Egg white: Difference between revisions
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==Denaturation== |
==Denaturation== |
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All proteins, including those in egg white, are made of long chains of [[amino acid]]s which are similar to beads on a string. In a raw egg, these chains are raveled up in a specifically arranged compact mass. Chemical bonds and interactions between the amino acids within each protein hold this mass in a specific shape and stop it from unraveling. As an egg cooks, the heat causes the bonds within the proteins to break, a process called [[Denaturation (biochemistry)|denaturation]].<ref>[[Elmhurst College]]</ref> As these proteins chains unfold and entangle with other proteins, new bonds form between these amino acids and the amino acids of neighboring proteins, causing the texture to change. At 62-65°C, the most heat sensitive protein in egg white, [[ovotransferrin]], constituting 12% of the egg white, starts its denaturation and the egg white starts setting. At 80°C, the main protein [[ovalbumin]] (54% of the egg white) |
All proteins, including those in egg white, are made of long chains of [[amino acid]]s which are similar to beads on a string. In a raw egg, these chains are raveled up in a specifically arranged compact mass. Chemical bonds and interactions between the amino acids within each protein hold this mass in a specific shape and stop it from unraveling. As an egg cooks, the heat causes the bonds within the proteins to break, a process called [[Denaturation (biochemistry)|denaturation]].<ref>[[Elmhurst College]]</ref> As these proteins chains unfold and entangle with other proteins, new bonds form between these amino acids and the amino acids of neighboring proteins, causing the texture to change. At 62-65°C, the most heat sensitive protein in egg white, [[ovotransferrin]], constituting 12% of the egg white, starts its denaturation and the egg white starts setting. At 80°C, the main protein [[ovalbumin]] (54% of the egg white) denatures. The denaturation and rearrangement at 80°C has caused the egg white to be firm.<ref> {{cite web|url=http://khymos.org/eggs.php |title=How to prepare the perfect boiled egg |accessdate=2008-11-04 |last=Lersch |first=Martin |work=khymos.org }}</ref> |
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==Egg white foam== |
==Egg white foam== |
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Revision as of 01:54, 20 August 2009
Egg white is the common name for the clear liquid (also called the albumen or the glair/glaire) contained within an egg. It is the cytoplasm of the egg, which until fertilization is a single cell (including the yolk). It consists mainly of about 15% proteins dissolved in water. Its primary natural purpose is to protect the egg yolk and provide additional nutrition for the growth of the embryo, as it is rich in proteins and also of high nutritional value. Unlike the egg yolk, it contains a negligible amount of fat. Egg whites have many culinary and non-culinary uses for humans.
Composition
The egg white is approximately two-thirds of the total egg's weight out of its shell with nearly 90% of that weight coming from water. The remaining weight of the egg white comes from protein, trace minerals, fatty material, vitamins, and glucose.[1] The U.S. large egg's white weighs 38 grams with 4.7 grams of protein, 0.3 grams of carbohydrate and 62 milligrams of sodium. The U.S. large egg white contains about 20 calories.[2] Egg white has no dietary cholesterol. Egg white contains approximately 40 different proteins.[3] Below is a list of the proteins found in egg whites by percentage along with their natural functions.[1][4]
- 54% Ovalbumin - Nourishment; blocks digestive enzymes
- 12% Ovotransferrin - Binds iron
- 11% Ovomucoid - Blocks digestive enzymes
- 4% Ovoglobulin G2
- 4% Ovoglobulin G3
- 3.5% Ovomucin
- 3.4% Lysozyme
- 1.5% Ovoinhibitor
- 1% Ovoglycoprotein
- 0.8% Flavoprotein
- 0.5% Ovomacroglobulin
- 0.5% Avidin
- 0.05% Cystatin
(Total listed 96.25%)
Uses
- It is often separated and used for cooking (for glairs, meringues, soufflés, and some omelettes), hence it derives its name: when egg white is beaten or cooked it turns white.
- In recipes calling for egg yolk, two egg whites can often be used to replace one egg yolk.
- It is sometimes used as a low-fat substitute for whole egg to stick breadcrumbs to meat or vegetables.
- In schools it is often used to teach pupils how to test for protein using Biuret reagent.
- It is used to remove sediments from champagne and beer and to clarify broths.
- It was used in the emulsion of traditional photographic paper.
- It was used in medieval medicine to treat wounds and broken bones.[5]
- They are recommended for consumption by chemotherapy and renal patients as a source of 90g of lean protein.[6][7]
- It is used by athletes and bodybuilders as a health food supplement, to aid in the building of muscle.[8]
- It can be used as a base for waterproof glues. [9]
- During egging vandalism the egg white can degrade house and car paint. After drying, it is extremely hard to remove.
- It is used to reduce crow's feet.
- Draftees who wished to avoid induction to the army would urinate over an egg white to skew their albumen count. This was especially popular during the Vietnam War.
Nutrition
| Nutritional value per 100 g (3.5 oz) | |||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Energy | 201 kJ (48 kcal) | ||||||||||||||||||||||||||||||||||
0.73 g | |||||||||||||||||||||||||||||||||||
0.17 g | |||||||||||||||||||||||||||||||||||
10.90 g | |||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||
| Other constituents | Quantity | ||||||||||||||||||||||||||||||||||
| Water | 87.57 g | ||||||||||||||||||||||||||||||||||
| Choline | 1.1 mg | ||||||||||||||||||||||||||||||||||
| Cholesterol | 0 mg | ||||||||||||||||||||||||||||||||||
One large egg contains 33 grams of white. | |||||||||||||||||||||||||||||||||||
| †Percentages estimated using US recommendations for adults,[10] except for potassium, which is estimated based on expert recommendation from the National Academies.[11] | |||||||||||||||||||||||||||||||||||
Biotin deficiency can be caused by excessive consumption of raw egg whites over a long period (months to years). Egg whites contain high levels of avidin, a protein that binds the vitamin biotin strongly.
Denaturation
All proteins, including those in egg white, are made of long chains of amino acids which are similar to beads on a string. In a raw egg, these chains are raveled up in a specifically arranged compact mass. Chemical bonds and interactions between the amino acids within each protein hold this mass in a specific shape and stop it from unraveling. As an egg cooks, the heat causes the bonds within the proteins to break, a process called denaturation.[12] As these proteins chains unfold and entangle with other proteins, new bonds form between these amino acids and the amino acids of neighboring proteins, causing the texture to change. At 62-65°C, the most heat sensitive protein in egg white, ovotransferrin, constituting 12% of the egg white, starts its denaturation and the egg white starts setting. At 80°C, the main protein ovalbumin (54% of the egg white) denatures. The denaturation and rearrangement at 80°C has caused the egg white to be firm.[13]
Egg white foam
Creating an egg foam
The physical stress of beating the egg white can create a foam. There are two types of physical stress caused by the beating of the egg whites with a whisk, the first being that the whisk drags the liquid through itself creating a force that unfolds the protein molecules. This process is called denaturation. The second stress 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 becomes a foam holding the incorporated air into place.[14]
Stabilizing egg white foam for culinary purposes
Copper Bowl
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 will have the same result as the copper bowl or a pinch of powdered copper supplement from a health store used in a glass bowl will yield the same result as well. Drawbacks of the copper bowl include the expense of the bowl itself, as well as the fact that the bowls are difficult to keep clean. Copper contamination from the bowl is minimal as a cup of foam will contain a tenth of one's daily normal intake level.[15]
Adding an acid
Cream of tartar (potassium bitartrate) is an acidic salt that can be used to change the pH of the egg white to an acidic range by boosting the number of free-floating hydrogen ions in the egg white. This has the effect of stabilizing the foam, and is therefore an alternative to using a copper bowl. 1/8 teaspoon/0.5g cream of tartar should be used per one egg white to create this effect. 1/2 teaspoon/2ml of lemon juice can also be used to create the same results. [16]
Health issues
Although egg whites are prized for 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.[17] Allergic reactions against egg white are more common than reactions against egg yolks.[18] In addition to true allergic reactions, some people experience a food intolerance to egg whites.[18]
See also
References
- ^ a b McGee, 77
- ^ McGee, 79
- ^ Exploratorium
- ^ Takehiko Yamamoto, Mujo Kim, Hen eggs
- ^ Gilbertus, 6
- ^ Fresh Egg Whites, Kosher Egg whites, Pure Protein Food - Eggology, Inc
- ^ "Transplant Chronicles" (pdf). National Kidney Foundation. Summer/Fall 2007. p. 11.
{{cite web}}: Check date values in:|date=(help) - ^ Eggology Official Website [1]
- ^ Glue of the Month, 2002 March [2]
- ^ United States Food and Drug Administration (2024). "Daily Value on the Nutrition and Supplement Facts Labels". FDA. Archived from the original on 2024-03-27. Retrieved 2024-03-28.
- ^ National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Food and Nutrition Board; Committee to Review the Dietary Reference Intakes for Sodium and Potassium (2019). "Chapter 4: Potassium: Dietary Reference Intakes for Adequacy". In Oria, Maria; Harrison, Meghan; Stallings, Virginia A. (eds.). Dietary Reference Intakes for Sodium and Potassium. The National Academies Collection: Reports funded by National Institutes of Health. Washington, DC: National Academies Press (US). pp. 120–121. doi:10.17226/25353. ISBN 978-0-309-48834-1. PMID 30844154. Retrieved 2024-12-05.
- ^ Elmhurst College
- ^ Lersch, Martin. "How to prepare the perfect boiled egg". khymos.org. Retrieved 2008-11-04.
- ^ McGee, 102
- ^ McGee, 102-103
- ^ McGee, 103
- ^ “Egg Allergy Facts” Asthma and Allergy Foundation of America
- ^ a b Arnaldo Cantani (2008). Pediatric Allergy, Asthma and Immunology. Berlin: Springer. pp. 710–713. ISBN 3-540-20768-6.
Works cited
- Elmhurst College, Denaturation Protein
- Exploratorium, Anatomy of an Egg
- Gilbertus. Compendium Medicine Gilberti Anglici Tam Morborum Universalium Quam Particularium Nondum Medicis Sed & Cyrurgicis Utilissimum. Lugduni: Impressum per Jacobum Sacconum, expensis Vincentii de Portonariis, 1510.
- Good Eats, Let Them Eat Foam. DVD. Television Food Network, June, 13 2001.
- McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner, 2004.
External links
- How to make albumen photographic paper
The dictionary definition of albumen at Wiktionary- The dictionary definition of glair at Wiktionary
Historically, glair (the white of the egg) was used as a varnish for egg tempra, oils and watercolor paintings.. When prepared by whisking it to a stiff froth and allowing it to settle for 24 hours. The liquid that would reside at the bottom of the bowl was glair.. Glair when added with an equal amount of water was used as a varnish to highlight paints. Upon drying it becomes waterproof...
When not diluted and left untouched for a couple of months, strain the glair, get used to the putrid odor, and the glair acts more of an adhesive then a varnish . Commonly called "La Putredo". It was used by the gilders as an adhesive in a variety of formulas for attaching Gold to manuscript illumination during the 14th and 15th century ... JERRY TRESSER (The Technique of Raised Gilding) Michelle Jordan publication 1992