The Impact of Lactic and Acetic Acid on Primary Beer Fermentation Performance and Secondary Re-Fermentation during Bottle-Conditioning with Active Dry Yeast

Abstract The presence of high concentrations of organic acids is known to adversely affect the efficiency and quality of ethanol fermentation. The growing popularity of sour beers warranted the exploration of strain-specific performance under optimal and suboptimal conditions similar to those found in sour beer production. The focus of this study was on the performance of select active dried yeast strains under artificially acidified conditions. Nine common brewing strains of active dried yeast were assessed based upon overall fermentation performance and their ability to metabolize maltotriose and maltose between 0.0% w/w − 1.0% w/w lactic acid and 0.0% w/w − 0.5% w/w acetic acid. A single strain of active dried yeast specifically selected and bred for bottle conditioning environments was assessed based upon its ability to metabolize glucose, and carbonate artificially acidified finished beer between 0.0%−1.6% w/w lactic acid and 0.0%−1.0% w/w acetic acid. This study confirmed the suitability of active dry brewing yeast for sour beer fermentations that meet or exceed the typical organic acid concentrations encountered in sour wort. The majority of the selected strains performed well in sour wort containing < 0.4% w/w lactic acid or < 0.1% w/w acetic acid. The importance of strain selection became apparent at concentrations exceeding these reported values, with two strains displaying almost no change in fermentation capabilities across the range of organic acid concentrations. Bottle conditioning remained unhindered by lactic acid up to 1.6% w/w, while acetic acid concentrations at and above 0.4% w/w significantly hindered bottle conditioning.