Old-world fermentation

Summertime heat has spoiled many a batch of homebrew. Most ale yeasts do well at about 70 degrees, but much above that will result in unpleasant off-flavors. I’ve had to pour out more than one batch that was fouled by heat.

But right now, a long-kept brewing secret from Norway is emerging as, among other things, a tool for brewers without air conditioning. It’s called kveik, a hardy and genetically distinct yeast type that has lived for centuries in the homes of small-scale brewers. They cultured and preserved this fermenting critter—often letting it dry onto wooden rings that could then be dipped into the next batch of brew—and, probably, traded their own unique house strains among one another, much the way people might save and trade seeds or vinegar mothers. Kveik, which produces heavy citrus and fruit flavors, was available only in Norway until recently, when it was dispensed to commercial yeast producers.

The yeast is still confined mostly to Europe, but word is spreading among brewers everywhere, and coaxing kveik farther and farther out of its ancient hiding places. In Chico, the Home Brew Shop regularly carries the “voss kveik” strain from Omega Yeast.

“In summers, it’s perfect for homebrewers,” says Novato homebrewer Kevin McMahon, who has been using kveik for many styles of beers—“farmhouse saisons, fruit beer, IPAs, pale ale, wild, you name it,” he says—for about three years. He has relied on kveik especially when making larger beer batches that wouldn’t fit in his refrigeration unit and had to be left fermenting in the hot ambient temperatures.

Cellarmaker Brewing Co. in San Francisco has made kveik beers, and Drake’s Brewing Co. just released the Kveik and Strata, a hazy IPA made with kviek yeast plus the new Strata variety of hop. And in Chico, Secret Trail Brewing Co. has been experimenting with the yeast and releasing it as part of its Explorer Series (small-batch beers released in the taproom on Mondays), said brewery co-owner Jesse Fischer. At press time, a Kveiking Valkyrie farmhouse blonde ale was on tap.

McMahon, in fact, expects this yeast to get popular, partly for its temperature tolerance and also for the marvelous fruit flavors it makes. He tells the story of when he entered an IPA made with kveik into a local contest. The judges mistook his beer, which smelled powerfully of pineapple and mango, for a fruit beer and advised him he had entered his ale into the wrong category.

“You’d have sworn there was tropical fruit in that beer,” McMahon says.

The yeast, when used at high temperatures, also works rapidly. Beers that might normally take a week to brew can be made literally overnight. (McMahon says he once fermented a 7 percent alcohol IPA in 18 hours using kveik.) That heat tolerance developed as a genetic attribute in a yeast that started and evolved in a Nordic country—where even in the summer temperatures are mild—seems strange, but that’s apparently what happened.

Kveik’s genetic isolation was so long and so extreme, in fact, that—even though it’s probably just a subspecies of ale yeast—it is being treated as “the fourth yeast,” McMahon says. The other three main beer yeast categories are ale yeast (Saccharomyces cerevisiae), lager yeast (S. pastorianus) and the wild yeasts of the Brettanomyces genus.

So, if this rare yeast, with its storied farmhouse country past, becomes popular, will it still be cool? Were the Beatles cool after they left Hamburg?

For now, kveik remains largely at the homebrewer’s scale, and I wonder: Which other craft breweries will join the trend? The heat of summer is upon us, so let the race begin.