Why are Eggshells Different Colours?

 Eggshells come in a wide range of colours and hues- not just the typical white or brown. Eggshells can vary in colour from white, to pale blue, chocolate brown, and more. But what determines the colour of an eggshell? Why are eggshells different colours? Why are certain eggs brown and others white? Can you predict eggshell colours?  Read on for answers to these questions and others.

Can you predict eggshell colours?

You can, actually! Eggshells colours are primarily determined by the genetics of the laying hen. The colour of a hen’s egg is determined by the breed of chicken that is laying the egg. You can often predict the colour eggs that a hen will lay by looking at the colour of the hen’s earlobes. In general, hens with light or white spotted earlobes typically lay white eggs. Hens with brown earlobes lay brown eggs.

But eggs don’t start out with their final colour! In fact, all eggs start out as white and receive their colouring while they travel through the hen’s oviduct. The pigment of the egg develops as it progresses through the oviduct. This pigment appears both on the inside and the outside of the shell. This process of the egg moving through the oviduct takes around 26 hours.  The hens that lay brown eggs deposit a pigment called protoporphyrin IX, which only appears late in this process. Protoporphyrin IX is made from heme, which is the compound that gives blood its red colour.

If you are grocery shopping in South Africa, chances are that most eggs you will find in the supermarkets are brown. This is due to the type of chicken breeds that are commonly farmed in South Africa, which are mainly breeds that produce brown eggs.  While the poultry breed determines the colour of the eggshell, the intensity of the colour depends on many factors. Certain factors such as age, diet and stressors can impact how much pigment a hen deposits onto her eggs. As hens age, they are more likely to lay eggs that are paler in colour.

Brown eggs have been known to lose their pigment in rare cases. This can be due to factors such stress, disease or the presence of chemotherapeutic agents. In most commercial egg operations careful attention is paid to health and safety. Producers monitor and assess egg colours and other qualities to ensure that the egg products are safe for human consumption, and that the hens are healthy.

Do different colour eggs taste different?

Brown and white eggs do not taste different from one another. However, other factors do play a role. The type of feed the hen ate, egg freshness, egg storage and preparation methods can affect the way that it tastes.

What are eggshells made of?

What makes up an eggshell?  An eggshell is composed of calcium carbonate crystals. Calcium carbonate is a chemical compound which is the main element of items such as eggshells, snail shells, pearls and seashells. Calcium carbonate is also known as CaCO3.

Eggshells are covered in thousands of tiny pores, which present a slightly grainy texture to the human eye. Eggshells are semipermeable membranes, which means that they allow air and moisture to pass through the pores.

What do eggshell colours mean for the nutritional value of the egg?

Some people believe that different eggshells have different nutritional benefits; this is untrue.  Besides how they look, there are no major differences between eggs of different colours and the nutritional value of the egg is not affected by the colour of the egg. Protein values, calories and other nutritional factors aren’t influenced by the colour of the egg.

No matter the colour of the shell, eggs are jam packed with healthy nutrients and vitamins to nourish and support your body.

For more amazing egg facts or information, head over to our egg facts page!

Published 02 June 2021