home Audience 6 Ingredients: 1 egg. The structure and composition of a chicken egg. Quail eggs: nutritional value

Ingredients: 1 egg. The structure and composition of a chicken egg. Quail eggs: nutritional value

Shell and membranes of the egg. The shell of eggs consists mainly of minerals, which account for 94-97%. Organic substances in the shell contain 3-6%.
The main mineral substance of the shell is calcium carbonate, which makes up on average 93% of the weight of the shell; a small part is magnesium carbonate (1.6%) and alkaline earth phosphates (0.45-1.37%). Due to the high content of calcium carbonate, which is easily absorbed by the body, the shell is a good mineral food for birds.
The organic substances that make up egg shells are poorly understood. It is indicated that shell proteins are close to collagens and keratins.
The pigmentation of the shell depends on the presence of ovoporphyrin, which in its chemical structure resembles hematoporphyrin, a substance that is closely related to the pigments of blood and bile.
The shell has an outer porous shell containing from 9,000 to 12,000 thin tubules (pores) through which air enters. Underneath it is an internal double shell membrane.
In a fresh state, the shell film allows air to pass freely. As the egg dries, gas permeability decreases significantly and sometimes stops. This is of great importance during incubation, since due to a decrease in gas exchange, the embryo dies from lack of oxygen. Puga air usually contains 18-20% oxygen.
Protein. The protein is a colloidal jelly-like substance, slightly colored; its reaction is alkaline (pH on average 8.4-8.6); has a specific gravity of 1.0459-1.0516; coagulates at 61°.
The chemical composition of chicken egg protein before the development of the embryo is as follows (in%):

The following proteins were found in chicken protein (in%):

The bulk of the protein is represented by egg albumin.
Very few proteins have been studied in as much detail as egg albumin from chicken eggs. It was first obtained in crystalline form by Hoffmeister (1890) by precipitation with ammonium sulfate.
Despite the fact that egg albumin forms crystals, it is not a homogeneous substance and is divided into two fractions by electrophoresis. The coagulation temperature of egg albumin is 64-67°; the isoelectric point is at pH 4.6.
After the ovalbumin crystals precipitate, a non-crystallizable protein called conalbumin remains in the filtrate.
Conalbumin is a flavoprotein, i.e. a complex protein with a prosthetic group consisting of natural flavin pigments.
The isoelectric point of conalbumin is at pH 6.1; its coagulation temperature is 55-60°.
Egg globulin makes up about 7% of all egg proteins. It is a typical globulin, is salted out with ammonium sulfate at half saturation, and when the protein is diluted with water, it precipitates in the form of flakes.
Immunochemical and electrophoretic studies revealed two antigenic globulin fractions in egg whites that differ from other proteins.
Good foaming ability when churning proteins is due to the presence of globulin.
Ovomucoid is a glucoprotein, the carbohydrate part of which makes up a fifth of the entire compound and consists of mannose, galactose and acetylglucosamine:

The carbohydrate part is connected to the proteins, apparently by an ester bond formed between the hydroxyl group of acetylglucosamine and the carboxyl groups of the protein. The carbohydrate component is easily separated by hydrolysis with barium hydroxide in a nitrogen atmosphere.
During thermal coagulation of egg white, ovomucoid does not coagulate. It is precipitated with ethyl alcohol.
Ovomucin is found in protein in small amounts and is usually found with ovomucoid. Ovomucin stabilizes the foam formed when beating egg whites.
Egg whites also contain the protein avidin. It is a basic glucoprotein, the isoelectric point of which is around pH 10. Avidin is obtained in crystalline form. Disorders in humans and animals observed when consuming large amounts of raw egg whites are due to the presence of avidin. Avidin binds to biotin (vitamin H), forming a biologically inactive biotin-avidin complex. The formation of such a complex in humans and animals leads to vitamin deficiency associated with a lack of biotin. In this case, a specific dermatitis disease is observed, accompanied by redness and peeling of the body.
In addition, egg white contains 3% lyeozyme, which has antibiotic properties. It makes it easier for the developing chicken to fight harmful microbes. The avidin-biotin complex is very similar to lysozyme; it is possible that both of these compounds are identical.
The following enzymes were found in egg white: tryptase, peptidase, amylase, lipase, oxidase, etc.
Protein liquefaction during long-term storage is associated with the breakdown of ovomucin by tryptase.
The amino acid composition of some chicken egg proteins is presented in Table. 39.

The mineral composition of the protein is as follows: 0.16% potassium; 0.16% sodium; 0.01% magnesium; 0.014% calcium; 0.001% iron; 0.21% sulfur; 0.017% phosphorus; 0.17% chlorine; 0. 0001% copper.
Of the functions that the protein shell has, the first one to mention is protective. Another important function of the protein shell is its ability to supply water to the developing organism; it is like a water reservoir.
Some of the minerals are absorbed by the embryo in dissolved form. This indicates another function of the protein shell: water not only protects the embryo from drying out, but also dissolves some minerals involved in the construction of the embryo.
Yolk. The yolk is a yellow, water-insoluble mass of slightly acidic reaction (pH 5.2-5.6). It is covered with a three-layer shell. The inner and outer layers are composed of ovomucin, and the middle one is made of ovokeratin. The substances present in the yolk are not contained at all in the egg white or are contained in it in the form of traces. The yolk is rich in lipids, which are lighter than the protein, so the yolk in an egg lying on its side floats up and approaches the shell, and if the egg lies for a long time, it can dry out to it.
The yolk contains 47-50% water; 15-17% protein; 28-36% lipids; 0.7-1.6% minerals; 0.7-1.0% carbohydrates.
Yolk proteins are represented by phosphoproteins, which are still relatively little studied. Three phosphoproteins were found in the yolk: vitellin, livetin, phosphovitin.
The main protein of the yolk is vitellin, which makes up about 80% of all yolk proteins. It contains 0.9% phosphorus. When exposed to ammonia, vitellic acid is cleaved from it, and upon acid hydrolysis of it, serine phosphorus ester is formed. Therefore, phosphoric acid is combined with protein in the same way as in casein.
The coagulation temperature of vitellin solution is 70-75°.
Vitellin is a source of essential amino acids and phosphorus for the developing chicken. In table Figure 39 shows the amino acid composition of vitellin.
Livetin is an atypical globulin. It is obtained by heating the filtrate remaining after the precipitation of vitellin. The isoelectric point of livetin lies at pH 4.8-6.0. Phosphorus content 0.05%, sulfur 1.8%.
In contrast to livetin, phosphovitin contains a lot of phosphorus (10%) and does not contain sulfur. Its molecular weight is 21,000. Each phosphovitin molecule contains 31 phosphorus atoms and 33 hydroxy amino acid residues. Obviously, phosphoric acid in phosphovitin, as well as in vitellin and casein, is associated with serine.
The yolk contains twice as much lipids (28-36%) as proteins, so the specific gravity of egg yolk is less (1.029) than egg white (1.048). Fats were found in the yolk; phosphatides - lecithin, cephalin, sphingomyelin; cerebrosides and sterols (cholesterol).
Using organic solvents (sulfur, petroleum ether, chloroform), a mixture of lipids called egg fat can be isolated from the yolk. Egg fat is in the yolk in an emulsified state. Part of the lecithin is complexed with vitellin. Egg fat has a yellow color and at elevated temperatures has a liquid consistency.
Egg fat triglycerides include oleic, linoleic, palmitinoleic, myristic, palmitic, stearic, and arachidonic acids. These acids, as well as phosphoglyceric acid, are found in free form in egg fat. Egg fat melts at 34-39°; its iodine number is 64-82. The acid number is, as a rule, small and ranges from 0.3-0.5.
Egg yolk is a rich source of phosphatides. It contains especially a lot of lecithin and cephalin.
The composition of egg yolk includes phosphatides both in free form and in combination with proteins - lipoproteins. About 50% of lecithin is associated with vitellin. The content of lecithin and cephalin in the yolk is approximately the same - about 4% of both.
To determine the content of bound lecithin, the yolk is preheated and then treated with ether. The yolk contains about 4% cholesterol, with free cholesterol accounting for 90%.
The color of the yolk is due to carotenoids, mainly xanthophyll and carotene, which are contained in the unsaponifiable fraction of fat, the former being three times greater than the latter.
Xanthophyll is a yellow substance; According to its chemical structure, it is a dioxy derivative of α-carotene.

The intensity of the color of the yolk depends on the content of carogenoids in food.
The yolk of an egg is rich in vitamins, which it contains in quantities that enable the development of a new organism. It contains 2.5-16 mg% vitamin A, 140-390 IU vitamin D, 55 mg% vitamin E, 0.2-0.4 mg% vitamin B1, 0.5-1.0 mg% vitamin B2, about 0.04 mg% vitamin PP, 6 mg% pantothenic acid, 20 mg% biotin, 0.02 mg% vitamin K.
The egg contains hormones, but their activity appears only during the development of the embryo,
A variety of enzymes that catalyze the breakdown and synthesis of carbohydrates, proteins and lipids, and redox enzymes are found in the egg yolk.
The mineral composition of the yolk is as follows: 0.116% potassium; 0.049% sodium; 0.144% calcium; 0.131% magnesium; 0.01% iron; 0.22% sulfur; 0.62% phosphorus; 0.18% chlorine; 0.0004% copper.
The mineral composition of the yolk differs significantly from the mineral composition of the white. The white is rich in potassium and sodium chlorides, the yolk has a high phosphorus content. Sulfur is contained in the white and yolk in almost equal quantities.
In table 40 shows the chemical composition of chicken eggs (the numbers are given for an average egg weight of 58 g).

The chemical composition of chicken and turkey eggs is very similar; Geese and duck eggs differ from them in having less water content and more fat. For example, a duck egg contains 70.8% water and 14.3% fat.
In table 41 shows some physical properties of the white and yolk of chicken eggs.

An egg is a single cell in a hard shell in which new life develops. For humans, a chicken egg is of particular value, as it contains a huge amount of useful substances.

Chemical composition

The composition of a chicken egg, the photo of which can be seen above, is unique. It contains the following elements:

A lot of vitamin A is contained in the yolk. Moreover, the more intense and saturated its color, the greater the amount of vitamin it will contain. This substance is responsible for the regeneration of the skin, promotes wound healing and prevents hair loss.
Vitamin E, which is also found in sufficient quantities, heals the human reproductive system and prolongs youth.
The yolk of an egg contains vitamin D. A lack of this element leads to the destruction of bone tissue. Therefore, it is extremely important to replenish your reserves of this vitamin throughout the year.
Of the microelements, the largest amount is potassium, which strengthens muscles. As well as iron, zinc, magnesium and phosphorus.
People with poor eyesight should consume chicken eggs as often as possible. The fact is that the yolk contains an element called lute, which helps restore visual acuity.
To prevent malignant breast tumors, women are recommended to eat one egg daily. This product contains a rather rare substance, choline, which can fight tumors.
Eggs are also recommended for people who want to conceive a child. A sufficiently large amount of folic acid and zinc restores reproductive functions and heals the genitourinary system.

In a word, the benefits of chicken eggs are enormous. They are recommended for use by children from a very early age. If a person is not allergic to eggs, then they can be eaten up to two pieces daily. Due to their rich composition and nutritional value, chicken eggs are included in all healthy diets.

Chicken egg size

As a rule, its parameters will depend on the breed of laying hen, its age, complementary feeding and housing conditions. For example, if a chicken constantly did not receive any nutrients, then this fact will certainly affect the quality of the egg. The bird will lay much worse. If laying hens are fed natural feed without the addition of antibiotics, then the eggs they lay will be classified as organic products and are valued much more highly.

Large eggs are laid by chickens over eight months old. Young birds produce small eggs. The quantity and size of this product also depends on the breed of laying hen. There are so-called egg chickens, among which the following breeds are distinguished: Leghorn, Hisek Brown, Loman Brown and High Line. Also, good large eggs are obtained from healthy birds that are kept in favorable conditions. If chickens are constantly cold or hungry, then all their energy will be spent searching for food or warmth. In this case, you should not expect a lot of eggs from her, but be content with a small amount of product and its small size. These eggs are worth much less.

Energy value

This product contains a sufficient amount of protein (12.7 g), a lot of fat (11.5 g) and a small amount of carbohydrates (less than 1 g). Eggs have a fairly high calorie content. So, per 100 g of product - 157 kilocalories. It has been noted that eggs are a valuable source of energy that perfectly satisfies hunger and gives energy. They are recommended to be consumed in the morning before the start of the working day. Vegetarians replace meat with this product if they feel a lack of certain elements. As already mentioned, the egg is one of the few products that is completely absorbed by the human body.

Benefit for health

The benefits of chicken eggs for the human body are as follows:

Due to the quinine content, this product is an excellent prevention of cancer.
Scientists have noticed that egg lovers are much less likely to suffer from osteoporosis than people who ignore this product.
Thanks to calcium and vitamin D, eggs significantly strengthen bone tissue. Doctors recommend that patients with limb fractures eat one to two eggs daily.
The potassium contained in this product strengthens the heart muscle and promotes the elasticity of blood vessels.
Thanks to zinc and folic acid, eggs contribute to the health of a woman’s reproductive system and help her bear a healthy child.

The product has a similar effect on men. Egg lovers are much less likely to suffer from prostatitis and have good potency.

Many people pay attention primarily to the size and condition of the shell. Experts advise evaluating the product according to the variety, storage conditions and GOST. It is believed that the healthiest eggs are those purchased on the market from small producers. There is an opinion that large poultry farms feed laying hens unhealthy food that contains antibiotics.

In order to protect yourself and your loved ones from such a purchase, it is best to find a trustworthy farmer and regularly purchase his own products. Very often, the breeder goes to meet regular customers halfway, shows clients his farmstead and talks in detail about the conditions of keeping the birds.

Storage and labeling

According to GOST, chicken eggs are marked as follows: the Latin letter D means that the shelf life of the product is only seven days. This egg will be considered dietary. The table product is marked with the letter C, and its shelf life is twenty-five days. The weight of an egg of the first category should be about sixty grams including the shell.

What is the yolk made of?

The chemical composition of a chicken egg yolk and white are somewhat different from each other. For example, it contains a huge amount of vitamin B12. The yolk has a rich color due to the presence of vitamin A in it. This important element is simply necessary for healing the skin, eliminating peeling and healing wounds. A lack of this vitamin leads to premature aging and the formation of wrinkles. In addition, thanks to vitamin PP, the walls of blood vessels are strengthened and their elasticity increases. The brighter the yolk, the more vitamin A it contains, which means its benefits are much higher.

As for other important elements, it boasts substances such as choline and melatonin. Moreover, the yolk of a raw egg will contain the largest amount of these substances.

Protein composition

This unique product has absolutely no fat, but is an important source of protein (protein). It contains a lot of microelements, including calcium, phosphorus and iron. The protein of a chicken egg contains amino acids that supply oxygen to brain cells. Unlike the yolk, the white is not advisable to eat raw. It contains an enzyme that destroys gastric juice. In addition, this product is a fairly powerful allergen, which also adversely affects human health. It contains only forty-eight kilocalories.

Eggs and cholesterol

Very often you can hear the opinion that eggs are a supplier of huge amounts of cholesterol, which is deposited on the walls of blood vessels. In fact, this product contains healthy cholesterol, which is a building material for the liver. However, the intake of cholesterol from foods is not at all necessary, since it is perfectly produced by the body itself. Therefore, a person will not be left without it.

Unfortunately, very often healthy products, along with vitamins and microelements, also contain harmful substances. For example, chicken yolk, which is known to be rich in essential elements, has quite a lot of cholesterol. People who monitor their health, as a rule, scrupulously calculate the amount of harmful and undesirable components. When it is not possible to completely give up eggs, you should reduce the consumption of other foods to a minimum. Thus, if a person eats two yolks during the day, then he should limit his consumption of milk or meat so as not to exceed the daily intake of cholesterol. After all, the body can easily cope with a small amount of it.

Unfortunately, many eggs in supermarkets contain antibiotics. They can be partially destroyed by heat treatment. In addition to antibiotics, these products also contain nitrates and other poisons. There is also a risk of salmonella infection. This is a rather unpleasant disease that sometimes ends in death. In addition, there is a category of people who are not recommended to eat eggs. These include primarily allergy sufferers and people with digestive tract problems. In psoriasis, eggs cause an exacerbation of the disease. Patients with cardiovascular diseases should be careful and consume this product as little as possible due to the presence of cholesterol in it.

Chicken eggs are a basic product that is included in the diet of almost all inhabitants of the earth. Even many “vegetarians” eat chicken eggs, not to mention traditionally eating people.

What explains such love (let's not be afraid of this word) for chicken eggs? What's useful about them? What about the harmful ones? And in general, is it possible to live without chicken eggs and still feel healthy?

We will try to answer these and some other questions in this article...

Chemical composition of a chicken egg

Chicken eggs: benefits

People who need easily accessible animal protein see the greatest benefit in chicken eggs. Because the protein components of this product are absorbed by the human body by 90-95 percent. True, in fairness it should be said that thermally processed protein is better absorbed. Therefore, eggs must be boiled. Fried eggs are also well digestible, but if you fry them in vegetable oil, then in addition to easily digestible protein, you will also receive a dose of free radicals formed inside the hot oil.

It should be understood that most of the vitamins and minerals are not found in the egg white, but in the yolk. This means that the ideal way to extract the maximum amount of nutrients contained in a chicken egg is to eat it soft-boiled or in the form of “Fried egg”, if you still prefer the fried version.

It is believed that chicken eggs, like the eggs of other birds, can have a positive effect on human brain activity, improving memory and activating nerve connections throughout the body.

Chicken eggs also affect other organs and systems of the human body. Thus, it was noticed that regular consumption of a small amount of eggs (up to 10 pieces per week) helps people preserve the skeletal system, including teeth, from destruction, and also reduces the risk of vision loss “as a result of old age.” In addition, chicken eggs protect the body from the formation of malignant tumors.

Separately, it should be said about cardiovascular diseases... Some time ago, scientists unanimously insisted that eggs are a source of bad cholesterol, which can clog and thereby lead to damage to human blood vessels. However, now eggs are accused of such “atrocities” less and less, because it turned out that chicken eggs not only do not add cholesterol to our body, but also destroy the cholesterol plaques already present in the blood vessels.

What other benefits are chicken eggs? In principle, they have a beneficial effect on the entire body, but eggs have the most noticeable effect on human hair. Moreover, it is not at all necessary to make egg masks. You can simply eat eggs regularly. Naturally, in this case, the effect will come a little later, but it will be much more lasting, because hair health mainly comes from the inside, and not from the outside.

The shell of chicken eggs also has beneficial properties, because it consists of calcium carbonate, which, as is known, is absorbed very, very well even by people who have difficulty absorbing calcium from food and pharmaceutical preparations.

There is also an opinion that chicken eggs smooth out the negative manifestations of nervous fatigue, protect a person from viruses and establish normal metabolism.

The myth about the color of a chicken egg shell

Many people still believe that the color of a chicken egg shell indicates the degree of its usefulness. Previously, no one even doubted this. Now they are increasingly saying that the color of an egg is not an indicator of usefulness, but only reflects what the bird was fed. Which is quite logical.

But! If overt dyes are not mixed into chickens’ food, then the color of the shell is really important and reflects the content of certain substances in the egg. Because the composition of eggs is entirely determined by the chickens’ diet. Therefore, the color of the egg still matters. True, there is no clear answer to the question: “Which egg is healthier: white or brown?” this understanding still does not give.

Damage to chicken eggs

Chicken eggs can really harm the body, moreover, their consumption is quite capable of jeopardizing even human life itself. However, this happens quite rarely, or rather:

if you are allergic to chicken eggs
if the egg is contaminated with salmonella

This ends the harm of chicken eggs. Unless you're going to eat whole trays of them...

As for cholesterol, we have already described above what’s what. Let us only add that there is still a risk of raising the level of cholesterol in the blood if a dish that includes chicken eggs is supplemented with bacon, lamb or beef chop. So think about what you eat and for what purpose.

The benefits and harms of raw chicken eggs

Most doctors are convinced that you should not eat raw chicken eggs. Because the risk of getting salmonellosis outweighs all possible advantages. This makes sense, but the hypothetical presence of salmonella in eggs is not at all a reason to refuse to eat raw chicken eggs.

Just know: you shouldn’t eat store-bought eggs raw, especially if they have already been converted to canteen status. But fresh homemade eggs from familiar chickens are quite acceptable and even welcome.

We hope we have dealt with salmonella. Let's now talk about how healthy a healthy chicken egg is.

The mineral and vitamin value of a chicken egg lies in its yolk. And from this point of view, eating raw eggs is preferable. However, raw “protein”, being in the gastrointestinal tract, can neutralize many beneficial substances contained in the yolk.

That is why it is advisable to eat raw chicken eggs in the following way: separate yolks and separate whites (with an interval of half an hour to an hour). We have already written above about the options for the most useful culinary processing (“Galazunya” and soft-boiled).

Use in cooking

As for the use of chicken eggs in cooking, any housewife can immediately name at least ten dishes in which this product is used. Therefore, there is no point in listing anything.

Another thing that is much more interesting is how to distinguish fresh eggs from “stale” (but suitable for human consumption) eggs in a store. This is done using a letter code used by the "producers" of chicken eggs.

Chicken eggs are a product that is present on the menu of almost every person. They can have a dark or light shell color - it depends on the breed of the chicken that laid the egg. But the color of the shell in no way affects the quality characteristics of the product.

The size of a chicken egg depends on several factors:

age of the bird;
the food she eats;
chicken breed;
conditions of detention.

We recommend reading:

In any case, chicken eggs have certain beneficial properties - they are determined by the chemical composition of the product.

Nutritional value 100 g:

Calorie content: 157 kcal
Proteins: 12.7 g
Fat: 11.5 g
Carbohydrates: 0.7 g

Water: 74.1 g
Saturated fatty acids: 3 g
Cholesterol: 570 mg
Mono- and disaccharides: 0.7 g
Ash: 1 g

Vitamins:

Macronutrients:

Microelements:

Did you know that the product in question is the only one that is absorbed by the human body almost completely (97-98%)? And at the same time, the chemical composition of a chicken egg contains all the vitamins and minerals necessary for normal life. Here are just a few of them:

lecithin – contained in the yolk, helps normalize the functioning of brain cells, dissolve existing plaques in blood vessels, improve liver function;
luten – significantly improves the level of vision;
– strengthens bone tissue;
choline – prevents cancer;
niacin – affects the formation of germ cells, increases brain performance;
– necessary during pregnancy.

Separately, it is worth saying that the benefits of a chicken egg for the human body lie not only in the white and yolk. The shell is very useful for its high calcium content - it can and even should be eaten. Of course, no one says that you can just take it and chew it; you will have to prepare this natural medicine to strengthen bones and normalize metabolic processes. To do this, you need to thoroughly wash the shells, boil them in water for 10 minutes, dry them and grind them to a powder. And in this form, you need to consume 3 grams of chicken egg shells every day, and in order for calcium to be better absorbed, you need to add 2-3 drops of lemon juice to the daily dose of “medicine”.

The calorie content of chicken eggs is high - 157 Kcal per 100 g of product. It’s not for nothing that boiled chicken eggs were (and are) given for breakfast in kindergartens and schools - they are easily accepted by the body, the stomach does not become full, but there are enough calories for vigorous activity, both physical and mental.

The benefits of chicken eggs

The fact that the product in question is truly beneficial for the human body is not questioned by any of the scientists and doctors. Judge for yourself what happens to the body with regular and moderate (!) consumption of chicken eggs.:

bone tissue is strengthened - this is especially important in childhood and old age;
prevention is carried out;
corrects liver function in case of simple diseases;
improves the condition of the walls of blood vessels - removes plaque from there, makes the walls more elastic;
serves as a prevention of breast cancer;
has a beneficial effect on the intrauterine development of the fetus;
increases brain performance, improves memory;
significantly increases concentration even during prolonged mental activity;
protects the optic nerve from weakening;
is the prevention of cataracts.

In addition, by eating 2 chicken eggs every day, a person provides his body with a daily dose of vitamins and minerals.

Damage to chicken eggs

The debate about the benefits and harms of the product in question has been going on for several decades. Of course, despite all the positive qualities of a chicken egg, it also has its drawbacks - this is precisely the harm that may be caused to the body.

You can also avoid ingesting too much “bad” cholesterol from chicken eggs by separating the white from the yolk. In this case, only protein, which does not contain cholesterol, will be eaten.

Secondly, many scientists and doctors note the danger of infection as a harmful property of chicken eggs. This infectious disease plays absolutely no role in the health of the chicken or the quality of the egg, but when it enters the human body it provokes the development of very complex, sometimes deadly, diseases.

And this issue can be resolved if you adhere to the following rules:

But in general, it’s worth knowing that recently the risk of contracting salmonellosis from chicken eggs has decreased significantly. This happened thanks to vaccination measures at poultry farms.

Thirdly, chicken eggs are recognized as an allergenic product. Indeed, people often develop characteristic signs of an allergic reaction - small rashes, redness of certain areas of the skin, itching. But you need to clarify right away:

Allergy to eggs most often manifests itself in children at a young age and goes away without a trace by the age of 5-7 years.
Even if you have an allergy in adulthood, you can only eat the yolk of the egg - the white contains a huge amount of protein, which serves as a provocateur of an allergic reaction.

And there is one more point - if diagnosed, chicken eggs can provoke the development of myocardial infarction or stroke. But even in this case, there is no categorical ban on eating the product in question - there is only a recommendation to avoid excessive consumption.

Some features of choosing chicken eggs

In stores you can often see chicken eggs with different markings - sometimes they are red, sometimes blue, with some letters and numbers. What does this all mean and what should you consider when purchasing the product in question?

Diet eggs are not stored at sub-zero temperatures; the shelf life is only 7 days. Dietary is not some kind/kind/type of chicken egg, it is simply a designation of “increased freshness.” This is where the dietary egg is marked with red ink.

A table egg is a product that has already passed the “dietary” stage, that is, at least 7 days have passed since the chicken laid the egg. This does not mean that the product has lost some of its beneficial properties, just that a table chicken egg is stored and sold according to different rules. Such eggs are stamped with the date of laying in blue ink. Table eggs can be stored at room temperature for no more than 25 days, and in the refrigerator for no more than 90 days.

Another point to consider when purchasing the product in question is the egg category. There are 3 main categories:

Category 1 – egg weight ranges from 55-64 g;
Category 2 - the egg will already weigh 45-55 g;
Category 3 – weight below 45 g.

There is another category, designated by the letter “B” - the eggs are very large, each reaching a weight of 75 grams. But such an egg is practically never found on store shelves. But selected chicken eggs are well known to consumers. The weight of such an egg is slightly greater than that of the same category 1 product.

Chicken eggs are a healthy product. And you can listen to different versions about how harmful/useful they are for a long time. We note that if you use the product in question moderately, without getting carried away, then the body will definitely benefit much more than harm.

Egg structure

A bird egg has a complex structure and is a highly differentiated egg (unfertilized, food egg) or an embryo at a certain stage of development with a supply of all the necessary biological substances for the subsequent individual development of the organism (fertilized egg).

The size, weight, morphological characteristics, chemical composition and physical properties of the egg depend on the genetic characteristics of the bird (species, breed, line, cross), age, housing conditions and feeding.

A bird's egg is a complex and highly differentiated egg cell surrounded by yolk and white, their membranes and shell.

Yolk located in the middle of the egg, it is an almost spherical body of yellow or orange color. In the center of the yolk is latebra– light yolk, concentrated in a flask shape. The yolk consists of alternating dark yellow and light yellow layers (12 or more), which are enclosed in a common thin and transparent yolk membrane (vitelin membrane) about 0.024 mm thick. It serves as a natural membrane separating the white and yolk, and has numerous gas-permeable structures. The suspension of raw yolk contains fat globules of various diameters - from 0.025 to 0.150 mm. The color of the yolk is due to carotenoid pigments and depends on the feeding of the laying hens. During embryogenesis, the yolk serves as a source of water and nutrients and performs thermoregulatory functions.

On the periphery of the yolk, under the vitelline membrane, there is a blastoderm with a diameter of 3-5 mm, which looks like a small whitish round spot.

Bird eggs are telolecithal type, i.e. The cytoplasm is concentrated at one pole of the egg, and nutrients (yolk) at the other. The fragmentation of the chicken embryo is incomplete, or meroblastic, in which the yolk does not acquire a cellular structure, but only the blastoderm divides, forming a disc-shaped accumulation of cells located above the yolk mass. The blastoderms of fertilized and unfertilized eggs differ in appearance. The blastodisc of an unfertilized egg is flat, opaque due to the concentration of protoplasm; vacuoles and depressions - lacunae - are sometimes formed in it.

The blastoderm of the fertilized egg is round, slightly convex, and has concentrically located transparent and opaque zones (zone pelucide and zone opaque). By the time the egg is laid, the blastoderm in the fertilized egg consists of two layers of cells, its central part is separated from the yolk by a subembryonic cavity. At this time, the blastoderm is in the early gastrula stage.

The egg white, which makes up its largest part, is divided into four layers (when pouring a fresh egg, the layering of the white is clearly visible). Around the yolk there is a small layer of internal dense protein - the hailstone layer (consists of thick collagen protein), which forms rope-like twisted strands along the major axis of the egg - hailstones (chalaza). On top of the inner dense protein there is a layer of internal liquid protein, almost free of mucin fibers. The next layer, the outer dense protein, occupies the largest volume of the entire protein. It contains many mucin fibers, which form its basis in the form of an interwoven mesh network filled with liquid protein; chalazas are attached to it. The content of dense protein is considered to be one of the main indicators of egg quality, since its quantity decreases with storage. The fourth layer is the outer liquid protein. There are almost no mucin fibers in the outer and inner liquid protein.

Egg white contains a sufficient supply of water for the developing embryo, as well as essential amino acids, vitamins and microelements. Many physical characteristics of protein depend on its water content (on average 87%).

Egg white includes several proteins (there are about 12 of them).

The egg white proteins are in electrostatic interaction with each other, which determines the state of the protein in the form of a gel. In turn, the interaction of egg proteins is controlled by the pH level of the protein, which in a fresh egg is normally 7.6-8.2.

The shell, consisting of calcium carbonate, is a dense outer shell that determines the shape of the egg and protects its contents from external influences. It consists of two layers: the inner, or papillary, which makes up one third of the thickness of the shell, and the outer, or spongy. The minerals of the papillary layer have a crystalline structure, while the spongy layer has an amorphous structure. The shell is permeated with numerous pores - tubules. The total number of pores in an egg shell ranges from 7 to 17 thousand, with more of them at the blunt end and fewer at the sharp end of the egg. The optimal thickness of a chicken egg shell is 0.35-0.38 mm.

The inner surface of the shell is lined with two membranes (membranes): the supra-albuginea and the sub-shell (tightly connected to the inner surface of the shell). They consist of protein fibers, tightly in contact with each other over the entire surface, with the exception of the area of the blunt end. In the area of the blunt end they diverge, forming an air chamber - a meadow. The air chamber plays an important role in the process of evaporation of moisture from the egg and during gas exchange of the embryo, especially during the transition to pulmonary respiration. The subshell membrane is presented in the form of a lattice filled with keratin, which has more than 20 million pores with a diameter of about 1 micron per 1 cm2. Liquids and gases pass through the shell diffusely. The top of the shell is covered with a supershell membrane - the cuticle.

The supra-shell membrane (cuticle; covers the shell from above) is very thin (0.05-0.01 mm) and transparent, consists of mucin, which envelops the egg when it leaves the bird’s genitals. The cuticle plays the role of a kind of bacterial filter for the egg. It protects the egg components from dust and regulates water evaporation. During storage, the cuticle is destroyed, and the surface of the egg becomes shiny as it ages. Removing the cuticle from an egg speeds up its aging and deterioration. The shell protects the contents of the egg from damage and serves as a source of minerals that are used to form the skeleton. Through the pores of the shell, moisture evaporates and gas exchange occurs during incubation.

Their approximate ratio in poultry eggs is as follows: 6 parts white, 3 parts yolk, 1 part shell. The optimal ratio of white to yolk in eggs is 2:1.

Chemical composition of the egg

The chemical composition of poultry eggs of different species differs somewhat. Thus, in the eggs of ducks and geese (that is, waterfowl), compared to other species (chicken, turkey, guinea fowl and quail), there is 2.4-4.5% less water and more fat (1.3-3.3 %), which developed evolutionarily.

It is known that the development of embryos of wild ducks and geese occurs in colder nests (usually near water bodies), therefore, an increased fat content in the egg with a simultaneous decrease in water in it contributes to normal embryogenesis.

In general, poultry eggs of any type consist of 70-75% water, which contains dissolved minerals, proteins, carbohydrates, vitamins and fats in the form of an emulsion. Water is one of the most important factors determining the possibility of embryonic development and the high physiological properties of an egg as a food product. The dry matter content relative to the whole egg is highest in the yolk - 45-48%, then in the shell with shells - 32-35 and in the white - about 20%.

Chemical composition of farm poultry eggs of different species, %

The shell of eggs consists of minerals, mainly calcium dioxide (94%), magnesium dioxide (1.5%) and phosphorus compounds (0.5%). The shell also contains organic substances (up to 4%) as binders of mineral salts. Shell proteins, mainly collagen, serve as the basis on which mineral salts are deposited during egg formation.

Egg white contains a lot of water (86-87%), various nutrients and B vitamins are dissolved in it. The main organic substances of protein are proteins - 9.7-11.5% (depending on the type of bird), and fats, carbohydrates and significantly less minerals.

Egg white includes several proteins, of which there are about 12.

Known chicken protein proteins

Amino acid composition of chicken egg proteins, %

Amino acid	Protein	Yolk	Subshell membrane	Shell
Cystine Lysine Histidine Arginine Aspartic acid Serine Glycine Glutamic acid Threonine Alanine Proline Tyrosine Methionine Valine Phenylalanine Leucine-isoleucine Tryptophan	1,04-1,31 5,54-6,00 1,77-1,80 4,78-5,32 7,81-8,53 3,77-4,57 2,79-2,49 9,14-10,08 4,40-4,17 4,30-4,49 5,74-5,35 1,78 2,02-1,54 5,26-5,28 3,49-3,31 11,71-12,05 0,9-1,32	0,90-0,91 6,44-6,48 1,57-1,67 6,03-6,25 8,90-9,09 4,85-4,87 2,53-2,61 8,76-8,83 5,26-5,55 4,16-4,10 9,01-8,60 2,08-1,90 1,10-0,99 4,68-4,51 2,93-2,70 10,78-11,27 1,37-1,04	4,82-2,60 5,72-6,00 2,50-2,01 5,88-5,40 10,98-8,48 3,86-2,50 4,59-3,41 24,40-8,71 16,30-3,84 11,83-3,36 5,23-6,01 1,85-0,82 2,51-2,11 4,14-4,93 4,43-4,45 7,86-7,84 0,70-0,28	12,67 3,66 0,86 8,88 3,83 - - 10,11 - - 3,83 2,54 - - - - 2,61

Of the carbohydrates, egg whites contain glucose and glycogen.

Egg white minerals are mainly calcium, phosphorus, magnesium, potassium, sodium, chlorine, sulfur and iron. Protein contains small amounts of aluminum, barium, boron, bromine, iodine, silicon, lithium, manganese, molybdenum, rubidium, silver, zinc, etc.

More than 70 enzymes have been found in egg whites, which play an important role in the breakdown of proteins during their assimilation by the embryo; vitamins of group B (B 2, B 3, B 4, B 5, B 6 and B 7), E, K and D; natural antibiotic lysozyme, which has bactericidal properties.

The chemical composition of the egg yolk is approximately the following: water 43.5-48%, dry matter 52-56.5%. Dry matter, in turn, consists of organic substances (proteins 32.3%, lipids 63.5%, carbohydrates 2.2%) - 98%, minerals - 2%. Thus, the main organic part of the yolk consists of fats. There is almost 2 times less protein in the yolk, and almost 30 times less carbohydrates and inorganic substances compared to the fat content. The composition of egg yolk fats includes fats themselves (62%), phospholipids (33%) and sterols (5%).

The main fatty acids in yolk are palmitic, stearic, oleic and linoleic. The presence of the last two is especially important for the initial stages of embryo development, since they are more accessible to it and are used by it earlier.

The yolk contains two types of protein: ovovitellin (78%) and ovolivetin (22%). The first of them (the main one) is rich in leucine, arginine and lysine, which account for almost 1/3 of all amino acids.

Of the mineral substances in the yolk, there are especially many compounds of phosphorus, calcium, potassium, sodium, iron, silicon, fluorine, iodine, copper, zinc, aluminum and manganese are also present.

In addition, the yolk is rich in vitamins. For example, the yolk of a chicken egg weighing 18 g contains: vitamin A (retinol) – 200-1000 IU; B, (thiamine) – 63-86 mcg; B 2 (riboflavin) – 70-137 mcg; B 3 (pantothenic acid) – 0.84-1.17 mcg; B 4 (choline) – 268 mg; B 5 (nicotinic acid) – 28.5 mcg; B 7 (biotin) – 0.6-9 mcg; B c (folic acid) – 5.47-6.44 mcg; D (calciferol) – 25-70 IU; E (tocopherol) – 0.8-1 mg.

Of the enzymes in the yolk, amylase, proteinase, dipeptidase, oxidase, etc. are present.

Pigments are found in all components of the egg, but the yolk is richest in pigments. Thus, the yolk of a chicken egg contains, mcg/g: xanthophylls – 0.33; lipochromes – 0.13 and b-carotene – 0.03.

The absolute amount of xanthophylls in the yolk depends on the amount and nature of the sources of carotenoids included in the diet, but the relative content of xanthophylls in the yolk is quite constant and amounts to 75-90% of the total amount of carotenoids. During egg incubation, embryos use mainly xanthophylls. The percentage of their use is higher, the less of them there is in the yolk of eggs.