Beer 101
A pair of UC biology majors takes a fresh look at one of the collegiate world’s most storied beverages.
When Kimberly Foote ’10 and Jessica Wilczek ’10 answer “Beer” to the question of what they’re studying in college, the range of reactions are what one might expect.
“We definitely get a few chuckles, and people definitely want to hear more about what we’re doing,” Foote says.
Chuckles, piqued interest, and from parents at least mild concern, perhaps coupled with head-shaking disbelief. Foote recalls, “When I first told her what I was thinking of doing for my senior research, my mom said, ‘Really? All that education? All that money?’”
Indeed, Foote and Wilczek have spent much of their senior years studying beer. That very notion calls up very familiar stereotypes of college life. So to debunk any visions of Animal House, some clarification is in order. This is not a consumption-related study. The lab partners are researching decomposition and degradation processes in beer involving light and temperature.
In other words, they’re exploring the causes of stale and light-struck, or skunked, beer taste.
Their research interest originated as a squabble between their research advisor, Assistant Professor of Biology Daniel Kurtz, and his daughter, Patti. One morning last year, Patti accosted her father as he was removing from the refrigerator bottles of beer that were leftover from a party she held the night before. She told him the beer would get “skunked” if it was taken and left out. While scientific literature supported his daughter’s assertion, Kurtz was skeptical. An academic scientist and former commercial scientist, he needed firsthand evidence.
When he returned to campus the following week, he shared the encounter with Foote, his teaching assistant at the time. The discussion quickly developed into a debate and, ultimately, a simple pilot study. In essence, Kurtz and Foote left some beer out in the sun for a few weeks that summer to see if Kurtz’s daughter’s prediction would be confirmed.
“And low and behold, it does get skunked,” Kurtz says.
Light on the subject
This outcome ended Kurtz’s skepticism. However, the pilot study did not provide scientifically relevant data. Now that the question of whether had been answered, Foote wanted to better understand why skunking occurred so that she could contribute to the growing body of scientific research on how to keep packaged beer tasting fresh.
While the incident involving the Kurtz family refrigerator suggested cooling (or lack of same) might play a role, Foote soon understood that the chemical puzzle she was considering was more a question of light than of heat.
Beer, specifically the hops that help flavor beer, is light sensitive. When light hits beer, it causes a photochemical reaction through which hop acids called isohumulones degenerate into 3-methylbut-2-ene-1-thiol, a sulfur-containing compound that is virtually identical to that present in a skunk’s spray.
So in essence Kurtz was partially correct. Removing the beer from refrigerated temperatures did not put it at risk of skunking. Exposing it to light, however, did. It was in fact the darkness of the refrigerator, not its coolness, that kept the pungent odor from occurring.
Foote explains, “We had found the process of skunking is largely determined by light penetration, not really having much to do with warmth. And we also came to the conclusion that it’s not largely detectable by taste, but definitely by smell.”
What’s more, the stale taste in beer occurs through a separate process. “And that’s where Jess came in,” Foote recalls.
Whereas Foote’s focus was on bad beer smell, Wilczek introduced the taste component of beer gone bad.
Bad-tasting beer is most commonly associated with staleness. Particularly when exposed to fluctuating temperatures, oxygen trapped in the bottling process can react with ethanol and fatty acids, producing trans-2-nonenal, which causes a distinctly bad flavor. “The same process applies to a whole bunch of grain-based stuff,” Foote says. “It’s like what happens when bread goes stale. It gets that horrible, cardboard-like taste.”
Case study
The two biology majors are not alone in their academic interest in beer. They have, in fact, joined an army of scientists studying the molecular properties of the popular beverage, including the groundbreaking researchers at the University of North Carolina and Ghent University in Belgium who first discovered the cause and explanation of skunked beer.
With Kurtz’s assistance, Foote and Wilczek are building on this foundation of knowledge by examining the role packaging plays in the degradation process. Specifically, their work is focusing on how the skunking/staling processes occur when beer is delivered in clear bottles, brown bottles, and aluminum cans.
It is, in effect, a case study in molecular science.
“We hypothesize that packaging pilsner lager in aluminum cans or in brown glass bottles will reduce or prevent this light-struck flavor or ‘skunking’ effect. In addition, the production of ‘stale’ flavor should be reduced by continuously cold storage,” Kurtz says.
The research will be carried out by means of duotrio sample comparisons. Subjects test a reference beer sample before partaking of the two coded samples. They then mark a ballot indicating which coded sample was more similar in taste or smell to the reference.
“These are sensory techniques that we’re using: trio testing, statistics, double-blind studies,” Wilczek explains. “We’re using everything we’ve learned in four years here.” She and Foote both attribute the robust design of the study to Kurtz’s tutelage in sensory evaluation, a specialty of his.
“Sensory psychophysics is his thing. He’s just very knowledgeable,” says Foote. “Anything that you have a question on he will clarify, and if you are on the wrong track, he’ll tell you about other techniques to get a better result.”
Even so, gaining approval from the College’s Institutional Research Board (IRB) – a requirement for studies involving human subjects – was less than a sure thing, given the subject matter.
“The IRB hears ‘beer’ and ‘human subjects’, and they think, ‘I don’t know about that,’” Wilczek says. “So there were many clarifications. In our testing we allow inhaling, wafting, and smelling for the olfaction portion of it. For the gustation or tasting we do not allow the subjects to drink the beer. It’s a sip and spit method, which is very common in sensory testing.”
No laughing matter
Foote and Wilczek are not dismayed by the chuckles or the movie references to beer-drinker favorites like Animal House and Beerfest. And while the biology majors are the first to admit their research is not of the world-saving variety, they believe their subject matter is important.
“Is it gene therapy or anything like that? No. But there’s a place for everything,” Wilczek says. “Our whole purpose behind this is to see how do we avoid these decompositions so you can get a better brew because a lot of people enjoy beer, and it’s an important question for beer companies.”
Important to the tune of nearly $100 billion in annual beer sales in the United States alone.
Kurtz, who worked as a research and development scientist for one of the U.S.’s largest consumer product companies before beginning his academic career, appreciates the often-overlooked value of consumer product science.
“In this country, or maybe in the west in general, one of the things that we do really well is look for ways to improve consumer products. So therefore we have hairdryers that dry and deodorants that do what they’re supposed to do. This is all the result of consumer research in product development,” he says. “Some product research is important in terms of saving the world and some is important just in terms of making life easier and more pleasurable. We have many products that do a really good job because people have done this work.”
As counterintuitive as it may seem to the skeptics, Foote and Wilczek are, through their study of beer, building a deeper and more profound understanding of the scientific process.
Wilczek, for her own part, sees this project as an opportunity to flesh out the knowledge she’s gained over the last four years. “The classes I’m taking now – we do research papers, we’re always sifting through the literature, and we’re doing hard chemical mechanisms all the time,” she says. “So for me it was a nice way to apply what I’m learning and just do it in a fun way that meant something to me.”
“They’re learning a little bit of chemistry in addition to the biology,” Kurtz says. “They’re learning a little bit about smell and taste and sensory procedures. Whether they go into sensory research as a field, they’re still learning how to ask the important questions, and I think they’ll be able to use that.”
Going “weird places”
More importantly, Kurtz adds, the study has helped foster in both students an element of inquisitiveness that he sees as an essential component in any scientific inquiry.
“You look at the lives of some of the great scientists, and some of them approached their work knowing exactly what they were looking for and the goal was to get there first. But a lot of the others just kept looking at things and realizing when something is odd that maybe it should be looked at more closely. I think many of the greatest discoveries have come from that,” he says. “We get caught up in asking questions that we think NIH is going to fund, but somewhere back there we maintain the inquisitiveness. And that’s how you get graduate students who can go off and explore things in weird places.”
While such “weird places” may lay ahead for both of these inquisitive minds, the two researchers are now considering immediate next steps. Wilczek is currently applying to medical schools, while Foote plans to pursue a research career after graduate school. Their deeper understanding of the research process, gained through the study of beer, will likely prove an asset in these pursuits.
What’s more, they’re glad for the opportunity to show their mentor that beer can be considered – in one sense, at least – an aid to higher learning.
“To a large extent,” Kurtz says, “they’re proving that I’m totally ignorant.”
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