Abstract
Diacetyl is an important flavour-active compound in beer fermentation because excessive concentration produces buttery notes and reduces product acceptability. This study examines biotechnological strategies for reducing diacetyl during industrial beer fermentation. Controlled fermentations were conducted using optimized yeast management, nutrient adjustment, temperature control, and maturation timing under industrial-style conditions. Alpha-acetolactate formation, diacetyl concentration, yeast viability, attenuation, pH reduction, ethanol production, amino nitrogen uptake, and sensory quality were measured. The results show that controlled yeast vitality and adequate amino nitrogen reduced precursor accumulation during active fermentation. Moderate temperature elevation during late fermentation accelerated diacetyl reduction without causing excessive ester or higher alcohol formation. Extended yeast contact improved diacetyl cleanup but required careful monitoring to avoid autolysis-related flavour defects. The study demonstrates that diacetyl reduction is most effective when yeast metabolism, nutrient balance, and maturation control are coordinated. This approach supports cleaner flavour and more consistent industrial beer production.