Stifling heat lifts spirits for Minnesota whiskey makers

Someone is pouring whiskey from a barrel
Sarah Lee, head distiller, helps Jace Marti, co-founder of Black Frost Distilling in New Ulm, Minn., draw whiskey from a cask inside the rick house on Thursday. The sweltering heat is helping with the pivotal process of whiskey maturation in drawing flavors from the wooden casks, especially during the recent heatwave across Minnesota.
Hannah Yang | MPR News

At Black Frost Distilling in New Ulm, fans blew air throughout the building’s main level this week in an effort to keep the distillery’s temperature consistent while whiskey fermented in barrels stored upstairs.  

With each step co-founder Jace Marti took, the oppressive heat and humidity increased as he climbed the stairs to the second floor rickhouse to check on the barrels.

“It is stifling up here,” said Marti when he reached the top step. Nearby, some barrels were oozing a small amount of liquid that Marti calls “barrel candy.”

Whiskey is aged in charred wooden barrels — typically made of oak, which has a lot of desirable flavors trapped inside the wood fibers. 

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Heat plays an important role in exposing those flavors and maturing the whiskey, said Marti. 

“When it heats up, the pressure inside builds and it forces it inside of the wood,” he said. “When it cools down and contracts, all that flavor is just pulled from the barrel.”

Someone is standing next to the barrels.
Jace Marti, co-founder of Black Frost Distilling in New Ulm, Minn. examines some of the whiskey casks inside the rickhouse on Thursday. Some barrels have what Marti calls "barrel candy" forming on the outside. It's liquid that has escaped from cracks in the barrels.
Hannah Yang | MPR News

High humidity also plays a role in creating great whiskey, said Sarah Lee, Black Frost’s head distiller.

“The humidity really helps. If you think about the climate in Kentucky or Tennessee, it’s a really warm, humid climate most of the year,” said Lee. “And we often think about that part of the country as where bourbon, where whiskey comes from. Where some of the best whiskeys in the U.S. come from.”

For Lee, the heat is a double-edged sword. It’s good for the whiskey, but the distillers don’t spend a lot of time in the rickhouse, if they can help it.  

“We mostly do (the work) early in the morning when it’s this warm, because in the afternoon, it gets even warmer and more humid here,” she said. “So, you can see we don’t spend a ton of time up here because it is so stifling, and the only thing that can handle this heat are barrels.”

Someone is pouring whiskey from a barrel
Jace Marti, co-founder of Black Frost Distilling, uses a whiskey thief to draw out the alcohol from the wooden cask to sample it inside the rickhouse on Thursday. The sweltering heatwave is helping with the pivotal process of whiskey maturation and expanding the wooden casks. Eventually, once the temperatures cool, the liquid will contract and draw the rich flavors from the barrels.
Hannah Yang | MPR News

Drought conditions could linger

Comfort aside, the heat has posed some other challenges. Drought conditions, dating back to last fall, affected the family farm that Black Frost gets its grains from. The winter wheat and rye crops failed. So, this summer, Marti said the distillery is relying on corn left over from last year’s harvest. 

“We’re kind of embracing that as our whiskeys are going to change from a year-to-year basis, because we’re using the previous year’s crop,” he said. “So, this year, we’re seeking out other farmers. You want to keep that Minnesota-grown grains. So, we’ve had to seek out other places that have had better luck (growing crops) than we did.”

While temperatures are returning to end-of-season averages, meteorologist Brent Hewett with the National Weather Service in Chanhassen said drought conditions could continue to plague grain farmers. 

“There is no sign of a huge pattern shift,” Hewett said. “So, it looks like we’ll see this drought continue into the early fall season, and likely gradually worsen as we remain drier than normal.”

Adapting and embracing change

Climate is an important conversation that Minnesota distillers are having, whether it’s about sourcing available ingredients or understanding how to adapt to the heat and use it to their advantage. Right now, they are using Mother Nature to do some of the work for them. 

But Marti said they also have to be prepared to pivot when Mother Nature isn’t cooperating. To survive he said distillers will have to be flexible, innovative and willing to adapt.

“Our whole concept is kind of embracing the Minnesota climate here and so we looked at the factors that are going to apply to our barrel aging,” he said. “So that’s looking at our environment and how we can utilize our warehouse and the way we do our processes to extract those specific flavors.”

Two person pose for a portrait
Jace Marti, co-founder, and Sarah Lee, head distiller, are inside of the rickhouse at Black Frost Distilling in New Ulm, Minn. on Thursday. The room is where the whiskey barrels are stored for maturation.
Hannah Yang | MPR News