Table of Contents
Development of a tractable model system to study microbial community succession during wood-ageing of beer on a lab scale
Bossaert, S., Kocijan, T., Winne, V., Van Opstaele, F., Schlich, J., Herrera-Malaver, B., Verstrepen, K. J., De Rouck, G., Lievens, B., Crauwels, S.
Wood-ageing of conventionally fermented beers is gaining increased attention in the production of sour beers with a noteworthy balance between sourness, wood aroma and flavour complexity due to the extraction of wood-derived compounds and the activity of many ‘wild’ microorganisms. However, up until now wood-ageing of craft beers remains an unpredictable process that often generates unexpected or undesirable results. In order to improve the consistency, predictability and overall quality of the resulting beer, more insight is needed into the microbial interactions between the wood and the microorganisms in the maturing beer. Therefore, the objective of this study was to develop a reproducible and easy-to-manipulate experimentally tractable system that can be used to study wood-ageing of beer on a lab scale. An in-vitro system was developed to mimic barrel-ageing in a 0.5 liter glass jar filled with beer and closed off by a wooden disk. Furthermore, the system was inoculated with a synthetic microbial community composed of four bacterial species (Acetobacter malorum, Gluconobacter oxydans, Lactobacillus brevis and Pediococcus damnosus) and four fungal species (Brettanomyces bruxellensis, Candida friedrichii, Pichia membranifaciens and Saccharomyces cerevisiae) that represent key microbes previously identified in wood-ageing experiments with 225-liter barrels. The in-vitro system was subjected to 60 days of ageing and microbial community dynamics and beer chemistry were compared with a 38-week industrial barrel-ageing experiment using the same beer. Results of qPCR assays targeting eight selected species and chemical analyses performed on regular time points revealed that in-vitro ageing showed resembling trends as those observed during barrel-ageing on an industrial scale. Altogether, the in-vitro system was found to be a robust and reproducible system that has great potential to perform more in-depth research about the intricate interactions between microbes, wood and maturing beer and to develop control strategies to improve the consistency, predictability and overall quality of the resulting beer.
Descriptors: in-vitro system, wood-ageing, microbial community, bacteria, yeast
BrewingScience, 76 (May/June 2023), pp. 73-91
