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Extraction of protein-derived thiols by protease treatment during mashing for improvement of flavor stability in beer has previously been shown to cause concomitant increase in free amino acid concentrations and thereby increased levels of unwanted Maillard reaction products during aging. The previous methodology, with addition of protease dosed at 50 mg of enzyme/kg of malt at the beginning of the protein rest during mashing, resulted in increased amino acid concentrations of approximately 40% and increased free thiol concentrations of approximately 50% in wort compared with a control without protease addition. The objective of this study was to reduce the amount of amino acids in wort obtained by protease treatment but still obtain a significant increase in protein-derived thiols. In this paper we demonstrate that by omitting the protein rest during mashing in combination with addition of a protease with a higher temperature optimum dosed at only 3 mg of enzyme/kg of malt, it is possible to increase thiol concentrations in wort by 30% and with only a maximum 10% increase in amino acid concentration compared with a control. Pilot brewing showed that beer brewed with addition of protease resulted in a 30% increase in total thiol concentration, along with a decrease in or no effect on the concentration of some amino acids but also an increase in the concentration of other amino acids. Sulfite concentration was increased by 37%, so the effect of increasing free thiol concentration on flavor stability during storage could not be evaluated. Overall, similar brewing and sensory characteristics were obtained compared with a control beer brewed without addition of protease. Foam stability was decreased by protease treatment, and formation of haze was reduced by protease treatment. Keywords: Proteases, Mashing, Protein thiols, Protein composition, Antioxidants, Amino acids
