Hordein is a glycoprotein

Glycoprotein

Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...

, present in barley

Barley

Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...

 and some other cereal

Cereal

Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...

s, together with gliadin

Gliadin

Gliadin is a glycoprotein present in wheat and several other cereals within the grass genus Triticum. Gliadins are prolamins and are separated on the basis of electrophoretic mobility and isoelectric focusing.- Types :...

 and other glycoproteins as gluten

Gluten

Gluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...

.

Some people are sensitive to hordein due to disorders such as celiac disease or gluten intolerance.

Along with gliadin (the gluten found in wheat), hordein is present in many foods and also may be found in beer. Hordein is usually the main problem for coeliacs wishing to drink beer.

Coeliacs are able to find specialist breads that are low in hordein, gliadin and other problematic glycoproteins, just as they can find gluten free beer

Gluten free beer

Gluten-free beer is beer made from ingredients that do not contain glycoproteins . People who have gluten intolerance have a reaction to certain proteins in the grains commonly used to make beer, barley and wheat...

which either uses ingredients that do not contain gluten, or otherwise has the amounts of gliadin or hordein present controlled to stated limits.