DEFINITION: Avidin

"Avidin is a tetrameric biotin-binding protein produced in the oviducts of birds, reptiles and amphibians deposited in the whites of their eggs. In chicken egg white, avidin makes up approximately 0.05% of total protein (approximately 1.8 mg 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 avidin is measured to be KD ≈ 10−15 M, making it one of the strongest known non-covalent bonds.

"In its tetrameric form, avidin is estimated to be between 66–69 kDa in size. Ten percent of the molecular weight is attributed to carbohydrate content composed of four to five mannose and three N-acetylglucosamine residues. The carbohydrate moieties of avidin contain at least three unique oligosaccharide structural types that are similar in structure and composition.

"Functional avidin is found only in raw egg, as the biotin avidity of the protein is destroyed by cooking. The natural function of avidin in eggs is not known, although it has been postulated to be made in the ovaduct as a bacterial growth-inhibitor, by binding biotin the bacteria need. As evidence for this, streptavidin, a loosely related protein with equal biotin affinity and a very similar binding site, is made by certain strains of Streptomyces bacteria, and is thought to serve to inhibit the growth of competing bacteria, in the manner of an antibiotic.

"A non-glycosylated form of avidin has been isolated from commercially prepared product; however, it is not conclusive as to whether the non-glycosylated form occurs naturally or is a product of the manufacturing process."

http://en.wikipedia.org/wiki/Avidin

Avidin, which is found in raw egg whites, blocks the uptake of Vitamin B6 (Biotin) causing a vitamin deficiency. You must cook the egg white to neutralize the Avidin and allow your body to safely digest the protein and utilize all its Amino acids. Unfortunately, cooking also starts to destroy the protein.

http://www.eggwhitesint.com/healthfacts.htm

REVIEW: Liquid Egg Whites

Egg white substitutes are perfect for recipes that call for extra egg whites.

One product that I like is: Liquid Egg Whites from Egg Whites International.

Egg Whites International's Liquid Egg Whites is all natural 100% pure liquid egg whites - USDA and it is Kosher approved. Their pure liquid egg whites are pasteurized, salmonella tested, and avidin neutralized. Pure Liquid Egg Whites are the purest form of protein known to man in the entire world and are 100% bio-available, which means none of the valuable Amino acids are wasted.

Although great for cooking, because the Liquid Egg Whites are completely tasteless and odorless, you can use them in place of water or milk when mixing your protein powders. Eight ounces of Liquid Egg Whites supply 26 grams of pure protein that is 100% bio-available so you only need to use half the amount of protein powder that you would normally mix with water or milk... your protein powders will last twice as long - saving you money.

Liquid Egg Whites also store very well. Opened containers of Liquid Egg Whites can be frozen for long term storage.