Abstract
Sour beer fermentation depends on controlled lactic acid bacteria activity because acid production, microbial balance, flavour development, and maturation stability are strongly connected. This study examines lactic acid bacteria control during sour beer fermentation and maturation. Controlled fermentations were prepared using selected lactic acid bacteria and brewing yeast under defined wort composition, temperature, oxygen exposure, and maturation conditions. Lactic acid concentration, pH reduction, microbial population balance, attenuation, volatile acidity, ester development, turbidity, and sensory quality were monitored. The results show that controlled lactic acid bacteria growth produced balanced acidity and stable sour character without excessive sharpness. Uncontrolled bacterial dominance increased acidity too rapidly and reduced flavour integration during maturation. Stable results were achieved when inoculation timing, temperature, and oxygen exposure were carefully managed. The study demonstrates that sour beer quality depends on guiding bacterial activity across both fermentation and maturation stages, rather than treating acidification as a separate process.