Alcohol

The word 'alcohol' is often used rather loosely when people talk about wine. In fact, alcohols (or alkanols) are a remarkably diverse family. The most important of them in wine, a monohydric alcohol, is ethyl alcohol (ethanol), sometimes called spirit of wine. It is produced during fermentation from dextrose and fructose: yeast breaks the sugar molecules down into ethyl alcohol. The highly toxic methyl alcohol (methanol), also known as wood alcohol, can be fatal to humans even in the tiniest quantities.

Fermentation also produces further 'medium' and 'higher' alcohols, known among other names as fusel oils. Although they are present in wine only in relatively tiny amounts, these alcohols are enormously influential, generally toxic and in some cases narcotic. At the same time they determine extremely important aroma and flavour characteristics of a wine. They also lend ethyl alcohol a certain 'staying power', even after the wine has been drunk and is in the body. With excessive consumption of wine they are partly responsible for the notorious hangover.

Another important companion of wine from the alcohol family is the precious glycerol.

One more point worth noting: when you cook with wine, ethyl alcohol (ethanol, commonly just called 'the alcohol') does not simply 'evaporate, burn off or boil away' quickly, as is often believed. This mistaken logic usually comes from the fact that alcohol reaches its boiling point (78.3°C or 173°F) well before water does (100°C or 212°F). In reality, water and alcohol in a mixture are hard to separate, and their boiling points shift more or less together, somewhere between 78.3° and 100° depending on the ratio of water to alcohol. If the mixture in the pan is overwhelmingly water with very little alcohol, the boiling point will sit only slightly below that of water. If it is mostly alcohol, the boiling point moves closer to that of alcohol. As the alcohol evaporates, the alcohol content of the liquid phase falls, the boiling point rises accordingly, and the alcohol content of the vapour phase falls too. Physicists also classify the water and alcohol mixture as a so-called 'azeotropic mixture' when liquid and vapour have exactly the same composition (and so can no longer be distilled any further). For alcohol (ethanol) and water, this 'azeotropic point' is reached at 96% vol (96% alcohol and 4% water). What does all this mean for us cooks and enthusiasts in practice? Very little. Happily, there are some studies with practical findings:

Flaschendruck

In 1992, a study by the University of Idaho, Washington State University and the US Department of Agriculture (USDA) showed that a wonderful dish such as coq au vin (where wine is of course a given in the preparation) is served at the end with between 4% and 49% of the original alcohol still in it. The same goes for the delicious flambéed bananas in our recipes section: once it has died down, the flame has consumed only about 20% of the total alcohol.

“For alcohol (ethanol) and water, this 'azeotropic point' is reached at 96% vol (96% alcohol and 4% water).

The amount of alcohol that remains after cooking depends on many variables (temperature, the design of the cooking vessel, whether a lid is used, how long you cook for, and so on). As a rule of thumb, if a dish is left uncooked (or prepared for cooking later) in the fridge overnight, almost all of the alcohol is still in the dish the next day. If the alcohol is added only during cooking and the dish is taken off the heat straight away, about 70% of the alcohol is retained. If a dish is mixed with alcohol and cooked for just 15 minutes, about 40% remains. After an hour, only about 25% is left. After 2.5 hours, just 5% or so remains. The longer we cook a dish with alcohol, the lower the remaining alcohol content will be.