September 15, 2014

The Industry Series: Tasting Tips from Cornell Flavour Chemist, Gavin Sacks

Close your eyes for a moment and think about what the ideal job might entail. If it involves tasting wine or beer while working, read on.

Meet Gavin Sacks, Associate Professor in Food Science in Cornell University’s College of Agricultural and Life Sciences (CALS), a person who spends plenty of time with a glass in one hand and a pen in the other. Sacks teaches courses that comprise part of Cornell’s interdisciplinary major in enology and viticulture, including Wine and Grapes: Analysis and Composition, and Wine and Grape Flavor Chemistry. With the teaching day done, Sacks gets down to the business of analyzing the flavour and aroma components of grapes and wine.

In this inaugural piece detailing careers within the beverage industry, Sacks––a flavour chemist who works closely with the New York State wine industry––tells us about how his work and research can enhance our appreciation of beer and wine. For those of us in search of tips about how to develop our palates, Sacks also spells out intriguing practical suggestions. And lest the beer-committed homebrewers among us despair at all the wine flowing early in this interview, stay with us for the ride. A greater awareness of the aromas that surround us can enable us to identity what went wrong––and what went right––with our beloved concoctions.

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I first met Gavin several years ago at a wine-tasting he had organized at the home of a mutual friend, and have had occasion since then to sit down to a meal, a few bottles of wine, and, from time to time, beer. What struck me very early on was his focus on the flaws he perceived. But not only that: it was the words he used to describe the flaws. Hitherto, wine appreciation for me had usually involved grasping after an elusive vocabulary to describe what was pleasant about the wine. Occasionally, it was about trying to pin what was objectionable with words such as “oxidized” and “corked.” Sure, pungent cat odours intruded upon polite conversation about the gooseberry and boxwood character of many a New Zealand Sauvignon Blanc, but this is as far as things went. Describing wine with biochemical terms like esters, fusels, and phenols? It took some getting used to. If memory serves me correctly, the first time I heard the word “Brettanomyces” was when Gavin uttered it apropos of a particularly funky wine from the northern reaches of the Côtes-du-Rhône. A problematic beast, this bug called Brettanomyces …

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A Tempest in a Tankard: What kind of research do you do? What are some of the most exciting aspects of your personal research, and what are some of the promising new directions opening up for your field in general?

Gavin Sacks: My research program focuses primarily on wine and grape flavor chemistry, and particularly on cultivars that are popular in New York State and other cool climates. Some very recent research projects by the lab include the following: determining factors that limit extraction of tannins during winemaking, especially in cool climates; determining the cause of sulfurous off-aroma appearance during bottle storage; and developing easy and inexpensive tools for measurement of sulfites and volatile acidity in the winery.

We have also performed research in collaboration with viticulturalists to understand how growing practices affect flavor chemistry. For example, it’s well-known that precursors of the compound responsible for the “kerosene and petrol-like” note of Riesling will increase if the grapes are highly exposed to sunlight. We have determined that the critical window for this exposure is just before veraison (color-change). This may be useful to a producer interested in avoiding or increasing the petrol character of their wine.

As far as future directions, one of the hottest topics right now in wine chemistry is understanding the interaction of wine and trace levels of oxygen during storage. Enologists have a good grip on what happens if wines are exposed to large quantities of oxygen (namely, oxidation and wine spoilage), but the effects seen with exposing wines to more typical levels encountered in barrel, tank, or bottle are harder to predict. Why do some wines improve in qualities such as color and mouthfeel following oxygen exposure, while others immediately brown, even though their chemical composition appears nearly identical? There are now storage tanks and some closures (not to mention micro-ox units) that allow in specific amounts of oxygen. That sounds great, but that’s only useful if a winemaker knows what to expect.

TT: Tell us a bit about your career trajectory. Did you have any inkling when you first started your undergraduate studies that you’d be working with the wine industry?

GS: When I completed my Ph.D. in chemistry, I had no expectations of working on wine for a career. I had a love of both teaching and research, and had planned to apply for traditional faculty positions in chemistry departments. I liked wine, but from a wine appreciation perspective. On a lark, I did a brief stint in a vineyard before starting a post-doc, which opened my eyes to the subject of wine and grape science. A few years later, when I saw that Cornell was advertising for a wine chemist, I thought “why not?”.

TT: How close are your ties with the wine industry of the Finger Lakes and the rest of New York State? Do wineries approach you/Cornell, or do you let it be known that you/Cornell can help them out?

GS: All of the Cornell enology faculty have close ties to Finger Lakes wineries as well as wineries in other New York State regions (Lake Erie, Long Island, etc.). My colleagues with extension appointments will work much more closely with commercial wineries on a day-to-day basis. This consultation work includes operating a wine and grape analysis lab with discounted rates for New York State winemakers, and organizing frequent workshops and short courses.

Although I do not have an extension appointment, I still work with wineries in the region, especially as part of collaborative research projects. For example, in a recent project, we were interested in understanding the persistence of a particular pesticide (elemental sulfur) on grapes that could lead to off-aromas during fermentation. We developed an easy technique to measure the pesticide, and distributed measurement kits to wineries. We then compiled results and presented them at winemaker conferences. Regional winemakers also host field trips by Cornell classes, provide guest lectures, and employ our students following graduation. TT: How much actual smelling and tasting do you do over the course of a given day or week?

GS: That will vary. In some of my spring classes, we may taste four to six wines per lecture, and if I’m also guest lecturing for other classes, and need to evaluate candidate wines ahead of time to confirm their appropriateness, that may mean a few dozen wines per week. I may also participate in a tasting session with other faculty and students, or else a local winemaker may drop by with some odd samples, all of which can mean another two to twenty wines in a day.

However, there are some weeks where the only wine I taste is what I drink with dinner. In sum, I think I taste fewer wines than many sommeliers or other wine professionals. But I probably taste a lot more weird and faulty stuff.

TT: How much of your research involves precision instruments, and how much of it relies on our notoriously capricious senses of smell and taste?

GS: It will depend on the project, and where we are in the project. A lot of wine research, my own and that of others, focuses on off-flavors. This isn’t because we like bad wine, but the reality is that most funding is available for fixing or avoiding problems. When was the last time you went to doctor because you were feeling great?

Many off-flavors are due to the presence of one or two chemical compounds in gross excess. Often, the initial work enologists do is to identify or confirm the identity of the offensive compounds, and then set up an instrumental method for their analysis. Subsequently, we use the instruments to see what factors affect the compound(s). Instruments offer better reproducibility, and don’t mind working through the evening, so they do the bulk of analysis. But at the end of the day, whether it’s a desirable or undesirable flavor, it’s important for us to use sensory panels to establish the initial target, and to confirm results once sample analysis is complete.

TT: Here’s a related question. How well do instruments quantify “smell” and “taste”? I’m assuming that they pick up on aspects of an aroma profile that we humans might miss at first.

GS: There are some things that can be predicted rather well by instrumental analysis. Sourness, for example, can be very well modeled in dry wines simply by determining the acid concentration via titration. The intensity of off-flavors can also often be modeled rather well, since these usually can be related to the presence of one compound in excess. There may be some variation in individual sensitivities to these off-flavors, but we can talk about averages for a population of wine consumers.

However, many aspects of flavor are hard to model from instrumental data. For example, “red fruit” and “black fruit” aromas arise from the presence and absence of lots of compounds, and predicting the intensity of these aromas is not easy. The same thing goes for a number of other wine terms, such as body. An added complication is that sensory panelists, even if they are wine professionals, often have a hard time using some sensory terms in a reproducible fashion. “Minerality,” for example, is notoriously difficult to get panelists to agree upon. TT: What kinds of overlap is there between the flavour and aroma compounds of beer and wine (and other spirits)? Can you give some examples of the chemical compounds, along with how we might describe their flavour and aroma?

GS: To my knowledge, there are no flavor compounds unique to wine. Anything that can be found in wine can also be found in beer (or spirits, or coffee), and vice versa. Wine and beer differ in chemical composition quantitatively, not qualitatively. If you spend enough time and money, any wine compound could be detected, if only in extremely trace concentrations. Some examples of compounds common to both beer and wine:

Diacetyl: “buttery” aroma, desirable in some wine styles like barrel aged Chardonnay, but often undesirable in crisp lager beers
4-mercapto-4-methyl-pentanone: “cat pee / grapefruit” aroma, important to the varietal character of both Sauvignon blanc wines and some hoppy IPAs
4-ethylguaiacol and 4-ethylphenol: “clove/phenolic/barnyard” aroma, produced by Brettanomyces yeast, essential to the character of many Belgian farmhouse ales, but often considered a fault when they dominate wine

Also, flavor chemists use the word “flavor” as a general term to describe smell, taste, and mouthfeel.

TT: What kind of advice would you give to craft beer enthusiasts or budding wine connoisseurs who want to get the most out of their tasting sessions?

GS: Never, ever taste a single wine or beer at a time. Humans are lousy at doing sensory evaluation on a single product in a vacuum; we’re much better at doing comparative studies.

The other recommendation I’d give is to remember that there are no unique flavor compounds or flavors to be found in wine or beer. So, try to smell and taste lots of things, not just wine or beer. Go to a perfume shop or a candle store or an auto parts store and sniff everything. Buy a bunch of obscure fruits from the local Asian market and taste them. You will have a lot more “aha” moments as a result.

TT: Do you have any suggestions on putting together home flavour and aroma kits so that people can expand their sensory horizons?

GS: As I mentioned above, smell and taste everything around you, within reason. Kits are okay for faults training, but a lot of real aromas aren’t very stable, and the kits do a so-so job in reproducing them (and they get worse during storage). If you smell something interesting, track it down, and figure out what the cause is.

TT: In one of our conversations, you mentioned a grant proposal that you’re working on for a hop analysis lab at Cornell University. Can you tell us more about what you and your colleagues envision for this lab, and why you think it’s important for both the hop industry and brewing industry?

GS: The proposal would be for a lab at Cornell to perform malt, hop, and beer analysis for the growing industry. We have a similar lab for wine and grape analyses. Currently, there are a lack of regional alternatives for these analyses for small and mid-size operations. For example, there is an interest in using New York State hops, but brewers want to know the concentration of alpha-acids, which will eventually lead to bitterness. Having a nearby lab to make these measurements with a fast turnaround time will help both regional growers and producers in the craft beer industry.

TT: What do you see to be some of the biggest challenges facing the Finger Lakes/New York State wine industry and the exploding craft beer industry? These industries are quite different, but perhaps there are some common challenges, or challenges unique to each industry.

GS: On the growing side, the humid conditions of our state take a toll in the form of fungal diseases for grapes, hops, and malting barley. In the wineries or breweries, smaller operations have the challenge that the winemaker/brewer may have wear a lot of hats: janitor, microbiologist, analytical chemist, accountant, sales and marketing guru, tasting room staff, human resources manager, and the like––all in the same day.

TT: What kinds of things are these industries getting right, in your opinion?

GS: I love the spirit of collaboration and openness among New York State winemakers and vineyard managers. They are almost invariably willing to help each other out with advice and accumulated knowledge, not to mention the occasional loan of equipment. For the most part, they recognize that their competition is with the rest of the wine world, not with each other, and that they need to work together to raise the profile of New York State wines. I don’t know the craft beer industry as well, but I expect that they have a similar attitude.

TT: It’s the end of the day and you want a drink. If it’s wine, what kind? If it’s beer, do you prefer the flavours and aromas of malt, or are you a “hophead”?

GS: Right now, since it’s late summer, I like refreshing and not too heavy. So, lower alcohol, crisp, balanced. So, for beer that means Kölsch and well-made Pilsner-type lagers; for wine, that may mean Riesling or dry rosé. Lots of malt and hops and oak and dense fruit and high alcohol have their place . . . just not right now.

TT: Are you able to sit down and just enjoy a glass of wine or beer without thinking of the chemical compounds, or without critiquing the flaws?

GS: That can be an occasional problem, especially if we’ve been focusing on faults in class. What I’ve learned to do is if I am really trying to enjoy wine or beer, I will buy a product type that I know nothing about. That way, I don’t the run the risk of getting too critical!

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Related Articles in the Industry Series

How To Become a Beer Liaison: An Interview with Genesee’s Sean Coughlin

Beeronomics: An Interview with Trey Malone

Further Reading/Viewing

Gavin Sacks featured on NPR/PRI’s Science Friday (January 2014)

Beer Judging Certification Program (BJCP)

BJCP Beer Fault List

Cicerone Certification Program

Images

Cornell clock tower: F.D. Hofer

Gavin Sacks: Cornell Department of Food Science (CALS)