From time to time someone will ask if their thirty-year-old bottle they got from their uncle on their 21st birthday is still drinkable. Just a heads up, it most likely isn’t.
Let’s first remember, wine isn’t much more than rotten grape juice captured just before it turns to vinegar. It takes a special combination of ingredients in a wine to make it eligible as age-worthy. Today I’d like to explain what those ingredients are, and how they contribute to the long life of a bottle.
1) Alcohol
It may come as no surprise that alcohol plays a crucial role in the longevity of a bottle of wine. Considering its value as an antiseptic, alcohol in wines actually helps prevent bacteria from appearing and developing in the bottle. The disinfectant properties of alcohol are so powerful that for most of human history wine was added to water in order to prevent people from getting sick due to lack of water filtration and purification techniques.
2) Acidity
The acids found in wine are found in the juice of grapes. Its an essential part of a wine and if acidity is too low the wine can seem "flat" or unrefreshing. An interesting thing about wine is that it actually undergoes a lot of chemical reactions after bottling which contribute to the changing flavors that occur over time. One of these changes is that acidity is generally lost over time. This means wines that start off with lower acidity levels to begin with will "flatten" out faster than wines with higher acidity levels.
3) Sugar
You may be surprised to find out that some of the longest lasting wines are also some of the sweetest. You'd think that sugar would contribute to bacterial growth but in super-sweet wines their is so much sugar present it is difficult for bacteria to actually start growing in the first place.
4) Tannin
Tannin is the part of a wine that gives you that dry-mouth effect. It's most notably present in heavy red wines and is found on the skin of a grape and in the wood of a barrel. Wines that are fermented for longer periods with the grape skins present often develop more tannic character than ones with less skin contact. Young tannins can sometimes be unpleasant in wines with high levels of them, but like acidity they break down over time. This means wines that seem overly tannic in the early years after bottling may find themselves in perfect balance after a few decades of aging.
Keep in mind...
It isn't just the contents of the bottle that contribute to the ageability of a wine. Wines have to be stored properly in order to last long periods of time.