Scientific Sleuthing and Bad Beers

Highlights from my conversation with Jon Roll, a UW professor of Bacteriology.  Roll teaches a brewing class for undergraduates, using professional equipment donated by MillerCoors.

I wrote a news story for my Science Journalism course about a beer tasting Roll led as part of the Wisconsin Science Festival, with some of the information from this interview. But, Roll had more interesting things to say about the science of brewing and the need for an conscious tasting than I could possibly fit into my 500 word story.

“We tend to be somewhat oblivious,” Roll said about the sense of taste.  He explained that learning about taste is a process of educating your tongue and educating your senses.

For him, the aha moment came when drinking beer with Roy Desrochers, a professional beer taster. Roll said he became much more aware of things he had not been aware of before, as Desrochers pointed things out.  “He was fascinated with the progression of flavors,” Roll explained, “From sweet to malt to bitter that slid down the back of your throat. The whole thing took like a minute from when you took the sip.”

In Roll’s class, his students have to learn to taste the subtleties of beer as well. There are common problems in the complex brewing process that can create a variety of “off-flavors” in the beer. To go back in the process a fix the mistake, brewers have to know what chemical compound is creating the off-flavor.  You can buy a kit of common off-flavors to practice with. They train themselves to identify these compounds by drinking beer purposely spiked with a common chemical culprit, so they form conscious associations between off-flavors and specific chemicals. Tastes and smells are hard to accurately convey to someone else, one might think “woodchips” and someone else might think “file cabinet”, in an example Roll gave.  By having all the tasters try the same chemicals in beer, they can learn to associate the taste with the compound, even if they describe the sense of that chemical differently.

In the brewing classes that Roll teaches at UW, his students use scientific sleuthing to track down how these specific chemicals were produced. Figuring out where that specific chemical came from requires tracing back through genetic regulation and biochemistry. Maybe the temperature was off slightly, causing certain enzymes to catalyze and unwanted breakdown. With their sense of taste attuned, the students can track the problem. This way, they understand how to alter the brewing to prevent the off-flavors. They can use the same techniques to replace specific successful flavors as well. At this point, Roll explained, human taste is still the most sensitive instrument we have for detecting trace amounts of certain things in our food and drink.

Although he’s not a tasting professional, Roll enjoys teaching about the science of beer. “Beer is all over in our society, history, heritage. The brewing industry is big in Wisconsin.  People enjoy learning about it.”   He also explained that beer is a great place to start talking about science because everyone is excited about beer and “there is so much science involved. Engineering, chemistry, gene regulation, put together in something very tangible.”


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