plants, insects, worms and snails in addition to seeds and grains, have a much higher nutritional value. Studies have shown that compared to eggs from hens that were fed only grains, such eggs ⅔ more vitamin A, 2 × more omega-3 fatty acids, 3 × more vitamin E, 4 to 6 × more vitamin D, 7 × have more beta-carotene, ⅓ less cholesterol and ¼ less saturated fat.

The physiological calorific value is 648  kJ (156 kcal) per 100  g of edible portion.

Information per 100 g of 1 edible portion:

Components proportion of
water 74.4 g
protein 12.8 g
fat 11.3 g
carbohydrates 0.7 g
Minerals 1.0 g
Minerals proportion of
sodium 145 mg 2
potassium 145 mg
magnesium 12 mg
Calcium 55 mg
manganese 70 µg 3
iron 2000 µg
copper 65 µg
zinc 1300 µg
phosphorus 215 mg
selenium 10 µg
sulfur 180 mg
iodine 10 µg
Vitamins proportion of
Vitamin A 270 µg
Vitamin D 3 µg
Vitamin E. 2000 µg
Vitamin K 9 µg
Vitamin B2 410 µg
Nicotinamide 85 µg
Pantothenic acid 1600 µg
Vitamin B6 75 µg
Biotin 25 µg
Folic acid 65 µg
Vitamin B12 2 µg
vitamin C 0 µg
amino acids proportion of
Arginine 4 890 mg
Histidine 4 330 mg
Isoleucine 930 mg
Leucine 1260 mg
Lysine 890 mg
Methionine 450 mg
Phenylalanine 800 mg
Threonine 710 mg
Tryptophan 230 mg
Tyrosine 590 mg
Valine 1120 mg
Lipids proportion of
saturated fat 3.1 g
Linoleic acid 1148 mg
α-linolenic acid 33 mg
EPA 4 mg
DHA 37 mg
Arachidonic acid 142 mg
cholesterol 425 mg
1 corresponds to about 2 medium-sized fresh eggs
21 g = 1000 mg
3 1 mg = 1000 µg

egg yolk

The physiological calorific value of egg yolk is 1459 kJ (353 kcal) per 100 g of edible portion.

Details per 100 g of edible portion:

Components proportion of
water 50.0 g
protein 16.1 g
fat 31.9 g
carbohydrates 0.3 g
Minerals 1.7 g

Egg white

The physiological calorific value of egg white is 202 kJ (47 kcal) per 100 g of edible portion.

Details per 100 g of edible portion:

Components proportion of
water 87.3 g
protein 11.1 g
fat 0.03 g
carbohydrates 0.7 g
Minerals 0.7 g

Color of the yolk

The color of the yolk is largely determined by the food. Corn and green fodder result in a darker yolk due to the carotenoids they contain . The color of the yolk is kept stable in commercial chicken farming by adding feed additives . For this purpose, paprika powder or natural carotenoids obtained by extraction , such as lutein , or, where permitted, predominantly synthesized carotenoids such as canthaxanthin , are added to the chicken feed . The yolk color preferred by consumers varies from region to region and has a north-south gradient in Europe. In northern states, eggs with yellow colored yolks are more popular, while in southern states gold-orange colored yolks are preferred. In Germany, too, there is this gap in the average consumer demand from yellow yolks in the north to gold-orange yolks in the south. The yolk color of organic eggs is lighter than that of conventionally produced eggs, as the addition of coloring agents to laying hen feed is generally prohibited in organic farming .

Fishy smell

The odor of fish that about 5% of chicken eggs give off is genetic. The cause is a genetic defect that leads to trimethylamine (TMA) being deposited in the yolk of eggs with predominantly brown shells. Due to the genetic defect in the feed such as is rapeseed given TMA precursor choline not through the liver - enzyme oxygenase to odorless trimethylamine oxide converted (TMAO) and excreted.

Identification of eggs

Egg labeling in Germany
Egg labeling in Austria

In the countries of the European Union , the labeling of eggs is subject to the regulations of the European marketing standards according to Regulation (EC) No. 589/2008.

Housing form and origin

From the producer code printed on each egg, the type of husbandry can be determined in the EU using the leading number:

The following letters designate the EU member state. The other numbers provide information about the exact origin (see egg labeling rules ). The allocation of the digits in Germany is organized by the responsible state authorities on the basis of the Laying Hen Farms Register Act.

The cages of laying hens is banned in Switzerland since 1992 and since January 2009 in Germany and Austria, in the EU since 2012. It has since been mainly through deep litter, replaced in Germany in exceptional cases by the so-called. Small group housing. There are no longer just four to five chickens in one cage, but up to 60 animals in a larger compartment, which allows a little more movement.

According to the official statistics, since 2009 more eggs in Germany have come from free-range than from cage.

In 2017 there were around 2.8 million laying hens in Switzerland. Around 1.7 million (60.4%) of them were kept free-range, around 610,000 in free-range farming (21.7%) and around 500,000 in organic farming (17.9%).

Eggs that are processed into products such as egg pasta or into dishes in gastronomy do not have to be labeled in Austria as of March 2016. The cage ban does not apply to them either. In 2014, 13,000 tons of eggs were imported from third countries, in 2015 already 18,000 tons and thus 1/6 of the consumption. The eggs come mainly from China, Singapore, Mexico and also from Ukraine, Argentina and India. The Chamber of Agriculture, Agrarmarkt Austria (AMA) and the Central Association of the Poultry Industry (ZAG) advocate a declaration obligation for these eggs in order to promote animal welfare and the competitiveness of domestic producers. At a press conference on March 9, 2016, reference was made to the information that had already been provided in Switzerland.

Quality characteristics of eggs

According to European food law, eggs are assigned to quality class A or B. The criteria for the highest quality class, A, are precisely defined in the European marketing standards for eggs (Regulation (EC) No. 589/2008, Article 2). Accordingly, this only includes eggs whose shell and cuticle are clean, undamaged and normal in shape, whose air chamber is no more than 6 mm high and immobile, whose yolk is only visible in the form of a shadow and without a clear outline and does not move significantly away from its central position. whose albumen is clear and transparent, and which have no foreign deposits or deposits and no foreign smell. Grade A eggs may not be washed either, in order to protect the cuticle; However, this does not apply in all states of the European Union, but only in those where washing eggs was already forbidden before June 1, 2003. Eggs cannot be washed in Germany and eggs washed abroad cannot be marketed. Only grade A eggs may be marketed to end consumers as table eggs.

Quality class B includes all eggs that do not meet the requirements of quality class A, but are still generally suitable as food. They are used in the food industry or in other branches of industry (such as for the manufacture of cosmetics ). The definitions of the EU marketing standards (Article 1, letters k, l, m) expressly exclude incubated and battered eggs from this, whereby eggs are considered to be incubated as soon as they have been placed in the incubator and as battered if the shell is damaged and membranes release the inside of the egg. In principle, eggs with the following quality defects are suitable for consumption and therefore belong to quality class B:

  • Dirt and moisture
  • Blood stains
  • Damaged but complete calcareous shell with intact shell skin (so-called cracked eggs)
  • Fine cracks in the lime shell, which expand under pressure, with intact shell skin (light cracks)
  • Enlarged air chamber over 6 mm high
  • Air chamber that can move freely between the egg white and the shell membrane (so-called runners or swimmers)
  • Yolk that does not hold steadily in the middle
  • Thin egg white
  • Deformations
  • Lime deposits on the shell

Grade B also includes washed eggs in those countries in which washing for Grade A is not permitted. If grade A eggs change in such a way that they no longer meet the requirements, they are downgraded to grade B.

However, the following are not marketable:

  • Eggs with no or inadequately formed lime shells (so-called flowing eggs)
  • Beaten eggs (broken eggs)
  • Eggs with discoloration of yolk or albumen
  • Blood eggs
  • Incubated eggs, whether fertilized or not
  • Eggs that are rotten or infected with fungi
  • Eggs with distinct smell or taste deviations

Sorting Class A eggs by weight

Depending on their weight, chicken eggs are divided into four (previously eight) weight classes:

Weight class description Weight
XL Very large 73 g and more
L. Large 63 to less than 73 g
M. medium 53 to under 63 g
S. Small under 53 g

quality control

Rejected, partially damaged eggs

The quality of chicken eggs is influenced by the health, keeping and feeding of the hens and by the house climate , transport and storage of the eggs. Quality deficiencies arise in particular due to incorrect feeding, poor hygiene , improper handling and long storage of the eggs. Depending on their condition, which is determined using various chemical and physical examination methods, the eggs are divided into quality classes or, in the worst case, they are excluded from marketing entirely.

Quality defects

Signs of aging

Properly stored chicken eggs remain in good condition for 3–4 weeks, but then signs of age become clearly noticeable. The following processes can be observed.

  • The egg loses water through the shell, the air chamber enlarges.
  • The thick part of the egg white becomes thinner due to the activity of its own enzymes .
  • The hailstones come off and partly also dissolve.
  • The yolk ball loses its stable position in the middle of the egg and moves to the sides.
  • The yolk ball loses its internal pressure - if you open the egg, it appears flat instead of arched.
  • The yolk membrane tears more easily.
  • The egg develops a typical bad smell and taste.

Microbial contamination

Freshly laid eggs are almost always germ-free inside. Infection in the hen's laying apparatus before the shell has formed (a so-called primary contamination ) occurs only very rarely , with the transmission of salmonella from clinically healthy animals to their eggs in particular . In contrast, the outside of an egg that has been laid is generally not aseptic. Also, for a secondary contamination of the Eiinneren undamaged chicken eggs are not very vulnerable; a high proportion can withstand long storage without being attacked by microorganisms . This is due to the fact that the two leaves of the shell skin, which lie immediately below the calcareous shell, form an extremely effective barrier against the penetration of microorganisms. The cuticle lying on the outside of the calcareous shell also closes the pores of the shell at least for a certain time after it has been laid, which is why it also prevents microbial spoilage by treating eggs gently and not washing them.

Nonetheless, contamination occurs especially after long periods of storage. The consequences are color changes, cloudiness, rot and mold spots .

Morphological defects and damage

Immediately after laying, some eggs do not meet the quality standards because, for example, the lime shell has not formed or has formed incompletely, or because the hens have been fed incorrectly because they have deviations in color, smell or taste. Eggs can be soiled and damaged after laying, which can be a sign of poor hygiene in the laying farm or improper handling of the eggs.

Common investigations

Chemical and physical examinations are customary to determine the possible quality defects of chicken eggs. By checking for typical signs of aging, an assessment of the egg age can also be made.

The x-ray ( sheer ) previously common in grocery stores gives indications of hatched or otherwise inhomogeneous inside of the eggs.

The swim test gives an indication of how fresh an egg is. This test is based on the fact that water inside evaporates through the bowl and the air bubble gradually gets larger. You put the egg in water and

  • When the egg is fresh, it will go under completely and lie flat on the bottom.
  • If it is a few days old, it lies on the floor and the blunt end is slightly upwards.
  • If the egg is vertical or almost vertical, it is less than two weeks old.
  • If it floats on the surface and the blunt end with the air bubble protrudes from the water, it is more than 3 weeks old.

An indication of the freshness of an already cooked egg is that the shell can be removed. If this can be easily removed, the egg is at least about four days old. In the case of very fresh eggs, the shell and the underlying skin adhere strongly to the egg, so that it can often only be peeled with damage.

Fresh eggs can be shaken more silently, while older eggs have formed a larger air bubble when they dry and can therefore slag.

To find out whether an egg is already cooked or still raw, you can place it on a flat surface and set it in rotation like a top. A boiled egg spins easily, a raw egg is more difficult to rotate and tends to lurch. Another possibility: If the egg is stopped abruptly and then released again immediately, you can tell the difference between fresh (it keeps turning) and boiled (it stops) egg.

Hairline cracks in the shell and structures inside the egg are assessed using fluoroscopy during sorting. This is to be distinguished from so-called shearing , where the development progress of incubated eggs is to be followed. With UV irradiation, roll marks that occur on metal cage bars can be detected using fluorescence .

Important chemically detectable indicator substances are succinic acid and 3-hydroxybutanoic acid . An increased content of succinic acid is characteristic of microbial spoilage, an increased content of 3-hydroxybutanoic acid, on the other hand, indicates fertilized and hatched eggs.


Mythology and Customs

Easter eggs with traditional Sorbian motifs
Hard-boiled chicken eggs colored into marbled Easter eggs
Blown eggs before and after painting for Easter

The egg appears in numerous myths and customs, which instead of a hen's egg can be the egg of another bird or animal and often does not come from any animal but was created by a first god. In many creation myths, the egg embodies the origin of life, often as a cosmic egg from which the world emerged in the form of an all-god. According to Finnish mythology, the Kalevala , the universe was created from seven eggs, six gold and one made of iron . Accordingly, the shell halves became heaven and earth, the egg yolk became the sun , the egg white became the moon, and the remaining shell pieces formed stars and clouds . The black yolk of the iron egg turned into a thundercloud. The egg also plays a role in Christianity. The Christian custom of giving Easter eggs takes place in belief in the resurrection of Christ . The Syrian doctor of the church Ephraem the Syrians wrote in the 4th century: "The grave jumps open like an egg." In Germany, the old custom of decorating eggs at Easter is particularly cultivated by the Sorbs . In the area around Bautzen , Easter eggs are artistically designed in the Sorbian tradition . Eggs that were laid on Maundy Thursday or Good Friday were thought to have special powers in the Middle Ages. They were first consecrated and then these Good Friday eggs were deposited in the house to protect it from flooding or fire.

Malformed chicken eggs were also known as witch eggs or cock eggs in the 19th century .

The egg oracle has been a method of divination since ancient times that has been handed down in European superstition and still plays a role in some traditional Asian cultures today.

Passover seder evening

The Seder plate starting clockwise at the top: Maror, Seroa, Charosset, Chaseret, Karpas, Beitzah (egg)

On the Seder evening of the Jewish Passover festival, the family (or the community) celebrate. Many egg dishes are eaten on the days of Passover.

Jewish dietary laws

Award of Jewish neutral food in the USA with "U Pareve"

Chicken eggs are neither fleshy nor milky , but parve . A hen's egg is kosher when it has been proven (when raw) to contain no trace of blood.


Some popular idioms are related to the chicken egg:

  • An amazingly simple solution is "the egg of Columbus "
  • Things that are difficult to distinguish resemble each other “like peas in two peas”.
  • Someone in financial trouble has to "sell the egg under the hen"
  • You can get something very cheap “for an apple and an egg”. These two things are commonly available in abundance on farms and can be given away without any problems.
  • Proverbial riddle: "Who came first, the chicken or the egg?" (See chicken and egg problem )
  • To be “the yellow of the egg”, something special; often used in negation
  • To “look like an egg” means to be properly dressed
  • "Treating something or someone like a raw egg" means handling the thing or person with extra care or caution
  • Eggs = turn out of round; fooling around in a figurative sense: arguing unevenly, not making a decision

See also



Web links

Commons : Chicken Egg  - Collection of images, videos and audio files
Wiktionary: Chicken egg  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Wilfried Brade: egg formation, egg quality, marketing standards for eggs . In: Wilfried Brade, Gerhard Flachowski, Lars Schrader (eds.): Laying chicken breeding and egg production (=  agricultural research . Special issue 322). vTI , Braunschweig 2008, ISBN 978-3-86576-047-0 (online: whole issue (PDF; 6.8 MB) or only the cited chapter (PDF; 1.2 MB) [accessed October 27, 2018]) .
  2. Why does an egg have two yolks?
  3. Seilnacht's Periodic Table of the Elements - Calcium , Physiology section, accessed 2014
  4. ^ CJ Sun et al: Global variation and uniformity of eggshell thickness for chicken eggs . In: Poultry Science , Part 91, Issue 10, October 1, 2012, pp. 2718-2721
  5. Dieter E. Zimmer : Chickens - Animals or Protein Machines? Rowohlt, Reinbek 1983, ISBN 978-3-499-17748-4 , chapter "Chicken and Egg - 42 Questions and Answers"
  6. KN Monira et al .: Effect of Breed and Holding Period on Egg Quality Characteristics of Chicken, Journal of Poultry science, 2003, pp. 261-263
  7. CES Lindqvist et al .: Red Jungle Fowl Have More Contrafreeloading than White Leghorn Layers: Effect of Food Deprivation and Consequences for Information Gain, Behavior . Part 139, No. 9, September 2002, pp. 1195-1209
  8. Report on the heaviest hen's egg.; accessed on March 19, 2019
  9. The dark side of egg production . Deutsche Welle ; Retrieved November 25, 2013
  10. ↑ Factory farming chicks, shredded in the garbage . Süddeutsche Zeitung ; Retrieved November 25, 2013
  11. a b c FAO production statistics 2018 (Livestock Primary> Eggs, hen, in shell or Eggs, hen, in shell (number )) FAO , Faostat; accessed on February 10, 2020.
  12. a b Crops and livestock products> Eggs, hen, in shell. In: Data> Trade., accessed on February 22, 2019 .
  13. ↑ Agricultural Report 2018
  14. ^ Food Supply - Livestock and Fish Primary Equivalent> Eggs. In: Data> Food Balance> Food supply quantity (kg / capita / yr)., accessed on February 22, 2019 .
  15. Simone Luchetta: Why Swiss eggs are more popular than they have been for a long time. In: . April 19, 2019. Retrieved April 19, 2019 .
  16. Imported eggs in processed foods are now also included. In: July 30, 2019, accessed July 30, 2019 .
  17. Fachserie 3 series 4.2.3 poultry ( Memento of 16 November 2016 Internet Archive )
  18. New ways for more animal welfare , A magazine of the Federal Ministry of Food and Agriculture, 1st edition, January 2016, p. 7
  19. ^ Livestock Primary> Eggs, hen, in shell (number). In: FAO production statistics for 2017., accessed on November 13, 2019 .
  20. Topagrar-Online from May 16, 2008
  21. Current information about Easter eggs . ( Memento from May 29, 2013 in the Internet Archive ) BMEL press release, April 2, 2012
  22. ^ Alan Eaton Davidson : The Oxford Companion to Food . Ed .: Tom Jaine. 3. Edition. Oxford University Press , New York 2014, ISBN 978-0-19-104072-6 , keyword “buttered eggs” .
  24. S. Englard, p Seifter: The Biochemical Functions of Ascorbic Acid. In: Annual Review of Nutrition. 6, 1986, pp. 365-406, doi: 10.1146 / .
  25. ^ Association for controlled alternative forms of animal husbandry e. V. (KAT) ( Memento from January 22, 2011 in the Internet Archive )
  26. K. Pietrzik, I. Golly, D. Loew: Handbuch Vitamins. Urban & Fischer Verlag, Elsevier, Munich 2008; Pp. 147-154, 416; ISBN 978-3-437-55361-5
  27. Mother Earth News, English-language version .
  28. ^ A b c German Research Institute for Food Chemistry [DFA], Garching (Hrsg.): Food table for practice . The little souci specialist - cabbage. 4th edition. Wissenschaftliche Verlagsgesellschaft, Stuttgart 2009, ISBN 978-3-8047-2541-6 , p. 88 ff .
  29. BASF Group: Animal Nutrition. Retrieved March 8, 2019 .
  30. Citranaxanthin> to intensify the red pigmentation of egg yolks for the feed industry | BTC Europe specialty chemicals. Retrieved March 7, 2019 .
  31. Laying Chicken Breeding and Egg Production - Recommendations for Practice. (PDF; 6.8 MB) Johann Heinrich von Thünen Institute , 2008, p. 23 f. , accessed March 7, 2019 ( ISBN 978-3-86576-047-0 ).
  32. Waldemar Ternes, Ludwig Acker, Siegfried Scholtyssek (ed.): Egg and egg products (=  basics and advances in food analysis and food technology . Volume 22 ). Parey, Berlin / Hamburg 1994, ISBN 3-489-63114-5 , pp. 175 ff .
  33. Katja Kretzschmar: Effect of flavin containing monooxygenase (FMO3) genotype on trimethylamine (TMA) content in the chicken egg yolk . In: Stuttgart: Eugen Ulmer, 1927- (Ed.): Archive for poultry science . 71, No. 5, 2007, ISSN  0003-9098 , pp. 200-206.
  34. a b c d e Regulation (EC) No. 589/2008 with implementing provisions for Regulation (EC) No. 1234/2007 of the Council with regard to the marketing standards for eggs
  35. Law on the registration of farms for keeping laying hens (Laying Hens Register Act - LegRegG) (PDF)
  36. Despite EU ban: 12 countries torture chickens., December 28, 2011
  37. Hen-keeping places and keeping of laying hens by type of housing ( Memento of November 17, 2010 in the Internet Archive ) Federal Statistical Office, Wiesbaden 2010
  38. Federal Office for Agriculture : Special evaluation 2018. Bern - the Swiss egg canton (PDF, 608 kB, 12.12.2018). (PDF) In: blw. . Retrieved December 14, 2018 .
  39. Economy: Labeling of processed eggs required ., March 9, 2016; accessed March 9, 2016.
  40. a b c d e f Karsten Fehlhaber, Josef Kleer, Fritz Kley (eds.): Handbook of food hygiene. Practical guide with scientific principles . Behr, Hamburg 2005, ISBN 978-3-89947-194-6 .
  41. a b c d Wolfgang Frede (Ed.): Handbook for food chemists. Food - consumer goods - cosmetics - animal feed . 3rd, completely revised edition. Springer, Berlin 2010, ISBN 978-3-642-01684-4 , pp. 551 ff .
  42. a b Waldemar Ternes , Alfred Täufel, Lieselotte Tunger, Martin Zobel (eds.): Food lexicon . 4th, comprehensively revised edition. Behr, Hamburg 2005, ISBN 3-89947-165-2 , pp. 283 .
  43. Interesting facts about the egg, best before date, time of egg use, storage. In: Retrieved March 7, 2019 .
  44. Exhibition shows one of the oldest chicken eggs in the world , Augsburger Allgemeine, April 15, 2014
  45. ^ Arnold Adolf Berthold: Contributions to anatomy, zootomy and physiology, Dieterich, 1831, p. 29 (Google Books)
  46. ^ Heinrich Rudolf Schinz: Description and illustration of the artificial nests and eggs of the birds which breed in Switzerland, Germany and the neighboring countries, Orell, 1819, p. 57 (Google Books)
  47. a b Brigitte Alsleben: Duden, speeches: dictionary of German idioms. Dudenverlag, Mannheim / Leipzig / Vienna / Zurich 2002, ISBN 3-411-04112-9 , p. 182
  48. Brigitte Alsleben: Duden, speeches: dictionary of German idioms. Dudenverlag, Mannheim / Leipzig / Vienna / Zurich 2002, ISBN 3-411-04112-9 , p. 285
  49. Brigitte Alsleben: Duden, speeches: dictionary of German idioms. Dudenverlag, Mannheim / Leipzig / Vienna / Zurich 2002, ISBN 3-411-04112-9 , p. 55.