The Weight of Wine

Stewards of the Vineyard

For Jim Kennedy, it’s all about mouth feel. The sensation of wine on the palate can be silky and smooth or coarse and hard. Wine experts call it texture. And along with color, taste and aroma, a luscious texture can cause some people to plunk down $100 or more on a bottle of Pinot noir or Cabernet.

Kennedy is a wine chemist in the OSU Department of Food Science and Technology, and he is trying to put his finger on what creates great texture in red wine. Armed with such information, he says, winemakers could add substantial value to Oregon’s wine production as well as to the grape crop itself. It was the state’s fourth most valuable fruit crop (behind winter pears, sweet cherries and apples) in 2005, worth about $36.5 million, according to the OSU Extension Service.

“If you think about how you sense red wine, first there’s the visual aspect,” Kennedy says. “Then you smell it. That’s the most complicated part of it. There are hundreds and hundreds of volatiles (aromatic compounds) in wine. Then you taste the wine. You’ve got organic acids and some alcohols. Then you feel the wine as it’s in your mouth. That’s the final sensation. I attribute it to tannins, that astringency, a dryness.”

Tannins — a class of compounds with arms-length names (proanthocyanidins, for example) that can readily react with proteins and other molecules — are the focus of Kennedy’s research. But texture is more complicated than tannins, and Kennedy and his colleagues are still trying to tease out all the factors. “We don’t have standards for texture,” he says. “It is such an elusive little thing to figure out, a tough nut to crack.”

The issue is critical for the wine industry. “Texture is one of the two or three sensory measures of great wine,” says Harry Peterson-Nedry, founder and winemaker at the Chehalem winery in Newberg and a member of the Oregon Wine Board. “The feel on the palate, the weight of the wine in the mouth, is extremely important.” Winemakers want to maximize texture, but they lack techniques that are reliable and effective, he adds.

A chemist with industrial experience in experimental design, Peterson-Nedry has provided wine samples for Kennedy’s texture experiments, and the two men have given joint presentations at the annual Oregon Wine Industry Symposium. “Jim Kennedy is one of the premier tannin chemists in the world,” he says. The wine board, which funds Kennedy’s research (along with the U.S. Department of Agriculture and the American Vineyard Foundation), is impressed with his multifaceted approach, collaborating with other OSU researchers with expertise in yeast, flavor and viticulture.

“We’re lucky to have Jim,” adds Rollin Soles, Soles, co-organizer of the annual symposium and winemaker at the Argyle Winery in Dundee. Kennedy’s research, he says, will create the tools for the industry to promote wine texture through practices in the vineyard and in the winery. And those tools need to be adaptable. “If you live in Oregon, you know how conditions can change from wet and cold one year to hot and dry the next. We have to move with Mother Nature to achieve balance in our wines,” he says.

In order to find the chemical fingerprint of texture, Kennedy and his colleagues are working with Peterson-Nedry, Soles and others in the industry to study growing conditions that influence the vigor of the vines and the chemical composition of the grapes. The location of grape clusters on the vine, says Kennedy, affects exposure to sunlight and tannin concentrations in grape skins. Researchers are monitoring the changing chemical environment inside growing fruit, starting from the time when tannins are first produced.

In the laboratory, they experiment with winemaking techniques and submit the results to chemical analysis and the ultimate judges — human tasters. (Lest this appear to be high living disguised as science, Kennedy says of one recent batch of samples, “They were all pathetic.”) Working with Kennedy is an international team of undergraduate and graduate students and a visiting professor and Ph.D. student from Chile on a Fulbright Scholarship.

They have made progress, publishing reports in agricultural and wine industry journals and offering information to growers at the annual Oregon industry symposium. But what they have is just part of the story. “We understand the skeleton (the tannins),” Kennedy says. “Now we’re going to put the flesh on.”

Kennedy has been studying tannins for more than a decade. During his doctoral research at UC Davis in the mid-1990s, Kennedy was looking for a change in tannins that could be related to winemakers’ perceptions of grape ripeness. “They can go out in the vineyard one day and say they (grapes) are not ripe, and the next day, they are,” says Kennedy. “Well, what’s an unripe tannin versus a ripe tannin? The winemakers would say, ‘we don’t know but we can identify it.'”

Despite developing new techniques for analyzing tannins, Kennedy didn’t answer the question in chemical terms during his work at Davis or during his subsequent fellowship at the University of Adelaide in Australia. Determining ripeness is still more art than science, and it remains a holy grail for scientists.

Kennedy’s passion for wine comes from more than chemistry and a desire to help an industry grow. He makes his own — about a barrel a year — and prefers reds. “I love making wine, and I love red wine, but I definitely leave the science out of it. Just the passion. It keeps me grounded in the laboratory,” he adds.

His first attempt at Pinot noir, Oregon’s signature wine, was less than successful. When he came to Corvallis in 2001, Kennedy bought the grapes, crushed them and fermented the juice. He had high hopes. The best wine he had ever tasted was a Pinot noir with a “velvety texture.” He learned first-hand why this grape has earned a reputation for difficulty. “It was the worst wine I ever made in my life,” he says.

When it comes to texture, some wines “carry” tannins better than others. Pinot noir is known as a “temperamental” grape. Tannin concentrations that work in a Zinfandel or a Cabernet can turn a Pinot noir harsh.

Moreover, the source of tannins makes a difference. Skin tannins tend to be “soft” and “more approachable” than seed tannins, says Kennedy, creating a wine that is ready to be consumed sooner. Thus, a selective emphasis on skin tannins helps winemakers produce a balanced wine that matches a trend in wine consumption. Most buyers tend to drink their wine within 24 hours of purchase.

Historically, Oregon’s wine industry has built a reputation for small, family-run businesses producing high-quality wines, especially Pinot noir. That grape accounts for about half of the state’s 14,000 acres of vineyards, which are concentrated in the north Willamette Valley’s hill country southwest of Portland. However, the industry is expanding at the southern end of the valley, eastward into the Columbia and Walla Walla valleys and into southern Oregon where it tends to be hotter and drier.

Kennedy and his colleagues hope their research will help to guide the industry’s growth. Their studies are maturing just as the texture of Oregon’s wine industry is changing, becoming a more robust reflection of the state.