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Quality Measures Inch Forward

March 2012
 
by Tim Patterson
 
 
I’ve written a couple columns recently about winemaking additives, boosters and enhancements of various sorts—one about how winemakers pick and choose among the bewildering range of products out there, one about “natural” winemakers who do their best to use none of them and still make great wine. It occurred to me that I was forgetting the most important additive of all: grapes.

In the past decade or two, growers and viticultural researchers have unearthed a good deal of information about how vineyard practices affect grape composition—trellising choices, deficit irrigation, clones and rootstocks, canopy management and precision viticulture in all its forms. At the same time, we have better, cheaper, faster and more accurate ways of measuring grape composition and knowing exactly what’s in those berries.

One might expect, therefore, that wineries would have upgraded their spec sheets for the grapes they buy, asking for and negotiating with growers about phenolic profiles, berry size, nutrient status or flavor precursors—something more than Brix and pH. One would, apparently, be wrong. Ripples of change are in the air, and market pressures more or less guarantee the slow but steady improvement of farming practices throughout the industry. But compared to the pace of development of miraculous new enzymes, tannin tougheners and yeast corpse by-products, changes in grape quality measurement are a very slow slog.

Bad old days
In the bad old days, wineries contracted for grapes simply on the basis of Brix, a very crude proxy for fruit ripeness. Sometimes this was supplemented by two other blunt indicators of grape chemistry: pH and acidity. More recently, it has become fashionable for winemakers to make picking decisions on the basis of taste, munching samples of grapes until the greenies seem to go away. And at the ultra-premium end of the grape and wine spectrum, yield restrictions have become a mantra and dropped fruit a point of pride, based on the belief that less fruit will automatically create more flavor.

All in all, this is a pretty poor set of criteria for picking vineyards and picking fruit, akin to selecting a bottle of wine for dinner based on the alcohol percentage and case production.

Grape berries are the single most important ingredients in wine, but of all the compounds in those berries, the sugars are the least interesting. Yes, some is indispensable as yeast food, but sugar’s primary job is to go away entirely during fermentation, in the process giving up the far more interesting aromatic precursors initially bound to sugar molecules. Sugar, if it is present in a finished wine at all, has a very simple flavor, no match for pyrazines, terpenes, noriseprenoids and a long list of other volatiles—and the same is true of its mischievous twin, alcohol. Sugar is boringly uniform; Pinot Blanc sugar is pretty much identical to Blaufränkisch sugar, only there’s usually less of it. If, for some reason, your grapes lack sufficient sugar, you can get some out of a bag. And, perhaps most problematic, Brix is a lousy ripeness proxy, since sugar development and flavor development run on separate tracks, even if they are both part of the same physiological railway system.

“Picking on taste” is supposed to remedy this problem by giving more direct access to flavor components. The trouble here is that grape flavors and flavor chemistry are light years away from finished wine flavors and chemistry; fermentation and aging transform the raw materials into something entirely different. But even if winemakers admit they can’t taste the finished wine on the vine, they believe they can taste the presence and decline and eventual disappearance of bitter, green flavors. This, too, is a pretty risky endeavor, since those potentially unpleasant elements can be masked in the fruit by polysaccharides, sugar and other things, and since the phenolic compounds that may lie behind the perception of greenness will themselves be radically transformed in the process of winemaking.

Finally, the belief that low yields always translate into better grapes and wine probably originated from observing that some of the world’s great wines come from low-yielding vines, and that massive overcropping surely produces insipid stuff. That bit of intelligence, however, has been transformed into something between a religion and a rural legend, resulting in wholly arbitrary yield targets and outbursts of fruit-dropping grapeocide.

The fallacy of fixating on tons per acre is easily exposed by the following thought experiment, courtesy of Doug Fletcher at Chimney Rock. Farmer Jones is widely known for growing the crappiest Cabernet Sauvignon in the Napa Valley—thin in flavor, short on color, underripe at any sugar level and green all over. The reason seems obvious: Farmer Jones brings in 10 tons of grapes per acre. Yielding to all the criticism, he rips out every other row of vines in his vineyard, and now grows 5 tons per acre of the crappiest Cabernet Sauvignon in the Napa Valley.

Grape quality can’t be reduced to tons per acre. It is a matter of balanced individual vines yielding the amount of fruit they can successfully ripen in a given locality, and not much more or less. Yield, even at the highest quality level, will vary enormously from situation to situation. Applying some magic number—3 tons per acre seems to be a popular upper limit for worthy fruit—across multiple growing regions and multiple grape varieties is, well, goofy.

These three criteria—Brix, field tasting and yield restriction—still dominate the industry, including its upper reaches. Markus Keller, viticultural researcher and author from Washington State University in Prosser, recounted the dilemma winemakers faced when cool weather in the fall of 2011 kept red grape Brix stuck at 21º far later than usual. Winemakers who insist they pick on taste found that the greenies were gone, but they still couldn’t bring themselves to pick until the sugar got up to 24º or 25º Brix.

“Deep down,” he says, “they’re still hooked on Brix.” He also wonders about winemakers whose version of “picking on taste” is chewing three berries and asking for a 30% crop reduction.

At Oregon State, extension viticulturist Patty Skinkis finds that many vineyards of Pinot Noir, already a low-yielding variety, get thinned down to targets based more on California metrics than Oregon&rsq uo;s conditions. “Crop thinning early or heavy,” she says, “doesn’t increase the rate of ripening. The sugars don’t necessarily go into the reduced crop of fruit, they can go into storage or canopy growth.” The state’s reported average yield is 2 tons per acre, but it could likely be a good bit higher and still yield good fruit, depending on the year.

At Cornell, researcher Gavin Sacks says people in New York talk a lot about yield targets, even if it isn’t clear how much sense that makes. His experience is that it’s possible to make good Riesling in the Finger Lakes at anywhere from half a ton to 8 tons per acre, but formulaic yield limits still get set.

Sacks’ colleague, Anna Katherine Mansfield, says that grape decision-making is “pretty much the same old, same old. Depending on where you are, people may just buy by weight. We’d like people to assess quality, think of grapes block by block, not just tonnage.”

Much of the industry, it seems, is still stuck in the bad old days when it comes to assessing grape quality. Can’t we do better than that?

Finding better criteria
The quest for more sophisticated criteria, alas, isn’t that easy. Growers and winemakers may have quite different ideas of what makes grape quality, and translating back and forth between the two different dialects can be frustrating. Academic researchers may have superior knowledge of the biochemical details, but they don’t call the shots. Joerg Bohlmann, a research botanist at the University of British Columbia, says he is “wary of telling winemakers what to do, what they should or should not do.” Winemakers themselves have to identify what they want, and researchers can them help find tools to get there.

Some elements of fruit composition are much harder to measure or control than others. In most of my phone interviews, I posed an extreme hypothetical question: If a winery was willing to pay a premium, could it entice a grower to produce grapes with more blueberry notes? After my informants all stopped laughing, several pointed out that even if the blueberry compound got maxed out, the flavor chemistry matrix is so complicated that the net result might be something else entirely. It’s rarely possible to reduce a wine quality descriptor to a compound, or even several of them. To make matters worse, the most appropriate set of measurements and metrics will likely vary by growing region, by grape variety and by the intended price point of the wine.

Some aspects of grape composition that could be modified by viticultural intervention are cheaper and simpler to fix in the winery. A good example here is grape nutrient status. In many cases, vines that regularly produce grapes deficient in assimilable nitrogen can get on track through some combination of cover cropping and/or foliar sprays, yielding fruit with a better nutrient profile and thus lowering the risk of stuck or sluggish fermentations. But solving nutrient problems in the cellar with a bag of DAP is quicker and cheaper than retrofitting vineyard practices. If a winery’s goal is more natural, terroir-driven wines, taking the trouble to produce grapes full of natural amino acids may be a better solution than packaged ammonia, but that’s unlikely to become an industry grapegrowing standard.

Phenolic profiles
Despite all these complications, some advances are being made in quantifying and specifying grape quality. The leading edge is probably in the measurement of red grape and wine phenolics, where relatively straightforward assays are now available, and where viticultural research has offered some avenues of control. Manipulating the amount and timing of sunlight exposure, adjusting crop loads and applying reduced deficit irrigation techniques can nudge grape phenolic profiles in the desired directions.

One prominent evangelist for phenolic profiling is Corey Beck, winemaker for Francis Ford Coppola Winery in Sonoma County’s Geyserville, Calif. For several years now, Beck and his cellar crew have employed the Adams-Harbertson tannin assay to profile phenolic content and development day by day for each red wine fermentation, yielding numbers for anthocyanins, tannins, total phenolics and “non-tannin phenolics” (monomeric catechins and so on.) The data, along with a complete juice-testing panel, is shared with growers, some of whom now have 10 years of records on different vineyard blocks.

The quantitative data helps concretize the quality judgments made by the winery in routing various blocks of grapes into different wines and tiers. Growers know how their grapes score, what program they go into and how they compare with other growers, and Coppola staff can discuss with them possible adjustments in the vineyard that could improve the value of the grapes. (See “Assay in Real Time,” Wines & Vines, October 2010.) “If you can make the economics work,” he says, “people will listen.” Beck was one of the speakers at a Jan. 25 panel titled “Productive Ways to Talk About Wine Quality” at the Unified Wine & Grape Symposium in Sacramento, Calif.

In a very different market segment, the toasty San Joaquin Valley, California State University, Fresno, professor and researcher Kaan Kultural and his team are exploring ways to improve the phenolic profiles of warm-climate, high-yield vineyards. Leaf removal right after fruit set turns out to be essential for banishing the greenies, and deficit irrigation techniques encourage smaller berry size and thus higher phenolic content in grapes from a region that has traditionally been thought of as producing flabby, pale fruit. Preliminary results appear in the final 2011 issue of the American Journal of Enology and Viticulture.

Several attempts have been made in Australia and elsewhere to use measurement of grape color on the vine as a predictor of eventual wine quality, using sensors attached to mechanical harvesters as they collect the fruit clusters. While this kind of color measurement is likely a better proxy than simple Brix levels, the results have been mixed.

White grapes harder to fix
In the Finger Lakes, on the other hand, better phenolic profiling may not be as valuable for a couple of reasons: The main struggle for red grapes is simply to get them ripe in such a cool climate, and the larger issue for the industry is the quality of white and hybrid grapes. (In this normally cool, humid climate, grape contracts often do specify the maximum acceptable proportion of rotted clusters, as well as the maximum infestations of Asian Lady Beetles.) Sacks at Cornell says that fixing problems in white grape composition in the vineyard is generally harder and less well understood than with reds. Mansfield notes that Finger Lakes growers were confronted in 2010 with an entirely novel problem, warm temperatures, leading to a surprising round of questions about harvest decisions in new circumstances.

If progress in developing new quality benchmarks is slow, some progress is at least being made in undermining knee-jerk reliance on some of the older ones, like the premium on savagely low yields. The evidence that balanced vines are more important than tons per acre is mounting, coming from both academic and industry trials. Beck mentioned one grower in El Dorado County, Calif., who discovered through consultations with Coppola that his grapes profiled (and tasted) much better at 5 tons per acre than at the mystical 3 tons. When potential customers wrinkle their noses at the yields for grower Ron Silva’s Silvaspoons Vineyards in Lodi, he walks them around the vineyards, shows them the farming and points out that his yields aren’t depressed by Eutypa and other vine maladies.

Farther south in the Central Valley, Kultural’s work has helped develop mechanized viticultural practices that deliver “textbook” balanced grape chemistry at 10-12 tons per acre. In fact, given the very warm Central Valley conditions, yields need to be higher than in cooler places, and attention to deficit irrigation, mechanized leafing and other practices can bring in very good fruit at what may sound like ridiculous tonnage. (You’d be surprised how many of those grapes end up in premium wine you are happy to drink.)

Back at Cornell, Sacks says that there is very little research shedding light on proper yield levels for cool-climate vinifera grapes, and Mansfield adds that there’s even less in the way of guidelines for the riparia-based hybrids she worked with a few years back at the University of Minnesota. Silva has developed a nice niche market in Iberian grape varieties, and his various Tintas and Tourigas and their kin show up in boutique bottlings at a lot of California wineries. But does anyone have a clue about how to crop Trincadeira? Any reason that should be another 3-ton wonder?

Oregon State University in Corvallis is conducting a fascinating series of trials designed to connect the dots all the way between side-by-side (or side-by-side-by-side) viticultural variations—cover crops, leaf removal, irrigation regimens—and finished wines, evaluated both for their chemistry and their sensory properties. That research probably won’t revolutionize Oregon grape contracts, but it’s the kind of work that can give both growers and winemakers more things to think about as they pursue quality.

What’s down the road?
For my last take on the question of grape quality, I figured I needed someone to gaze into a crystal ball for me, and that meant putting in a call to Leo McCloskey at Enologix, a winemaking consulting firm with a stellar, high-end client list. Currently, Enologix offers a series of tests, nine in all, which can be performed while grapes are on the vine and nearing harvest ripeness; the combined tests, Enologix says, will predict finished wine chemistry, potential longevity, what market style the grapes are suited for and, by implication, how the wine will fare with critics. He describes their approach, ferreting out potential market value from grape chemistry, as the “Moneyball” of wine consulting.

Further down the road, McCloskey thinks that “advanced farming”—farming that shifts gears nimbly to deal with seasonal variations in the vineyard—will become much more widespread. Even more important, he says, is that “advanced installation”—establishing vineyards to get the most out of their ecosystem of soil, climate, plant material, row orientation, irrigation, etc.—will also become commoditized, spread throughout at least the premium parts of the industry. The upshot will be that every area will be farmed up to its potential—some better than others, and some suited to Cabernet, some Pinot Noir, and so on.

But while we wait for the eventual triumph of reliably superior grapes, which will probably occur over time, we may have to put up with a few more decades of winemakers chewing on grapes and worrying about Brix levels. Another reason winemaking resists being reduced to a science.

Tim Patterson is the author of “Home Winemaking for Dummies.” He writes about wine and makes his own in Berkeley, Calif. Years of experience as a journalist, combined with a contrarian streak, make him interested in getting to the bottom of wine stories, casting a critical eye on conventional wisdom in the process.

 
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