The year was 2015. The vintage was 2000. The location was a restaurant in Valencia, Spain. The wine was white, in theory; it was actually the color of honey. It smelled like sherry, beeswax, sultanas, straw, tea, and old wood. It smelled — mature.
Was it oxidized, or just oxidative? And what’s the difference, anyway?
Let’s back up
Oxygen plays a significant role in the complex chain of events that transform grape juice into wine.
In the winery, oxygen starts its work the minute the grapes pop open and expose their juice to air. Wine gets a shot of O2 when a winemaker works the juice in the fermenter to re-wet the pulp that floats to the top. Ditto when the wine’s transferred into aging vessels or is moved between them during élevage, a process called racking. Lees stirring, bâtonnage, introduces oxygen, too. Oak is porous, and oak barrels, with their high surface to volume ratio, provide more exposure than larger wood tanks. Bottling can also aerate the wine.
Along the way, oxygen cranks through myriad chemical reactions. Some of them modulate a wine’s tannins or tame vegetal notes. Other processes turn grape polyphenols into molecules called aldehydes, which have a nutlike flavor; aged Sherry has an abundance of one type, acetaldehyde. Red grapes have more phenolics than white grapes, so red wine is more protected from oxygen’s chemical effects.
Although oxygen is critical to wine’s evolution, too much of a good thing is a bad thing. Oxygen can readily ruin a wine, even before it gets into the bottle.
Given all of this complexity, winemakers must constantly make choices about oxygen exposure — usually with a stylistic aim in mind.
Some winemakers embrace so-called oxidative winemaking, exposing their wine to copious air early on so they’ll have some of those savory, tertiary qualities on release. There’s evidence that subjecting a wine to oxygen early in its life can actually fortify it against later exposure.
Other winemakers may choose to aggressively limit oxygen, a technique called reductive winemaking; reduction is the opposite chemical reaction to oxidation. They use stainless steel instead of oak and handle the wine as little as possible. Reductive wines retain their fruit-freshness and can be long-lived, but in youth, they may need aeration before serving.
The bottle closure also enters the winemaker’s calculus. Screw caps and glass ampules admit much less air, while natural corks admit more. Synthetic closures are designed to admit a preferred amount of oxygen, depending on a winemaker’s preference. Aluminum cans provide a near-impermeable seal. Meanwhile, the plastic bags used for boxed wine are somewhat gas permeable; boxed wines should be drunk young.
Aging gracefully — or not
As a bottle ages, oxygen works its inexorable magic, softening a wine’s edges, burnishing its structure and flavors.
Red wine shifts from purplish ruby to garnet, and its tannins turn silky. White wine shifts from watery yellow to gold, and its robe becomes silken. Both styles also pick up new flavors and aromas; these effects were historically called bottle bouquet, although the expression has become unfashionable.
But given too much oxygen — from protracted aging or from accidental exposure, like a failed cork — the wine fades like an old flower.
Red wines turn brick red, then brown, and their texture becomes dusty. White wines turn gold, then tan. Both styles lose their fruit. They may taste bitter and flat, and even like vinegar. Their vitality and refreshment have drained away. These wines are now oxidized.
You can mimic this effect by leaving a wine open on the counter for a few days. Or just buy a boxed white wine and forget about it for a year.
Oxidative wines to try:
Some of the world’s most revered wines are made in an oxidative style. Lightly oxidative wines may exhibit flavors of dried fruits, brioche, toast, and nuts, while heavier styles have sherried flavors of hazelnut and dark honey. Try:
- Orange wines, which are exposed to more oxygen during winemaking than most white wines.
- Red Reservas, from Spain, and Riservas, from Italy, which are required by law to spend significant time in cask and bottle before release.
- Vintage Champagne, which spends years en tirage and bottle.
- Vin jaune, from France’s Jura, which is aged in barrels with significant head space.
- Oloroso Sherry, which ages in cask, but, unlike other sherry styles, without a protective layer of flor yeast.
- Tawny Port, which spends decades in wooden barrels, darkening to a deep, red-brown.