Characteristics of eggshell

Functions of an eggshell

What’s in an eggshell?

Eggshells are mainly composed of calcium carbonate but also of calcium phosphate and magnesium carbonate,… in very small amounts.

We should note that an eggshell is not a smooth, impervious surface, but, on the contrary, it contains thousands of pores (over 7000), allowing the chick to breath and, therefore, the inside maintenance of the egg.

In addition, it is covered by a thin layer that covers the pores and increases its ability to protect the inside of an egg against external strange agents. For this reason, eggs must not be washed until just before consumption, because water takes this outer layer and could alter the egg preservation.

Function on an eggshell

An eggshell represents an approximate 10% of the total weight of the egg and its role is to protect its contents because of its hardness and thickness. (See eggshell properties)

Is the egg shell edible?

Egg shell

Photo of eggshell membrane. Note how attached is to the shell

Although eggshell is very rich in calcium, this calcium is little available and absorbable by the body and can not be eaten directly. Moreover, eating it will produce intestinal tract lesions.

However, there are techniques that are used in some regions of the world to soften it and to make it edible.

The softening base is produced by any acidic substance. Thus, eggshells can be used as an additional source of calcium in areas and populations with low purchasing power and potential nutritional deficiencies due to insufficient intake of this important mineral.

Different colour eggs

Eggs in the market with different color in the shell

How thick and what color should eggshells have?

Eggshell thickness can vary according to how the hen has been fed, being more fragile if it has not been fed properly. We can find different breeds of hens, so we obviously can find in the market eggs of different colors, from almost white, to other brown or dark brown.

The color of an egg does not imply any difference in its qualities and nutritional properties.

Related information:

Eggshell properties

Eggshell decoration

Egg yolk

Egg white

punto rojo More information on eggs.

This article was endorsed by Elisenda Carballido - Dietitian nutritionist. Postgraduate in Phytotherapy and master in Nutrition and Metabolism.
Written by Editorial Botanical-online team in charge of content writing

29 September, 2022

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