Eggshell membrane or shell membrane is the clear film lining

eggshell An eggshell is the outer covering of a hard-shelled egg (biology), egg and of some forms of eggs with soft outer coats. Worm eggs Nematode eggs present a two layered structure: an external vitellin layer made of chitin that confers mechanical ...

s, visible when one peels a boiled

bird egg Bird eggs are laid by the females and range in quantity from one (as in condors) to up to seventeen (the grey partridge). Avian clutch size, Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been ...

. Chicken eggshell membranes are used as a

dietary supplement A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill (pharmacy), pill, capsule (pharmacy), capsule, tablet (pharmacy), tablet, powder, or liquid. A supplement can provide nutrients eithe ...

. Eggshell membrane is derived commercially from the eggshells of industrial processors. In the United States, egg-breaking facilities generate more than 24 billion broken eggshells every year. There are various ways in which the membrane is separated from the shell, including chemical, mechanical, steam, and vacuum processes. Attachment of the soft organic fibrous membrane to the hard calcite shell is essential for proper chick embryonic development and growth (via ensuring association of the chorioallantoic membrane, and in allowing for air-sac formation at the blunt end of the egg). This attachment between dissimilar materials is facilitated by a structural interdigitation of fibers into each mammillae at the microscale, and reciprocally, at the nanoscale, mineral spiking into fibers directly at the interface

Composition

Eggshell membrane is primarily composed of fibrous

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s such as

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

type I. Eggshell membranes also contain

glycosaminoglycan Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case o ...

s, such as

dermatan sulfate Dermatan sulfate is a glycosaminoglycan (formerly called a mucopolysaccharide) found mostly in skin, but also in blood vessels, heart valves, tendons, and lungs. It is also referred to as chondroitin sulfate B, although it is no longer classifi ...

chondroitin sulfate Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars (N-Acetylgalactosamine, N-acetylgalactosamine and glucuronic acid). It is usually found attached to proteins as part of a proteoglycan. A chondroit ...

, and sulfated

glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...

s including

hexosamines Hexosamines are amino sugars created by adding an amine group to a hexose. Examples include: * Fructosamine (based upon fructose) * Galactosamine (based upon galactose) * Glucosamine (based upon glucose) * Mannosamine (based upon mannose) Ext ...

, such as

glucosamine Glucosamine (C6H13NO5) is an amino sugar and a prominent precursor in the biochemical synthesis of glycosylated proteins and lipids. Glucosamine is part of the structure of two polysaccharides, chitosan and chitin. Glucosamine is one of the mo ...

. Other components identified in eggshell membranes are

hyaluronic acid Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminog ...

sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" () was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this group is ''N''-acetylneuraminic acid ...

desmosine Desmosine is an amino acid found uniquely in elastin, a protein found in connective tissue such as skin, lungs, and Elastic artery, elastic arteries. Desmosine is a component of elastin and cross links with its isomer, isodesmosine, giving elast ...

, isodesmosine,

ovotransferrin Ovotransferrin (conalbumin) is a glycoprotein of Egg white, egg white albumen. Egg white albumen is composed of multiple proteins, of which ovotransferrin is the most heat reliable. It has a molecular weight of 76,000 Dalton (unit), daltons and ...

, lysyl oxidase,

lysozyme Lysozyme (, muramidase, ''N''-acetylmuramide glycanhydrolase; systematic name peptidoglycan ''N''-acetylmuramoylhydrolase) is an antimicrobial enzyme produced by animals that forms part of the innate immune system. It is a glycoside hydrolase ...

, and β-N-acetylglucosaminidase.

Uses

Shell membrane is mainly used as a dietary supplement in a partially

hydrolyzed Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysi ...

powder form.

References

{{Authority control Eggs (food) Dietary supplements