Eggs: description, nutritional values, freshness

The eggs they are foods rich in iron and high quality proteins, free of carbohydrates, calcium and vitamin C. Let's find out more about the nutritional values ​​and how to recognize their freshness. 

> 1. What are eggs

> 2. Nutritional values ​​of eggs

> 3. How to recognize fresh eggs

> 4. Curiosities about eggs

Eggs: description, nutritional values, freshness



What are eggs

With the word "eggs", not followed by any other specification, refers to those of hen (otherwise the name of the bird from which they come must be specified).
The egg is formed by three structures: an external, the shell, a medium, the egg white or albumen, an internal, the red or egg yolk.

Il shell it is made up of about 95% calcium carbonate (necessary for the chick to calcify the bones if the egg were fertilized). The shell is porous and of a color ranging from white to brown depending on the pigments of blood origin, typical of some breeds of hens. When the egg is perfectly fresh, it has a characteristic opaque and greasy appearance due to a very thin layer of mucin that is deposited on its surface just before it is laid.

THEalbumen, essentially of a proteinic nature, it suspends the yolk inside.

Il egg yolk, whose more or less yellow color essentially depends on the feeding and outdoor life of the laying hens (it is above all the carotenoids that give a darker color) but also on the breed, since some hens are not able to absorb the carotenoids present in the diet and therefore lay pale eggs. Therefore the color of the yolk does not necessarily have to be related to the nutritional power of the egg, as well as the color of the shell.

In relation to freshness, eggs are divided into three categories:

  • category A Extra. These are the very fresh, untreated and unrefrigerated eggs that can be marketed up to the ninth day after laying (or the seventh day after packing); after this period they lose the qualification of "extra" and can be marketed with the sole reference to category A;
  • category A. They are fresh, untreated and unrefrigerated eggs; the minimum storage term indicated on the label is calculated in 28 days from the deposition date;
  • B category. They are second quality or "downgraded" eggs, which cannot be transferred directly to the consumer but only to industrial companies in the food sector to be transformed into egg products, or to the non-food industry.

Based on the weight, eggs are classified into:

  • XL - Very large: 73 g and more
  • L - Large: 63 g more but less than 73 g
  • M - Averages: 53 g and more but less than 63 g
  • S - Small: less than 52 g.


Nutritional value of eggs

Eggs do not represent, as many believe, a complete food from a nutritional point of view since they lack carbohydrates, calcium and vitamin C..

They are, however, an excellent food for the protein quality, present both in the albumen and in the red, in a proportion of 13% of the total weight.
The egg white represents about 60% of the weight and contains, in addition to water (85%) also various proteins, among which the most abundant are ovalbumin (54%).

The red contains phosphorated proteins, lipoproteins and lecithin, a phospholipid component extracted for the first time from the egg and containing among other things the choline which is particularly essential for nerve cells.

Furthermore, all vitamins are present in the egg (vitamin A and D in significant quantities) with the exception of vitamin C.

As for the mineral constituents, the egg is rich in iron, present in assimilable form, of calcium, phosphorus, potassium and magnesium.


The properties of the egg and how and when to consume it


How to recognize fresh eggs?

Regarding the age of the egg, it is necessary to know that the larger the inner tube, the older it is: it can be seen by light examination (candling), observing the egg in transparency once placed in front of a light source.

La egg shape it also gives indications on the state of freshness since, with the passing of the days from the deposition, the testaceous membrane (double internal membrane) adheres less and less to the inner face of the shell, while the albumen begins to thin.

The yolk membrane thins, so that this, which is spherical upon deposition, flattens and, in the most advanced cases, also breaks due to the increase in volume caused by the water absorbed by osmosis from the albumen. For this test of freshness it is necessary to break the egg in a plate and observe its characteristics: the more the yolk is turgid and round and the egg white firm and dense, the fresher the egg is.

Another proof of freshness is the egg buoyancy test. The egg is immersed in an aqueous solution with 10% sodium chloride (table salt); since the fresh egg has a higher specific weight, once immersed in the solution it settles on the bottom, otherwise it will stay closer to the surface the less fresh it is.


Curiosities about eggs

The egg white can be difficult to digest due to the difficulty in being attacked by gastric juices, with consequent irritation of the intestinal mucous membranes. For this reason it is preferable to cook the egg white, also eliminating an antivitamin factor (avidin and precisely an anti-vitamin H) which is present in the egg white but which is thermolabile. 

In fact it has been seen that the lightly boiled egg (how can it be soft-boiled) leaves the stomach in less than 2 hours, the fresh one after 2 hours and the hard or omelette after 3 hours, the same average time required for meat. 

Eggs are often believed to harm the liver or predispose to circulatory diseases, due to the presence of high amounts of cholesterol in the yolk (about 250 mg per yolk).

It should be remembered that, being the quantity of cholesterol produced by our organism much higher, it certainly cannot be the quantity present in the egg that significantly influences the level of cholesterol in the blood, unless it is abused (more than 2 eggs per week). 

Eggs can be contraindicated only in gallstones, as they can cause contractions of the gallbladder walls, resulting in colic spasms.


How to replace eggs in recipes


Other articles on eggs:
> The egg yolk is rich in vitamin H
> Rock partridge eggs against seasonal allergies
> How to make an egg-free omelette?


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