By Jeremy Zoss
Is yeast the most underappreciated ingredient in beer brewing? Kevin Welch thinks so. The founder of Boom Island Brewing knows a thing or two about the subject. Before founding his brewery, Welch spent time traveling around Belgium and brewing at 13 of country’s most innovative breweries. When he returned, he brought back a secret weapon of sorts: nine strains of yeast straight from the source breweries. He uses these yeast strains to recreate the qualities found in the beers that inspired him.
Welch said he first started thinking about opening a brewery 13 years ago when he was a craft beer fan well-versed in the flavors of hops and malt. A new doorway in flavor was opened for him when he tried his first Belgian Tripel.
“There were flavor aspects present that were not malt and were not hops, the two aspects that I was familiar with,” he said. “There were spice flavors that were not created by spices. They were created by yeast. Wow. It completely had my head spinning.”
Welch spent the next four years studying Belgian beers, and when he decided to start a Belgian-focused brewery, he and his wife knew they had to go to the source for inspiration. They spent two summers in Belgium working in breweries as part of informal internships.
“I picked up so much knowledge from my own personal heroes in the Belgian brewing scene,” he said. “In my mind, they’re like world-class concert musicians. I picked up everything I could from them, and a few yeast strains along the way.”
When he returned, Welch re-cultivated his yeast strains and now uses them as the primary fermentation yeasts in Boom Island’s beers. With multiple Belgian strains at his disposal, each of Boom Island’s beers uses a different yeast strain in primary fermentation. He said re-cultivating yeast strains isn’t difficult, but must be done under strict conditions.
“It’s general microbiology 101,” he said. “You want to get as close to lab condition as possible.”
Welch can’t divulge which breweries the yeast strains came from or how he transported them back to the U.S., but he considers his use of these original strains to be an homage to the brewers he studies with. He doesn’t try to imitate their beers or use the yeast strains in exactly the same way, but rather uses them to create his own original flavors that still recall the yeast’s Belgian roots.
According to Welch, one of the reasons yeast is so much more prevalent in Belgian brewing than German or English brewing is that Belgian’s history of invasion and colonization left it without any sort of beer purity law. As a result, Belgian brewers had “absolute freedom of expression” to use spices, grains, and other techniques that would be forbidden by Germany’s beer purity law. Yeast can impart notes of honey, cloves and other spices, so it was natural for Belgian brewers to use yeast to push for complex flavor notes that other brewing cultures shied away from.
In addition to imparting flavor notes to beer, Welch said that yeast is an underappreciated part of beer for another extremely important reason: it’s the ingredient responsible for fermentation. Without yeast, there is no beer.
“We don’t make the beer,” he said. “We make the malt syrup. That’s what the brewer makes. The yeast makes beer.”