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.”

Taste Tests

I really like the taste of beer.  And so do many other people.  But “beer” obviously isn’t just one flavor, they vary in complexity from watery Natural Light to a complex craft-brewed Stout. There is such a variety of tastes that make up beers that the taste of beer can be hard to explain. Luckily, yesterday, at a beer tasting at the Wisconsin Science Festival, we learned how the sense we call “taste” really works.  We were each served a tray full of little labeled cups, full of mysterious liquids that definitely were not beer.

Jon Roll, a UW prof who teaches beer brewing courses, led the discussion. He explained that the tongue really only tastes 5 things, sweet, salty, sour, bitter, and umami. The rest of our sense of “taste” is actually the aromas of food, experienced by the nose.  The nose senses food aromas through two pathways. First, we inhale the scent of the food outside our mouths. We typically call this smell. However, when the aromas of food in our mouths reaches the nose through the nasal passageway, we refer to that as the taste of the food. Even though the olfactory nerves in the nose are responding the same we seem to mentally seperate these two processes.  We say that the roasting turkey smells good and then it tastes good too.  But when we say we are enjoying the taste, it is largely because of the smell.

We tasted sweet water. Then we tasted really sweet water. Blech. Then, going back for another sip of the first sample was striking, it tastes just like water.  Roll explained that the taste buds can get desensitized pretty easily to some flavors, so we stop registering them.  This is potentially a big concern for the manufactures of food, how to keep something tasting good all the way to the last sip without losing our sensitivity to the flavor?

Most of the receptors in the mouth for bitterness, we discovered, are near the back of the tongue and throat. Because of this, professional beer tasters always swallow the beer they are testing.  Unlike wine tasters, who can swirl it around in their mouths and then spit it out to describe the flavors, the bitterness component of beer is best sensed by swallowing. No one in the audience seemed upset to find out that we had to actually drink the beer.

To understand the role of our noses, Roll asked us to pinch our noses tight while rubbing a gum drop on our tongue.  It just tasted sweet. It wasn’t until you released your nose that the flavor of cinnamon became apparent. We looked silly, but we did it again. Same thing with spearmint. And orange.

However, your tongue does more that just taste the 5 famous flavors.  It also has physical responses to some flavors that can be called mouth-feel.  Taste something strongly sour, and your mouth puckers up and starts salivation.  Drink tea or red wine and the tannins can make your tongue feel strangely dry, even though you are drinking a liquid.

When we were finally served a sampler of beers, everyone was better equipped to describe what they tasted.  People sipped beer holding their noses, and then re-sipped with noses functional normally.  Complex beers like the porter we tried have a progression of flavors, from the early aromas of coffee or caramel, sweet in the middle, a pleasantly bitter finish.  In my opinion, it was the best one at the event. But, other people preferred the floral and bitter IPA.  To each their own tastes, apparently.