Eggshell Colours; What do they mean?


If you’re used to the standard brown or white eggshells, you may not know that chicken eggs also come in a wider range of colours ranging from blue, to green, to chocolate brown and more!  If you’ve ever wondered how or why eggshells get their colouring, we’ve got the answers for you.

What are eggshells made of?

Before we dive into what determines eggshell colours, let’s explore what eggshells are made of.

An eggshell is made of calcium carbonate crystals. Calcium carbonate, also known as CaCO3 is a chemical compound which is the main component of items such as eggshells, snail shells, pearls and seashells.

Slightly grainy to the human eye, eggshells are covered in thousands of tiny pores. Eggshells are semipermeable membranes, allowing air and moisture to pass through the pores. Eggshells also include a thin outermost coating known as the bloom that keeps bacteria and dust from entering into the shell.

What do Hens’ earlobes have to do with it?

Eggshells colours are primarily determined by the genetic makeup of the laying hen. The colour of a hen’s egg is determined by the breed of chicken that is laying the egg, and you can predict the colour eggs that a hen will lay by the colour of the hen’s earlobes. Hens with white earlobes typically lay white eggs, while those with brown earlobes lay brown eggs.

Fun fact: all eggs start out as white and receive their colouring while they travel through the hen’s oviduct. The colour develops as it progresses through the oviduct. Chickens that lay brown eggs deposit a pigment This process through the oviduct takes around 26 hours and the shell takes approximately 20 hours to be completed.

In South Africa, most eggs you find in the supermarkets are brown. This is due to the chicken breeds that are commonly farmed in South Africa. And while the colour of the egg is determined by the poultry breed, the intensity of the colour depends on many factors. Factors such as age, diet and stressors can impact how much pigment a hen deposits onto her eggs.

In rare cases, brown eggs have been known to lose their pigment and, in some cases, can be due to stress, age, chemotherapeutic agents or disease. In most commercial egg operations, egg colours are closely monitored to ensure the health and wellbeing of the hens and the safety of the eggs.

Does eggshell colour affect the nutritional value of the egg?

In short, no. Besides how they look, there are no major differences between eggs of different colours and the nutritional value of the egg is not impacted by the colour of the egg. Protein values, calories and other nutritional factors aren’t influenced by the colour of the egg but will be impacted by the size of the egg- a jumbo egg will naturally contain more protein than a smaller egg.

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