Ageing is one of those things that distinguishes wine from almost every other alcoholic drink. It’s the natural acidity present in wine which stops bacteria from developing and spoiling it, thereby allowing ageing to actually happen.
But not all wine is suitable for ageing. In fact, the vast majority of wine sold around the world is designed to be drunk no more than a couple of years after it’s bottled.
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It’s also important to distinguish between what happens in the winery to age the wine and what happens once the wine is in the bottle.
So, many wineries – in Rioja for example – will mature their best wines in oak barrels which helps both to increase the complexity of the flavours in the wine as well as incorporating some of the flavours of the oak itself. So next time you drink a Rioja Crianza or Reserva, see if you can pick up some of the sweet vanilla or spicy notes that are a characteristic of wines aged in wooden barrels.
Bear in mind that how much flavour is imparted by the barrel will depend on all sorts of factors like the type of wood used, how long the wine spends in the barrel before bottling , or the size of the barrel. Remember, the smaller the barrel the greater the percentage of the wine will be in direct contact with the wood, so the influence of the barrel will be that much more apparent.
Barrel maturing is also considered a good first step for wines which are designed to be aged subsequently in the bottle for a good few years before they are opened and enjoyed.
A wine’s ability to age gracefully in the bottle depends a lot on what’s in it – specifically, the levels of flavour compounds and chemical compounds, or phenolics present in the wine.
One of the important ones is tannin – that’s the compound particularly present in grape skins, pips and stems which can cause astringency, or a puckering up in the mouth. Acidity too is important – wines with a lower pH are better suited for ageing.
Another important factor is temperature. Ageing wines like a steady temperature somewhere between 10 – 15ºC and a little bit of humidity to ensure the cork doesn’t dry out and contract and let in too much oxygen.
So what happens when a wine ages? Essentially, those phenolics that we talked about just now continue reacting with each other. In red wines, that tends to make then softer and gentler – what wine tasters might rather annoyingly refer to as "more approachable"! Colour too will change – typically from a deeper purple to a lighter brick red.
White wines too go through a similar process, although wine experts understand it far less than for red wines. Phenolics, for example, seem to play a slightly different role. For example, white wines made from the Riesling grape seem to be able to age for longer than Chardonnays, despite the higher content of phenolics in the latter.
Anyway, that's all getting too techy. The important thing to note is that white wines' colour will change with age – going from yellow to more golden or brown with age.
So that's it for our introduction into the world of wine ageing. Keep an eye out for further articles where we'll go into more detail about some of the technical aspects of ageing.