If we think about the color of egg shell the classic will immediately come to mind rosebut we know well that eggs can also be colored white. In truth, there are also eggs, of course celestial, green or brownand we are not talking about duck, quail or pheasant eggs, but about classic eggs hen. So what is this difference in shell color due to? All eggs are made of calcium carbonate, a porous material. The hen produces a secretion inside the oviduct to lubricate the passage of the egg and this secretion contains the pigments which will give color to the egg shell without influencing its internal color, in most cases. The most common pigment is la protoporphyrin IXwhich gives pink eggs, but there is also the biliverdinresponsible for more imaginative colors, from blue to green. The type of pigment (or lack thereof) depends on the breed of hen, so this is a factor genetic, while the intensity of the coloring may depend on the age of the hen.
Why the egg shell is colored and what changes between white and pink eggs
The coloring of the outer shell of the egg occurs when the hen lays it. In this phase, the egg shell, composed mainly of calcium carbonate and covered by a thin non-calcified protective film which is called cuticle, it is already fully formed. However, the material it is made of is porous, so it can absorb substances it comes into contact with.
So after the egg is already fully formed, the hen produces a glandular secretion which serves to lubricate the passage of the egg along the oviduct. This secretion typically contains a pigment which differs depending on the breed. When the hen’s secretion comes into contact and reacts with the calcium carbonate in the shell, the pigment contained in the secretion is absorbed and the egg becomes coloured.
If the shell is white it simply means that the secretion deposited on the shell is not pigmented. In the case of pink eggs, however, the most common pigment of all will be inside: protoporphyrin IX. This last case is the most common because among the hens that produce eggs with pink shells there are those more predisposed to laying eggs, also called hens laying hens (which produce approximately 1 egg per day) and therefore more used in intensive farming. Pink or cream colored eggs are often laid by purebred hens Sussex; other breeds include Plymouth Rock, Amrock, Moroseta and Lohmann.
Even white eggs are not unusual: there are, in fact, some breeds such as the Padovana or the Livornese, which are nevertheless egg-laying. That’s why it’s not so strange to find them in the supermarket.
What are the breeds of chickens that lay eggs with blue, green and brown shells
Chicken eggs aren’t just pink or white. There is a category of naturally colored eggs called Easter, like colored Easter eggs.
Among these, the most famous type is the egg with the colored shell heavenly. The chickens produce them Araucana. This is a characteristic breed of Chile that produces around 200 eggs a year, usually smaller than those we are used to. The blue color is given by the pigment biliverdinpresent in the glandular secretion of these hens.
The colored eggs are also particular brown chicken chocolate Maransa French breed. And from the cross between an Araucana hen and a Marans a hybrid breed named was born Olive Egger which, as the word itself says, is capable of producing colored eggs greengiven by the combination of the two pigments: biliverdin and protoporphyrin IX. Clearly these are breeds that are not found in intensive farming but only locally.
However, even the same hen can produce more or less colored shells. They affect the nuances the age of the animal, the physical condition, but also how long the egg stays in the oviduct, because the longer it stays there, the more pigment it absorbs.
Is the color of the outer shell related to that of the yolk?
No, the color of the external shell is absolutely not related to the internal one. The latter in fact depends on thediet of the hen, a factor that influences the yolk in particular, which can vary from the lightest yellow to the most intense orange. This is not the only case in which the animal’s diet influences its colours. Carotenoids are in fact responsible for the pink color of flamingos, or the color of chicken, which can be pinkish white or yellow depending on what it eats.
However, we have an exception to the rule. The Araucana hen in very rare cases can give a little blue color to the yolk. This may happen because in this breed the pigment biliverdin is produced together with the shell and not at the time of egg laying. Only due to this synchronism is it therefore possible but very rare for the color to attack even inside the egg.
