Rapid Beer Fermentation: The Effect of Vacuum Pressure on a Pilot Scale Lager Fermentation

Changes to industrial fermentation processes are rare, largely due to the impact on viability for Saccharomyces spp., related to environmental stresses during the process such as: osmotic pressure, ethanol concentration, dissolved CO2. This research studied yeast behavior during a High Gravity (HG) fermentation under partial vacuum pressure during standard brewing operations. This was accomplished by controlling the temperature and pressure of 30 L pilot fermentations. An experimental lager wort recipe with "Diamond" lager yeast (Saccharomyces pastorianus) was used in this study. The modified process conducted at 24.1 kPa of pressure in the headspace was compared to a control process at standard atmospheric pressure (101.3 kPa). This research showed that at 15 degrees C, lager fermentations (14-15 degrees P) fermented up to 30% faster under vacuum, with an increase in the number of yeast cells in suspension of up to 100%. The rate of sugar consumption under vacuum was greater compared to the control, thus increasing the rate of ethanol production. The removal of volatile CO2 is one hypothesized mechanism for these results. The total ethanol production, pH and yeast viability did not differ significantly between the control and modified process. The application of vacuum during brewing resulted in an increased fermentation rate and number of yeast cells in suspension during fermentation.