(523c) Research into the fermentation process at the University of Florida

Fermented beverages have been around for thousands of years and have been utilized by nearly every culture. These products have become one of the latest food trends, including novel products and opportunities for innovation. This presentation will detail some of the projects currently underway at the University of Florida, as well as opportunities and challenges for the industry. One such project is the application of vacuum during industrial fermentations. Changes to industrial brewing fermentation processes are generally rare, largely due to the impact on the viability of organisms involved. This is related to environmental stresses during the process such as: osmotic pressure, ethanol concentration, dissolved CO₂, etc. Fermentation under vacuum has been shown to dramatically increase the rate of the fermentation, possibly by removing inhibitor compounds such as CO₂. This study explored the applications of this finding in brewing, high density brewing and distillation industries. Specifically, the effect of vacuum pressure control on ethanol production rates, volatile loss (including ethanol) and flavor development for standard and high gravity brewing operations were examined. This was accomplished by controlling the temperature and pressure in pilot fermentations ranging from 4-40L. “Diamond” Lager and “Belle Saison” Ale yeasts, provided by Lallemand were used for High Gravity (HG) and Very High Gravity (VHG) fermentations respectively. The modified process (3.5psia) was compared to a control process at standard pressure (14.7psia). Volatiles analysis was performed using a Stratum purge and trap unit, and identified using GC-MS. This research showed that at 15°C, a lager fermentation (14-15°Brix) under vacuum pressure fermented faster (~15-30%), with an increase (~15%-100%) in the number of cells in suspension (depending upon the initial density). The rate of sugar consumption under vacuum was greater compared to the control, thus increasing the rate of ethanol production. Vacuum fermentation reached the final batch ethanol formation 80 hours (~3days) before the control. The removal of volatile CO₂ is one hypothesized mechanism for these results. When a condenser was attached to the tank for volatile retention, there was no measured loss of ethanol. Under vacuum, more higher alcohols (~86%) and esters (~78%) were present in the final product compared to the control. This research shows that vacuum pressure has a positive effect upon the fermentation rate. Additionally, vacuum fermentation shows a higher generation of volatile compounds, having a significant impact upon the product flavor profile. This research can also be exploited by industries where the volatile metabolites produced are the desired product.