It is a wonderful thing to experience first hand the evolution of a fine quality red from a brightly coloured, berry fruited wine to a brick red, complex wine with characters of cigar box and spice. Wines such as these tend to disappear all too quickly from your glass, slipping effortlessly over your palate.

‘What exactly happens in this aging process though? This is the question we hope, in some part, to answer for you in this article – part one in a series of three on aging wine.

The most apparent change is often that observed in a wine’s intensity and shade of colour. In red wines this is largely due to reactions involving anthocyanins, the molecules that provide colour. These are typically purple in youth and exist in a dissolved state in the wine. With time the oxidation process changes these pigments to brick red, then brown. These anthocyanins also combine with tannin molecules to form large anthocyanin-tannin complexes, forming sediment that falls out of solution and leaves behind less tannin and intensity of colour.

The colour compounds present in white wines also react with oxygen, changing from white to golden then brown. While some aged white wines are darker than others, if cellared well this is usually related more to style than the aging process: for instance oaked whites are generally darker than unoaked whites.

The changes observed in the bouquet (nose) and flavour (palate) of a wine over time are often similar, moving from primary characters in young wines to developed characters in aged wines. For instance, Chardonnay can show melon, stonefruits and citrus in youth, then butter, toast and spice with age. Cabernet Sauvignon can show blackcurrant and red berry in youth, then tobacco leaf, cigar box and spice with age.

Finally, tactile senses are used by the tongue when assessing the body, texture and mouthfeel of a wine. The changes observed here can vary widely, however in general many wines become softer with age, particularly red wines. Body and mouthfeel are largely due to fruit weight and the balance of sugar, alcohol, acidity and tannin present. These components can change independently of each other over time, creating an overall change in mouthfeel greater than the actual changes. For instance, acidity can accentuate tannin and mask sugar, thus a decrease in acidity may result in a wine of greater ‘perceived’ sweetness and softer tannin structure.

In terms of actual changes over time, small amounts of water evaporate, increasing the concentration of the remaining components such as alcohol and sugar. This change is negligible though, and alcohol and sugar levels are not likely to change greatly with age. Acidity, however, can decrease as ‘tartrate crystals’ (potassium bitartrate) are ‘thrown’ from the wine, often leaving deposits on the cork. Finally, as mentioned above, tannin compounds combine with colour molecules to form sediment in red wines, leaving a softer, less astringent mouthfeel behind. When this is combined with a decrease in acidity, it is understandable that aged wines often seem ‘softer and rounder’. However, wines that age well have usually been produced with longevity in mind and are built with the necessary structure, fruit weight and balance to age gracefully.

While we have tried to keep the explanation fairly simple in this article (a little chemistry was bound to creep in!), if you are interested in a more detailed answer, ‘Wine Science’ by Jamie Goode is a complete text on the science of wine.

In the next issue of MAGNUM we will discuss cellaring wine – how to cellar, when to drink, and a hotly debated topic: the difference screw caps make.

Text by Shae Cooney. Photography Simon Westlake.