^ Equipment & process line design

Text by Lucien Joppen, images by Schneder Weisse

Stainless Steel World interviewed Hans-Peter Drexler, brewmaster at the Schneider Weisse brewery, in the village of Kelheim, south-west of the city of the Regensburg. Schneider Weisse is world-renowned among beer enthusiasts for its range of Weissbier-types. Bavaria is the birthplace of wheat beers, which its recipe carefully guarded by the German ‘Reinheitsgebot’, a beer purity law dating back to 1872.

Over the years, Bavarian weissbier has emerged as an ‘export-Schlager’ for the many breweries in the German Bundesstaat. “Originally, Weissbier was a hyperlocal product, which was distributed and consumed in and around the breweries. As a result, the lifetime of a batch was only two to three weeks. Nowadays, Weissbier is an international product distributed and consumed worldwide. As such, its shelf life has been extended to 12 months.”

Low tolerance

The longer lifetime of Weissbier, coupled with restrictions on the use of additives/preservatives (see box EHEDG), means breweries must adhere to strict manufacturing hygiene standards to avoid micro-organisms that affect the quality of the product over time. Schneider-Weisse has an additional constraint as its brewing process is based on the authentic method, meaning the brewmasters add the yeast to the wort in open tanks.

Furthermore, the final fermentation stage continues inside the closed bottle. By doing so, the taste profile of the beer is enhanced, giving the iconic Weissbeer its unique position in the wonderful world of Weissbier.

As everything – in this case the taste profile – comes at a price, Schneider Weisse cannot compromise on quality assurance as tolerance levels (i.e. for micro-organisms) are almost zero.

Tricky business

First, a brief overview of the brewing process of traditional wheat beer (see process diagram). In the brewhouse, the beer goes through a standard, if more complex mashing, followed by routine boiling.

The tricky business starts in the fermentation stage, where all the ‘biochemistry-magic’ happens. During 5 to 6 days, the wheat beer is brewed, driven by the yeast in combination with the chilled wort. In a room comparable to a basketball court, the open fermentation vessels that bubble and burp like witches’ cauldrons.

According to Hans-Peter Drexler, open fermentation allows for little influence of micro-organisms that do not have a place in the brewing process. “These open fermenters are very hard to control; the biggest challenge is to keep the biological balance correct. If deviations occur, this will impact the quality of our product. As our beers are not pasteurised before bottling we have no way of killing these micro-organisms as a last line of defence.”

Highly reactive yeast

As Hans-Peter Drexler explains, the conditions in the fermentation room are quite favourable for micro-organisms with temperatures around 15°C. One would almost expect a clean room approach, see the production of infant formula, but this is not the case, Drexler says. “You could compare our production with the manufacturing process of cheese. Of course, we adhere to strict cleaning practices and make sure that employees who enter the fermentation room are dressed and sanitised accordingly to HACCP (Hazard Analysis Critical Control Points).

However, we use micro-organisms in the yeast so the room is not sterile. It doesn’t have to be as the type of yeast, and the fermentation process, contribute to an environment in which ‘alien micro-organisms’ have a slim chance of survival. We use a highly-reactive yeast strain that, feeding on malt sugars, colonises the brew and subsequently leaves hardly any feedstock for other organisms to feed on. We have invested a lot of time and effort to cultivate a robust yeast strain. We also decided not to re-use yeast, as was common practice, but to use fresh yeast and sell excess/left-over yeast for animal feed.”

Taste deviations

Not uncommon in food and beverage manufacturing, Schneider Weisse has been confronted with product recalls in the past. These were not related to food safety but fluctuations in quality. This happened roughly 15 years ago, when Mr. Drexler was already working for the brewery. “The traditional brewing process is quite challenging, given the relatively high processing temperatures and the absence of a pasteurisation step before bottling. We always test the quality of each batch in our in-house laboratory, and product faults have occurred before, but could always be corrected. However, at that particular timeframe in 2004, the microbiological balance within the process seemed more seriously disturbed and out of our control, resulting in a significant increase in product faults. These were related to the taste profile that was affected through Lactobacillus.”

Difficult to clean

Since Mr. Drexler and his colleagues didn’t know what caused the fluctuations, they decided to systematically investigate all probable causes. “We suspected that the decline in product quality had to be related to some source of microbiological contamination, and together with the experts of GEA – one of our suppliers – we started looking into those parts of the installation that were the most difficult to clean, suspecting that product residue build-up was the cause of concern. We replaced some couplings and valves but, unfortunately, this didn’t solve the problem. We then moved to less-hazardous areas like the whirlpool, where the cooked wort is rotated to secrete the turbid residues which are gathered at the bottom of the whirlpool while the remaining clear wort is pumped out from above.”

Replacement of process line

Mr. Drexler and his team found out that the drain valves within the whirlpool didn’t comply with the latest EHEDG Guidelines, so these were replaced by GEA-valves that didn’t have any dead spaces. “This measure resulted in an instant improvement of the beer quality, but we weren’t quite there yet. We discussed the cleaning circumstances of buffer tanks, that were situated between the fermentation and the bottling process, and discussed different possibilities to improve them, while at the same time also considering the effects of every intervention on the final taste of our beer. We had to go about very carefully, because obtaining a consistent beer quality was just one goal we wanted to achieve, the other was to preserve the original taste of our wheat beer.”

It became clear that the process line in its entirety needed to be reviewed. “I am in favour of a more holistic approach. Of course, you need to look at individual components, but if you ignore the line as a whole, you are going to miss out. In our case, we have changed and retrofitted process lines that were designed and installed in a suboptimal way. For example, we found many cases of bad welding, and we were also surprised at the surface condition of some parts of the piping. There were also spaces in the piping that facilitated product build-up that made it harder for our CIP-system to clean the installation.”

Wider audience, same beer

The aforementioned operation took roughly four years, spanning the period between 2004 and 2008. “During this time frame, we have succeeded in gradually implementing hygienic engineering and design in a traditional brewing process, without making a compromise on food safety or taste. We did it step-by-step, without breaking the bank and without losing our identity and credibility as one of the best Bavarian brewing houses since 1872.

And thanks to our commitment and the expertise of the professionals at GEA and EHEDG, we haven’t had any problems since 2008. We protect our strong legacy, our traditions including our Reinheitsgebot. The only difference is that our products are enjoyed by a wider audience all over the world.”

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