Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens, it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. [1] It forms around fertilized or unfertilized egg yolks. The primary natural purpose of egg white is to protect the yolk and provide additional nutrition for the growth of the embryo (when fertilized). Egg white consists primarily of about 90% water into which about 10% proteins (including albumins, mucoproteins, and globulins) are dissolved. Unlike the yolk, which is high in lipids (fats), egg white contains almost no fat, and carbohydrate content is less than 1%. Egg whites contain about 56% of the protein in the egg. Egg white has many uses in food (e.g. meringue, mousse) as well as many other uses (e.g. in the preparation of vaccines such as those for influenza [2] ).
Egg white makes up around two-thirds of a chicken egg by weight. Water constitutes about 90% of this, with protein, trace minerals, fatty material, vitamins, and glucose contributing the remainder. [3] A raw U.S. large egg contains around 33 grams of egg white with 3.6 grams of protein, 0.24 grams of carbohydrate and 55 milligrams of sodium. It contains no cholesterol and the energy content is about 17 calories. [3] Egg white is an alkaline solution and contains around 149 proteins. [4] [ full citation needed ] The table below lists the major proteins in egg whites by percentage and their natural functions. [3] [5] [ page needed ]
Protein | Abundance |
---|---|
Ovalbumin | 54% |
Ovotransferrin | 12% |
Ovomucoid | 11% |
Ovoglobulin G2 | 4% |
Ovoglobulin G3 | 4% |
Ovomucin | 3.5% |
Lysozyme | 3.4% |
Ovoinhibitor | 1.5% |
Ovoglycoprotein | 1% |
Flavoprotein | 0.8% |
Ovomacroglobulin | 0.5% |
Avidin | 0.05% |
Cystatin | 0.05% |
Ovalbumin is the most abundant protein in albumen. Classed as phosphoglycoprotein, during storage, it converts into s-ovalbumin (5% at the time of laying) and can reach up to 80% after six months of cold storage. Ovalbumin in solution is heat-resistant. Denaturation temperature is around 84 °C, but it can be easily denatured by physical stresses. Conalbumin/ovotransferrin is a glycoprotein which has the capacity to bind the bi- and trivalent metal cations into a complex and is more heat sensitive than ovalbumin. At its isoelectric pH (6.5), it can bind two cations and assume a red or yellow color. These metal complexes are more heat stable than the native state. Ovomucoid is the major allergen from egg white and is a heat-resistant glycoprotein found to be a trypsin inhibitor. Lysozyme is a holoprotein which can lyse the wall of certain Gram-positive bacteria and is found at high levels in the chalaziferous layer and the chalazae which anchor the yolk towards the middle of the egg. Ovomucin is a glycoprotein which may contribute to the gel-like structure of thick albumen. The amount of ovomucin in the thick albumen is four times as great as in the thin albumen.[ citation needed ]
The physical stress of beating egg whites can create a foam. Two types of physical stress are caused by beating them with a whisk: denaturation and coagulation.
Denaturation occurs as the whisk drags the liquid through itself, creating a force that unfolds the protein molecules.
Coagulation comes from the mixing of air into the whites, which causes the proteins to come out of their natural state. These denatured proteins gather together where the air and water meet and create multiple bonds with the other unraveled proteins, and thus become a foam, holding the incorporated air in place; because the proteins consist of amino acids, some are hydrophilic (attracted to water) and some are hydrophobic (repelled by water). [7] [3]
When beating egg whites, they are classified in three stages according to the peaks they form when the beater is lifted: soft, firm, and stiff peaks. Overbeaten eggs take on a dry appearance, and eventually collapse. Egg whites do not beat up correctly if they are exposed to any form of fat, such as cooking oils or the fats contained in egg yolk.
Copper bowls have been used in France since the 18th century to stabilize egg foams. The copper in the bowl assists in creating a tighter bond in reactive sulfur items such as egg whites. The bond created is so tight that the sulfurs are prevented from reacting with any other material. A silver-plated bowl has the same result as the copper bowl, as will a pinch of powdered copper supplement from a health store used in a glass bowl. Drawbacks of the copper bowl include the expense of the bowl itself, and that the bowls are difficult to keep clean. Copper contamination from the bowl is minimal, as a cup of foam contains a tenth of a human's normal daily intake level. [3] [8]
Although egg whites are prized as a source of low-fat, high-protein nutrition, a small number of people cannot eat them. Egg allergy is more common among infants than adults, and most children will outgrow it by the age of five. [9] Allergic reactions against egg white are more common than reactions against egg yolks. [10] In addition to true allergic reactions, some people experience a food intolerance to egg whites. [11] [10]
Eggs are susceptible to Salmonella contamination. Thorough cooking eliminates the direct threat (i.e. cooked egg whites that are solid and not runny), but the threat of cross-contamination remains if people handle contaminated eggs and then touch other foods or items in the kitchen, thus spreading the bacteria. In August 2010, the FDA ordered the recall of 380 million eggs because of possible Salmonella contamination. [12]
Cooked eggs are a good source of biotin. However, daily consumption of raw egg whites for several months may result in biotin deficiency, due to their avidin content, as the avidin tightly binds biotin and prevents its absorption. [13]
Egg white is a fining agent that can be used in the clarification and stabilization of wine. Egg white can also be added to shaken cocktails to create a delicate froth. Some protein powders also use egg whites as a primary source of protein.
The albumen from egg white was used as a binding agent in early photography during an 1855-90 period; such prints were called albumen prints.
In the 1750s, egg whites were believed to prevent swelling, and were used for that purpose. To help soothe areas of skin that were afflicted, egg white mixed with Armenian bole could help restore the fibers. Egg whites are also used in bookbinding during the gilding process, where it is referred to as 'glaire', and to give a book cover shine. [14]
Biotin (also known as vitamin B7 or vitamin H) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. The name biotin, borrowed from the German Biotin, derives from the Ancient Greek word βίοτος (bíotos; 'life') and the suffix "-in" (a suffix used in chemistry usually to indicate 'forming'). Biotin appears as a white, needle-like crystalline solid.
Mayonnaise, colloquially referred to as "mayo", is a thick, cold, and creamy sauce commonly used on sandwiches, hamburgers, composed salads, and French fries. It also forms the base for various other sauces, such as tartar sauce, fry sauce, remoulade, salsa golf, ranch dressing, and rouille.
Marshmallow is a confectionery made from sugar, water and gelatin whipped to a solid-but-soft consistency. It is used as a filling in baking or molded into shapes and coated with corn starch. This sugar confection is inspired by a medicinal confection made from Althaea officinalis, the marsh-mallow plant.
Meringue is a type of dessert or candy, of French origin, traditionally made from whipped egg whites and sugar, and occasionally an acidic ingredient such as lemon, vinegar, or cream of tartar. A binding agent such as salt, flour or gelatin may also be added to the eggs. The key to the formation of a good meringue is the formation of stiff peaks by denaturing the protein ovalbumin via mechanical shear.
Angel food cake, or angel cake, is a type of sponge cake made with egg whites, flour, and sugar. A whipping agent, such as cream of tartar, is commonly added. It differs from other cakes because it uses no butter. Its aerated texture comes from whipped egg white. Angel food cake originated in the United States and first became popular in the late 19th century. It gained its unique reputation along with its name due to its light and fluffy texture and white color.
Among animals which produce eggs, the yolk is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example because they are laid in situations where the food supply is sufficient or because the embryo develops in the parent's body, which supplies the food, usually through a placenta. Reproductive systems in which the mother's body supplies the embryo directly are said to be matrotrophic; those in which the embryo is supplied by yolk are said to be lecithotrophic. In many species, such as all birds, and most reptiles and insects, the yolk takes the form of a special storage organ constructed in the reproductive tract of the mother. In many other animals, especially very small species such as some fish and invertebrates, the yolk material is not in a special organ, but inside the egg cell.
Eggnog, historically also known as a milk punch or an egg milk punch when alcoholic beverages are added, is a rich, chilled, sweetened, dairy-based beverage. It is traditionally made with milk, cream, sugar, egg yolks, and whipped egg whites. A distilled spirit such as brandy, rum, whiskey or bourbon is often a key ingredient.
Balut is a fertilized developing egg embryo that is boiled or steamed and eaten from the shell. It is commonly sold as street food most notably in the Philippines, and Vietnam.
Salmonellosis is a symptomatic infection caused by bacteria of the Salmonella type. It is the most common disease to be known as food poisoning, these are defined as diseases, usually either infectious or toxic in nature, caused by agents that enter the body through the ingestion of food. In humans, the most common symptoms are diarrhea, fever, abdominal cramps, and vomiting. Symptoms typically occur between 12 hours and 36 hours after exposure, and last from two to seven days. Occasionally more significant disease can result in dehydration. The old, young, and others with a weakened immune system are more likely to develop severe disease. Specific types of Salmonella can result in typhoid fever or paratyphoid fever. Typhoid fever and paratyphoid fever are specific types of salmonellosis, known collectively as enteric fever, and are, respectively, caused by salmonella typhi and paratyphi bacteria, which are only found in humans. Most commonly, salmonellosis cases arise from salmonella bacteria from animals, and chicken is a major source for these infections.
Separating eggs is a process, generally used in cooking, in which the egg yolk is removed from the egg white. This allows one part of the egg to be used without the other part, or each part to be treated in different ways. Recipes for custard call for egg yolks, for example.
Avidin is a tetrameric biotin-binding protein produced in the oviducts of birds, reptiles and amphibians and deposited in the whites of their eggs. Dimeric members of the avidin family are also found in some bacteria. In chicken egg white, avidin makes up approximately 0.05% of total protein (approximately 1800 μg per egg). The tetrameric protein contains four identical subunits (homotetramer), each of which can bind to biotin (Vitamin B7, vitamin H) with a high degree of affinity and specificity. The dissociation constant of the avidin-biotin complex is measured to be KD ≈ 10−15 M, making it one of the strongest known non-covalent bonds.
Indigenous ice cream, also known as sxusem, is a Canadian whipped confection made from soapberries and other various fruits; it has been eaten as a traditional dessert by many First Nations peoples. It has been suggested that it was first produced in the Interior Salish territory of British Columbia which was located in the upper basins of the Columbia and Fraser rivers, and included tribes such as the Columbia, Lillooet, and Shuswap among others.
Boiled eggs are typically from a chicken, and are cooked with their shells unbroken, usually by immersion in boiling water. Hard-boiled or hard-cooked eggs are cooked so that the egg white and egg yolk both solidify, while soft-boiled eggs may leave the yolk, and sometimes the white, at least partially liquid and raw. Boiled eggs are a popular breakfast food around the world.
A poached egg is an egg that has been cooked outside the shell by poaching. This method of preparation can yield more delicately cooked eggs than higher temperature methods such as boiling. Poached eggs can be found in several dishes.
Egg allergy is an immune hypersensitivity to proteins found in chicken eggs, and possibly goose, duck, or turkey eggs. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus.
Low-temperature cooking is a cooking technique that uses temperatures in the range of about 60 to 90 °C for a prolonged time to cook food. Low-temperature cooking methods include sous vide cooking, slow cooking using a slow cooker, cooking in a normal oven which has a minimal setting of about 70 °C (158 °F), and using a combi steamer providing exact temperature control. The traditional cooking pit also cooks food at low temperature.
Humans and their hominid relatives have consumed eggs for millions of years. The most widely consumed eggs are those of fowl, especially chickens. People in Southeast Asia began harvesting chicken eggs for food by 1500 BCE. Eggs of other birds, such as ducks and ostriches, are eaten regularly but much less commonly than those of chickens. People may also eat the eggs of reptiles, amphibians, and fish. Fish eggs consumed as food are known as roe or caviar.
Vitellin is a protein found in the egg yolk. It is a phosphoprotein. Vitellin is a generic name for major of many yolk proteins.
Egg substitutes are food products which can be used to replace eggs in cooking and baking. Common reasons a cook may choose to use an egg substitute instead of egg(s) include having an egg allergy, adhering to a vegan diet or a vegetarian diet of a type that omits eggs, having concerns about the level of animal welfare or environmental burden associated with egg farming, or worries about potential Salmonella contamination when using raw eggs. There is a growing movement to address some of these concerns via third-party certifications, but because many labels in the industry remain confusing or intentionally misleading, some consumers distrust them and may use egg substitutes instead.
Aquafaba is the viscous water in which legume seeds such as chickpeas have been cooked. Its use in cuisine was the discovery of the French musician Joël Roessel.
Translation of "Blanc d'oeuf," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, vol. 2. Paris, 1752