Creating conditions for graceful aging.
Popularity has waned for the third style: wines that make us think. Distinctive wines-of-place call upon us to ponder new experiences (we might call this the "hmm ..." style or perhaps the "aha" style). They don't run with the traffic, and that is their appeal. Way more head-scratching than giggling.
While Internet chatter about the importance of this type of wine far exceeds the public's interest as expressed in dollars spent, it's also the genre most winemakers get in the game to make, and is also their path to being taken seriously by sommeliers and critics. And although these are not the grocery store commodity wines that move most of the boxes today, distinctive wines-of-place produced in tiny quantities in every corner of North America today comprise the overwhelming majority of red wine labels.
The test of time is an important dimension of these wines of discovery. Every wine has a trajectory in time. A fruit-forward impact wine compares to a reserve-style vin-de-garde as a pop fly compares to a line drive. Generally, the better a wine tastes in youth, the shorter its life expectancy. Every winemaker would love to produce wines that drink well both in youth and age, and widening the are of a wine's trajectory is certainly the winemaker's Holy Grail. It is also an attempt to defy gravity.
The wise winemaker chooses the wine's purpose early on. Choices favoring one or another style begin in the vineyard years before harvest, starting with its location and variety selection, and culminating in harvest maturity decisions. In recent years, many techniques have been developed in both the vineyard and the cellar that can push wines into early affability or instead increase longevity and profundity. With skill, you can do both.
The aim of postmodern winemaking is to capture what nature has put in a vineyard's grapes and present it with grace and balance. In our view, winemaking is a branch of cuisine--the ultimate slow food--and has much in common with the making of sauces, because the soulfulness of flavor integration is a result of refining its structure. Granted, the particles that make up the structure of a wine are not tiny beads of butter, but instead are made up of phenolic chains that aggregate into tiny globs called colloids. But in both cases, the particles' shapes and sizes affect their power to integrate flavors. For this reason, wine's texture is strongly related to its aroma.
Control of tannin polymerization is a central postmodern skill. Small, stable colloids not only impart finesse and soulfulness in youth, they also prolong wine's longevity. Poorly formed tannins form unstable colloids that fail to integrate aromas and also precipitate readily. When this happens, similar to the curdling of a sauce, aromatic integration is lost. Elements previously married become individually apparent, resulting in wine that seems over-oaked, vegetal or Bretty. Wines with well-formed structure can carry much higher concentrations of these aromatic elements without offending the nose.
The willful formation of structural integrity is termed by the French "elevage" a word for raising horses, with no good English equivalent. In describing a person, bien eleve means properly brought up. As in raising children, elevage is an active process. Like all good cooking, it requires training and attention to detail. Winemakers will always say they do the minimum. Try that on your 3-year-old. Still, a good winemaker, like a good parent, strives to become invisible. The final product must sing its song of place, and the skill of the winemaker should go unnoticed, like the work of an able piano tuner.
Connecting the dots
During the past two decades, a picture has slowly emerged of the nature of wine structure. While much of this mental construct lacks direct confirmation, the same could be said for the periodic table during its first 100 years. It has been my privilege since 1997 to work closely with Patrick Ducournau's OenoDev group from Madiran, France. OenoDev has painstakingly knit together a working hypothesis by combining empirical observations of many thousands of wines with significant recent advances in phenolic chemistry, largely centered at Montpelier under Michel Moutounet and Veronique Chenier, but also involving the Australian Wine Research Institute's Tannin Project, Roger Boulton's work on co-pigmentation, and Doug Adam's polymerization studies at the University of California, Davis.
I was able to contribute to this brain trust Vinovation's trials with ultrafiltration, through which we obtained unique evidence of non-covalent bonding that empowered investigations of colloidal behavior in red wine. Through my consulting work, I also have had the opportunity to road test the emerging theory by working with hundreds of winemakers and thousands of wines during the past decade.
I am the first to concede that this view of wine structure is little more than a useful working construct, but I have found it of substantial utility in guiding winemaking decisions. In winemaking today, scientific verification is not the engine of progress. It is the caboose. Like any cooking technique, empirical successes initially drive theory. What follows is thus probably not true in all its elements. But there is no doubt about its usefulness as a guiding schema.
Building better wine
Tannins already exist in the ripe berry skins and seeds as polymers. But these are unlike those we are trying to build in finished wine. Unstable in acid solution, they are hydrolyzed as soon as they are released into fermenting must. Skin tannins break down into units called flavonoids, principally catechin and epicatechin. These familiar 15-carbon, three-ring units polymerize again over months and years, spontaneously forming either non-oxidative or oxidative chains that won't break down. Driven together by the polarity of water, these chains aggregate into colloids whose size is related to the chain length.
The key to fine colloidal structure is to promote early polymerization, but at the same time to prevent it from getting out of hand. It turns out that the key to good structure is a good concentration of red anthocyanin pigment. Color caps off tannins, leading to wines with more finesse.
The mechanism of oxidative polymerization was elucidated in 1986 by Vernon Singleton, (Am. J. Enol. & Vitic., March 1987; 38:69-77) who found that two -OH groups next door to one another on a phenolic ring, otherwise known as an ortho-diphenolic structure, could take up an [O.sub.2] molecule and become highly reactive to bridging to other phenols.
Bizarrely enough, Singleton found that this double -OH structure is recreated at the end of the reaction, available to react over and over, resulting in a cascading polymerization effect. Ortho-diphenols will attack other phenols, which themselves may lack adjacent -OH groups, but when they do so, polymerization is terminated. The principle constituents in young red wine that can fulfill this role are monomer-ic anthocyanin pigments. Thus the importance of reactive color to good structure is a central tenet.
But time is of the essence. Similar in molecular layout to their three-ring catechin cousins, anthocyanins differ in possessing an aromatic C-ring with a stabilizing glucose tacked onto it, without which they decompose rapidly. Monomeric anthocyanins are vulnerable to depletion through a wide variety of perils including adsorption by suspended yeast, enzymatic attack (in which the C-ring is destabilized by removal of its esterified glucose) and oxidative C-ring cleavage. Once incorporated into polymers, the anthocyanins become protected, also shedding their susceptibility to sulfite bleaching. Thus it is imperative to jump on oxygenation immediately after alcoholic fermentation is complete.
The golden ratio
It has been empirically determined that a molar ratio of 4:1 total phenols to anthocyanins is ideal for good structure. Since anthocyanins are phenols, too, this means the ideal polymer has about six catechins, with anthocyanins on each end, with a total molecular weight around 2,000. Yet these aggregate into colloids that pass only with difficulty through a 100,000 MW ultrafilter, demonstrating that several dozen such oligomers are aggregated into the colloid, and hinting at the potential for sterile filtration to disrupt structure (0.45[micro] corresponds to about 250,000 MW).
Color stabilization is a strong motivation for prompt introduction of oxygen as soon as primary fermentation is complete, if only for a few days. Splashing will not suffice. Since tannin polymerization is energetically favored over oxidative ring cleavage, it is critical to introduce oxygen at a rate slow enough to be entirely taken up by this reaction. This is referred to as Phase I micro-oxygenation and requires high performance diffusion equipment, which produces extremely small bubbles of pure oxygen that can readily dissolve into the wine before reaching the wine's surface.
Oxygenation at this early stage does not shorten the wine's life; paradoxically it increases anti-oxidative power by stimulating latent phenolic reactivity. In fact, stopping abruptly will simulate reductive behavior, which is not a bad thing, but rather a sign of longevity potential. Oxygen treatment may be extended to balance reductive strength to the desired balance, depending on the intended aging trajectory. Tannins move from green to hard, lose their graininess and gain volume in the mouth due to an expanded structure, eventually softening into a plush, stable mouthfeel.
Even if oxygen is not employed, although anthocyanins will be wasted, the remaining color will still improve structural finesse. Despite its high tannin levels, Syrah texture is dependably soft, while Pinot Noir is notoriously susceptible to the coarse, dry mouthfeel associated with over-polymerized tannins. In most Vitis vinifera cultivars, the glucose guardian of their anthocyanins is protected by an attached two carbon acyl group, which prevents insertion into the active site of most glucose-loving enzymes. But Pinot Noir pigments lack acylation. Moreover, the grape's weak tannins are insufficient to promote good yeast settling. The suspended solids in consequence adsorb pigment and also out-compete the phenols' appetite for oxygen, thwarting oxidative polymerization. Pinot is a tough town.
A season in heaven or hell
Although each vineyard has its own charms and virtues, it is a universal fact of life that red wines with low color/tannin ratios form coarse, grainy tannins that lack integrative properties and shelf life. The path to sound structure, integrative tannins and longevity involves:
* balancing the vine,
* picking at the proper moment,
* effective co-extraction and
* structural stabilization.
Any misstep in this chain of events means there is little that can be done to enhance structure without interventions in the winery such as component blending and lees incorporation.
Within a growing season, efforts are generally focused on vine balance, a topic of great complexity that merits a separate column. For now, the focus is on optimizing the development of flavor, tannin, and most of all, color. Pigment and flavor elements are formed in grapes beginning at veraison in order to attract birds to ingest mature seeds. This shift in the vine's attention from green growth to reproduction is known as Cycle Two, which the vineyard enologist strives to encourage through balancing light exposure, air movement, judicious nutrient availability and moderate water stress. If Cycle Two does not proceed enthusiastically, it is best to have highly colored components available for blending.
If all goes well with Cycle Two, an optimum moment for picking is the next critical step. Underripe grapes may not contain the optimum concentration of anthocyanins, may be difficult to extract, and also may not have evolved desired fruit flavor density. Cellular deterioration in the skin releases pectinases that greatly aid extraction by reducing pulpiness and releasing pigment. Malic acid reduction is advantageous to mouthfeel because high titratable acidity over-stimulates salivary response, resulting in flavor dilution and excessive salivary protein, leading to coarse mouthfeel.
These difficulties pale in comparison to the perils of overripeness. To work well in the cellar, the reactive potential of tannins and anthocyanins must be protected from field oxidation. We are trying to make a tannin souffle, and if the eggs are already scrambled, nothing can be done in the kitchen. The tannins that result from excessive hang time are not stable, and will become grainy and dirty in short order, imparting neither anti-oxidative strength nor aromatic integration to the wine.
Field oxidation also robs musts of monomeric anthocyanins. It is not enough to have good color--the color must be un-polymerized so it is still reactive and able to fulfill its role as a cap on tannin chains. High pHs associated with extended hang time also will suppress the rate of pigment stabilization through aldehyde bridging (mediated by the low pH carbocation form), instead promoting browning.
Sugar metabolism and the vagaries of raisining and dilution from dew and rain have little to do with maturity, and Brix is an unreliable harvest index. It is, however, an excellent guide to eventual alcohol content--but as we shall see, elevated alcohol is an enemy of extraction.
In 1974, Pascal Ribereau-Gayon published in The Chemistry of Winemaking (Advances in Chemistry Series, 137, pp. 50-87) a color plate that revealed a mysterious reality: By themselves, anthocyanins are not very soluble in 12% alcohol, and they confer only a light pink color. If wine is a solution, red wine is not possible. He then showed how, in combination with tannins, the anthocyanins became deep red. Although no one knew what to make of this at the time, he was really demonstrating that color and tannin form colloidal structures.
Recent enlightenments on the nature of extraction invite us to forget everything we thought we knew on the subject. Most winemakers concentrate on the methods of extraction: pump-over vs. punch-down vs. delestage; vigor and frequency of mixing; temperature of extraction; use of pectinolytic enzymes and so forth. In 2001, Roger Boulton published a review of a decade of research on co-pigmentation (Food Chem. 73:423-432. 2001), which revealed that winemakers were barking up the wrong tree.
Boulton's revelations concerning the makeup of co-pigmentation colloids showed that a color molecule was not going anywhere unless it could pair with a monomeric cofactor, generally a catechin or epicatechin but preferably a more planar "super cofactor" such as quercetin, a UV protectant that grapes produce if clusters are exposed to light early in the season. Boulton showed that these extractive colloid intermediates were entirely composed of monomers; hence oxidatively polymerized tannins resulting from extended hang time do not assist extraction, nor do most oak tannin products.
Boulton's findings elucidated the wisdom of the practice of field blending and co-fermentation of varieties practiced in many European appellations, where tannic whites are included with well-colored, tannin-deficient reds: Palomino in Garnacha in the Rioja, Viognier with Syrah in the Rhone, Trebbiano with Sangiovese in Chianti, as well as the interplanting in old California vineyards of small amounts of Petite Sirah, Carignane or Mataro with Zinfandel, Barbera or Grenache.
In optimizing cofactor from other sources, gallic acid, a breakdown product of ellagitannins from oak, is an excellent cofactor. It is not available from the surface of toasted oak barrels or alternatives. But beware: Untoasted oak typically contains the planky aromatic defect trans-2-nonenol unless it is carefully air-cured in a manner that does not build up TCA; thus it should only be purchased from a reputable supplier and used immediately.
Co-pigmentation colloids are not stable, and they convert into other structures depending on conditions. If young reds are deprived of oxygen, dry, grainy tannins will result, and precipitation may occur. Since water polarity is the driving force holding the colloids together, this precipitation may even take place near the end of high-Brix fermentations as elevated alcohol destabilizes the colloids, driving pigment back into the skins or to the bottom of the tank--another peril of extended maturity. Bitartrate crystals may also take up pigment and carry it into sediment.
Bring it all back home
If one follows the formula to encourage balance in the vine, harvests ripe but not overripe, and balances the must for co-extraction, the elements for graceful aging will result. We have bought our ticket, but we have not arrived. In fact, if the fruit is exceptional, we have now created quite a monster: aggressive, reductive and rather unpleasant. Taming this beast, feeding its appetite for oxygen, will provide the driving force for our tannin souffle. Judicious blending and proper oak choices are best made immediately. With my apologies for the cliffhanger ending, the ins and outs of elevage technique are the subject of my next article.
Clark Smith is winemaker for WineSmith, founder of the wine technology firm Vinovation. He is a leading authority on American wines and lectures widely on an ancient yet innovative view of winemaking. To comment on this column, e-mail email@example.com.
* Recent techniques can help the winemaker push wines into early affability or instead increase longevity; and, with skill, do both.
* Control of tannin polymerization is a central postmodern skill.
* The key to good structure is a good concentration of red anthocyanin pigment.
* If one encourages balance in the vine, harvests ripe but not overripe, and balances the must for co-extraction, the elements for graceful aging will result.