Hydrolysis of (1->4)-alpha-D-glucosidic linkages in polysaccharides so as to remove successive maltose units from the non-reducing ends of the chains. Optimum pH is 5. Highly active at acidic pH range 4-7. Retains over 80% of maximum activity at 4.0. At higher pH values the activity decreases markedly, with more than 50% of activity lost at pH 8.0. Causes an allergic reaction in human. Recombinant protein binds to IgE in 41% of the 17 European wheat food-allergic patients tested. Six of these patients have a history of wheat-induced anaphylaxis. Estimation by logistic regression indicates a 24-fold higher probability of the relative risk of beta-amylase-reactive patients to develop a wheat-induced anaphylaxis. Induces degranulation of the humanized rat basophilic leukemia (RBL) cells and releases hexosaminidase from them. Belongs to the glycosyl hydrolase 14 family.