Cover Story
What's Really In That Wine?
Get two wine geeks together over a glass of wine, and you’re likely to hear a discussion about whether the beverage in question is a result more of the vineyard it came from or the winemaker who chaperoned it into the bottle. But what’s in that glass depends even more fundamentally on something else: trust.
We like to assume we’re drinking what the label says, but are we? Is it really wine, or was it manufactured to look and taste like wine? Could there be something life-threatening in the first sip? Is it really a 2008 North Coast Pinot Noir, or a 2007 Central Coast Grenache macerated with some flower petals?
Ours is not a trustworthy species, alas. The more global the food and wine supply chain grows, the more the bonds of trust are stretched and, occasionally and spectacularly, torn. From melanin in milk powder from China to the periodic falsification of Kona coffee; from the ongoing saga of the fake Thomas Jefferson Bordeaux bottles to the recent flap over the Languedocian roots of Gallo’s Red Bicyclette Pinot Noir, things may not be what they seem to be. It’s not often that we quote Ronald Reagan approvingly, but we probably should appropriate his simple slogan for arms control negotiations with the Soviet Union: Trust—but verify.
Authentication has many faces. Particularly in the food world, the danger of harmful products looms large. For both food and wine, the questions of whether a product is what it says it is and comes from where it says it comes from are increasingly coming to the fore. For wine in particular, progress in methods of authentication holds out another tantalizing prospect: finding the unique fingerprint of a particular terroir.
All these concerns and more were in the air at a two-day symposium about Progress in Authentication of Food and Wine held March 21-22, part of the annual meetings of the American Chemical Society in San Francisco. Two-dozen research presentations from around the world provided a fascinating glimpse into what we know, what we don’t, and what we may be able to know soon.
Chemical markers
This being a meeting of chemists, the natural emphasis was on using advanced technology to identify and detect chemical markers that could verify or prove a product claim false. The opening overview by Dr. Gary Takeoka of the USDA, however, provided a reminder of the importance of good old-fashioned fraud detection methods. Takeoka cited the example of a scandal over alleged cage-free eggs in Britain in 2006. The fraudulent supplier of said eggs was exposed initially when truck drivers testified that they were hauling battery-cage chicken eggs into the facility, then hauling the same eggs out labeled as “free range;” and by a look at the books, showing great quantities of battery eggs purchased and cage-free eggs sold. Only later did careful microscopic analysis reveal the telltale markings of cage wire on the shells.
After that, the technology quickly became more advanced. Roberto Consonni from the National Council of Research in Milan, Italy, described promising work being done with nuclear magnetic resonance (NMR). This allows for identification of the presence and concentration level of several metabolites in a single experiment, an approach enhanced by multivariate statistical methods. Consonni’s group has been focusing on questions of geographical origin, a very hot topic in policy debates about protection of local and regional products. His data demonstrated the NMR approach’s ability to distinguish between two olive oils from different sides of a single lake.
Dr. Stefano Sforza of the University of Parma, Italy, looked at how DNA, peptides and other molecular markers can be analyzed through high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) methods. The applications he presented include identification of GMO-free foods, distinguishing tomato and olive cultivars, and sleuthing out cheese production methods by the analysis of oligopeptides. Of huge importance to those with allergies, this method can detect the presence of hidden allergens when products such as muesli contain undisclosed contaminants such as peanuts.
One of the more intriguing markers, discussed in two separate presentations, was the level of a particular isotope, carbon-14. Carbon-14 occurs in nature in the atmosphere at a constant, very low level, the result of cosmic ray interactions with nitrogen. It is distinct from the carbon isotopes that make up the carbon dioxide produced by the burning of fossil fuels. But during the era o
f atmospheric nuclear testing, 1955-63, 14C levels spiked, and ever since they have been steadily declining down to near-pre-testing levels. Bruce Buchholz of the Lawrence Livermore National Laboratory, Calif., and Graham Jones of the University of Adelaide, Australia, showed how various analytical techniques can allow for vintage-dating of wines from recent decades, based on the level of 14C, the “bomb pulse.”
Two speakers from Germany turned their attention to oak—one parsing out what is oak and what is grape in aromas arising from barrel-aged wine, and one demonstrating that barriques and oak chips leave distinguishable chemical trails.
Other presentations focused on methods for the identification of wine varietals through analysis of flavonols and other compounds. Jim Kennedy, now with the Australian Wine Research Institute, offered a cautionary perspective, suggesting that variations in phenolic compounds within a single variety, over time, and because of different production methods, make grape-based phenolics less than ideally suited for determining red wine varietal authenticity.
Testing for terroir
Two presentations focused more directly on the identification of wine terroir. Ulrich Fischer, of the DLR Rheinpfalz research organization in Germany, presented an overview of an elaborate five-year terroir study he and several colleagues have been conducting. The project looks at Riesling planted on five different soils in different climate zones and vinified with different winemaking methods, all carefully plotted out for good controls—different climate regions with the same soils, different winemaking on the same vineyard’s grapes, etc. The study employs both chemical analysis and rigorous sensory evaluation—correlating, for example, the distinct chemical profiles from soil differences with recognizable sensory properties through descriptive analysis.
Best of all for hard-core terroir seekers, Régis Gougeon from the University of Burgundy, France, posed a question that got down to brass tacks: Can we distinguish the wines from the different vineyards around Vosne Romanée—Romanée-Conti, La Tâche, Richebourg and all the rest? His team is getting close. Gougeon showed the power of non-targeted methods, high-resolution mass spectrometry “snapshots” of the chemodiversity of the thousands of metabolites that flow from the complex interaction of grape, environment and human activity.
Authentication is a work in progress, reflected among other things in the title of the symposium, the second the ACS has held. At this point, if someone is willing to pay for it, we can figure out with some certainty if that bottle you’re drinking is really wine; how much alcohol it contains; whether it’s made from vinifera, labrusca or rutabaga; if it’s old or young, probably even the vintage (if it’s a post-bomb harvest); and whether the acid came from grapes or a bag, and the oak influence from barrels or chips.
It’s harder to establish with certainty that the wine is a Pinot Noir, or whether the grapes were grown organically (unless there is pesticide residue), or exactly how it was blended. It’s tougher yet to prove what clone was involved, whether Biodynamic farming was involved, or exactly what plot of slate it was grown on.
We’re getting closer to knowing those things every year. But besides providing puzzles for chemists to solve, does anybody care?
Sooner or later
Sue Ebeler, a flavor chemist at the University of California, Davis, and one of the two organizers of the ACS symposium, said that authentication may not yet be much of an issue, but in a global economy, it can’t be ignored. She noted that the EU has begun to put a considerable amount of time and money into developing authentication control methods, and that even in the U.S., country-of-origin labeling requirements are starting to come on line, raising the possibility of fraud and the necessity for rigorous testing.
In the chemistry world, she said, attention to this area is growing, as evidenced by the increased interest since the first ACS symposium on the topic five years ago. Funding for research right now comes in part from industry, in part from government, in part simply because the chemistry itself is fascinating. For now, she said, “The high-end auction wines, the investor-class wines, will get most of the publicity. But in the long run, the potential for fraud and the need for authentication lie much more in the mass market.”
A graduate of UC Davis’ school of enology and viticulture, John Buechsenstein now teaches extension courses there as well as at The Culinary Institute of America at Greystone. As an active winemaker in California’s North Coast, he is constantly exploring the world of enology and sensory analysis. Tim Patterson is a regular columnist for Wines & Vines. To comment on this article, e-mail edit@winesandvines.com.
