Volume 95 Issue 24 | pp. 22-23 | C&EN Talks With
Issue Date: June 12, 2017 | Web Date: June 6, 2017

The secret to great wine? Organic chemistry.

Wine chemist Andrew Waterhouse talks about teaching a generation of winemakers
Department: Science & Technology
Keywords: food science, wine, wine chemistry, Andrew Waterhouse
Credit: Eleni Kardaras Photography
Andrew Waterhouse poses with a bottle of wine.
Credit: Eleni Kardaras Photography

Hometown: Davis, Calif.

Education: Ph.D., synthetic organic chemistry, University of California, Berkeley

Professional highlight: Honorary doctorate from the University of Bordeaux, a school with a wine program that dates back to 1880, the same year the viticulture and enology program started at the University of California

Favorite molecule: Acetaldehyde, which is a key wine oxidation product

Favorite way to enjoy a glass of wine: Barrel sampling with friends

Favorite city: Ljubljana, Slovenia. “The food is wonderful; things are organized; there are many excellent local wines to taste and not too many tourists.”

For Andrew L. Waterhouse, being tasked with wine selection when having drinks with family, friends, or inquisitive journalists is something of an occupational hazard. “It’s just part of the job,” the professor of viticulture and enology at the University of California, Davis, says.

It’s a good bet that Waterhouse will pick a winning wine. He’s widely respected for his expansive knowledge of wine chemistry and has educated a generation of winemakers during his 26 years teaching in UC Davis’s world-renowned program.

But Waterhouse hasn’t always been a wine connoisseur. With training in natural product synthesis, he started his career at a different school teaching organic chemistry primarily to premed students and researching conformational analysis of polysaccharides. One day, while paging through C&EN on a flight, Waterhouse saw a job posting for an assistant professor of viticulture and enology at UC Davis. He wanted to return to the West Coast, where he went to school, so he applied.

“As soon as I heard I got the job, I started reading,” he remembers. “Professionally, I knew nothing. I was a wine lover, but I had no idea what was in wine, really, other than alcohol.” Now he studies wine’s complex natural products, such as flavonoids. “Winemakers call it chicken wire chemistry,” he says, because the hexagons in the flavonoid structures resemble chicken wire to those untrained in chemistry.

Waterhouse says when he first started at UC Davis he tried to teach organic chemistry to budding winemakers the same way he taught it to premeds. “It didn’t work,” he says. For example, when he taught his students about terpenes—important flavor compounds in certain wines such as Rieslings—he discussed how the compounds undergo acid-catalyzed rearrangement during aging.

“I was showing the students allylic cations forming, rearranging, and eliminating. And it was completely useless to them,” he says. “They have to understand something about terpene chemistry, but they don’t have to understand mechanistic transformations from one terpene to another.” This made Waterhouse completely rethink how he taught chemistry to these students. He needed to talk about chemistry that would be useful in wine making. “That’s why they take classes—they want to understand what’s happening so they can manage it better. It’s a very applied use of chemistry.”

And students of wine chemistry differ from premeds in another way, Waterhouse found. Whether the wine-making students are pursuing bachelor’s, master’s, or doctoral degrees, all approach the subject with passion, Waterhouse says. “When I was teaching organic chemistry to premeds, they had no interest in the subject. They just needed an A. It was a hurdle class for them and they didn’t like it.” That’s not the case with the students he teaches at UC Davis, he says. “They really want to know the information, and they want to know why it is useful.”

In 2016, after 25 years as a wine chemist, Waterhouse decided to create a resource for others who might be interested in teaching the subject or for chemists who are just interested in knowing more about the chemistry of wine. Along with Cornell University’s Gavin L. Sacks and the University of Adelaide’s David W. Jeffery, he coauthored “Understanding Wine Chemistry.”

The book, he says, is different from other wine chemistry resources because it focuses on the organic chemistry of wine. “Most of the chemists in the field are analytical chemists, and they’re very good at that, but when they write about it, they focus on analytical issues, such as comparing analytical results with taste and sensory results.” While that’s important, Waterhouse says, he and his coauthors wanted to create a book on the chemical reactions that take place in wine.

“Just by understanding the chemistry you can intervene in very simple ways,” Waterhouse notes. For example, sauvignon blanc wines from New Zealand are known for a guava- and passion-fruit-type aroma, but that fruity note would often be missing after storage. An organic chemist figured out that the aroma arises from an ester that can hydrolyze. Now, New Zealand winemakers keep the sauvignon blanc as cold as they can until it’s bottled and shipped, thus preserving that flavor. “So understanding chemistry is very powerful, even in wine making,” Waterhouse points out.

But, Waterhouse is quick to add, chemistry does not have all the answers. “When I came to Davis, I thought all we have to do is figure out what are the key molecules that are present in great wine. Many people have this idea, and I was not any different. It turns out that there have been a lot of smart people thinking about this for a really long time,” he says.

“What I’ve discovered is that it’s not really just the chemistry that makes wine interesting or valuable. There’s a lot more behind the story of wine than chemistry. I know that might be disappointing for some chemists, but the reality is that people love wine. And people love wine not just because of the way it tastes. They love wine for many reasons,” he says. “When you’re a winemaker one of the key things you have to be able to do is convey a message about your product—a story about yourself or the land or the history of the property. Those things are, in some way, more important to a wine drinker than wine that just tastes good.”

Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
John Casey (Wed Jun 07 01:14:40 EDT 2017)
By convention colour, by convention sweet, by convention bitter; in reality, nothing but atoms and the void. Democritus.

Democritus didn't know much about chemistry, but he was adamant that taste was dependent on composition. What is more interesting to me is the changes that take place after bottling, viz., the acid hydrolysis of glycosides and saccharides, the decline and seasonal fluctuations of the Redox Potential (temperature?) and the absorption of some volatile substances by the cork.
Kurt Burris (Wed Jun 07 20:46:20 EDT 2017)
I was lucky enough to be in Andy's debut class of VEN 124. He is a great professor (but I deserved an A not an A-). I don't remember the terpenes though. Sorry Andy!
Christian Paul Ramos (Thu Jun 08 11:08:29 EDT 2017)
I am a chemist from the Philippines. I now taking my Master's in Chemistry and I am thinking of organic chem in alcoholic drinks to be my general topic. I also would like to know more about the field and probably have MS and PhD in the same field. I am also inclined now in metal-organic frameworks which is a inorganic and organic in nature. Thank you!

PS: Nice article! I am motivated to be a wine chemist!!!
Nico Azios (Thu Jun 08 15:16:36 EDT 2017)
As a biochemist-turned winemaker, I greatly respect Waterhouse's knowledge of wine chemistry. Just yesterday I happened to be reading an article he co-authored about oxidation prevention as I research ways to better my wines. He is a great asset to winemakers and our craft.
Gordon W. Gribble (Fri Jun 09 06:36:16 EDT 2017)
As an organic chemistry professor/winemaker for nearly 40 years I look forward to Professor Waterhouse's book. I have a question regarding wine in contact with synthetic corks. Will taste and aroma be affected? My favorite wine compound is 2-isobutyl-3-methoxypyrazine.
John Casey (Mon Jun 12 02:16:09 EDT 2017)
Synthetic stoppers do not exclude atmospheric oxygen from bottled wine, and they also 'scalp' volatile flavours from the wine. Not everyone likes methoxy-pyrazines!
David Jeffery (Tue Jun 13 18:20:11 EDT 2017)
Hi Gordon, I hope you enjoy the book. Corks (especially synthetic) can scalp aromas from wine. Clean corks can even adsorb compounds from within wine that are associated with cork taint (haloanisoles). Your favourite compound is one of the most potent odorants in wine. When we work with it in the lab it can stink the whole building out if we're not careful!
Andrew Waterhouse (Tue Jun 13 21:26:12 EDT 2017)
Synthetic corks do not have the taint problem of natural corks (trichloroanisole) but both natural and synthetic do adsorb some non-polar substances that have aroma potential. In general they impart very little to the wine. Some tasters refer to a slight (normal) cork aroma. There is negligible effect on actual taste, i.e. sweet, sour, bitter by closures.
Damilola Daramola (Sat Jun 10 16:51:45 EDT 2017)
This is awesome, I recently took an interest in wine-making and Dr. Waterhouse would be an excellent resource. Just found the aforementioned authored book through the university library
Eric Hope (Wed Jun 14 22:02:14 EDT 2017)
I am a chemist for 40 years and a wine maker for 45. I just planted my first 10 acres of vineyard two years ago and started production in my new winery! Frightened and excited. I've enjoyed the article and others so I am open to any advice that can be offered to me.
John Casey (Sat Jun 17 02:24:21 EDT 2017)
Halo-anisoles are largely an environmental problem, and corks are particularly vulnerable because of their 2-3 square metres of internal surface area. Like Dr Who's Tardis, a cork is larger on the inside than it is on the outside. This gives a cork significant capacity to ad/absorb volatile compounds from the wine and over a period of time the flavour of the wine is refined; it also absorbs sulfide-like odours (SLO) from the wine.
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