Heat Damage / Maderization

Wines can be heat damaged during transportation or storage. Bad shipping or storage can subject a wine to enough heat to make it taste maderized, or cooked. Maderized is a tasting term for a wine that has become over-mature, oxidized and with a cooked taste, and oxidized wines are also called maderized. In mature dessert-style wines, the same word is used for a brownish color and a slightly sweet, somewhat caramelized and often nutty character. Wine left for prolonged periods in hot places can lose its fresh fruit characteristics, and enough heat makes it taste cooked.

• Heat damage can happen during transportation or storage, for example when wine is left for prolonged periods in hot places such as direct sunlight in a shop window
• Accidental maderization shows as cooked, stewed fruit and a loss of freshness
• Once a wine has been exposed to heat, nothing can reverse any damage that may have occurred
• A cooked wine is not unsafe: it will not make you sick

There is no single agreed limit. Wine Spectator advises that wine stored above 70°F (21°C) ages more quickly than is usually desirable, that prolonged temperatures above 70°F may damage a wine's freshness or cook it, and that above 80°F (27°C) you start to risk heat damage; a few hours of heat above 70°F should not damage your wine. Jancis Robinson describes 75°F (24°C) as "an entirely anecdotal maximum" for a cellar. The Australian Wine Research Institute (AWRI) notes that any storage place above 25°C (77°F) for long periods, or 40°C (104°F) for short periods, can affect wine quality, and says it is not currently possible to define a specific temperature, or time at a given temperature, at which a particular wine will begin to show damage. How sensitive a wine is depends on its winemaking history and composition. Heat damage is also hard to predict: two identical bottles exposed to the same amount of heat might not fare the same way.

• Temperatures higher than 70°F (21°C) age a wine more quickly than is usually desirable
• Above 80°F (27°C) the risk of heat damage begins
• A few hours of heat above 70°F should not damage a wine
• A common rule of thumb is that chemical reaction rates double for every 10°C (18°F) rise in temperature, though this depends on the specific reaction
• Two identical bottles exposed to the same heat might not fare the same way

When a bottle of wine gets hot, the liquid inside expands, and the only place it can go is out. The wine can push the cork up or seep past it, leaving sticky signs on the neck, a sticky or discolored top of the cork, or a label stained by wine that leaked out through the cork. If heat has made the wine expand and leak out of the cork a bit, you might find a sticky mess when you remove the capsule; this is a hint the wine may have been exposed to heat, not proof it is ruined. These signs do not always mean the wine is ruined, and such physical damage from heat does not necessarily mean the quality of the wine has been affected. A cork can also start to push out because it was put in a bit wonky, because of microbial spoilage or refermentation in the bottle, or because the wine froze. In the glass, a cooked wine's fruit flavors taste stewed, baked or canned instead of fresh, there can be a baked or burnt note, caramel notes can show up too, the aromas and flavors seem flat, and the color can take on a more brownish hue. A heat-damaged wine can lose its fresh fruit characteristics and taste dull and stale. The only way to know for sure is to open the bottle and taste it.

• Before opening: a cork pushed up, sticky residue on the neck or cork top, or a label stained by leaked wine
• These are clues, not proof: a bottle that seeped wine can still taste fine
• Other causes of a pushed cork include a cork put in crooked, refermentation in the bottle, and freezing
• In the glass: stewed, baked or canned fruit, flat aromas and flavors, and a browner color
• The only way to know is to open the bottle and taste

Elevated temperatures experienced through the supply chain can accelerate wine development and reduce shelf life, and these changes may go unnoticed until the wine reaches the consumer. The chemical changes produced by elevated temperatures are generally more prominent in white wines than in red wines. The most noticeable effects are a loss of fruity aroma compounds, premature browning, loss of sulfur dioxide, and negative attributes generated through oxidation reactions. Red wines also experience a reduction in anthocyanins and an increase in polymeric pigments, and heat can affect their color, flavor, mouthfeel and aroma. Heat and air can work together: heat exposure can force the cork out, and once the seal is compromised the wine will become oxidized. If the cork expands and contracts, that process can also let oxygen into the bottle.

• Heat speeds up wine development and shortens shelf life
• Effects are generally more prominent in white wines than in red wines
• Main effects: loss of fruity aromas, premature browning and loss of sulfur dioxide
• Red wines lose anthocyanins and gain polymeric pigments
• A cork pushed out by heat compromises the seal and lets the wine oxidize

Madeira is a fortified wine: fermentation is stopped by adding wine alcohol at 96% vol. It is then aged by one of two processes, estufagem or canteiro. In estufagem, the wine is placed in stainless steel tanks heated by a coil through which hot water circulates, for no less than 3 months, at a temperature between 45 and 50°C (113 and 122°F). After estufagem, the wine rests for at least 90 days at ambient temperature. In canteiro, the wines are aged in casks, usually on the upper floors of the lodges where temperatures are higher, for a minimum of 2 years. The name comes from the wooden beams, called canteiros, on which the casks rest. Canteiro is an oxidative ageing in cask.

• Estufagem: stainless steel tanks heated to between 45 and 50°C (113 and 122°F) for no less than 3 months
• After estufagem, at least 90 days of rest at ambient temperature
• Canteiro: casks aged usually on the warmer upper floors of the lodges for a minimum of 2 years
• Canteiro is named for the wooden beams that support the casks

Wine Spectator calls heat "enemy number one for wine." Wine needs relative cool, about 13°C (55°F), with no dramatic swings of temperature. The ideal range is between 45°F and 65°F (7°C and 18°C), and 55°F is often cited as close to perfect. Avoiding rapid, extreme or frequent temperature swings matters more than achieving a perfect 55°F. Place wine racks away from heat and direct sunlight, and rule out the kitchen, laundry room or boiler room, where hot temperatures could affect your wines. Jancis Robinson names spots by a cooker or on top of a fridge, where there are frequent blasts of hot air, as the worst place to store wine. In a garage, keep an eye on the temperature during the summer months, and remember that an unheated garage in winter can freeze wine; insulating a garage can mediate those highs and lows. Keeping wine in a household refrigerator is fine for up to a couple of months, but not for the longer term. Never leave wine in a car's trunk. Shipping carries risk too: in 2003 a container of wine shipped from Australia to a Hong Kong importer arrived warm to the touch, the temperature inside was 34°C (93°F) an hour later, and nearly all the bottles had their corks popped out or bulging out from the capsule.

• Keep wine at about 55°F (13°C), with no dramatic swings of temperature
• Consistency matters more than hitting a perfect 55°F
• Store wine away from heat and direct sunlight; rule out the kitchen, laundry room and boiler room
• Watch garage temperatures in summer, and protect wine from freezing in winter
• A household fridge is fine for up to a couple of months, not for long-term storage

Primary sources: https://www.awri.com.au/wp-content/uploads/TN09.pdf, https://www.awri.com.au/wp-content/uploads/2011/07/Technical_Review_Issue_224_Scrimgeour.pdf, https://vinhomadeira.com/o-vinho-madeira/vinificacao-e-envelhecimento. Secondary sources: https://www.wsetglobal.com/knowledge-centre/blog/2023/august/24/common-wine-faults-and-how-to-spot-them, https://www.decanter.com/learn/maderized-46269/, https://www.jancisrobinson.com/articles/wines-squirrel-away, https://www.jancisrobinson.com/articles/what-happens-to-your-wine-en-route, https://www.winespectator.com/articles/is-it-safe-to-drink-wine-from-a-cooked-bottle-where-the-cork-has-popped-up-a-bit-45567, https://www.winespectator.com/articles/wine-in-hot-car-ruined-55587, https://www.winespectator.com/articles/does-wine-go-bad-if-it-gets-hot-57214, https://www.winespectator.com/articles/are-there-clues-to-bad-wine-storage-56682, https://www.winespectator.com/articles/cork-pushed-out-wine-bottle-ok-to-drink, https://www.winespectator.com/articles/how-to-store-wine-temperature-humidity-coolers-and-more, https://www.winespectator.com/articles/cellaring-secrets-223, https://www.winespectator.com/articles/will-my-wines-get-too-cold-in-the-garage, https://www.winespectator.com/glossary/index/word/m, https://www.winespectator.com/articles/the-moment-of-truth-14375, https://www.winespectator.com/glossary/show/id/oxidized, https://www.winespectator.com/articles/what-does-a-cooked-wine-taste-like-5482, https://www.jancisrobinson.com/learn/drinking-wine/how-to-store-wine. Last verified 2026-11-02