Test & measurement
PRECISE YEAST CONTROL Rogg says that together with his team of 35 employees, he makes “beers with character” that should be well balanced and as pure as possible, but definitely not run of the mill. The unique ideas from some of the craft brewers, who belong to his customer base, surpass anything Rogg has experienced to date as a traditional brewer. He nevertheless keeps an open mind. “The craft beer movement has greatly stimulated the brewing industry and I’ve learned a lot of new things,” adds Rogg. Some craft brewers rely on dry yeast, which poses challenges. “We basically have to permanently monitor the yeast to determine how far along the alcohol fermentation process is and to know when to pressurise the tank to make sure we get the necessary amount of carbon dioxide into the beer. At the end of the day, we will only produce a high-quality beer if the yeast really feels at home,” explains Rogg. Dry yeast must be mixed with precisely tempered water before being added to the tank. Not paying close attention to the temperature puts the fermentation at risk. “The fermentation monitor helps us see immediately if something is not right with the fermentation level. You can then interrupt the process at an early stage and replace the yeast,” says Rogg. This is why the “pitching” yeast is so important, because it makes an important contribution to the productivity of the fermentation, the behaviour during maturation and preservation of the desired quality. The quality of the pitching yeast can be determined by evaluating the ethanol formation rate, the formation of common metabolic byproducts or the consumption of nutrients during fermentation. The detailed, highly precise and repeatable measurement values from the Fermentation Monitor QWX43 are reliable indicators of the ethanol formation and nutrient depletions. In addition, the increase in the number of yeast cells at the beginning of the process can be determined by observing the increase in viscosity of the medium. By comparing current process data with data from the previous fermentation processes, the brewer can decide whether to replace the existing yeast. The highly precise measurement values from
the Fermentation Monitor QWX43 and the ability to compare multiple batches are furthermore extremely helpful tools for exact compliance with legal requirements. The alcohol content of a beer can deviate from the value indicated on the label by a maximum of 0.5 percentage points. “If a brewer realises during a comparison of the batches that a beer is moving towards a critical deviation, he can adapt the brewing process by using less malt, for example,” explains Rogg.
THE RIGHT COMBINATION Precise monitoring of the fermentation process is made possible because the Fermentation Monitor QWX43 multisensor combines different measurement principles – vibronics and ultrasound – in a single sensor system. The
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The Fermentation Monitor QWX43 multisensor from Endress+Hauser with the two characteristic sensor paddles and temperature probe.
vibronics technology involves the use of what are known as piezoelectric elements that excite a sensor in the form of a tuning fork to make it oscillate. Information regarding the density of the medium can then be derived. The lower the oscillation frequency, the higher the density. The piezoelectric elements also generate a high- frequency ultrasound signal between the oscillating forks, the speed of which can be determined with high precision and which varies depending on the composition of the medium Density and acoustic velocity are important measurements because both change during fermentation. Density decreases as the sugar breaks down, as well as when alcohol forms or the content increases. Acoustic velocity does not change uniformly, however: it decreases as the sugar breaks down and increases as the alcohol content rises. Taken on their own, the behavior of density and acoustic velocity would not make it possible to determine the reaction mechanisms during fermentation or the ratio of alcohol to extract content over the course of the fermentation. The alcohol content and extract reduction can be represented independently only by intelligently linking the measured variables and incorporating numerous empirically determined reaction kinetics.
The instrument can also recognise which fermentation state the process currently finds itself in. The same sensor can also be used to reliably distinguish between the fermentable and non-fermentable sugars in the wort before
fermentation starts. This enables optimal quality control and planning. The Fermentation Monitor QWX43 furthermore features two intelligently positioned temperature sensors. Together, all of this ensures that a multisensor instrument like the Fermentation Monitor QWX43 can represent the fermentation process in a more holistic fashion than a single-purpose density or acoustic velocity instrument.
SUMMARY The Fermentation Monitor QWX43, which combines three different measurement processes in a single instrument and measures all relevant parameters, enables continuous and automatic monitoring of the fermentation process. Brewers save time and effort since the instrument replaces laboratory analysis and spindle sampling. The brewing processes can be optimised with measurement data. The level, extract and alcohol content during fermentation can be retrieved via an app, eliminating the need to be on site. This is especially interesting for cuckoo brewers who outsource the production of their beers to contract breweries – and for contract brewers who can offer their customers additional services. The Fermentation Monitor QWX43 is also available in a version that integrates directly into the brewer’s process control system instead of utilising an app.
Endress+Hauser
www.endress.com February 2024 Instrumentation Monthly
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