The Grape’s Decisive Moment

An event of monumental importance to wine lovers has just occurred. Incredibly, it happened almost simultaneously in every wine region north of the equator.

It’s called veraison, and it marks the beginning of the grape ripening process. Barring unforeseen meteorological events such as unseasonably cold temperatures and biblical rains, the Northern Hemisphere’s table wine crop will be ripe enough for winemaking in about six weeks.

Veraison is a massive physiological shift on a berry small scale. Since early spring the grape vines have been working furiously to set the stage for what is now happening inside every grape: bursts of electricity, the rise and fall of whole families of organic compounds, the appearance of strange entities called flavenoids. In other words, a scene that Hollywood’s top special-effects wizards might spend millions of dollars emulating.

The noble grape is an enigma wrapped in a skin wrapped in a canopy of little solar panels called leaves. Choosing the right moment to harvest is the wine producer’s single most important decision. It has been so for thousands of years and yet, as the Northern Hemisphere’s vintage 2000 commences, the wherefores and whys of wine grape ripeness remain largely mysterious.

The fundamental principle of the growing season is cumulative effect: Each phase capitalizes on what happened during the previous period and in its turn sets up the next one. Picture an old-fashioned seaman’s telescope being slowly extended. As each section opens out from the prior one, the field of vision narrows and the result--the wine--comes into better focus. A vintage wine is not merely the product of the growing season but a lens through which we finally gain a sensory image of how the grapes ripened that year.

All through the spring and early summer, it’s as if the vine is building a machine. At veraison, the machine turns over and begins to whir, generating intense activity inside each and every grape in the vineyard.

“Veraison represents a huge change, a major change in the physiology of the [grape] berry,” says UC Davis professor and ripening expert Douglas O. Adams. “It goes from an organ that is accumulating acids to one that is metabolizing acids, from an organ that’s not accumulating sugar to one that’s accumulating sugar at a higher rate than any other fruit we know about.”

Aside from the grape’s prodigious ability to concentrate sugars, it differs from other fruits in several ways. One is the relatively long time between color change and harvest. Tomatoes are ready to eat within a few days of showing color, apples inside 10 days. Grapes take six weeks or more to mature.

Another difference is the accumulation of tartaric acid. Unlike less-stable malic acid (also found abundantly in apples, peaches and strawberries), tartaric acid remains undiminished in the finished wine. That accounts for the tartness that sets grape wines aside from other fermented fruits.

And then there’s “hang time,” the term growers use to describe the extra time grapes spend hanging on the vine after they reach a basic sugar ripeness suitable for winemaking. Often a kind of sea change occurs during hang time, which can elevate a good vintage to greatness.

“The concept of hang time wraps up a lot of different subtle phenomena which can occur between 23 and 25 Brix,” Adams says. “There are a lot of important changes aside from small shifts in sugar and acid. The berry gets softer as the cell walls gradually break down. More pectin is released, and that influences mouth feel and tannin perception. There are subtle changes in the molecular weight of the tannins. The flavoring compounds can change dramatically. It’s a continuously moving composition.”

Within the arc of that composition, the sensory qualities of the grapes are changing constantly. The aromas, flavors, tannins, acids and colors that characterize wines made from grapes harvested early in the ripening curve are not the same as those appearing in wines from late-harvested grapes.

The general spectrum runs from a green, vegetative character in the former to a raisiny quality in the latter. Often the entire evolution of the sensory profile from green through red and black fruits to raisin will occur well within the accepted technical definition of ripeness.

The shift is a little different for each grape. Sauvignon Blanc goes from cut grass and jalapeno-like aromas and flavors toward melon-like impressions. Cabernet Sauvignon moves away from green olive and bell pepper toward clear Bing cherry and on into cassis. Zinfandel and Syrah (Shiraz) are notorious for suddenly turning super-sweet through dehydration.

There is a point along the continuum of maturity at which, theoretically at least, the time is just right for picking--but different vignerons may well call that moment at different times, according to what kind of wine they’re trying to make.

Growers have tools to help them decide when to pick. The hand-held refractometer can be used to measure the Brix level (sugar content) of grapes while walking the rows in the days leading up to the big event. Laboratory analysis of ripening grapes can give critical information about sugar-acid pH balance. Still, deciding when to pick is nowhere near an exact science; it often comes down to an impulse based on personal taste and experience.

The target is a precise point in the harvest window when elusive qualities such as balance, finesse and elegance are captured. The rewards of accurate picking, especially single-vineyard wines from superb sites, can be extraordinary sublimations of the vine’s (and the grower’s) efforts.

Among many examples of perfect ripeness from my recent tasting, the beautifully clear, round and crisply melon-like flavor of a Groth Vineyards Sauvignon Blanc ’99 speaks of long days and cool nights in the heart of Napa Valley. The liquid crystal palate of a Trimbach Clos St. Hune Riesling ’91 is the essence of a gravelly churchyard in Alsace.

A Coche-Dury Meursault ’90 beams with the full-bodied, succulent essence of a slope tilted perfectly toward the sun, with each small vine laboring steadily to ripen golden bunches of Chardonnay. A wine from the other side of the world, the Tim Adams Shiraz ’93 from a Clare Valley vineyard called Aberfeldy, is a clear expression of big, old vines basking in the temperate heat and warm red earth of a charmed little cranny in South Australia. And the Ridge Vineyards “Geyserville” ’91 is the radiant purple image of gnarled century-old Zinfandel, Carignane and Petite Sirah vines with their roots plunged deep into the volcanic soil of northern Sonoma County.

In each case, ripeness means something different. In every case, it means something wonderful, potentially something like a bottled miracle.

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Smith is writer-at-large for Wine & Spirits Magazine.