Presenter: Rudolf Michel, GEA Brewery Systems, Kitzingen, Germany. Coauthor(s): Kristina Boee, GEA Brewery Systems, Kitzingen, Germany; Udo Funk, GEA Process Engineering Inc., Hudson, WI.
For the fermentation and maturation of beer, the brewmaster has access to only a small number of tools to control and optimize the processes—recipe parameters: temperature, pressure and time; process parameter: gravity of the wort, yeast strain; continuous fermentation and maturation processes; mixing of the tank. The complex mixture of fermenting wort and yeast cells normally reacts very quickly to changes in the temperature and pressure profile or to additional application of “stress.” GEA Brewery Systems has developed the system ECO-FERM™ to improve performance during fermentation and cooling down to cold maturation temperatures. This provides a process using jet mixing in a cylindroconical tank (CCT). A jet without any movable parts is installed in the cone of a CCT using the Venturi principle, so only one-third of the total flow inside the CCT is pumped around with a circulation pump. Approximately 10% of the carbon dioxide produced during fermentation is dissolved in the beer; the other 90% bubbles up to the liquid surface, forming a bubble column in the CCT. This bubble column leads to an upward movement of the liquid in the center of the CCT and consequently to a downward movement at the cooled shell of the tank. The jet in the cone provides powerful support of this natural upward motion. Improvement of this upward flow will keep a larger number of active yeast cells in suspension, and in addition, yeast cells on their way down to the cone are sucked from the jet and resuspended in the fermenting liquid. More yeast cells in motion will speed up the chemical reactions. The hydraulic jet also improves temperature homogeneity in the tank and significantly enhances the heat transfer coefficient at the tank shell. The paper presents first results from an industrial application in a 2,660-hL CCT with worts of 14°P. For all trails a wort batch of 5,320 hL was used to avoid differences resulting from brewhouse operations. The batch was divided into a tank equipped with ECO-FERM™ and a reference tank using the standard process of the brewery. The results cover process duration and temperature homogeneity, as well as analytical results of the beers, including DLG tastings
Rudolf Michel received both his engineering and his Ph.D. degrees from the Technical University of Munich at Weihenstephan. He was a member of the scientific staff at the Institute of Chemical Engineering at Weihenstephan, working on the mechanisms of hot-break separation in a whirlpool tank and on hygienic design of armatures and pipe work systems in the food industry. Rudolf’s industrial experience includes an apprenticeship as brewer and maltster at Mahr’s Bräu in Bamberg, Germany. He joined GEA Brewery Systems in June 2000 as director of brewing and technology and has been involved in major brewing projects and research works around the world for GEA Brewery Systems. Currently, he is leading the research and development team dealing with improvements in brewing technology and environmental aspects of the brewing industry. He is a member of DBMB and has published more than 64 papers.