RITUALS OF WINE: Perfection

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How Wines Age

The one thing that distinguishes wine from almost every other beverage is that a good wine gets better as it gets older.  Ageing a wine lets wonderful changes occur inside the bottle.  It sometimes also increases the value of the bottle.

Ageing wines in a Sydney restaurant wine cellar

The sad fact is that the vast proportion of wines sold today are not designed for ageing and in fact do not benefit from it.  It is an oft-quoted statistic in the wine trade that 80% of wine sold in Australia is consumed within two hours of purchase.  Accordingly, winemakers have taken notice of this and produced wine that simply does not get better with age.  There are, however, many producers that make wines capable of ageing.  The reason that one would take the time to age a wine is to savour the “bottle development characters” – flavours that can only come from keeping a wine for a number of years before drinking it.

How Red Wines Age

The main things that change when you age a red wine are:

• The wine tastes softer,
• The colour changes from deep purple to brick red,
• Sediment accumulates in the bottle,
• The flavours change from fruit flavours to a more complex “bottle development” flavour profile.

The ageing process is often described as a slow oxidation.  Once all the available oxygen in the bottle and in the wine is used up, the environment in the wine bottle becomes “reductive”.  The acidity of a wine preserves the freshness during the bottle ageing process.  In red wines, the phenolics also protect the wine from fast oxidation by reacting with oxygen before other flavourful components of the wine do.[1]

The reason that these changes occur is the behaviour of phenolics in the wine.  Phenolics (or polyphenolics or polyphenols) are:

“A very large group of highly reactive chemical compounds of which phenol is the basic building block.  These include many natural colour pigments such as the anthocyans of fruit and dark-skinned grapes, most natural vegetable tannins such as occur in grapes, and many flavour compounds.”[2]

Phenolics occur naturally and at high concentrations in grapes.  The darker the grape skin, generally the higher the concentration of phenolics. 

When grapes are crushed in the winery, the skin cells lose their pigments to the grape juice.  The Anthocyan pigments combine with the tannins to form the pigments of a maturing wine.  As the wine ages, the pigment forms larger and larger polymers which eventually cannot remain soluble, so they precipitate out as solid sediment.[3]

This means that wines that were very astringent in their youth can soften with time and become wonderful wines to drink when mature.  So holding a bottle up to the light to see how much sediment has precipitated out can sometimes give an indication as to how old the wine is.  This, however, depends on the storage temperature and the amount of phenolics originally in the wine at bottling.

During the process of bottle ageing, the red wine undergoes other slow reactions, which make the intensity of the fruit flavours more subdued, change the intensity of the colour, aroma and flavour in ways that make combined effect more complex on the palate than it does was as a young wine. 

One of these reactions is when acids attached to the glucose detach and contribute to the flavour of an older wine.[4]  Another reaction is the flavour compounds responsible for the initial primary aromas of the grapes and those from the fermentation (the secondary aromas) interact with each other and with the phenolics.   Gradually, the smell of the wine becomes a third aroma, a subtle group of tertiary aromas that typify an aged wine.[5]

Another process that occurs during the ageing of wine is that aldehydes begin to oxidize and esters are formed from the combination of wine acids with alcohols.  

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How Colours Change With Age: Red Wine

From The Global Encyclopaedia of Wine, p.49

Seen here is a 1993 shiraz (left) and a 1981 shiraz (right).  The younger shiraz still has some plum colours in the middle of the glass.  Importantly, around the rim of the glass you can still see some crimson colours.  When very young, red wines have a purple hue around the rim. 

The older shiraz is not as deep in colour in the middle of the glass.  The rim is now a brick red – the usual indicia of age in a red.

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How White Wines Age

White wines do not have the same high level of phenolics that red wines do when first bottled.  The slow oxidation of white wine gradually turns the wine a deeper golden colour, and then eventually it turns brown. 

White wines that have the capacity to age well are usually high in acid.  Very few of them undergo malolactic fermentation either.  From a winemaking point of view, wines that can age for a long time sometimes are bottled with high levels of sulphur dioxide to preserve the wine over its expected life.

The question of malolactic fermentation is important with chardonnays.  Malolactic fermentation (or “MLF” or “malo”) is the conversion of malic acid into lactic acid and carbon dioxide.  After fermentation, winemakers will add lactic bacteria to the wine as a “secondary fermentation.”  It adds flavour and complexity to young chardonnays, but has the effect of shortening the cellaring potential of the wine. 

When white wines age, the colour becomes more intense.  A young wine will typically be a pale straw colour.  This deepens with age to yellow and very old whites often go a golden colour.  Finally, however, a white wine will turn brown.

The causes of the colour change are changes in the phenolics in the wine, although science is yet definitively to describe the chemical process of white wine ageing.

As white wines age, they often pick up flavours and characters such as toast, fig, honey and caramel. 

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How Colours Change With Age: White Wine

From The Global Encyclopaedia of Wine

On the left is a 1994 riesling and on the right is a 1983 riesling.  The younger wine on the left is a pale lemon with a tinge of green around the rim.  The tinge of green is a handy indicator of a young wine.  The older wine on the right is a deeper golden colour in the middle of the glass and has lost the green tinge around the rim.  The deeper colour is due to the impact of oxygen as the wine ages.