β-Amylase, a thiol-containing exo-enzyme, attacks the starch molecule from the nonreducing end and liberates disaccharide β-maltose units. Maltose, a reducing disaccharide, is the main fermentable sugar of wort. At least four β-amylase components with similar antigenic properties have been identified in barley using gel chromatography. In contrast to α-
amylase, β-amylase is synthesized in the starch endosperm during the development of the barley grain. As the barley grain ripens, β-amylase becomes ineffective because it is bound to protein. During the course of germination, however, the bound enzyme is apparently released by endospermal proteinases resulting in an increase in the free and active forms of β-amylase