Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/9/1996
Publication Date: N/A
Technical Abstract: The proteinases of germinating barley are important, because they hydrolyze storage proteins into amino acids that can be used by the growing plant. They are also critical to the malting and brewing processes. We are studying the synthesis and degradation, during malting and brewing, of the rate limiting endoproteinases and area characterizing them. This research will lead to more efficient ways to develop barley lines having improved malting quality. We have purified and characterized two cysteine class endoproteinases from green malt (4-day germinated barley). These enzymes both hydrolyze extracted hordein preparations. They also have hydrolytic specificities that are optimal for quickly hydrolyzing the repetitive amino acid portions of hordein molecules. We have also developed two-dimensional (2-D) separation methods that allow us to rapidly and reliably analyze the endoproteinases in malting and brewing fractions. These methods indicate that there are at least 45 endoproteolytic activities in green malt. Most of these activities form between germination days 2 and 5 of the malting process. Representatives of all four of the proteinase classes; cysteine-, serine-, aspartic- and metalloproteinases, are present. Analysis of green malt fractions removed during the various phases of malt kilning indicate that, contrary to some previous speculation, there is little loss of endoproteolytic activity during kilning. During mashing, using a double mashing process and conditions similar to those used in most US breweries, the endoproteinases are stable during the protein rest, but are rapidly destroyed during starch conversion at 72 C.