Ask Decanter

We answer a selection of your trickier wine queries

Iam planning to build a small cellar in my basement, where the temperature ranges between 18°C and 19°C all year round, with a humidity of 35-55%. I know the ideal for cellaring is 11-12°C, but is the range of 18-19°C still appropriate? Valentin Voinov, Canada

Your enquiry touches on two core wine storage considerations – humidity and temperature. Fashions have changed. Fifty years ago, an underground ‘wet’ or damp cellar was deemed perfect for wine, and rightly so. Now, lifting or soiled labels are considered an impediment to the fine-wine dining experience, though commercially minded producers are applying more damp-resistant labels, taking a lead from the Champagne houses.

Though your humidity range estimate of 35-55% offers no likelihood of label loss or deterioration, low levels of humidity will, over time, damage your wine. Fine wine should be stored at 65-70%, allowing the best corks to permit only 1mg of oxygen to enter the bottle per year. This moderates the process of wine developing complexity, softening tannins, and keeps the identity and vital statistics secured to your bottles. A fluctuating temperature range of 18°-19°C is immaterial – it is the level that is not appropriate.

Tutankhamun knew how to protect wine. His tomb, discovered deep underground more than 3,000 years after his burial, contained 40 wine storage jugs. Today’s vessel – glass bottle and cork – lain on its side at 13°C does the same, but for the living. The appropriate temperature is 12°C-13°C. Higher temperatures accelerate detrimentally the change in colour, aroma and taste – as the amount of free SO2 diminishes, the wine becomes more susceptible to oxidation. Back to cellar basics!

Sebastian Riley-Smith replies: Why don’t producers put sulphur dioxide levels on wine labels? I’d be interested in a winemaker’s perspective.

SO2 (sulphites, as it is referred to on labels) is present in all wine naturally, and added to most to act as an antimicrobial and antioxidant. It works by binding to the offending item – be it microbial or oxide – effectively removing the offensive presence of the problem. When each molecule of SO2 does so, it becomes ‘bound’ and is no longer able to attach to anything else. So there are two different kinds of SO2 in wine: bound SO2 and free SO2. The bound SO2 has done its job, the free is available to prevent any further deterioration in the wine. Both together are referred to as total SO2.

While the total SO2 is fairly stable, the free SO2 – the active part – constantly changes, so the free SO2 at bottling will not be the same, or even similar to, the free SO2 when you open the bottle. Because of that continuous change, regulations measure the more stable total SO2. Permitted levels have been reduced considerably over time and organic wines have lower legal limits than conventional ones. Red wines are limited to lower SO2 levels than white wines.

Nigel Greening replies:

The UK and EU currently apply the following limits for all wines sold there: reds up to 150mg/L (100mg/L organic), and still dry whites to 200mg/L (150mg/L organic).

White wines need higher levels of SO2 to protect them as they don’t have the tannins and phenolics of red wines – these compounds are also antioxidant in nature so they help protect red wines. There are separate, higher limits for sparkling and sweet wines. But it is probably the active, free sulphur that will react with people sensitive to it. And because that continually changes, even from one bottle to another, it can’t be measured.

Hence the lack of what would otherwise be a useful ingredient labelling: frustrating for producers as well as customers.