Bicarbonate Inhibition and Its Impact on Brettanomyces bruxellensis Ability to Produce Flavor Compounds

Water chemistry and the utilization of brewing salts such as gypsum, magnesium sulfate and bicarbonates, have been well documented for Saccharomyces cerevisiae, however, there has been limited published research on the impact bicarbonates have on Brettanomyces, especially in a brewing application. The objective of this project was to look at varying levels of added bicarbonates (0, 50, 75 and 100 mg/L) to identify correlations between bicarbonate content and the fermentation activity of Brettanomyces bruxellensis within beer. Two, 58.7 L brews with a target OG of 1.040 were brewed using a recirculating infusion mash system and mixed-together using a mash mixer to create one, 117.4 L batch to reduce variability. The batch was split into three, 37.9 L allotments and treated as triplicates. The beer was hopped to 20 IBUs using Bravo hops. Brettanomyces bruxellensis was propagated prior to being pitched at 1.2 million cells per degree Plato. After inoculation, the triplicates were stored at 21 degrees C until fermentation was completed. The reduction in gravity caused by the Brettanomyces was followed using a digital airlock and a benchtop densitometer. GC-MS was used for the analysis of the volatile compounds within the experimental beers. Statistical analysis (p < 0.05) showed that there were significant differences between the fermentation activity, including flavor compound production, of the different batches brewed at different bicarbonate levels. The total concentration of volatiles ranged from 69.76 to 83.4 mg/L within the different beers. It was concluded that the varying levels of bicarbonates had an impact not only on the fermentation, but also on the volatile compounds.

Automated summary

This study investigated the impact of varying levels of bicarbonates on the fermentation activity and volatile compound production of Brettanomyces in beer. Results showed significant differences in fermentation activity and volatile compound production among batches brewed at different bicarbonate levels. The conclusion was that bicarbonate levels not only affected fermentation, but also influenced the volatile compounds in the beer.