Egg white

Egg white is the clear liquid found inside an egg.

Scientists and chefs often call this liquid albumen, glair, or glaire. In chickens, this substance forms from secretions in the anterior section of the hen's oviduct. This process happens as the egg passes through the bird. The white forms around the yolk, regardless of whether that yolk is fertilized. Its primary natural purpose is to protect the yolk. It also provides essential nutrition for a growing embryo.

The composition of egg white is mostly water. About 90% of the weight is water. The remaining 10% consists of dissolved proteins, trace minerals, vitamins, and glucose. Egg white contains about 56% of the total protein found in an entire egg. Unlike the yolk, which is high in lipids, or fats, the white contains almost no fat. Carbohydrate content is also very low, at less than 1%. A large U.S. egg contains approximately 33 grams of egg white. This includes 3.6 grams of protein and 55 milligrams of sodium. It contains no cholesterol and provides about 17 calories.

There are roughly 149 different proteins within the egg white solution. Ovalbumin is the most abundant protein, making up 54% of the total protein content. During storage, ovalbumin can convert into s-ovalbumin. This can reach levels of 80% after six months of cold storage. Other important proteins include ovotransferrin, which is a glycoprotein at 12%. Ovomucoid is another major protein at 11%. It acts as a trypsin inhibitor and is a primary allergen. Lysozyme is a holoprotein found at high levels in the chalazae. These structures anchor the yolk in the middle of the egg.

Physical stress can change how these proteins behave through a process called denaturation. When you beat egg whites with a whisk, the force unfolds the protein molecules. This is known as denaturation. A second process called coagulation occurs when air is mixed into the whites. These denatured proteins gather where air and water meet. They create multiple bonds with other unraveled proteins to form a foam. This foam holds the incorporated air in place. When beating whites, they reach three distinct stages: soft, firm, and stiff peaks. Overbeaten eggs will eventually collapse and look dry.

Cooking and chemistry can also influence the stability of these foams. Egg whites will not beat correctly if they touch any fat. This includes cooking oils or fats from the egg yolk. Since the 18th century, some chefs in France have used copper bowls to stabilize foams. The copper assists in creating a tight bond with reactive sulfur items. This prevents the sulfur from reacting with other materials. Silver-plated bowls or a pinch of copper supplement can also work. However, copper bowls can be expensive and difficult to clean.

Egg whites have a long history of use in art and medicine. Between 1855 and 1890, albumen was used as a binding agent in early photography. These were known as albumen prints. In bookbinding, the term glaire is used when egg white acts as an adhesive for gold leaf. It also serves as a binder for pigments in manuscripts. In the 1750s, people believed egg whites could prevent swelling. They sometimes mixed egg white with Armenian bole to soothe skin. Today, egg white is also used in the preparation of vaccines, such as those for influenza.

While egg whites are a high-protein food, there are some health considerations. Allergic reactions to egg white are more common than reactions to yolks. These allergies are more frequent in infants than in adults. Most children typically outgrow the allergy by age five. There is also a risk of Salmonella contamination in eggs. Thorough cooking eliminates this direct threat by making the whites solid. However, cross-contamination can still occur in kitchens. Additionally, eating raw egg whites daily for months may cause a biotin deficiency. This happens because the protein avidin binds to biotin and prevents its absorption.