ARS | Publication request: ENDOPROTEINASES OF BARLEY AND MALT AND THEIR ENDOGENOUS INHIBITORS

Submitted to: Cereal Conference Royal Australian Chemical Institute Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 1995
Publication Date: N/A

Technical Abstract: The hydrolysis of barley proteins during malting is very important to obtaining a high quality malt, because the resulting low-molecular-weight nitrogenous compounds affect several aspects of brewing and beer quality. The goal of this research is to define the hydrolysis systems of barley and green malt (germinated barley) so that, eventually, it will be possible to develop improved malting barleys and/or to alter malting and mashing procedures to obtain improved beers. It was originally thought that only a few cysteine proteinases were involved, so we purified and studied two green malt cysteine endoproteinases that seemed to be intimately involved in storage protein hydrolysis. During this process, it became obvious that there were many endoproteinases in green malt, so we developed two two-dimensional (2-D) separation systems that allowed us to study these multiple proteinases without the necessity of individually purifying each of them. We found at least 50 endoproteinase activities in green malt, including representatives of each of the four proteinase classes. There are also compounds in barley and malt, termed endogenous inhibitors, that specifically inhibit the activities of certain green malt proteinases. By modifying the activities of the malt endoproteinases, these compounds can obviously affect malting quality. We have partially characterized the endogenous inhibitors from barley and malt and have purified and studied two of the barley inhibitors. We are now working to further define the protein hydrolyzing system by further studying the endoproteinases that appear to be most active in green malt endosperm tissue, the endogenous inhibitors present, and how these two biochemical groups interact.