Ageing Potential of Wines: The Mystery Revealed

Some wines can be enjoyed immediately upon release, while others need to be waited for a long time before they can be enjoyed. What makes that certain bottles evolve differently than others? What are the structural elements of the wine that do explain the ageing potential of a wine? Depending on the kind of wine - be it white, red, sparkling or fortified - the answers to the ageing potential of a wine will be different and closely linked to the way the winemaker will vinify.

Ageing potential of a wine is the period of time during which the wine will be enjoyable to drink. It depends on its structure: acidity, flavor intensity and concentration, tannins for reds, alcohol levels, sugar content for sweet wines, among other main factors. Since ageing wine is essentially a process of slow oxidation, all the above elements have to be present in sufficient amounts to slow down that process as much as possible and assure complexity, length and balance to the wine. Winemakers can use different tools during vinification to influence the ageing potential, such as grape management, vinification method, acidity, oxygen and SO₂ management as well as blending techniques.

   

Grapes

The first decision a winemaker has to make is how s/he will use the grapes: destemmed or whole bunches. Whole bunches add structure to the fruit, providing an extra strength and firmness to the tannins, as well as a greater complexity. At the same time, it avoids over extraction and rusticity, thus participating in the overall balance of a wine and therefore assuring an extra ageing potential. David Croix, from Domaine des Croix in Burgundy, uses whole bunches in his Beaune 1^er Cru les Bressandes but not in his entry level Bourgogne regional level. The first one has an average ageing potential of 8 to 10 years, depending on vintage, while the second one will only keep for 3 to 4 years.

Techniques

After that, the winemaker has to decide on the method of production of his/her wine, either traditional vinification or other techniques such as thermovinification (flash detente having a quite similar effect). Thermovinification is a process during which grape must is heated to 60ºC to 80ºC for a period of 20 to 30 minutes to liberate anthocyanins from the skins and then cooling it down to fermentation temperature before pressing and fermenting like a typical white wine. Since vinification is similar to that of a white wine, ageing potential of wines is limited due to a low phenolic content. This is what explains why most of the wines made by the Cave Cooperative de Sauveterre-Blasimon-Espiet in Entre-Deux-Mers in Bordeaux have a limited ageing potential. Wines are fruity, easy-drinking and with low tannins.

However, when traditional winemaking is involved, the winemaker has to decide on extraction techniques, involving cap management, fortification handling and temperature administration.

As far as cap management is concerned, for reds, the winemaker can use either punching down, pumping over or rack and return. These techniques deal with the temperature within the cap. Punching down immerges the cap, pumping over sprinkles the cap with wine taken from the bottom of the vat and rack and return puts the wine in another vat before returning it to the initial one. Punching down is the method where the spread of the temperature across the vat is the least efficient and rack and return the most efficient. Therefore, the former is more extractive than the latter. However, punching down and rack and return, when applied to the right grape variety, can assure an adapted extraction, assuring good tannin level. For instance, at Cambria Estate, in Santa Maria Valley, South California, Barbara's Signature Pinot Noir, the top cuvee at the winery, is punched down in order to get a full body Pinot Noir with a deep color and a firm tannic structure and a prolonged ageing potential of 10 to 12 years, depending on vintage. However, if structure to assure improved evolution in the bottle is the aim at Cambria Estate, overall balance to assure the same goal is what Boekenhoutskloof winemaker, Marc Kent, is looking for when he uses delestage 2 times per day during fermentation for his top Syrah wine. Pigeage would result in over-extraction and in an unbalanced wine with less ageing potential.

In fortified wines, extraction techniques also have an impact on ageing potential. At Quinta do Infantado, winemaker Joao Roseira, proceeds to a first fortification up to 10% abv prior the final one, without killing the yeasts. This results in higher alcohol levels allowing a better extraction of tannins prior to the second fortification process and therefore in an increased potential for evolution. On the contrary, Rozes only makes one fortification when residual sugar reaches around 100 g/l, resulting in a lighter wine, with a more limited life span.

Temperature during alcoholic fermentation has a direct impact on potential for ageing. High temperature will increase the rate of extraction of color, tannin and phenolic compounds. Lower temperature will retain more volatile flavor compounds but will be less effective at extracting phenolics. But it is the combination of temperature and length of fermentation that will have an influence on ageing potential. At Tommasi winery in Veneto, Valpolicella will undergo a fermentation of 8 days at 30ºC whereas Amarone's fermentation will last for 40 days at 22ºC. The result is a low tannin wine for the Valpolicella with a limited life and a higher extract for Amarone conferring the wine an ageing potential of 10 to 15 years, depending on vintage conditions.

Malolactic Conversion

Acidity is another element which is part of the structure participating in the ageing potential of a wine. Malolactic conversion (MLF) management is a way to handle acidity levels in wine. MLF transforms the more aggressive malic acid into a softer lactic acid under the action of malic acid bacteria. In South Africa, Klein Constantia, located in the cooler Cape Peninsula, does perform MLF on their Cap Classic method in order to decrease total acidity and pH and assure an overall balance of its sparkling wines. Conversely, Graham Beck, located in the warmer Robertson inland area, needs to block MLF to assure freshness and balance - hence ageing potential - to its range of sparkling wines.

Lees

Talking about sparkling, in traditional method sparklings, ageing on lees, has a reductive effect, therefore protecting the wine from oxygen during lees ageing and brings an increased complexity to the wine, both contributing to the life span of the wine. Billecart Salmon Cuvee Nicolas François, aged for 10 years on lees has a minimum ageing potential of 10 to 12 years, depending on vintage. On the contrary, a Prosecco wine, made with the Charmat method, where lees contact is reduced to a few months, ageing potential is very limited.

Oxygen

Oxygen management is also part of how long a wine can age. At Sineli Estates in Marlborough, New Zealand, Sauvignon Blanc is handled reductively to keep freshness and to preserve aromas of passionfruit and grapefruit, giving a wine with a limited shelf life. A very different technique is used by Domaine Vincent Dureuil Janthial in Rully, Burgundy. Hyperoxidation consists in oxygenating the juice at the beginning of the process is one way to avoid an oxidized wine at the end. The sooner the wine is in contact with oxygen, the better the wine will manage it in following operations. This way, Vincent's wines have an increased ageing potential. Oxygen in fortified wines has also an effect on ageing potential. A Manzanilla wine, vinfied under velo de flor, is protected from oxygen and will be drunk young to access its delicate salty and yeasty aromas. At the other end of the Sherry spectrum, an Oloroso, aged under oxidative conditions from the beginning, will be a wine that will be able to keep in bottle for many years, since every component that could be spoiled by oxygen, has already been oxidized.

Then, SO2 has both an antioxidant role, inhibiting oxidation enzymes, allowing the wine to age longer and a antimicrobial role. Values between 0,8 and 1,5 mg/l (ppm) molecular SO₂ are sufficient to inhibit the growth of most wild yeasts and bacteria. In order to assure a long ageing in bottle for his wines, Jean-Paul Jamet, at Domaine Jamet in Cote Rotie, adds SO₂ at three stages: prior to fermentation (40-50 mg/l) to control microbial contamination during fermentation, post MLF, again 40 to 50 mg/l and at bottling - 10-20 mg/l, all within the legal EU limits of 150 mg/l for red wines.

Blending

Finally, blending allows to combine wines with complementary characteristics to assure enough structure for a wine to age. For his Redoma Branco Reserva wine, Dirk Niepoort in the Douro, combines wines from Arinto and Rabigato grape varieties, among others. Both retain a high degree of acidity and therefore contribute to build a strong backbone completed by intense fruit and a well-integrated alcohol, all giving an ageing potential of 8 to 10 years to this wine, depending on vintage.

 

As a conclusion, a winemaker has many tools to influence the ageing potential of a wine, from grape reception, deciding whether to destem or not, through the choice of the vinification or production method, be it traditional or thermovinification for still wines or Charmat or traditional method for sparkling wines. Then extraction methods, action on MLF, O₂ exposure levels, use of SO₂ and blending also do influence the ageing potential of a wine. Since they all have an impact on the overall structure of the wine and its evolution, their role is key.

 

Published in ISSUE 102 on Fine Wine and Liquor

 

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