Wort stripping based on thermal desorption supports the classic boiling process with a more efficient evaporation and without using additional thermal energy

Engineering Session
Roland Feilner, KRONES AG, Neutaubling - Germany

ABSTRACT: Wort stripping after wort boiling or the whirlpool process is an efficient way to reduce the amount of unwanted volatile substances, which are formed post-boil primarily during the whirlpool rest period. The focus lies mainly on free dimethyl sulfide (DMS) and volatile Strecker aldehydes and reduced fatty acids. Due to high temperatures present in the whirlpool, reactions like degradation of DMS precursor and aroma formation are maintained. Immediately before cooling the wort stripping system evaporates newly formed DMS. Thus it is not necessary to evaporate the total amount of undesired volatile substances, because stripping is one more system in the process, which can reduce these reaction products. A new kind of stripping system is based on a specific evaporation process, which is based on the desorption of volatile substances without using primary energy. The innovative design using a special inlet leads to the total covering of the entire internal surface area of the stripping vessel by an even but turbulent trickle film. Besides the generation of an efficient, uniform, and turbulent layer, the stripping gas keeps up the driving gradient between the gas and liquid phase. Based on this, the quantity of the expelled substances is controlled via the stripping gas volume. To evaluate the efficiency of evaporation, it is important to understand the evaporation behavior of single unwanted aroma compounds under reduced influencing parameters. Therefore the big matrix of wort is reduced to pure water, and the temperature dependent volatilities of these aroma compounds are determined. With this knowledge a basis for the description of evaporation efficiency is generated. In the course of this work, small-scale laboratory trials were verified by an upstream pilot trial, where also the geometry and volume of the stripping gas of the system was varied. While these investigations describe a reproducible quantitative reduction of unwanted aroma compounds, further investigations of this work are dealing with the rate of the reduction reactions. Thereby correlations to the current dynamic parameters can be arranged for further optimization of the brewhouse process. The stripping gas control function of the new stripping system enables the operator to react specifically based on the terms of malt quality like DMS-precursor content and wort parameters at a very low energy level combined with the same beer quality and an unchanged beer character. A significant reduction in energy input with thermal treatment and a simultaneously better wort quality could be realized. Reasons for this are a highly efficient stripping process, which uses the existing thermal energy of the wort instead of adding primary thermal energy.

Roland Feilner (born in 1981) finished his apprenticeship as a brewer and maltster. After that he studied food science technology in Weihenstephan and graduated in 2006 as an engineer. His career entry with Krones AG, Germany, started with membrane filtration of beer. At the same time, he worked as a process and development engineer for thermal product treatment. Additionally the degassing of beverages and juices was one of his main development areas. Currently he is responsible for new developments in wort treatment and process technology as a technical specialist in the Krones R&D Division. Furthermore he has been a post-graduate at the Technical University of Berlin since June 2011. His area of research is the reduction of unwanted flavors in wort, with a desorption-based stripping process.