Columnist, Food

After my recent column describing how vintage charts guide us in deciding when to pull those treasured collectible bottles from our cellars, a reader emailed with a straightforward request: Please explain why a two-year-old wine tastes different from the same wine that’s seven years old.

As with many simple questions, there is no simple answer. Wine is alive. Its ability to age is what sets it apart from all other beverages. Beer goes stale over time. Soda goes flat. Liquor might not spoil, but then again, it doesn’t transform. Wine mimics our life cycle: It starts young, then matures into a more complete and harmonious drink, maybe even going through a brooding teenage phase before reaching its peak performance level. Eventually, it begins to decline and, ultimately, dies. That is one reason we romanticize wine, why it is expensive, exclusive and intimidating.

Some of the author's favorite wines aging (hopefully gracefully) in his cellar. (Dave McIntyre )

This is one of those times I wish I had studied any of the many sciences that winemakers employ on a daily basis; in this case, chemistry. I ‘m not sure I could provide a thorough explanation of the process even if I did fully understand it, and scientists acknowledge the process isn’t entirely clear to us yet.

In an oversimplified nutshell: Red wine grapes have substances called phenols, especially anthocyanins in and near the skin and tannins in the skin, seeds and stems. Anthocyanins give color, tannins add structure. Winemakers try to enhance these phenols in the vineyard through reducing crop yields and other techniques, and in the winery by “cold soaking” the grapes before ensuring a slow fermentation to extract as much color as possible. Other decisions, such as whether to ferment the grapes with or without the stems, affect the tannin level in the finished wine. Oak barrels add their own tannins as the wines age.

Over time, the phenols in the wine evolve. They combine until they can no longer remain suspended in the solution; then they fall out as sediment. The wine becomes lighter in color, from purple to ruby, to garnet and finally brown. As the tannins fade, the wine becomes less astringent and tastes sweeter.

Many more factors are involved, of course. An age-worthy wine should be low in pH (high acidity), secured from oxygen (good cork or other closures are important) and, most of all, stored properly. That’s why you see wine bottles lying on their sides in racks; keeping the wine against the cork prevents the cork from drying out and letting air into the bottle. Temperature is even more important, because heat speeds the aging process. So collectors invest in special wine refrigerators or expensive cooling units designed to keep a wine cellar at about 57 degrees. Extended summer power outages are their nemesis.

Certain grape varieties have higher levels of phenols: Cabernet sauvignon, syrah and nebbiolo, for example, are considered to be especially age-worthy red wines.

For white wines, the key components to allow extended aging are acidity and sugar. That’s why Rieslings, especially sweet ones, and Sauternes age magnificently over decades (again, if stored properly). White Bordeaux, typically blends of sauvignon blanc and semillon aged in barrel, will often age well for decades.

For most wines, and most wine drinkers, this question may be moot. The vast majority of wine is consumed within a few days of purchase. And it’s made for that: designed for everyday enjoyment rather than collecting or investment. These wines may improve in bottle for a few years, or they may fall apart and turn toward vinegar rather quickly.

That’s why I’m suspicious of studies claiming to prove that cheap wines are as good as expensive wines. These are usually “man on the street” surveys showing that consumers on average prefer softer and fruitier over big and tannic. They conclude we’re being ripped off by wineries and experts who flip for rare, expensive bottlings.

So why do wines taste different over time? The best will improve for many years, because they have the characteristics that help them mature. Cheaper wines, designed for everyday drinking, will fall apart if we keep them for even a few years. The way we treat the wines, through temperature and storage, is also key. As always, the best wine experience is a combination of the vineyard, the vintner, the occasion and, ultimately, the drinker.

If you really get bitten by the wine bug and find yourself amassing a collection (buying wine is almost as fun as drinking it), you might want to invest in temperature-controlled storage to protect your investment. Or lower the house thermostat a few degrees and figure your wines will age a little faster than the vintage charts predict. If you can limit your purchases to the bottles you’ll drink over the next few weeks, you don’t need to worry about how the wines will age.

But when you happen to come across a forgotten bottle in your basement or closet, pop it open. You may have discovered a treasure.