How do we know which wines need ageing before we drink them? Well, as I wrote in “Do We Really Need to Age Wine Once We Bring it Home?”, posted on June 22, 2009 on this wine blog, more than 90% (some say 95%) of the wine produced in the world doesn’t need to (or shouldn’t) be aged before you drink it. However, I also mentioned that there is some wine that definitely benefits from a little more bottle age. The puzzle is figuring out which wines should be aged and why.
More often than not, it’s big, full-bodied red wines that can not only survive, but improve with long-term ageing. However, there are also some white wines that will improve after a period of cellaring. Good German Riesling can age for 3 decades or more, and Chenin Blancs from the Loire, and white Burgundies can also be candidates for laying down.
So, how do we know which wines can age? Let’s start by discussing the 5 key elements in wine: fruit concentration, acidity, alcohol, tannins (more so in red wine), and sweetness (more so in white wine). To begin with, a wine that can successfully age must have these elements in balance. The wine may, indeed, taste harsh and unintegrated, but none of these elements should be overly dominant. The fruit should also be at the perfect ripeness level: overripe fruit will oxidize easily, while underripe fruit will never lose its “greeness”.
Okay, we have a balanced young wine that seems a bit astringent or austere and probably needs some ageing to integrate the aromas and flavours and soften the wine. How does it work?
Red and white wines do not age the same due to their differing chemical compositions. Research is still being conducted to determine exactly what happens in the ageing process of a wine. It’s still a bit of a mystery with many unanswered questions, so let me start by attempting to explain, without getting too technical, the changes that take place in a red wine as it matures, as far as we know.
Red wine contains large amounts of chemical compounds called phenols. There are a variety of these phenolic compounds and they are responsible for different characteristics of the wine. The phenolic compounds responsible for the colour of a red wine are called “anthocyanins”. Tannins are also phenolic compounds, as are those responsible for some of the aroma and flavour of a wine, which are simply called “flavour compounds” or “aroma compounds”. Phenols are found largely in the skins, stems, and pips (seeds) of grapes, but some can also be found in the juice and pulp. Some tannins may also be leached out of the oak and into the wine during barrel maturation. Phenolic compounds also serve as anti-oxidants in wine thus allowing for longer ageing times. Oxygen causes wine to decompose.
A young red wine will contain primary, and usually secondary aromas and flavours. Primary aromas are the typical aromas for that specific grape variety. For example, Cabernet Sauvignon is known for having distinct black currant or cassis aromas, and Gewurztraminer is known for its lychee fruit and rose petal aromas. Secondary aromas are those that are created during such winemaking processes as fermentation and oak ageing. Some typical secondary aromas are the yeasty, bready aromas from fermentation and lees ageing, and the spicy, vanilla, or toasty aromas from oak ageing. As a wine matures it loses the primary aromas, and the secondary aromas become less evident. A whole new set of aromas and flavours evolve which are known as tertiary aromas, and are described as the bouquet of a wine.
One of the most obvious changes to an ageing wine is its colour. A red wine starts out as a vibrant purply-red colour. During the ageing process you’ll notice it change to garnet, then to brick (some prefer to call it “terra cotta”), and, when over-the-hill, to brown. Essentially it changes from dark to light. As the colour changes the tannins will also become noticeably softer and more integrated into the wine. It is believed that the anthocyanins and tannins interact with small amounts of oxygen stored in the wine and bind together to create larger compounds which then precipitate and fall to the bottom of the bottle. This this dark reddish sediment can be distinctly seen in bottles of older red wine. Thus, the colour becomes lighter and the tannins soften because now there are less anthocyanins and tannins in the wine.
Another very important, but less obvious, change to take place is that of “esterification”. Esters are compounds formed by a reaction of acids, alcohol, and small amounts of oxygen in the wine. Hydrogen ions serve as the catalysts for these reactions. The esters produced contribute flavours and aromas to a wine and can be formed during both the fermentation process, and the ageing process. The reactions that take place do not diminish the amount of acid or alcohol in the wine. However, the perception of acidity will become less noticeable, probably due to the fact that other compounds of the wine have develped more and the wine has gained complexity. When the wine is very old and other compounds have begun to degrade, the acidity will again become more prominant. Aromas that evolve from the production of these flavourful esters during the ageing process are known as tertiary aromas.
Even less is known about how white wine ages. White wines have significantly less phenolic compounds than red wine due to the fact that the must (the unfermentate grape juice) only spends a very short length of time, if any time at all, in contact with the skins of the grapes. Grapes used for white wine making are pressed and the juice is typically removed from the skins before fermentation begins. As a result, the ageing of white wine is very different from that of red wine. White wine becomes darker and browner with age probably due to slow oxidation. As I mentioned earlier, phenolic compounds act as anti-oxidants and because white wine has far less of these than red wine it is at much greater risk of oxidation.
The longevity of a white wine is directly linked to the pH level and amount of acidity present. Wines with low pH and higher acidity are the better candidates for long-term ageing, with the acid acting as a preservative in the wine. German Rieslings and Loire Valley Chenin Blancs are just two examples of high acid wines that have cellaring potential.
I hope this explains some of the mystery of which wines you can age and what happens to the wine as it sits in its bottle in your wine cellar. Please remember that bottles should be kept in a cool, dark place, away from vibration and strong odors. The ideal temperature is from 13-16°C and humidity should be about 70-75%. If you don’t have a climate-controlled wine cellar (most of us don’t) make sure that where you store your wine is at as constant a temperature as possible. Areas that have changes in temperature can be harmful to wine as it ages. For example, it’s better to store wine in an area that has a constant temperature of 18°C than it is in a place that is 12°C in the winter and 17°C in the summer.