Radeberger Gruppe KG, Binding Brewery, Frankfurt: a case study in using the Yeast Monitor for automatic pitching rate control
In 2003, the Binding Brewery in Frankfurt installed the Aber Instruments Yeast Monitor to automatically dose the correct amount of live yeast at the start of each fermentation. This unique instrument measures the LIVE yeast cell concentration on-line by using a probe that produces a radio-frequency impedance field. Yeast cells with an intact cell membrane become polarised by the radio-frequency field used by the Yeast Monitor and the measured capacitance is proportional to the amount of viable yeast passing the probe. The Yeast Monitor probe can be used directly in a yeast main and is insensitive to trub, dead cells and gas bubbles. Three years later, Sales and Marketing Director for Aber, Dr John Carvell and Dr Georg Siems from their local distributor, IUL Instruments GmbH visited the brewery to see how yeast pitching was being done today.
According to Mrs Elke Schuermeyer and Dr Andreas Ludwig from the Radeberger Gruppe Central Laboratory, the original method to calculate the amount of yeast to add was derived from an on-line optical sensor placed directly in the yeast main. The optical system had never provided a satisfactory solution for yeast pitching and the probe required frequent calibration. When the optical probe eventually failed, the supplier was unable to complete a repair. After consultation with the Technical University Munich, Weihenstephan, a decision was made to replace the optical sensor with the Yeast Monitor (Model 320+). The new system was installed and commissioned by IUL Instruments from Koenigswinter.
At Binding one bottom fermenting yeast strain is used for variety of beer brands and the yeast is added as quickly as possible into the first brew. The target cell concentration of 15million live cells/ml in the 3,600Hl fermenters (2,800Hl working volume) is consistently achieved with the Yeast Monitor. The Binding brewery has an output of approx. 1.8million Hl and is part of the Radeberger Gruppe KG, the largest brewing group in Germany with a total output of approx. 13 million Hl (domestic output 2005).
The three main benefits from having the Yeast Monitor at the Binding Brewery are seen as:
1. The instrument allows each fermenter to be dosed with a consistent amount of live yeast.
2. Automation eliminates the need for yeast brink samples to be taken for live cell concentration measurement. The traditional methods for live cell counting such (eg using the Haemocytometer with a viability stain) are flawed and have many weak points.
3. The Yeast Monitor requires minimal maintenance: a routine monthly check is made to compare the Yeast Monitor reading with the live cell concentration but the instrument settings are not changed. As a consequence, the Yeast Monitor is completely integrated into the process.
The Yeast Monitor is used in over 100 different breweries across the world and in Germany the reference sites also include the Holsten and Koenig breweries and the much smaller Coelner Hofbraeu Josef Frueh brewery in Cologne (less than 0.5million Hl). Some of the breweries using the Yeast Monitor have multiple yeast strains and the ability of the instrument to be calibrated for up to 10 different yeast strains is seen by some brewing groups as a major advantage in yeast management.
There has been a sharp increase in the use of this on-line instrument in the mid-sized breweries since the launch of a much lower cost version, the Aber Yeast Monitor 710 at Interbrau in 2005. The pricing of the new Yeast Monitor system is now similar to placing a pair of on-line turbidometric sensors in the wort main: typically the two optical sensors are located upstream and downstream of the yeast injection point. Differential turbidity based systems are still used in some of the German breweries but they are seen to have several distinct disadvantages:
1. Where yeast is pitched in-line with the wort, it is best practise to add the slurry as quickly as possible. This ensures that fermentation has a rapid start and all the yeast is exposed, more or less simultaneously, to the transition from storage conditions to suspension in oxygenated wort. Most turbidometric systems require the yeast to be dosed throughout most of the period of wort filling and therefore yeast pitched early in the filling process will be in a different physiological state to that pitched later on.
2. Significant errors can occur using the turbidometric system with a highly flocculent yeast and the system does correct for changes in non-yeast solids in the yeast slurry (entrained yeast trub). This often results in underpitching of the live yeast into the wort.
3. The set points for the turbidometric method must be determined empirically for individual yeast and wort combinations.
It is likely that the "Yeast Monitor" will now become the accepted method for yeast pitching in automated breweries. Already with groups like Interbrew (now Inbev), Anheuser Busch, Miller, Suntory and Coors it has become the standard group practise and in many cases, contract breweries for specific beer brands are required to have the instrument as part of their yeast management operation.
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