Shell membrane

Eggshell membrane or shell membrane is the clear film lining the eggshell, visible when one peels a boiled egg. Chicken eggshell membrane is used as a dietary supplement, having the objective of reducing or treating osteoarthritis or other stiffness and pain of the joints.

Eggshell membrane is primarily composed of fibrous proteins such as collagen type I. However, eggshell membranes have also been shown to contain glycosaminoglycans, such as dermatan sulfate and chondroitin sulfate and sulfated glycoproteins including hexosamines, such as glucosamine. Other components identified in eggshell membranes are hyaluronic acid, sialic acid, desmosine and isodesmosine, ovotransferrin, lysyl oxidase, lysozyme, and β-N-acetylglucosaminidase.

Eggshell membrane is commercially derived from the eggshells of industrial egg processors. In the United States, egg-breaking facilities generate more than 24 billion eggshells every year. There are various ways in which the membrane of an eggshell is separated from the shell, including chemical, mechanical, steam and vacuum processes: see Eggshell and protein membrane separation. The isolated membrane is then partially hydrolyzed and dried to produce a powder, distributed as eggshell membrane (EM).

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