Berliner Weisse – a traditional beer through the ages, part 1: How has its character changed?

In the 19th century, Berliner Weisse could be found all over Berlin. However in the last few decades, it has been reduced to a niche existence. Recently, craft brewers around the world have rediscovered this traditional style of beer. In the first part of his article, the author focuses on the original composition of the fermentation cultures and on the question of how the hygienic conditions from more than 100 years ago influenced the flavor of this sour beer.

By Dr. Peter Lietz

Brewers around the world are vying to revive the ‘original’ Berliner Weisse, which hit the peak of its popularity toward the end of the 19th and the beginning of the 20th century. Of course, the question is: What did Berliner Weisse actually taste like back then? Was there even a specific method for producing it? No samples remain from this era, so we are forced to draw our conclusions about the flavor based on contemporary sources.

The numerous studies conducted and published in the early 20th century by VLB Berlin under the auspices of Franz Schönfeld (1866 – 1940) indicate that in addition to the quality of the pitching yeast mixed with lactic acid bacteria, the specific local conditions of the respective brewery had a decisive impact on the quality of the Berliner Weisse produced. This included the wooden tools that were common at the time, the open cooling systems, and also the poorly developed state of cleaning technology during the period.

Brewing area of the weiss beer brewery owned by A. Landré, ca. 1883

In December 1907, Schönfeld held a lecture for bartenders who served weiss beer. In it, he described the Berliner Weisse of the early 20th century as follows: “It should be clear, with a nice lasting head after pouring; it should taste pleasantly tart and wine-like, with a fine bouquet and heavy carbonation.” In the same piece published in 1908 in the Wochenschrift für Brauerei weekly brewery journal, he added: “But as everywhere, there are so many exceptions when it comes to weiss beer that these exceptions often outnumber the rule.” This statement makes one thing clear: In the heyday of this classic beer, there wasn’t just one weiss beer; there were many different versions of it.

Population of microorganisms nearly impossible to control

One special characteristic of weiss beer at the time was that the breweries would deliver the young beer to the bars shortly after it was produced. The fermentation process would then be completed in the cellars of the bars, and the bar tenders would bottle the young beer themselves – often adding water to it. Over the years, the hygienic conditions in both the breweries and the bars formed different ‘communities’ of microbes in the beer as it aged. These blends of microbial cultures must have had a significant influence on the aroma and acidity of the beer, particularly when the beer was stored for a year or longer. Generally, that influence was positive, but it could also have been negative in some cases. Another special characteristic of this sour, top fermented beer is that it was not brewed according to Emil Christian Hansen’s (1842–1909) rules of pure fermentation, but rather according to the principles of ‘natural pure culture’ developed by Max Delbrück (1850–1919). Consequently, it was not implausible that unwanted microorganisms would gain the upper hand in this mixed fermentation process, potentially causing the beer to spoil. Today, when we talk about the ‘original’ Berliner Weisse, we should keep in mind that there must have been a number of very different versions of this beer, with different aromas and levels of acidity.

In the courtyard at Brauerei Willner, ready for a parade

Traditional craft brewing was less than hygienic

Not only were many recipes and the extensive knowledge of the brewmasters lost with the closure of countless small weiss beer breweries in the late 19th century, it is particularly unfortunate from a present-day perspective that numerous special microorganisms were also irrevocably lost along with those breweries. According to Schönfeld’s accounts, these mixed microbial cultures were very difficult to control. Mixed microbial cultures generally separate again quite quickly, regardless of whether the cultures are of the same genus or different species; this is due to the varying generation times of the microorganisms involved. Additionally, the breweries' equipment – generally consisting of untreated tuns, barrels, and tools made of wood – had a significant influence on the development of these mixed populations of microorganisms. Paul Lindner made this point in an article he wrote for the Wochenschrift für Brauerei back in 1900. “Those who are knowledgeable about the anatomy of wood will immediately recognize that the wide wooden– and often numerous – conduits present in all breweries are very well suited to serve as a lair for all manner of microbes.” Lindner also pointed out the many sources of contamination in the breweries at the turn of the 20th century.

We know today that biofilms composed of a broad range of different microorganisms are formed in the pores of the wood. These microorganisms are capable of exchanging metabolites and gene sequences among one another. In that sense, the wooden tools and barrels used in weiss beer breweries in the 19th and early 20th centuries offered ideal conditions for a range of different weiss beer cultures to grow. Additionally, in the 18th century, it was rumored that some brewers of weiss beer in Berlin eschewed well water in favor of the likely highly polluted water from the local River Spree. This is a further indicator that people at the time were unaware of how important the microflora were to the quality of the beer.

'Berliner Weisse' sign (Michael Weidner collection)

Development of Berlin-style weiss beer in the era of pure fermentation

Naturally, the brewers at the end of the 18th century already knew about the importance of cleaning to the beer production process. However, it was not yet possible for them to combat unwanted microbes or biofilms with the cleaning tools available to them at the time such as water and brushes, let alone to disinfect their equipment. The longer a batch of beer was stored in (contaminated) wooden barrels, the easier it was for bacteria, such as the Sarcina bacteria that brewers of weiss beer particularly feared, to grow. This could lead to the beer becoming ‘ropy’, which meant that it developed a slimy consistency. Other bacteria would lend the beer an obvious diacetyl ‘buttery’ flavor or an unpleasant acidic note.

The ‘original’ Berliner Weisse of the late 19th century disappeared from the market with the closure of the original weiss beer breweries and the associated departure from traditional craft brewing and with the movement toward modern brewing in facilities designed for optimum hygiene. Returning to traditional brewing methods with wooden barrels and unchecked microbial cultures would be a dangerous game with unpredictable financial risks. Rather, modern brewers who want to revive this interesting beverage would be well advised to draw on the experience and insight of past brewmasters and scientists, discussed at many October Conventions and documented in VLB Berlin’s weekly journals from the late 19th and early 20th centuries. Brewing top fermented beers based on the original Berliner Weisse requires special top fermenting cultured yeasts that are also capable of fermenting dextrins with lower molecular weight. However, more research is needed here in order to cultivate these special types of yeast.

Any potential research would need to place particular focus on selecting the appropriate lactic acid bacteria. Top fermented cultured yeasts and lactic acid cultures should be kept separate as pure cultures. The young beers should be blended together at the end of the process to achieve the desired acidity and aroma. Pasteurizing the lactic acid component before blending will help to prevent uncontrolled acidification after the fact. Only a relatively small number of 19th century weiss beer organisms still exist today, so it would be advisable to first search through the collection of available cultures, then to focus on isolating productive strains. It certainly would not be wise to replace Saccharomyces cerevisiae with a wild strain of Brettanomyces yeast as a culture. If the intention is to create entirely new flavors, it might be worth considering a selection of special secondary fermentation yeasts with individual cultures from the Brettanomyces (B. bruxellensis, B. brevis, B. claussenii) and Hansenula genera. Brewers could also fall back on other types of yeast that are known to produce stronger flavor substances. The important thing is that the cultures have a stable range of by-products and can be cultivated separately, and that the fermented product is pasteurized before it is added to the beer base. Breweries that would like to add a ‘Berlin-style weiss beer’ to their product range should look for a selection of special malt varieties. Above all, however, the brewing process should involve productive weiss beer cultures with their own ‘Berlinstyle weiss beer’ flavor, possibly also with a slight hint of acidity. If brewers can ensure consistent quality, they will be rewarded with loyal, grateful customers.

The second part of this article will focus on the microorganisms that were likely involved in the production of Berliner Weisse in the past. It will appear soon.

Comprehensive information on this subject is available in the book "Die Berliner Weisse – Ein Stück Berliner Geschichte" (‘Berliner Weisse – A Piece of Berlin History’), published by VLB and written by Gerolf Annemüller, Hans-J. Manger, and Peter Lietz.