Master Sommelier John Szabo presents a series of articles offering practical advice on building a wine cellar as a source of personal enjoyment and investment. This is Part 3.2, consisting of three instalments focused on proper wine storage conditions.
See Part 1 of Proper Wine Storage, which deals with the importance of temperature in maintain a healthy wine collection.
Perhaps even more important than hitting a perfect 52–58°F is maintaining a constant and stable temperature. The reason again is simple science: as liquids warm, they expand, putting pressure on the cork. A protruding cork is a telltale sign that a bottle of wine was over-heated at some point, as is wine leakage around the capsule. The air (and evaporated wine) in the headspace of a bottle is also pushed out through the permeable cork. When the liquid cools, it contracts, creating a vacuum in the headspace, and air is sucked in through the cork to rebalance. Regular fluctuations cause fresh air (oxygen) to be repeatedly drawn into the bottle, which then reacts with, and damages (oxidizes) the wine. This is bad. You’ll have noticed bottles with low fill levels (ullage) — this is normal after 40 or 50 years or more even in a proper cellar as wine naturally evaporates — but it’s another sign of poor storage in younger bottles, indicating that wine has been prematurely forced out and replaced with air.
Temperature fluctuations should thus be minimized in both magnitude and frequency at all costs. A range of about 5°F would be an acceptable level of fluctuation, say between winter and summer — even better if it happens very gradually. But a fluctuation of just a degree or two can be very damaging if it occurs daily or weekly. It would be preferable to store wine at a slightly higher than recommended but stable temperature than at a cooler but regularly fluctuating temperature range.
A proper cellar should include a specialized max-min thermometer to monitor temperature fluctuations. Be sure to use one with a liquid probe and keep it in a water-filled bottle – it’s the liquid temperature (the wine) that matters, not the ambient air temperature (here’s a fancy, Bluetooth enabled example). Thanks to thermal mass — liquid takes longer to warm than air, for one, and the insulating effect of glass — a wine’s temperature will change much more gradually than the surrounding air. This means that a short spell of warmer ambient temperatures, like when you open the cellar door, is not a concern.
>> Stable conditions are important when shipping wine. Xpeditr’s temperature controlled vehicles ensure your valuable collection stays safe on its entire journey.
Assuming that you have some, or all of the wines in your collection under cork, relative humidity levels should range between 60 and 80 percent. This will maximize the lifespan of the cork, keeping it moist, elastic, intact and functioning, and reduce premature oxidation. This is the reason it’s recommended to store cork-closed wines on their side, so the wine stays in contact with the cork and keeps it moist. But corks will still dry out even in bottles that are laying down. The top of the cork is exposed to the air, and if humidity is too low, it will begin to shrink and crack as it dries, allowing air to seep in. Humidity naturally fluctuates between seasons, higher in summer and lower in winter, so some form of humidity moderation in the cellar is need in most climates. And while high humidity (80% and above) won’t cause any damage to corks, it will allow mold and mildews to flourish, potentially ruining labels or even causing a hazardous environment.
Considering the inevitable ingress of ambient air into wine over time (hopefully minimized as much as possible, as noted above), wine logically needs to be kept in an odour-free environment, lest those odorous molecules end up in your wine. Obvious things to avoid are any strong-smelling chemicals, open paint cans, solvents, etc. It’s also preferable to store your perishable food products elsewhere, like potatoes, onions, garlic, root vegetables, dried mushrooms, and the like. Brief exposure is not a concern — it would take many months/years to taint a wine, but these are things best kept separate from your wine cellar.
Light damages wine, so bottles should be kept in a dark environment. The phenomenon called light strike occurs when a wine is exposed to too much UV light, like sunlight. Wines in clear glass bottles are especially susceptible, but although dark green or brown glass absorbs most UV light, even a small amount can react with certain sulfur-containing amino acids in wine to form undesirable, smelly sulfur compounds (i.e., smells like onion, garlic, cabbage). Light can also react with tartaric acid in wine to form hydrogen peroxide, which in turn rapidly oxidizes colour pigments, turning white wines yellow and red wines brown. These effects are irreversible. Low level lighting will not damage wines.
To be continued…
>> Temperature and humidity issues can wreak havoc on your wine collection? Our team has saved many home cellars and transformed them back into stable wine environment. Get in touch to set up a consultation.