A longitudinal study of fungal communities on wooden washbacks and in washback wood at a Scotch Malt whisky distillery

The use of wooden washbacks for the fermentation stage within Scotch Malt whisky production remains commonplace despite the move towards stainless steel vessels that are easier to maintain and clean. The reasons for this are not simply aesthetic but due to the inherent attributes of wood, such as heat-insulating capacity. Studies of wooden cider maturation vats have demonstrated that surfaces possess a unique, individual microbial profile, even with rigorous cleaning regimes in place. The composition of microorganisms inhabiting wooden washbacks is currently unknown, with studies of the microbial communities associated with Scotch whisky production so far focussed on microorganisms recovered during fermentation. In this study, swab samples were taken from the interior and exterior of washbacks, including one newly installed washback, at a Scotch malt whisky distillery during a silent period, and subsequently one year later during a period of active production. Samples were subject to culture-dependent and culture-independent analysis for comparison of the fungal communities present during a silent period vs. active production. A section of wood from a decommissioned washback was obtained from the distillery and subsequently stored for 6-months before culture-dependent analysis and scanning electron microscopy were applied to study fungal microorganisms at various depths up to 12mm. Analysis revealed a consistent microbiome on washback exteriors during active production, which shifts during the distillery silent season. Distillery-derived microorganisms were recovered from washback wood after removal from the distillery. Studying the fungal communities present on washbacks, and their presence in the wood over time provides key information on the organisms persisting in the distillery environment and potentially entering and influencing the whisky production process.