Optimizing Fermentation Time and pH in Primary Souring of Beer Through Co-Fermentation with Saccharomyces cerevisiae and Lachancea thermotolerans

This study investigates mixed fermentations of Lachancea thermotolerans and Saccharomyces cerevisiae as a strategy to reduce fermentation time in sour beer production while preserving the acidification benefits of L. thermotolerans (~3,5 pH). Fermentations were conducted at 20 °C and 25 °C using pure and mixed cultures at ratios ranging from 1:10 to 1:40 (S. cerevisiae to L. thermotolerans). Extract concentration and pH were monitored daily during the fermentation process. Alcohol content, total acidity, and FAN were also measured. A sensory evaluation was also performed for all final products.

Final pH values remained consistently low across all mixed fermentations (ranging from ~ 3.7 to 3.63), regardless of ratio or temperature. However, fermentation time was notably reduced in the presence of S. cerevisiae, especially at higher temperatures and higher ratios. At 25 °C, mixed fermentations completed up to 30% faster than pure L. thermotolerans cultures.

Sensory analysis indicated that mixed fermentations at 20 °C and higher L. thermotolerans ratios yielded more desirable sensory profiles, with citrus and floral notes. These findings support that the use of targeted co-inoculation strategies can effectively accelerate sour beer production while preserving the acidic and aromatic quality characteristics of L. thermotolerans fermentations.