Ingredient Information

Function

The egg yolk is the yellow portion of the egg. It is held in the middle by the chalazae (kə-lā'zē), the thick white strands of the albumen. Composed of protein, fat, vitamins, and minerals, egg yolk is the most nutritious part of the egg and contains all of the known vitamins with the exception of vitamin C. In particular, the yolk is composed of 16% protein, 49% water and 32% fat. in addition, it thickens at 149°F and becomes firm at 158°F. However, yolk will need to stay at 158°F for a few minutes in order to coagulate properly without scrambling.

Egg yolk falls into many different functional categories. For instance, it is a coloring agent, a binder, a coagulant (thickens fluids to solids), a humectant (helps absorb moisture), and an an emulsifier (prevents separation of fluids). Yolk is also used for its nutritional properties and flavor.

Because the yolk is a very effective as an emulsifier, it is used in many salad dressings and sauces. As such, egg is one of the few natural substances that has the ability the bond with oil and water. Egg yolks with some of the water removed work well for emulsification because it concentrates the compounds used in this process, such as lecithin. It can also thicken and bind when heated due to the denaturing of the proteins (when the structure of a protein is caused to unfold, so that its original properties are diminished or eliminated). This makes egg yolk popular for use in meat and meat substitute patties and hot creamy sauces, such as carbonara and hollandaise.

Other Use and Industries

Aside from food uses, egg yolk is widely utilized in the field of medicine. For instance, many antibodies are extracted from egg yolk and used in pharmaceuticals. Moreover, choline and lecithin are extracted for use in Alzheimer patients for the positive effects on memory and the brain. Egg yolk has also been used for cosmetic purposes. To illustrate, it can made into a hair mask to help repair damaged hair and has also been used to make skin masks for people who have sensitive skin. There are many recipes for egg skin care that can be made at home.

Health Effects

Egg yolks are considered to be a healthy food choice. This is because they contain many macronutrients and micronutrients, especially B vitamins, iodine, and selenium. The egg yolk is the richest source of natural choline, which is important for cognitive function and brain development. Choline also plays a role in B vitamin absorption, including folic acid, which is especially important for women of childbearing age.

Cholesterol in an egg resides in the yolk so that it is one of the top sources of dietary cholesterol. People with heart disease or at high risk for heart problems may need to consume eggs minimally. Nonetheless, studies have shown that the benefits of consuming egg outweigh the risks.

Salmonella is a concern for egg. Although less than 1% of hens pass salmonella on through the egg, it is still a risk. Food poisoning can be avoided by cooking eggs completely, white and yolk. Other sources of salmonella on the egg come from dirty eggs that are mishandled and not properly cleaned after being laid. However, hen houses have been designed to keep eggs as clean as possible, and eggs are washed thoroughly before processing to eliminate any bacterial contamination.

Origins

Egg yolk is removed from the eggs after they are inspected and cleaned. The eggs are then broken, and the yolks are separated from the whites. At this point the egg yolk is frozen, refrigerated, or further processed into a powder. Egg yolk is used in food manufacturing because of its functionality. In fact, it is hard to replace egg yolk and retain all the functionality without replacing it with numerous ingredients.