Enhancing Lager and Ale Complexity: Secondary Fermentation for Flavor Diversification and Increased Stability

Bottle conditioning via refermentation involves introducing fermentable sugars and yeast to packaged beer, enabling secondary fermentation in sealed bottles. These beers result in natural carbonation, complex flavor development, and enhanced stability through continued yeast activity and maturation. Despite its widespread use in brewing, the mechanisms of Saccharomyces and Brettanomyces in bottle fermentation and conditioning, particularly in lager brewing, remain poorly understood, limiting optimization and consistent outcomes in flavor evolution and beer stability. However, increasing consumer interest in complex lager flavors has driven innovations in lager applications.

This study investigates the impact of bottle refermentation utilizing a range of Saccharomyces strains and a Brettanomyces strain with the aim to optimize and categorize lager flavor profile developments and stability. Pilot-scale fermentations (4 hL brew/50 L fermentations) were standardized with a base lager wort enabling comparisons of refermented beers to force-carbonated controls. Key flavor compounds including esters, alcohols, phenols, and organic acids were analyzed via chromatography. Additionally, foam stability, haze formation, and pH were also assessed. Cutting edge sensory profiling was conducted by trained panelists utilizing Quantitative Descriptive Analysis (QDA).

Combining analytical and sensory analysis, the results provide evidence that bottle refermentation significantly enhanced flavor complexity in lagers. Flavor profiles ranged from neutral characteristics to fruity and floral notes dependent on the Saccharomyces strain. Storage conditions including temperature and time directly and consistently impacted distinct Brettanomyces phenolic and fruity character. All refermented beers produced reductions in off-flavors including diacetyl and aldehydes compared to force-carbonated controls. Additionally, foam stability varied by yeast strain, while haze levels remained relatively stable across the conditions. This study highlights the potential of bottle refermentation to enhance the diversity of lager flavor profiles while maintaining long-term flavor stability. These findings suggest that refermentation provides a practical and innovative approach to expand the sensory complexity of lagers, aligning with evolving consumer preferences while preserving the traditional quality attributes that define the style, thus offering valuable insights for both brewers and the industry.