IDENTIFICATION AND CHARACTERISATION OF BEER POLYPEPTIDES DERIVED FROM BARLEY HORDEINS

Abstract

Two groups off hordein‐reactive antibodies (cross‐reactive in barley with B/C monomers or subunits from the B/D‐hordein aggregates) were used for the analysis of malt, wort and beer. A number of additional lower molecular weight hordein‐derived polypeptides were present in water extracts of malts and worts, and protease inhibitors or higher mash‐in temperature had a stabilising effect on certain hordein‐derived polypeptides. The solubilisation profiles of hordein polypeptides monitored by specific immunological methods were clearly different from total wort polypeptides monitored by the Bradford method. There were also differences between the profiles for the two groups of hordein‐derived polypeptides with the solubilisation of polypeptides recognised by antibody with specificity for the subunits from the B/D aggregates being especially temperature dependent. Beer samples mainly contained hordein‐derived polypeptides of lower molecular weight than barley hordeins with polypeptides in the B and C molecular weight regions being lost during the brewing process. Beer polypeptides (Mr > 50,000) were recognised by antibodies cross‐reactive with the subunits from the B/D aggregates in barley. A number of lower molecular weight polypeptides (Mr < 30,000) were recognised by antibodies with specificity for B and C hordeins; a subset of the latter antibody group bound to a specific Mr 23,000 beer polypeptide.