Beer Chemistry and History 101 with Gerri at Summit

Gerri Kustelski takes a break from the quality assurance department to teach us about beer.

by Becky Lang

Gerri Kustelski a chemist at the Summit Brewing Company in St. Paul, where she heads up quality assurance for their analytical lab. Photo by Carey Matthews.

More than 50 years ago, Gerri Kustelski found the beer industry a worthwhile place for a woman with a chemistry degree. After saying no-thank-you to a large local tech corporation that had offered a male friend more money for the same position, she headed to Hamm’s, where she heard there was an all-female lab. There, she found the brewery life to her liking, and found it paid better too. Now she’s a chemist at the Summit Brewing Company in St. Paul, where she heads up quality assurance for their analytical lab.

Considering her science chops, Kustelski talks about beer differently than most people. For her, it’s a matter of numbers, levels, logic, temperature, chemical reactions and even a little bit of history. We tapped her vast stores of knowledge to create a beginner’s guide to looking at beer through smart goggles.


Why Craft Beers Taste So Good

“I think one fascinating thing about beer as we know it now in the U.S. is that with the introduction of craft beer, we have been introduced to a myriad of styles and flavors,” Kustelski says. “Previous to the ‘70s when it started, the American public, unless they had traveled in Europe, had only experienced American lager.”

This American lager is golden in color, low in hops and milder, less flavorful in taste. You’ve probably had it at plenty of backyard barbecues and college parties. Once the craft beer explosion happened, people got the option to try beers of all colors, levels of depth and bitterness, and flavor notes.

According to Kustelski, the vast new rainbow of beer flavors that emerged came about thanks to the fact that brewers started using different varieties of malts, hops and yeast available to them.

“There is an enzyme system in each one of the grains that when it starts growing, it becomes active and starts converting those starches into sugars that provide energy,” she explains. “The brewer wants to activate the enzyme systems but he doesn’t want to grow a plant.”
“When you’re malting, you can just do that basic thing, get those enzymes activated and dry it,” she explains. “That’s called pale malt, and that’s the basis for most brewing as we know it.”This is done by soaking the grains in water and then drying them when they first start to sprout. The brewer then grinds them, adds water and then heats this slurry to a temperature where these enzymes are active.

But some maltster might caramelize the sugars, roast the grains longer and heat them up in all kinds of different ways. This is a large part of what creates the many flavors unique to craft beers, from a caramel sweetness to a coffee-like richness. All from drying and roasting the grain all kinds of different ways.

Why Yeast Matters

The malt isn’t the only thing that adds flavor—the yeast plays a part as well.

Yeast’s biggest factors are alcohol and carbon dioxide, but each strain of yeast produces different compounds that can produce specific flavors.

“Probably the best example that you might be familiar with is the Hefeweizen,” Kutelski explains. “It’s not just a wheat beer—it uses a very specific yeast that produces compounds that give it a banana-clove aroma and taste.”

“Part of being a good brewer is choosing the proper yeast so you end up with style you want,” Kustelski says.

Why Beer is Best Kept Cold

You know those people who tell you that you may as well throw beers away if they sit out for too long? Before you yell at them, consider that there’s actually science behind that.

“Beer is really fragile,” Kustelski explains. “It doesn’t like temperature change. It doesn’t like being exposed to air.” Air exposure oxidizes beer, which changes it’s flavor.

Kustelski advises going straight to the source for the ideal flavor.

“The best beer you’re ever going to have is if you come to a brewery and drink it at their bars, because it’s been kept fresh, cold and hasn’t been transported.”

For the regular beer-lover, she suggests buying beer out of the fridge at the liquor store and putting it straight into your own fridge.

Why Beer Can Get Skunky

“People use that term incorrectly a lot when they mean just bad,” Kutelski explains. “Skunk smells like a skunk.”

The reason why beers can start to smell skunky is that the presence of ultraviolet light can change beers that have been traditionally hopped, creating the same compound that a skunk uses for scent. She says this is especially common when drinking out of a clear, glass bottle.

That’s why Summit bottles are brown, she points out.

Why Kids Used to Drink Beer

Kustelski has a clear reverence for beer.

“If you stop and think about it, beer allowed humanity to continue existing,” she reflects. “Back when people first started living in towns, they knew nothing about sanitation, so their water became contaminated and polluted.”

At the time, beer was one of the only beverages that contained water that had already been boiled —so even kids drank it for cleaner hydration. But before you imagine buzzed toddlers running all over, know that this might have been unlikely. Kutelski speculates that beer was a lot less strong back then.


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