Effect of the respiro-fermentative balance during yeast propagation on fermentation and wort attenuation

Impact of propagation time on yeast physiology during bottle conditioning of beer on an industrial scale

Bottle conditioning occurs when yeast and a fermentable extract are added to beer prior to packaging. Aside from ethanol and carbon dioxide production, this process can minimize the production of off-flavors and increase the shelf-life of beer. The advantages of bottle conditioning rely on the yeast being able to quickly referment the beer and maintain viability during storage. In this study, a commercial ale yeast was propagated in wort on a large scale (30 hL) for 24 h or 72 h and seeded into pale ale beer for bottle conditioning. We found that yeast propagated until the post-diauxic shift (72 h) provided better longevity in the bottle and improved foam stability compared to the 24 h propagated yeast. At the time of seeding, yeast propagated for 72 h showed an upregulation of proteins involved in cellular respiration and general stress pathways that may indicate responses toward mitigating cellular stress levels.