What happens to wine’s flavor as it ages?

When wines are young, we taste their primary flavors, like grassiness in Sauvignon Blanc, plum in Merlot, apricot in Viognier or citrus in Riesling. We may also notice some secondary notes associated with winemaking techniques, like the vanilla flavor of oak or buttery nuances from malolactic fermentation.

When wines age, we start speaking about tertiary notes, or flavors that come from development. This could mean young, bold notions of fresh fruit that become gradually more subdued and reminiscent of dried fruit. Other flavors, previously hidden by bold primary notes, come to the fore, like honey, herbal notes, hay, mushroom, stone and earth.

What causes these changes? Nothing in wine is ever static. Acids and alcohols react to form new compounds. Other compounds can dissolve, only to combine again in another fashion. These processes happen constantly and at different rates. Every time you open a bottle, you catch the wine at another stage in its development, with new and different nuances. While the proportion of alcohol, acids and sugars stay the same, the flavors continue to change.

How texture develops in wine?

Texturally, the wines also change. Dry, aged white wines can become almost viscous and oily, while reds tend to feel smoother. This is due to phenolic compounds like tannins falling out as sediment over time.

In a young wine, these compounds repel each other, staying small enough to remain suspended in the wine. As the wine ages, they lose their charge and start to combine, forming chains and becoming larger and heavier. This reduces the surface area of the tannins, causing them taste smoother, rounder and gentler.

Once these combined compounds become too large, they fall out of suspension as sediment. Some red wines throw heavy sediment, others almost none. 

How wine color changes with age?

One of the most visible processes in an evolving wine is slow oxidation. Color is the most obvious indicator of this.

As white wines age, they often evolve from pale lemon or golden to amber and even brown. Vivid salmon-hued rosés can take on onion skin tones as they age. As reds develop, oxidation often moves them from the purple end of the spectrum toward tawny or brown hues.

While young reds can be opaque when held against a white background, mature reds often show a lighter color around the edges. This is known as "rim."

The rate of oxidation depends on the amount of air left in the neck of the bottle after it was sealed, and how permeable the closure is. Traditionally, natural cork has allowed minimal oxygen exchange, which is why most wines deemed ageworthy are still bottled under cork. However, since cork is a natural product, there is no such thing as uniformity. This can cause considerable bottle variation in the same case of wine.

Which wines can age?

It’s often assumed that only the finest, most expensive wines can age, but any wellmade wine stands a good chance of developing.

Entry-level wines from good wineries can easily age from three to five years, unless they’re made for primary, aromatic appeal like an easy Moscato. Wines that have real concentration of flavor, with a good balance of alcohol, acidity and texture, should age well.

But some wines are made specifically for extended aging, like very extracted reds with bold tannins that need some time to mellow. These comprise many of the fine wines of classic European and New World regions..

White wines that can especially benefit from aging include Riesling, Sémillon, Chenin Blanc, Furmint, white Bordeaux-style blends, white oak-aged Rioja, oak-aged Sauvignon Blanc and good Chardonnay. Some Albariño, Garganega and other lesserknown regional grapes can also age well.

Well-made reds age wonderfully, even for just three to five years. It’s often surprising how well they can keep their freshness. Some countries have legally defined terms for wines that were aged before release. Look out for Reserva and Gran Reserva (Spain), Riserva (Italy) and Garrafeira and Reserva (Portugal). These wines already have some bottle age, but they can be cellared further. Also look out for so-called "library" or "museum" releases from wineries.

Some very high-quality rosés can also age, though the vast majority are made for immediate consumption.

Quality sparkling wines, particularly those made by traditional bottle fermentation, can also age. This includes both white and rosé sparkling wines. If they are still on their lees (yeast residue from the second fermentation) in the cellar of the producer, they can age for decades. In this scenario, the lees act as protection from oxidation.

However, once sparkling wines are disgorged and taken off this yeast residue, they can still age well. In fact, very young sparkling wines often benefit from a year or two of ottle age. With many years of post-disgorgement bottle age, the mousse, or foam you get when you pour a glass, becomes softer.

Fortified wines are released generally when they’re ready to drink. Due to their high alcohol levels, they’re more protected from the ravages of time than unfortified wines. A prime example here is Madeira, which can age effortlessly for decades. Two fortified wines that prove exceptions are fino and Manzanilla Sherry, which should be consumed while young and fresh.

Very sweet wines, with their high sugar concentration, also age immensely well. The sugar acts as a preservative, even if the alcohol is low.

How should wine be stored for aging?

Bottles destined for aging need dark and cool storage around 53-57°F (12°C-14°C). The temperature should remain constant to allow for slow, even maturation. Higher temperatures accelerate the rate of chemical reactions in a wine, which can be detrimental to the wine’s structure and cause it to "cook," making fruit flavors taste mushy and baked. Darkness is also important, as ultraviolet rays in light can spoil wine.

How can I tell if an older wine is still good to drink?

To tell if an older vintage is past its prime, use the same technique you’d use to judge any wine. Bring it to the correct drinking temperature, open it, pour, swirl and smell. If it smells good, taste a little. If you like it, it’s good to drink.

Red wines which have thrown sediment should be stood upright for 24 hours before opening so the sediment can settle. These may also benefit from being decanted.

Why age wines?

Some wines take time to reveal their true nature. While softened tannins are one way that a wine’s age expresses itself, its tertiary notes are also often more complex and rewarding than younger, more one-dimensional primary fruit notes.

Once age allows fruit flavors to subside, a magical new world of flavor opens up. Cabernet Sauvignon and Merlot become suggestive of dried tobacco leaf and cigar box. Syrah develops smoky, visceral notes of cured meat and violets. Nebbiolo and Sangiovese become heady with lifted notes of sour cherry and rose. Riesling and Chenin Blancs can seem like chamomile tincture, while Pinot Noir attains an aura of fallen leaves, earth and undergrowth.

These are all acquired tastes, far removed from the initial accessibility of youthful fruit. But these are sought specifically by many wine lovers. Even after years, you may feel the restraint of a cool season or the dry heat of a hot summer in these wines. At the height of their development, mature wines speak eloquently of time and place. Tasting historic wines that have withstood decades, and even centuries, is a transcendent experience.