Author
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Jones, Berne |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 5/29/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The endoproteinases that form during the malting of barley play important roles in determining the soluble protein levels of worts prepared from the malt. The soluble protein levels, in turn, can affect many aspects of the beers made from these worts, including their haziness, foam characteristics, extent of fermentation, etc. We have been characterizing these endoproteinases for several years and are now trying to determine which are important for solubilizing proteins during mashing and how endogenous barley and malt proteinase inhibitors affect this solubilization. Unmalted barley contains little endoproteolytic activity, most of which is due to aspartic class enzymes. Most of the endoproteinases form between days 1 and 3 of the 'germination' phase of malting. They are very resistant to destruction during kilning to 85C, but are readily inactivated during mashing at about 60C. Class-specific protease inhibitor studies with ASBC 'Congress' mashes indicate that most of the protein solubilization that occurs during mashing is due to cysteine proteinases, with lesser amounts being caused by aspartic- and metalloproteinases. The wort soluble protein levels are strongly affected by compounds that alter the activities of the endoproteinases; adding cysteine to mashes greatly enhances wort soluble protein levels while supplementing mashes with endogenous barley or malt endoproteinase inhibitors lowers them. |