Oshkosh brewers have a much longer history with sour beer than you might expect. Beginning in the 1870s brewers here regularly produced sours. It began with a handful of small, southside breweries specializing in Berliner Weisse-style beers. It was carried into the early 1900s by the Oshkosh Brewing Company. But when OBC stopped production of its Berliner Weisse around 1910, it brought an end to the brewing of sours here. A century later, Fifth Ward Brewing is bringing it back.
Last Friday, Fifth Ward released its third in a sour series the brewery initiated at the end of February. The latest in that line is Blackberry Frootenanny, a sour ale conditioned on 126 pounds of blackberries and 84 pounds of raspberries.
It’s a wonderful beer with a depth of flavor you rarely encounter in one so light and refreshing. The jammy sweetness from all that fruit pairs nicely with the tart snap of the base beer. Brewers Ian Wenger and Zach Clark of Fifth Ward built their sour base using a process known as kettle souring. Like most brewing techniques, it’s as much art as science.
The process begins like that of any beer: you make wort, the sweet liquid that results from the combination of warm water and malted barley. The wort is then run off into the boil kettle. This is where things get strange.
“Instead, of boiling it, we go up to just under a boil and then we drop the temperature back down to about 105 -108,” says Clark. At that point, the wort is spiked with a generous serving of lactobacillus.
The lactobacillus goes to work chewing up sugars in the wort and producing lactic acid as a byproduct. The goal is to achieve a clean sour flavor that isn’t bracing. Some brewers rely on taste to know when they’ve hit that sweet spot. Others use the PH of the wort as their guide. At Fifth Ward they do both.
“If the PH gets down to 3.6-3.8 that’s when it gets extremely tart and sour,” Clark says. “We don’t want that. We shoot for a PH of about 4. The lacto we have works fast, so you really have to watch it.”
Clark isn’t a fan of tasting the wort at this point. “It weirds me out,” he says. Wenger, on the other hand, gets right in there. “It smells kind of like tomato soup,” Wenger says. “And it’s like sweet still. It’s sweet and sour. It is weird.”
When they’ve got what they’re looking for, the kettle is cranked back up, the boil begins and the brew day proceeds like most any other. The beer was fermented with the Fifth Wards house ale strain. The final product comes in at 6% ABV and 16 calculated IBUs.
The process Fifth Ward uses is sometimes referred to as the Francke method. It was developed in Germany about 1905 but has only recently been adopted by American brewers. It’s very likely Clark and Wenger are the first commercial brewers in Oshkosh to have taken this approach to making sours. With Blackberry Frootenanny they’ve nailed the technique. It’s a beer to seek out.