Extraction, Separation, and Purification of Wheat Gluten Proteins and Related Proteins of Barley, Rye, and Oats

The wheat proteins, which are active in celiac disease and other glutenrelated conditions, are defined as prolamins, in that they are soluble as individual subunits in alcohol-water mixtures, such as 50% (v/v) aqueous propan-1-ol or 60–70% (v/v) aqueous ethanol. However, in wheat grain and flour, about half of these subunits are present in polymers that are not soluble in alcohol-water mixtures unless disulfide bonds between the component subunits are reduced using an agent such as 2-mercaptoethanol (2-ME) or dithiothreitol (DTT). These alcohol-insoluble polymers are traditionally called glutenins and the related alcohol-soluble monomers are called gliadins; the two groups of proteins together form the major part of the gluten fraction. Gluten can be readily prepared from wheat by washing dough to remove the bulk of the starch, cell-wall material, and soluble components. It is a cohesive viscoelastic mass that contains, in addition to the gluten proteins, small amounts of other proteins, residual starch (about 25% dry wt), and lipid.