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Taming tannins

Wine science and the quest for texture

By | December 15, 2006

America has become a nation of viniculturists: wine is now produced in every state in the union. But can New World wines seriously rival revered Old World vintages? Chemist James Kennedy, a Professor of Food Science and Technology at Oregon State University, is certain they can, "so long as we make wines well, and making wines well means realizing there's lots of room for scientists in the wine industry." Kennedy delivered the second lecture in the New York Academy of Sciences' "Science of Food" lecture series in New York City on Monday evening (Dec. 11). His topic was the compounds that have taken on the mystery of the alchemical amongst red wine producers: tannins. Tannins are the astringent plant polyphenols that bind and precipitate proteins. Botanists describe them as defensive compounds that protect plants from bacteria and fungi and deter herbivores through their astringency and their interference with digestion. For organic chemists, tannins are what make us pucker up from eating pomegranates, persimmons, or green bananas -- tannin molecules combine with the protein molecules in our saliva, disabling the saliva's ability to lubricate the mouth. Medical researchers are focused on the therapeutic potential of tannins, including recent work showing that the phenolic compounds in red wine decrease the risk of atherosclerotic disease. Kennedy's own view of tannins has the balance and clarity of a 1982 Bordeaux: "Tannins equal texture." Kennedy explains that unlike researchers who want to capture the health properties of tannins, "I am a wine quality guy. I want to make Robert Parker happy." Parker is the world's leading wine critic, and his take on tannins can be as intoxicating as anything that comes in a glass. His highest scoring red wines have "rich," or "loamy," "velvety," "ultrafine," "silky," "caressing" and even "racy" tannins. When tannins dominate a wine, they become "huge," or "grippy," "muscular" and -- memorably -- "flannel-like." But if tannins make a red wine, they can also break it. All winemakers want to avoid reviews that recoil from their wines as over-astringent, when an over-abundance of tannins, or the wrong tannins, have rendered the wines aggressive or "green." Tannins are localized in the solid tissues of the grape. Stem tannins are generally avoided because they impart a vegetal flavor, and seed tannins also have coarser properties, so winemakers are learning techniques that maximize tannin extraction from the skins and control extraction from seeds. The seeds are, however, highly favored by vintners as a precise measurement of a grape's readiness for harvest. Tannins are produced early in the growing season and oxidize with time -- seeds begin green and turn incrementally brown as the grape ripens. Kennedy described the scene: "As it comes close to harvest, you'll see growers pacing up and down their vineyards, plucking out seeds, inspecting their color and chewing and crunching on them." Vintners have become fixated on tannin levels, and they are seeking out specialists like Kennedy to help them control the amount, quality and types of tannin in their wines. Kennedy worked with one vineyard to unravel the mystery of why two plots a spit away from each other, growing the same grapes, should produce on the one hand, bottles of wine that could be sold for $75, and on the other, bottles worth just $38. The winemakers knew what made the $75 wine better -- it had much higher tannin concentrations. But they needed Kennedy to explain how that had happened. His task was to match the chemistry of the wine to the exact geographical location: to its micro-, macro- and meso-climate, and its canopy management . The answer lay in sun exposure and irrigation: GIS technology revealed that the quality vines exposed more soil between the rows. The sunnier soil was drier, and a drier soil was, in this case, optimal. The vineyard couldn't make more sun or move their established vines, so they responded to Kennedy's findings by planting moisture-sucking ground-cover between the vines in the under-achieving plot. Their $38 wine now costs a good deal more. "A hundred years ago, the father of fermentation science, Louis Pasteur, began to explain what happens in red wine stored in oak barrels. Since then, the developments in wine science have been truly remarkable," Kennedy concluded. The best wine producers are realizing that wine-making is both an art and a science, and requires a delicate balance of old and new techniques. Fermentation, for example, can be computer-controlled, its gravity monitored, and specific temperature profiles maintained. And US partnerships between vintners and scientists are paying off. In 1976, an infamous blind tasting of Californian and French wines led to the all-French jury declaring Californian wines superior. The Paris Judgment, as it became known, was recreated this year, and after all the slurping and spitting, the results were the same. The lesson of this contest exceeds national bombast. US wines have developed all the complexity of Old World vintages and, crucially, are aging beautifully. Kate Thomas mail@the-scientist.com Links within this article: James Kennedy http://oregonstate.edu/dept/foodsci/faculty/jak.htm K. Thomas, "From chemist to chef," The Scientist, Dec. 1, 2006 http://www.the-scientist.com/article/display/36661/ P. Hagan, "Fresh heart for red wine drinkers," The Scientist, Dec. 31, 2001 http://www.the-scientist.com/article/display/20118/ Robert Parker http://www.erobertparker.com/ The Paris Judgment http://en.wikipedia.org/wiki/Paris_Wine_Tasting_of_1976 2006 wine competition http://news.bbc.co.uk/2/hi/europe/5013910.stm
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Avatar of: Adrienne Burke

Adrienne Burke

Posts: 1

December 19, 2006

You can hear more from Kennedy on this topic in an interview with NYAS associate editor Adelle Caravanos at http://www.nyas.org/snc/podcasts.asp#1047\n\n

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