MEASUREMENT OF BETA-AMYLASE IN MALTING BARLEY (HORDEUM-VULGARE L.) .2. THE EFFECT OF GERMINATION AND KILNING

The level of beta-amylase in germinating barley grain and the kilned m alt has been examined by assaying for activity, quantitative ELISA and immunoblotting using antibodies specific to beta-amylase. During germ ination there is a substantial increase in combined beta-amylase activ ity; the sum of beta-amylase soluble in aqueous salt solutions and tha t extracted in the presence of beta-mercaptoethanol (ME). Although pre vious studies have attributed this increase to activation of beta-amyl ase, here we report that the increase in activity is matched by an inc rease in the level of combined beta-amylase protein as measured by ELI SA. Most, if not all, of this additional active beta-amylase protein i s made available by the release of beta-amylase from a newly described latent fraction between day 1 and 4 of germination. The latent fracti on is extractable with a solution of 1% sodium dodecyl sulphate and 1% ME. Assessment of barley grain and malt from commercial maltsters has confirmed that similar increases in combined beta-amylase activity oc cur in commercial malt houses. kilning results in up to a 46% reductio n in beta-amylase activity which is associated with a similar reductio n in the level of beta-amylase protein measured by ELISA. (C) 1997 Aca demic Press Limited.