Abstract
Serial repitching is common in brewery operations, but yeast viability can decline across generations due to ethanol stress, storage conditions, nutrient depletion, and repeated physiological load. This study investigates yeast viability prediction during serial repitching using fermentation process signals. Yeast crops were reused across multiple fermentation cycles, while density decline, pH change, temperature profile, fermentation duration, attenuation, oxygen exposure, and yeast storage time were recorded. Cell viability, membrane integrity, glycogen reserve, and fermentation performance were evaluated as response indicators. The results show that delayed density reduction, slower pH decline, and extended fermentation duration were strongly associated with reduced yeast viability in later repitching cycles. Stable temperature control and shorter storage time improved viability retention. The study demonstrates that process signals can provide early warning of yeast decline before visible fermentation failure occurs. Predictive monitoring supports better repitching decisions, reduces batch risk, and improves consistency in brewery fermentation management.