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When Oscar Wilde wrote that only shallow people don't judge by appearances, he could have been referring to red wine. Depth of color and hue reveal much about a wine's style and yield clues about its aging potential. Dark reds often have notable concentration, and while denseness of color doesn't always ensure intensity of flavor, ripe grapes tend to be dark grapes.
Red wines today are generally darker than was once typical. "In the last 10 or 15 years, we've been getting riper grapes with more flavor and richness," says Napa vintner Philip Togni, who makes Cabernet from his property on Spring Mountain. "And it's very difficult to get ripe [Cabernet] without lots of color."
Color in wine grapes is only skin deep. With the exception of hybrid varieties, all of the pigments, called anthocyanins, develop in the skin (not the pulp) during the ripening process. Anthocyanins are phenolic molecules commonly found in plants, and they account for the red, blue and purple colors in leaves, fruits and flowers. In grapes, their quantity and chemical structure varies according to a number of factors, such as grape variety, weather conditions and growing techniques.
Just as people vary in skin tone, certain grapes naturally have more anthocyanin. Syrah, Cabernet Sauvignon and Petite Sirah are three of the darkest grape varieties, whereas Pinot Noir and Nebbiolo (the grape in Barolo and Barbaresco) are typically lighter. Since only the skin contains pigment, smaller berries with a higher ratio of skin to pulp yield deeper colors.
In Napa, top Cabernet producers sometimes pick fruit with nearly 15 percent potential alcohol. And harvesting such ripe grapes often translates to very dark wines. That's not necessarily because their skins have more pigment, but because extremely ripe grapes have fragile cell walls that make it easier to extract pigments. Barring fall storms, grapes at the end of the season also often lose moisture, which concentrates the pigments.
Inky reds trigger a Pavlovian response in many wine lovers, who associate depth of color with intensity and concentration. Vintners recognize this consumer preference and know that it's in their financial interest to do everything possible to maximize color. "It's just easier to sell a dark wine," says Adam Lee, co-owner of Sonoma-based Siduri Wines, which makes 7,500 cases per year, mostly of Pinot Noir and Syrah.
Viticultural techniques that increase color, such as yield reduction, also produce grapes of greater concentration and flavor intensity. That's been the case in Piedmont, according to Luciano Sandrone, one of the region's leading producers of Barolo, Barbera and Dolcetto. As harvest approaches, he does lab tests that analyze the color potential in the skins every three to five days.
Francisco Hurtado, general director and winemaker at Marqués de Riscal in Rioja, says that color at harvest is a crucial consideration. "All our lives, we've been selecting grapes by sugar. Now we're selecting by skin color. We find it corresponds more closely to the quality we're looking for than simply potential alcohol," Hurtado says.
Color potential is also influenced by techniques controlling the vegetative growth of the vines. Judicious removal of foliage can darken skins because sunlight catalyzes pigment formation, as well as minimizing undesirable vegetal flavors. But it's a balancing act, since excessive sun and heat diminish anthocyanins.
Dark grapes don't always translate to dark wine, so vintners strive to increase color extraction during the production process. A survey of 100 vintners might elicit 100 different methods for maximizing color. One favored approach is known as a prefermentation cold soak, whereby vintners harvest early in the morning while fruit is still cold, then crush the grapes and allow the juice and skins to macerate. The cold soak allows natural grape enzymes to degrade the skin cells and release more pigment. (Some estates, especially those that make Pinot Noir, add enzymes to the must.)
Left untended, the mass of skins (called the cap) floats on top of the fermenting must. To extract tannin and flavor, vintners employ a variety of maceration techniques such as pumping juice over the cap and punching the cap into the must. Some estates favor rotary fermentors, horizontal vats that increase juice contact with skins and promote color extraction.
What vintners don't do can be just as important. Fining and filtering -- techniques meant mostly to reduce tannin, clarify wine and eliminate microbes -- can also remove color. Most producers also minimize the addition of the essential preservative sulfur, which can diminish pigmentation.
Although the appearance of a red wine depends upon factors such as varietal composition, vintage and production techniques, all reds follow the same general template -- with age, hues change and colors lighten. Very young reds made with deeply pigmented grapes can be practically opaque, with dark purple tones that appear almost black; young wines made from lighter varieties are redder, with little if any purple.
A number of factors influence a wine's aging capacity, most notably its ability to withstand oxidation. All things being equal, wines with darker color age better, since anthocyanins, like tannins, are antioxidants that preserve fruit character.
Inky purple tones lighten over time, giving way to ruby and brick-orange colors. As reds get too old, they either turn pale and watery or become brown from oxidation. The pace of this transition depends on the chemical structure of the particular wine. For example, a top-tier Bordeaux, such as a great vintage of Château Latour, can preserve its dark, ruby color for several decades. However, wines such as Beaujolais Nouveau can lose color intensity just a few months after bottling.
Orange or brown hues in a young bottle reveal inferior winemaking or inappropriately warm storage or shipping conditions (high temperatures accelerate oxidation, which robs wine of fruit richness). On the other hand, purple tones in a supposedly older bottle should raise a warning flag that the wine may be something other than advertised.
The chemistry of color is one of the most complex and hotly disputed topics among winemakers and academics. Recent research suggests that much of the purple color in young reds, as well as color stability during aging, is not a function of the quantity of anthocyanins so much as the presence of other molecules that bind to anthocyanins and magnify their intensity, much as a dollop of neon dramatically amplifies pigments.
Whatever the chemistry at work, a vocal minority of vintners -- most notably some Pinot Noir producers -- dispute the significance of achieving dark color in reds. Since Pinot Noir berries usually have less pigment than other major red varieties, it's extremely difficult to craft a very dark Pinot Noir. But that doesn't necessarily mean that light-colored wines are inferior, as is often demonstrated by older Burgundies that may have faint color yet have memorable fragrance and complexity. In fact, dark red Burgundy was traditionally so uncommon that for decades it was assumed to be the result of illegal blending with wines from southern France.
Still, other vintners claim that some dark-hued wines are the result of picking overripe grapes, which can lack freshness and elegance. Josh Jensen, owner of Calera Wine Co., in San Benito County on the California Central Coast, suspects that some of the darker California Pinots may result from the addition of other varieties such as Syrah or Carignane. "That's the ultimate no-no with Pinot," says Jensen, who bases that opinion on his own failed experiments with Zinfandel additions in the 1970s. "You can't add a drop of another variety without losing that shimmering magic." (Under federal regulations, a "varietal" bottling need contain only 75 percent of the named grape variety.)
But times have changed, and most estates in Burgundy, Oregon and California typically make darker Pinot Noir now than was common 15 years ago. Some of the greatest producers in Burgundy, such as Domaine Leroy and Domaine Dugat-Py, consistently achieve unusual depth of color. Much of that results from lower yields and viticulture that better minimizes rot, which imparts color-reducing enzymes. Pinot producers around the world now also farm new vineyards planted with clones specifically selected for dark skins.
Ultimately, the majority of today's vintners see a dark, saturated hue as a testimonial to careful viticulture and conscientious winemaking. "If you don't have color in the grapes, you won't get it [in the wine], however much you muck around," says Togni, who's crystal clear about his own goals. "I don't want to make any see-through Cabernets."