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ARS Home » Midwest Area » Madison, Wisconsin » Cereal Crops Research » Research » Publications at this Location » Publication #77340


item Jones, Berne

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 12/2/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Malt is used to make beer. To make good beer, the malt needs to contain a specific, intermediate concentration of amino acids and small peptides. These compounds are formed in the malt by enzymes (proteinases) that degrade proteins. There are ways people can adjust their malting and brewing procedures to get either higher or lower amounts of these protein-hydrolyzing enzymes in their malt or beer. However, until now no one has known exactly when the enzymes form during the malting process or when they are destroyed during brewing. This work was carried out to determine when the enzymes form during malting and when they are destroyed during malting and brewing. Knowledge of these things would make it possible for the maltsters and brewers to vary their procedures to maximize the efficiency of their processes and to produce higher quality beers and malts. We found that the proteinases form during the latter stages of malting and that they are not destroyed during the last stage of malting, where high temperatures are used. This means that maltsters do not have to work to lower the temperatures of their procedures. During the early stages of brewing, however, the enzymes were quickly destroyed. This means that if the brewers need to have high amounts of amino acids to complete the brewing process, they need to carefully regulate the temperature during these early stages. This work will indicate to the maltsters and brewers how they can alter their methods to produce improved products and will show researchers how they can develope barleys that have improved malting and brewing quality. 

Technical Abstract: The proteinases of germinating barley hydrolyze storage proteins into amino acids that are used by the growing plant or, during brewing, by the yeasts. They are critical for malting and brewing because during these procedures some, but not all, of the barley storage proteins must be degraded to small peptides and amino acids. In order to produce improved malting barley varieties and to improve malting and brewing meythods, it is imperative that we know when the endoproteinases form in the germinating barley and when they are destroyed during either malting or mashing. This study was carried out to determine what endoproteinases are present in ungerminated barley, which form during malting, whether they are stable to the high temperatures of malt kilning, and when, during the mashing process, the proteinases are inactivated. Our results indicate that there are very few endoproteinases in ungerminated barley, and that most of those in green malt are synthesized during days 2 to 5 of the germination stage of malting. The endoproteinases that form during malting are almost all stable during kilning. Through the initial phases of mashing the endoproteinases are very stable, but as soon as the temperature of the mash is raised to 72C for conversion, they are quickly degraded. Only small amounts of proteolytic activity are present at the end of mashing. This information will help researchers develope barleys that have improved malting quality and will make it possible for maltsters and brewers to vary their processing methods to adjust the soluble protein levels of their products.