Author
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Jones, Berne |
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Budde, Allen |
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Submitted to: Barley Newsletter
Publication Type: Abstract Only Publication Acceptance Date: 7/10/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: For years, there has been controversy about how and when protein degradation occurs during malting and the mashing step of brewing. We have studied these questions by adding class-specific and endogenous protease inhibitors to Morex and Harrington malt mashes. Addition of individual chemical inhibitors showed that the majority of the protein solubilization during mashing was due to cysteine endoproteinases, but that the aspartic and metalloproteinases also contributed. By adding mixtures of the class-specific inhibitors to mashes and mashing ungerminated barley, we showed that about a third of the final 'soluble protein' of worts was preformed in the barley that was malted, 43% was solubilized during malting and the remaining quarter was released during mashing. By adding preparations of endogenous endoproteinase inhibitors that were extracted from either barley or malt, we were able to significantly lower the wort soluble protein levels and, conversely, these levels could be strongly increased by the addition of cysteine to mashes. Industry has indicated that it would prefer to have lower soluble protein levels in commercial worts. From this work, it appears that this could be achieved by: a, lowering the levels of cysteine proteinases that are present in newly developed barley cvs; b, increasing the amounts of active endogenous inhibitors that are in the mashes; or c, lowering the level of reducing agents in the mashes. Alternatively, the soluble protein levels of worts could be strongly increased by the addition of cysteine or (probably) other reducing agents to the worts. |
