Effect of Reducing and Oxidizing Agents and pH on Malt Endoproteolytic Activities and Brewing Mashes

The activities of the four endoproteinase classes of malted barley are known to vary with pH, and it seemed likely that the cysteine enzyme activities could be altered by redox agents. This study determined how altering the pH and adding redox agents to mashes influenced the worts that were produced...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2003-12, Vol.51 (25), p.7504-7512
Main Authors: Jones, Berne L, Budde, A. D
Format: Article
Language:English
Subjects:
Beers
Biological and medical sciences
Cysteine - pharmacology
Diamide - pharmacology
Dithiothreitol - pharmacology
Edible Grain - enzymology
Endopeptidases - metabolism
Fermented food industries
Food Handling
Food industries
Fundamental and applied biological sciences. Psychology
Hordeum - enzymology
Hot Temperature
Hydrogen Peroxide - pharmacology
Hydrogen-Ion Concentration
Hydrolysis
Mercaptoethanol - pharmacology
Oxidants - pharmacology
Protease Inhibitors - pharmacology
Reducing Agents - pharmacology
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Summary:The activities of the four endoproteinase classes of malted barley are known to vary with pH, and it seemed likely that the cysteine enzyme activities could be altered by redox agents. This study determined how altering the pH and adding redox agents to mashes influenced the worts that were produced during the brewing process. The reducing agents cysteine·HCl, dithiothreitol, and β-mercaptoethanol increased the proteolysis that occurred in malt extracts and mashes. This increased proteolysis was negated by the addition of the oxidizing agents diamide or hydrogen peroxide. The addition of reducing agents to mashes increased the soluble protein, free amino nitrogen (FAN), and extract values of their resultant worts, and this effect was abolished by the concomitant addition of oxidizing agents. Raising the pH values of the mashes strongly reduced their proteolytic activities, soluble protein, FAN, and extract values, but not their β-glucan levels. These results show that several of the major aspects of malting and brewing quality can be adjusted by varying the pH and redox qualitites of mashes, which could be helpful to brewers. These results also strengthen the previous proposal made by Buchanan et al. that the redox status of plants may play a significant part in controlling their physiology. Keywords: Hordeum vulgare; barley; proteinases; soluble protein; cysteine; oxidizing agents; reducing agents; diamide
ISSN:0021-8561
1520-5118
DOI:10.1021/jf030206u