A technique to conclude the stage of fermentation from easy, accessible on-line measurements

Yeast and Fermentation Session
Martin S Lutz, ProLeiT AG, Herzogenaurach, Germany

ABSTRACT: Finding the right moment to stop fermentation and release a tank for cooling down or pumping over to a lagering tank is a common task in the fermentation cellar. Usually this moment is determined by regular gravity measurements as a trend in a standard fermentation diagram. Additionally the measurement of the VDK concentration gives the final assurance that the fermentation stage can be ended. Both measurements require the manual taking of the samples and then analysis by the brewer or in the laboratory, which means a lot of effort. In our work we investigated the possibility of concluding from easy accessible data the progress of the extract attenuation and so determining the current status of the fermentation. From a good start of the fermentation on the first day we measured the temperature and pressure on the tanks, which is standard in an automated fermentation cellar, and also looked at the activation of the cooling valves. With this we can deduct the amount of cooling energy needed related to the degree of fermentation. The system has to be adapted to local circumstances in the brewery and the influences of different wort types. The results achieved indicate that the different stages of the fermentation process can be distinguished. In particular, the end point of the main fermentation can be predicted with enough accuracy for the brewery to reduce the amount of sampling needed. Only one control analysis should be necessary to assure that the degree of attenuation is in a certain range and then to release the tank for switching over to the lagering phase. As soon as the system parameters are introduced and stable results are obtained there can also be a full automatic end to the fermentation period without additional sample taking. This reduces the workload in the cellar and provides significant advantages, for example, on weekends when nobody has to come to the brewery for this task. In the presentation real process values for a large brewery are shown, and conclusions from the experiment are explained.

Martin Lutz graduated as a brewmaster from Weihenstephan University in Munich. After several years of working in medium- and small-sized breweries, he joined ProLeiT AG in its business field of brewery automation. He has gained profound knowledge in the various aspects of this business and is connecting the technological requirements of the brewmaster with the possibilities and structures of modern process control systems.