Measurement of Beta-amylase in Malting Barley (Hordeum vulgare L.). II. The Effect of Germination and Kilning

Author： Evans D.E. Wallace W. Lance R.C.M. MacLeod L.C.

ISSN： 0733-5210

Source： Journal of Cereal Science, Vol.26, Iss.2, 1997-09, pp. : 241-250

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Abstract

The level of beta-amylase in germinating barley grain and the kilned malt has been examined by assaying for activity, quantitative ELISA and immunoblotting using antibodies specific to beta-amylase. During germination there is a substantial increase in combined beta-amylase activity; the sum of beta-amylase soluble in aqueous salt solutions and that extracted in the presence of beta-mercaptoethanol (ME). Although previous studies have attributed this increase to activation of beta-amylase, here we report that the increase in activity is matched by an increase in the level of combined beta-amylase protein as measured by ELISA. Most, if not all, of this additional active beta-amylase protein is made available by the release of beta-amylase from a newly described latent fraction between day 1 and 4 of germination. The latent fraction 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 occur in commercial malt houses. Kilning results in up to a 46% reduction in beta-amylase activity which is associated with a similar reduction in the level of beta-amylase protein measured by ELISA.