Yeast Propagators

Yeast Propagators for Breweries

Perfect yeast management is one of the key starting points for improving beer quality. Yeast management must occur at a uniformly high level so that consistently high beer quality is ensured. A yeast propagation system would enable you to meet this requirement without any difficulty, allowing you to focus on other matters related to beer quality.

A yeast propagation system helps to achieve two key objectives. The first objective is the propagation of just the yeast which achieves the desired taste in the beer. Foreign yeast and bacteria are not reproduced to any significant extent when a propagation system is used. The second objective involves ensuring a vital (healthy and fermentable) yeast in the brewery.

The vitality of the yeast is reduced as a result of stressful situations for the yeast organism during normal brewery operation. Stressful situations involve repeated yeast pitching and they cannot be avoided. The yeast is subject to pressures, changes in pressure, shear forces, unsuitable temperatures, changes in temperature, osmotic stresses (differences in concentration) due to water or beers with too high an alcohol content for the yeast. If the vitality of the yeast is reduced, this will result in longer processing times as well as a less attractive beer flavour.

30% freshly propagated yeast is added for each pitch in the fermentation tank if a yeast propagation system is used. The industrial yeast in the brewery is thus always kept clean and it maintains its vitality. This ratio ensures that beer with a consistent taste is produced. Customers are after all perfectly able to detect differences in taste. The smoothness of a beer is a sign of high quality.

Yeast Propagator

Functional description

Our yeast propagation systems are single tank systems. The system's tank is depressurised or is operated with a minimum overpressure. This is kept to a minimum as pressure is a stress factor for the yeast organism. Pressure-free operation requires sufficient unfilled space in the tank. Once the tank and the system have undergone thorough CIP cleaning, the tank is filled with sterile wort up to approximately 20% of the liquid volume (not the tank volume). The wort is cooled down to propagation temperature (14-20°C) and ventilated with sterile air. Ventilation occurs in a transfer line. Then the yeast is passed from a Carlsberg flask into the propagation tank or the transfer line via a sampling valve.

The control provides the necessary lead time for the yeast with the propagation programme. The process time is dependent on the yeast quantity supplied. The propagation programme consists of a temperature programme, a circulation programme and a ventilation programme. The propagation will continue until only the desired residual extract is present. A residual extract is necessary as the yeast will change undesirably without the appropriate nutrients (mutation). Then the tank is filled to 100% of the liquid volume (approximately 55% of the tank volume) and the yeast propagation procedure is repeated in the same way as it was carried out for the first 20%. Finally, approximately 80% of the fill volume is removed from the propagation tank and used for "pitching" of the fermentation tanks. The remaining 20% of the fill volume is filled back up to 100% of the fill volume (55% of tank volume) with tempered sterile wort to act as a starter culture. No addition of yeast from the Carlsberg flask is required in this case. This process can, however, not be repeated indefinitely as the tank and the system must undergo thorough CIP cleaning following several yeast cycles. The yeast propagation process starts all over again after each CIP cleaning cycle, which means that fresh, vital yeast is always obtained.