Impact of various levels of unmalted oats (Avena sativa L.) on the quality and processability of mashes, worts, and beers

The brewing industry is facing an ever increasing challenge to become more cost-effective, while at the same time maintaining or improving product quality. Brewing with unmalted oats (Avena sativa L.) has the potential to reduce the costs of raw materials. However, the replacement of malted barley with unmalted oats can also adversely affect the quality and processability of mashes, worts, and beers. In this study, brewing with unmalted oats (0-40%) and malted barley was carried out in a 60-L pilot plant. The impact of various levels of oats on mashing, lautering, and fermentation performance was monitored in detail and the quality of the final beers was evaluated using Lab-on-a-Chip capillary electrophoresis as well as standard methods specified by Mitteleuropäische Brautechnische Analysenkommission (MEBAK), European Brewery Convention (EBC), or the American Society of Brewing Chemists (ASBC). It has been found that the β-glucan content and viscosity of mashes and worts increased significantly with increasing amounts of oats. In addition, the use of 20% or more oat adjunct resulted in a clearly increased lautering time. The replacement of barley malt with unmalted oats also had adverse effects on total soluble nitrogen (TSN), free amino nitrogen (FAN), and extract levels in worts. The foam stability of the final beers decreased significantly using 20% oats or more. However, their sensory quality improved with increasing levels of oat adjunct.