BETA-AMYLASE ACTIVITY IN COMMERCIAL GLUTEN

The nature of beta-amylase activity in commercial wheat gluten was exa mined. Forty-nine samples of vital wheat gluten from five countries we re tested and found to contain large amounts of both 'free' (water sol uble) and 'bound' (extracted with reducing agents, papain or concentra ted saline) beta-amylase, although the distinction between these two c ategories proved somewhat arbitrary. beta-Amylase was not active at ex tremes of pH (<3 or >9) but activity was restored on neutralisation. P otassium cyanide reversibly inhibited both 'free' and 'bound' enzyme. 2',3'-Epoxypropyl alpha-D-glucopyranoside irreversibly inhibited the e nzyme, but competing solvolysis made this method impractical for large -scale work. Significant variation was found between the levels of bet a-amylase activity in commercial gluten samples (the means of beta-amy lase activity for individual countries ranged from 1.88 to 3.12 U mg(- 1) gluten) but this variation was not correlated with bread-baking qua lity. beta-Amylase activity of gluten declined with storage, especiall y after 2 years, but bread-baking quality was not affected. The declin e in beta-amylase activity of experimentally heat-treated gluten was r elated to the decline of bread-baking quality. Exceptionally low beta- amylase activity could be used as a 'marker' for gluten that has been heat damaged during the drying process.