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15 March 2017

Possibilities for Optimising Wort Preparation – Part 1

Wort preparation is at the heart of beer production as the wort to be fermented is prepared from the natural raw materials water, malt and hops. The various steps are based on different unit operations. This five-part series of publications aims at improving evaporation of undesirable aroma substances. Part 1 covers practical implementation of DMS calculation published in BRAUWELT International No. 4, 2014, pp. 217-219, No. 5, 2014, pp. 284-288, No. 6, 2014, pp. 354-357.

The possibility of calculating DMS evolution over the individual steps of beer production was described in the above-mentioned series of publications and results given [1-4]. In the present article, wort preparation is recorded and optimised in terms of DMS reduction in a medium-sized brewery. Advantages resulting for practical implementation are highlighted.

Starting Situation

Kirner Privatbrauerei Ph. & C. Andres GmbH & Co. KG is a medium-sized private brewery located in the region of the River Nahe, in the western part of Germany. The brewhouse comprises a mash tun, a mash copper, a lauter tun, a wort copper and a whirlpool and energy recovery (evaporative condenser). Before the turn of the century, overall evaporation was ten per cent, this was reduced to currently four per cent keeping pace with advancing technological optimisation. This involved extensive and complex measurements of DMS, DMSP, extract, TBI and other parameters, with the associated labour and analysis costs.

Based on the previous series of publications, the process owners in Kirn wondered whether the evaporation characteristics of the existing brewhouse could be calculated and predicted. The major question: can overall evaporation be reduced further?

The brewhouse was evaluated in terms of process engineering and rate of evaporation calculated. The result is presented below.

Calculation of Brewhouse

In order to calculate and predict DMS and DMSP levels at the end of wort preparation, various data is required, available in every brewery as a matter of course. This includes data on vessel size, rate of evaporation, boiler circulation capacity and associated process times and temperatures. Information on DMS and DMSP levels respectively in malt are important as they may vary. This information can be found in the delivery documents. All these parameters and allowing for re-formation and evaporation make it possible to calculate final DMS in the wort at mid-time of cooling based on the individual steps of wort preparation (see [1-4] for details).

This data is used for formulating a spreadsheet tool whose input interface looks like that in Table 1, by way of example. Table 1 lists vessel sizes and data on energy input. The wort preparation programme and malt parameters are not included. Using various formulations of questions, it is possible to “play around” with all these parameters: in what way does a reduced circulation speed (rate of circulation) change the evaporation process? What is the effect of a higher temperature during final mash pumping on DMS levels? In what way do DMS levels improve/deteriorate when prolonging the whirlpool rest? Is it possible to go below the 100 µg/l threshold when reducing overall evaporation? Did DMS levels in malt rise, does overall evaporation have to be adapted? Or is it necessary to extend hot holding in order to break down more DMSP? Should a secondary evaporation system be used and, if yes, what would be the reduction compared to the existing system?

The master brewer himself will be in a position, using the spreadsheet tool, to answer all these questions arising from changes in process parameters and having prevented DMS evaporation specific to a particular brew to-date. The quality of these calculations has been verified and validated several times [1-4]. In the context of this research work, wort samples taken from the boiler were again analysed for DMS and DMSP. Let us repeat the question: Is it possible to reduce overall evaporation even further? ...