A. R. BHAT (1), R. Smith (2), C. Giblin (2), J. P. Carvell (1);
(1) Aber Instruments Ltd., Aberystwyth, U.K.; (2) Meantime Brewing Company, London, U.K.
Technical Session 2 - Industrial Yeast Management
Sunday, June 14
Market expansion and continuous process innovation spells the need for more sophisticated yeast management systems in craft breweries. Managing yeast is of utmost importance, since consistent fermentation performance and beer quality are heavily influenced by the accuracy of pitching the exact amount of live yeast into a fermenter. Precise regulation of pitching is the key to ensuring consistent performance in terms of fermentation cycle times, extent of yeast growth, the related efficiency of extract conversion, and the formation of yeast-derived beer flavor components. Larger commercial brewers tend to set very tight tolerances on yeast pitching rates and these need to be within ±10% of the target rate. Although most of the bigger breweries have created customized yeast dosing systems using online dielectric spectroscopy to automate their pitching, this is not always possible in the case of expanding craft breweries. There is a strong need for an affordable portable yeast dosing skid that can be connected to different yeast storage vessels/fermenters in a craft brewery, has an integrated local PLC and flow meter in its design, and can perform cone-to-cone pitching as well. In this paper, we report the performance, functioning, and benefits of a new yeast pitching skid incorporating online dielectric spectroscopy, at the Meantime Brewing Company, London, U.K. Working with different recipes, the skid was first used successfully to accurately pitch different concentrations of yeast in a fermenter, depending on the brand of beer being used. Accuracy of pitching using mass and the skid was compared. Interestingly, when mass was used to pitch yeast into the fermenter, the viable yeast concentration was overestimated, hence pitching fewer liters of yeast than necessary. This led to slower fermentations and inadequate fermentation performance. In contrast, the automatic skid estimated the right amount of live yeast, thus pitching the appropriate viable liters of yeast essential for an improved fermentation performance. The average difference in the number of liters pitched for four different brews was about 100 L or 1 hL. In addition, the °Plato (expressed as the average of four brews) was seen to decrease quicker when yeast was pitched using the skid, as compared to when it was pitched using mass. This could be due to the fact that adequate numbers of live yeast cells were pitched at the beginning of fermentation using the skid to convert the sugars in the wort into alcohol more efficiently. Improvement in fermentation performance leads to time, energy, and cost savings. Overall, the yeast pitching module helped to obtain a more uniform fermentation profile, thus making planning easier. Significant improvement in batch-to-batch consistency was also observed after its adoption.
ya Bhat received his Ph.D. and M.S. degrees in biotechnology and microbiology from reputed universities in the United Kingdom. Having performed his M.S. dissertation project on the Aber Biomass Monitor, he is presently working as a product applications manager for Aber Instruments Ltd, Aberystwyth, U.K. With rich academic and industrial experience behind him, he takes special interest in measurement of cell concentration in various brewing and biopharmaceutical processes.