Effect of unmalted oats (Avena sativa L.) on the quality of high-gravity mashes and worts without or with exogenous enzyme addition

Abstract

Barley malt is the preferred brewing material these days because of its high extract content and high enzyme activities. However, when substituting malted barley with oats to create a unique beer flavor and aroma, endogenous malt enzymes become the limiting factor. Therefore, the objectives of this study were to evaluate the effect of 10–40 % unmalted oats on the quality of high-gravity mashes/worts and to investigate the limitations of endogenous malt enzymes as well as the benefits of the application of industrial enzymes. The enzyme mix Ondea® Pro was found to be particularly suitable for mashing with unmalted oats and was therefore used in the present rheological tests and laboratory-scale mashing trials. In order to gain detailed information about the biochemical processes occurring during mashing, the quality of mashes was comprehensively analyzed after each mash rest using standard methods described by Mitteleuropaische Brautechnische Analysenkommission and Lab-on-a-Chip capillary electrophoresis. Mashing with up to 40 % oats resulted in increased mash consistencies, color/pH (20 °C) values, β-glucan concentrations, wort viscosities 12.0 %, and filtration times as well as decreased FAN and extract contents. The application of Ondea® Pro enormously increased the color of worts despite lower pH values but considerably improved the quality and processability of 30 or 40 % oat-containing mashes/worts. However, the substitution of up to 20 % barley malt with unmalted oats can easily be realized without the addition of exogenous enzymes.