Disc stack centrifuge operating parameters and their impact on yeast physiology

Hydrodynamic stresses imposed on brewing cells of Saccharomyces cerevisiae during beer processing can have a detrimental impact on beer quality. The use of centrifuges has become an efficient way to increase brewery throughput as they decrease clarification times and improve fermenter and tank conditioning efficiency. The effect of a disc stack centrifuge on yeast and beer physical stability has been investigated. In this study, a commercial ale yeast strain has been subjected to different operating conditions during centrifugation. Cell viability and intracellular p^H decreased due to processing conditions encountered during yeast cropping with a centrifuge. A relationship has been established that yeast cell wall mannan, an unfilterable haze constituent, as a function of G-force and centrifugation cycles, is released from the cell wall while concurrently, particle sizes between 0.5-2.8 µm and beer haze increased. Furthermore, yeast intracellular glycogen and trehalose levels were depleted as a result of centrifugation. © 2008 The Institute of Brewing & Distilling.