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Name: Keith
Status: teacher
Grade: 9-12
Location: CA
Country: N/A
Date: July 2006

Question:
When cooking with wine and various forms of alcohol, does the alcohol evaporate or burn off? What temperature does this type of alcohol burn at?



Replies:
Keith,

The alcohol in alcoholic beverages is ethanol. In its pure form, ethanol has a boiling point of 78.3C. Since the boiling point of water is 100C one should expect that the ethanol can be boiled off before the water is completely removed from the cooking sauce.

You may have heard that ethanol and water form an azeotrope. At 95% ethanol to water, the vapor formed has the same exact composition as that of the solution, the two-component system acts as though it were a pure compound (at least as far as boiling point is concerned) and has a boiling point of 78.15C. At this point, no amount of distillation or careful heating can preferentially boil off the ethanol. However, wines and spirits are usually under 100 proof (50% ethanol). Thus this issue of azeotrope formation is not a concern. The sauce never gets to be 95% ethanol (quite the contrary).

Still, in most cooking processes, the length of time of heating or flambeing is not sufficient to remove *all* the alcohol. There will be a trace amount of alcohol in the sauce.

Greg (Roberto Gregorius)


Depending upon the recipe, either/both processes can occur. Ethanol boils at about 78 C., so if wine or other alcoholic ingredient is simmered/boiled at a temperature of about the boiling point of water, 100 C. the ethanol with evaporate. On the other hand, if the source of ethanol is in a more concentrated form, e.g. rum, brandy, or fortified wine, and the recipe is heated over an open flame, as is done in some recipes, the ethanol vapor can ignite and burn -- usually with a blue flame. No other alcohols than ethanol (C2H5OH) are used in cooking to my knowledge because other alcohols such as methanol or propanol are toxic, or taste bad.

Vince Calder


Well, I don't think that they meant that it actually burns the alcohol off, but rather that it boils off, as alcohol is more volatile than water. Unless you flambé the stuff, the alcohol doesn't burn.

As it turns out, the view that cooking removes all alcohol is erroneous. Some of the alcohol will boil away, but usually not all of it. If you add wine to a soup and only gently simmer the soup in a covered pot, most of the alcohol will remain in the soup. On the other hand, if you add brandy to a sauce and heat it over high heat until the sauce is much thicker in consistency, most of the alcohol will boil away. Basically, it depends on how thoroughly you cook down the liquid.

Richard Barrans



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