Utilisation of Defined Media towards Evaluating Brewing Ale Yeast Fermentation in Small Scale Batches

The utilisation of high gravity wort possessing a higher sugar content is frequently used to increase the capacity and efficiency of beer production. In such an environment, osmotic stress, lower nutrient availability, ethanol toxicity and elevated CO2 concentrations may decrease the sustainability of yeast performance and have a negative impact on the desired end product. Traditionally, apparent attenuation has been used as a standard measure of fermentability. Here, we describe a miniature fermentation assay with a defined fermentation media that could be used to assess fermentability on a small scale, including determination of the original gravity and final gravity of the medium for trials using four yeast strains. The results obtained using the defined media were approximately comparable to those obtained using regular wort in terms of their real attenuation limits and specific gravity, although the defined media demonstrated lower final pH values compared to the wort for several strains. With further optimisation, the mini fermentation process applied to a defined medium could provide the foundation for future analytical research into the brewing process, using techniques such as high-performance liquid chromatography (HPLC) and quantitative polymerase chain reaction (qPCR).