Characterisation of barley-associated bacteria and their impact on wort separation performance

Wort separation is one of the rate-limiting steps in the brewhouse. It is a complex process, influenced by barley components such as proteins, β-glucans, residual starch and lipids. Filtration performance may also be influenced by microbial biofilms forming on the outer layers of the grains. This study aimed to identify the main barley-associated bacteria influencing wort separation efficiency. Next-generation sequencing was applied to characterise indigenous bacterial communities associated with Overture barley from different geographical locations as well as the bacterial population dynamics during laboratory-scale malting. In order to study the weakened filtration performance potentially caused by induced bacterial biofilm formation, a small portion of barley (5–12%) was subjected to mild husk damage prior to steeping. The bacterial communities were dominated by Gammaproteobacteria, accounting for >70% of the total bacterial population. Bacterial growth induction significantly decreased wort filtration performance. A content of ~12% of injured grains decreased the rate of wort separation by up to 25%, with over 10% lower extract yields. This study showed that bacteria associated with barley are one of the key factors influencing wort separation.