As the hop capital of America, the Yakima Valley has long had a reputation for hop-forward beers. After all, the valley is a mecca for fresh hops, allowing brewers to simply drive down the road during harvest to pick up these flavorful cones straight from the source.

But there’s another style of beer that lends well to celebrating the valley’s agricultural bounty: sours.

A sour is a beer that’s intentionally made for acidity to shine through, giving off its tart, sour characteristics and lending itself to often be complemented by the addition of fresh fruit for balance.

It’s not a new style by any means. In fact, sour beers have been around for centuries.

During the Industrial Revolution, brewers didn’t really have the same sanitation standards or equipment they have available now, so they would brew some beer and let it sit open. Along the way, the liquid would collect bacteria that was introduced from the air, and because certain types of bacteria are acid-producing, it’s fair to say that brewers back in the day most likely found themselves in sour territory inadvertently a time or two.

Since then, sour beers have come a long way. There are two main ways the industry goes about making a sour. Brewers can make what’s called a kettle sour — or a quick sour — which allows the wort of the beer to quickly ferment with acid-producing bacteria in the kettle. Or, they can opt for a more traditional route like Varietal Brewing Company in Sunnyside does as they work to showcase one of the most robust sour beer programs in the valley.

Depending on the goal of the sour, when co-owner and brewer Chris Baum brews a beer, it will be fermented all the way in a stainless-steel fermenter, or it will end up in a barrel.

“We put it in wooden barrels with wild yeast and allow those to feed on the residual proteins in the beer,” Baum said. Essentially, acid-producing bacteria feed on the dead yeast, creating the acid that gives way to a sour’s tart characteristics throughout the process.

Two of the most common types of bacteria intentionally introduced to sour beers are lactic acid, producing pediococcus, and lactobacillus, which is also found in many food products and candies.

Then, it’s typically time to add fruit for a layered flavor profile.

“We have access to so much fresh fruit here,” said Baum. At Varietal, they’ve done sours including blueberries from Wycoff Farms, peaches from CLS Farms and even a Syrah sour using grapes from Discovery Vineyard.

The barrel plays a role in the final product as well, and luckily, barrels are easy to come by in Yakima Valley’s wine country.

“We prefer to use neutral wine barrels,” Baum said. “A wine barrel has more body to them than compared to a liquor barrel.” And the brewery has been able to collaborate with local wineries such as Co Dinn Cellars, Cote Bonneville, Fortuity Cellars and J.B. Neufeld to get unique wine barrels to age sours.

A sour might spend one year in barrel, or it might spend three, depending on the end goal. “The time in barrel depends on what you’re doing,” Baum said.

Along the way, the brewer is fighting what’s called acetobacter. Just like in winemaking, acetobacter creates vinegar out of oxygen and alcohol, so the liquid in barrel is often tested along the way to make sure everything that’s happening in the barrel is balanced and going according to plan.

“The key to making sour beer, the way we make it, it’s all about blending,” said Baum. “Not all sours are created equal.”

Single Hill is another brewery featuring sour options on the tap menu, and the sours featured in their Rocketship Series, especially Raz Rocketship, have become wildly popular.

The history of this sour, however, goes back further than Single Hill’s opening in 2018. According to co-founder Ty Paxton, a Berliner Weisse beer was featured at Single Hill co-founder and head brewer Zach Turner’s wedding, and then it made an appearance at his brother’s wedding and Paxton’s wedding, fondly earning the name Hitched. That made way for the inspiration of the Rocketship Series, ultimately leading to Single Hill’s Treeline Series, allowing more room for collaboration with local produce growers to make a sour beer.

Single Hill released its Treeline Series at the end of February, with three fruited beers in the lineup, including two golden ales aged in wine barrels with local fruit. The third beer, Star Time, was a kettle sour aged in French oak barrels, with Sugar Time Peaches and Honey Star Plums added for refermenting.

“These were gorgeous ripe fruits from Johnson Orchards,” said Turner. “Because they were fresh, we were able to wait until the fruit was perfectly ripe, and then I was able to spend an afternoon processing fruit with my 2-year-old daughter to make this beer.”

And as fans of Single Hill picked up a bottle or tried a pint of what they dubbed as summer in a glass, it truly showed off the many sweet ways Yakima breweries and produce farmers are working together.

“Yakima’s agricultural bounty is very special to us and part of the basis of planting our brewery here in the valley,” Paxton said. “The benefits of using Yakima Valley fruit is we’re able to use the freshest ingredients possible as well as highlight our local partnerships with the farms.”