Chicken egg yolk

Foods, Animal source foods, Eggs, Bird eggs, Chicken egg

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

Consumption area(s): This product is consumed in the same countries where chicken eggs are eaten, and for more specific details about its distribution, please refer to the corresponding page.

Introduction

The chicken egg yolk is the inner part of the chicken egg, whose main function is to provide the nutrients needed for the embryo’s development. In bird species, it usually appears as a bright yellow sphere and is kept suspended in the center of the egg white thanks to two spiral-shaped filaments called chalaze.

Description of chicken egg yolk

The yolk, along with the actual ovum (which, if fertilized, becomes the embryo), is enclosed in a vitelline membrane, whose structure is quite different from that of a typical cell membrane. Contrary to common belief, the yolk is not part of the egg cell’s cytoplasm, but is located outside the oolemma—unlike what happens, for example, in frog eggs. Because of this, it is inaccurate to describe the yolk and the ovum as a single giant cell.

From a nutritional perspective, the yolk of a chicken egg is a rich source of micronutrients, including vitamins and minerals. It also contains all the lipids and cholesterol found in the egg and contributes a significant portion of its protein content.

Sometimes, eggs with a double yolk can be found. These form when ovulation is accelerated or when two yolks fuse together. Eggs with multiple yolks are usually unsuitable for hatching, since the simultaneous development of more than one embryo prevents the process from being completed. Though extremely rare, there are documented cases of eggs containing three yolks.

There are also eggs that are completely yolk-free, known as “dwarf eggs” or “wind eggs,” once referred to as “cock eggs.” These unusual eggs often result from a young hen’s early laying attempts. However, even adult hens may produce such eggs if a piece of internal tissue detaches and triggers egg formation, creating a fully shelled egg with no nutritional content. Since these eggs lack reproductive material, folk tradition wrongly attributed their origin to cocks.

Finally, the color of the yolk is heavily influenced by the animal’s diet: higher amounts of carotenoids or xanthophylls in the feed result in a deeper hue. However, a vivid color doesn’t necessarily indicate higher nutritional value, as some pigments don’t offer any real benefit to the human body. The range of yolk colors is surprisingly broad—from almost colorless to vivid orange, red, or even olive green, depending on the ingested compounds. A diet enriched with foods like peppers can intensify these shades, producing eggs with strikingly colored yolks.

Nutritional facts table

Please note that nutritional values may vary slightly depending on the individual egg.

Nutrients	Per 100 g
Calories (kcal)	325
Total fat (g)	29.1
———Saturated fat (g)	9.82
Cholesterol (mg)	1337
Sodium (mg)	43
Total carbohydrates (g)	0
———Dietary fiber (g)	0
———Total sugar (g)	0
Protein (g)	15.8

Recipes that use this product as an ingredient:

Carbonara (Pasta alla Carbonara)