MEASUREMENT OF BETA-AMYLASE IN MALTING BARLEY (HORDEUM-VULGARE L.) .1. DEVELOPMENT OF A QUANTITATIVE ELISA FOR BETA-AMYLASE

A double antibody, sandwich enzyme-linked immunosorbent assay (ELISA) was developed using polyclonal antibodies specific to beta-amylase to estimate the amount of 'free' (soluble in aqueous saline solution) or 'combined' (extracted with saline solution including reducing agent) b eta-amylase protein hi barley grain and malt. This ELISA was used to q uantify the amount of beta-amylase in barley grain and malt from four varieties grown at nine sites in South Australia in 1993. The antibody used to develop the ELISA reacted differently with beta-amylase depen ding on whether the source was barley grain or malt, and on the beta-a mylase band pattern in isoelectric focussing (IEF) of the barley varie ty. On the basis of their IEF band patterns barley varieties were divi ded into two types, designated Bmy1-Sd1 and Bmy1-Sd2. Malting resulted in proteolytic cleavage of the beta-amylase peptide with a reduction in the apparent molecular weight of up to M-r 4000 and the appearance of new malt beta-amylase IEF bands that were more basic. The new malt beta-amylase IEF band patterns still allowed the identification of the Bmy1-Sd1 and Bmy1-Sd2 IEF types despite the change in molecular weigh t and pI. The data obtained using the beta-amylase ELISA were highly c orrelated with beta-amylase activity for both the free and combined fr actions when the IEF band pattern and its source, barley grain or malt , were taken into account. (C) 1997 Academic Press Limited.