Abstract
Mixed-culture sour beer fermentation requires controlled acidification because lactic acid bacteria, yeast, oxygen exposure, and maturation time jointly shape acidity, aroma complexity, and flavour balance. This study examines controlled acidification strategies for mixed-culture sour beer production. Fermentations were prepared using defined lactic acid bacteria and yeast culture ratios under controlled wort composition, inoculation timing, temperature, and maturation conditions. pH decline, lactic acid concentration, volatile acidity, attenuation, yeast viability, ester formation, phenolic expression, turbidity, and sensory sourness were evaluated. The results show that staged bacterial inoculation produced smoother acid development than uncontrolled co-fermentation. Rapid acidification created sharp sourness and reduced flavour integration, while delayed bacterial growth produced weak sour character. Balanced culture timing supported stable acidity, aroma complexity, and maturation quality. The study demonstrates that sour beer fermentation should be managed through acidification rate, microbial balance, and maturation control rather than pH reduction alone.