Chicken egg

Foods, Animal source foods, Eggs, Bird eggs

Animal species that lays them: Chicken (Gallus gallus domesticus)

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Introduction

The chicken egg is a type of egg that allows hens to transport a (potentially) fertilized egg cell and later incubate the newly formed embryo.

Shape and morphology of chicken egg

This kind of egg has a shape that lies somewhere between spherical and pyriform or conical, and its structure is composed of the same main parts found in any bird egg: the shell (1), the membranes (2 and 3, visible when peeling a hard-boiled egg), the chalazae (4 and 13), the yolk (10 and 11, whose color can range from deep orange to almost colorless depending on the hen’s diet), and the albumen or egg white (5, 6, 12).

One important aspect to highlight is that the color of the shell is determined by the pigments deposited during egg formation and varies depending on the species and breed, typically ranging from brown to white. In general, chickens with white earlobes tend to lay white eggs, while those with red earlobes usually produce brown eggs.

Although shell color does not affect the nutritional value of the egg, there are often cultural preferences that influence consumer choices. Brown eggs, for instance, are less suitable for candling (the process of inspecting eggs using light), which makes blood spots more visible. As a result, they may be less acceptable to individuals who avoid the consumption of animal blood for religious reasons.

Lastly, attention should be given to the air cell (14), a small air pocket that forms at the blunt end of the egg after it is laid. This feature is particularly important in cooking, as it helps determine the freshness of the egg. Freshly laid eggs have a tiny air cell and are dense enough to sink when placed in a bowl of water. Over time, however, air enters through the pores of the shell, the air cell expands, and the egg becomes less dense, eventually floating. Therefore, an egg that sinks is very fresh, while one that floats is old and should be discarded.

The culinary history of chicken eggs

Chickens, likely domesticated for their egg-laying abilities, are descended from wild junglefowl native to Southeast Asia and India. They were first introduced to Mesopotamia and Egypt around 1500 BCE. Their arrival in Ancient Greece occurred roughly seven centuries later, where they became part of the local culinary tradition, eventually replacing quail eggs.

In Ancient Rome, chicken eggs, bread, olives, and wine made up the typical appetizer (gustatio) served at banquets. The phrase “ab ovo usque ad mala” (“from the egg to the apples“) was used to describe a complete meal, from start to finish.

During the Middle Ages, eggs were forbidden during Lent, both for their nutritional value and for practical reasons, such as giving hens time to rest and reducing feed consumption during periods of scarcity.

In 17th-century France, people began preparing eggs mixed with acidic fruit juices, a combination that may have inspired the creation of lemon curd. In the 19th century, the dried egg industry experienced rapid growth, peaking during World War II, primarily to supply military forces.

In 1911, Joseph Coyle invented the egg carton in Smithers, Canada, to solve the issue of eggs breaking during transport. In the following decades, polystyrene cartons became popular for offering better protection, but in the 21st century, growing environmental awareness has led to the return of paper-based, recycled, and biodegradable cartons, now widely used again.

Classification of bird eggs

Chicken eggs can be classified both by weight and by the breed of the hen that laid them. Regarding weight, the categories are:

• Small egg, S (weight less than 53 g)
• Medium egg, M (weight equal to or greater than 53 g and less than 63 g)
• Large egg, L (weight equal to or greater than 63 g and less than 73 g)
• Extra-large egg, XL (weight equal to or greater than 73 g)

Regarding the breeds of hens, eggs are divided into:

• Amrocks chicken egg
• Ancona chicken egg
• Australorp chicken egg
• Bernevelder chicken egg
• Dominicana chicken egg
• Hamburg chicken egg
• Lakenfelder chicken egg
• Legbar chicken egg
• Livornese chicken egg
• Marans chicken egg
• New Hampshire chicken egg
• Olive Egger chicken egg
• Padovana chicken egg
• Plymouth Rock chicken egg
• Polverara chicken egg
• Rhode Island chicken egg
• Sicilian chicken egg
• Spanish White-faced chicken egg
• Sussex chicken egg
• Valdarno chicken egg
• Vorwerk chicken egg
• Wyandotte chicken egg

Moreover, since in cooking the egg is not always used whole, it is useful to list its two edible components and dedicate separate pages to each:

• Egg white (Albumen)
• Egg yolk

Nutritional facts table

Nutrients	Per 100 g
Calories (kcal)	143
Total fat (g)	9.5
———Saturated fat (g)	3.1
Cholesterol (mg)	372
Sodium (mg)	142
Total carbohydrates (g)	0.7
———Dietary fiber (g)	0
———Total sugar (g)	0.4
Protein (g)	13