Biological and hydrodynamic stress influences on brewing yeast strains' physiological status during beer production
Chlup, Paul H.
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Biological hydrodynamic stress influences on yeast and the resulting consequences on beer stability have been investigated. Yeast cells subjected to stress during beer production have a negative effect on its physiological status. Cell wall and membrane constituents determine the cells capacity to adapt to stress. A relationship has been established that yeast cell wall mannan, an unfilterable haze constituent, as a function of hydrodynamic stress exposure, is released from the cell wall while concurrently, particle size in the supernatant, and beer haze increased. In high gravity wort (20 °Plato), compared to lower gravity wort (12 °Plato), there is an increase in the number of damaged cells and lower intracellular glycogen and trehalose levels, indicating stressed cells. Cell viability and intracellular pH decreased due to processing conditions encountered during yeast cropping with a centrifuge. Furthermore, yeast intracellular glycogen and trehalose levels were depleted as a result of centrifugation. A comprehensive evaluation of yeast fermentation predictors such as viability, damaged cells, intracellular pH (PHi), intracellular glycogen and trehalose is of vital importance. The flow cytometer is able to rapidly reform numerous accurate yeast physiology analyses, providing information that will optimize yeast management circuits, improve fermentation efficiency resulting in enhanced beer quality.