By Amy Tindell

I remember my first legal purchase of alcohol fondly: I was only 20 years old, but had embarked on that Dartmouth College right of passage called the “FSP,” or foreign study program. At long last I sat on a high bar stool in a Berlin bar, eagerly taking in the long menu of beers I didn’t know, and made my selection based on name alone: the Berliner Weisse. As long as I studied in Berlin, I would do as Berliners do.

Clearly, I didn’t know what I was getting into. The bartender smiled kindly at my accented order, and inquired, “Mit schuss?” After I responded with a “Wie bitte?” – a polite form of “huh?” – the bartender explained, slowly and (not yet giving up on me) in German, that many people preferred to add “schuss,” a sweet syrup, to balance the taste of the very sour Weisse. I chose the himbeere (red raspberry) over the palmeister (herbal green) flavor. Given the unsophisticated state of my palate at the time, schuss was probably a good choice.

That day was almost exactly 16 years ago, and over those years I’d heard barely a peep from the Berline Weisse… until this summer. Suddenly American craft breweries, including Dogfish Head, New Belgium, Firestone Walker, and The Tap Brewing Company have picked up on the style and interpreted it for the modern market. Today the Berliner Weisse is a sour, fruity, effervescent, low-alcohol wheat beer. The sour taste results from fermentation with a mixed culture of top-fermenting yeast and Lactobacillus bacteria, a microorganism that produces lactic acid and carbon dioxide as it digests the wort.  Lactobacillus is commonly used in food processing; it obligingly ferments our cabbage to create sauerkraut and sours our milk to produce creamy yogurt.

These modern American breweries are borrowing from old European traditions. While the precise origins of Berliner Weisse are unknown, two stories emerge as the most popular. The first gives credit to the Huguenots, 17th century religious refugees who migrated to the Berlin area from France and Switzerland. The Huguenots would have picked up Weisse brewing techniques involving Lactobacillus and wheat malt as they passed through Flanders, home of the witbeer and lambic styles. Another theory goes back to the 1520s, with brewer Cord Broihan’s modification of a popular Hamburg beer, which he called Halberstädter Broihan. The style was perfected by Berlin brewers and became fashionable in the 1640s. Whatever its origins, by the early 1800s, the beer was sufficiently popular that Napoleon’s troops famously dubbed it as “the Champagne of the north” during their occupation of Berlin.

That first trip to a Berlin bar piqued my curiosity as to how such a beer was first made and commercialized. Some stretching of my German language skills at a local library revealed that historically, a Berliner Weisse wort was not boiled, allowing Lactobacillus already present on the grain to make its way into the primary fermentation with Brettanomyces ale yeast. As brewers perfected the technique, they learned that the yeast and lactic acid bacteria could be pitched together, and the higher the temperature range, e.g. 63–68° F as opposed to 57–64° F, the more sour the beer would become. Brewers further developed the process after that main fermentation to include kräusening the beer before bottling. This carbonation process, applied most often to lager beers but also to traditional wheat beers, adds freshly fermenting beer to bottle-ready beer, preventing yeast from becoming dormant during the second fermentation and maturation in the bottle, which can take up to two years.

A more contemporary and predictable process starts at low gravity and splits the wort in half for the first fermentation: half is inoculated with ale yeast (Saccharomyces cerevisiae) and the other half with Lactobacillus. After about four weeks, the wort is blended, filtered, stored at 41–50° F for about 13 months. The beer is bottled with a fresh addition of kräusen that includes only the yeast (no Lactobacillus). This modern technique is frowned upon by traditionalists and tends to produce less sour beers.

Part of the reason that Berliner Weisse, along with other sour beers, have been slow to trend is that maintaining Lactobacillus in a brewery is risky, because of the high probably that it could spoil other beers through cross-contamination. Most breweries require separate, dedicated equipment for these beers.

Another reason for the slow trend is that beer drinkers are still developing their palates, and even the most sophisticated American imbibers have been too busy familiarizing their taste buds with the bitter flavors of hops to entertain the sour notes of these traditional European styles. Nonetheless, the recent boom of craft breweries has resulted in an increased willingness to experiment, both on the part of brewers and consumers. As a somewhat unique American consumer, however, I got my start at this traditional, European end of the brewing spectrum. After 16 years and many diversions in my beer education, I’m ready to return to my German roots.