Flaming Science

[paulraphael]

Does anyone know of a good discussion on what flaming does to the composition of booze? There's some conventional wisdom that it burns off all the alcohol but this clearly isn't the case.

I just did an experiment where I weighed some cognac, flamed it, and weighed it again (don't worry; it was cheap). It lost 30% of its mass. It was originally 40% alcohol (by volume, so we can assume it's a bit less than 40% alcohol by mass). If all the lost mass was alcohol, then we'd expect over 3/4 of the alcohol to be burned off, leaving cognac that's less than 10% alcohol.

But it tasted much stronger than this. In fact it didn't taste all that different from the unflamed cognac. Which makes me wonder it a lot of water was being evaporated in the process, leaving behind cognac that's slightly lower in alcohol, but in general more concentrated.

Thoughts?

This came up because I'm experimenting with cognac in ice creams, and I'm trying to get as much flavor as possible wiithout too much anti-freeze.

[docsconz]

Interesting. It certainly makes sense that the heat from the flame would evaporate some water as well as burn some alcohol. Unfortunately, I can't tell you if that is actually the case though.

[slkinsey]

I just did an experiment where I weighed some cognac, flamed it, and weighed it again (don't worry; it was cheap). It lost 30% of its mass. It was originally 40% alcohol (by volume, so we can assume it's a bit less than 40% alcohol by mass). If all the lost mass was alcohol, then we'd expect over 3/4 of the alcohol to be burned off, leaving cognac that's less than 10% alcohol.

40% abv cognac is 31.5% alcohol by weight, which corresponds fairly interestingly with your observed weight loss.

Edited November 16, 2008 by slkinsey (log)

[slkinsey]

Interesting chart here: http://homecooking.about.com/library/archive/blalcohol12.htm

[Sebastian]

alcohol does something else that's unique - it's called an azeotrope, which means that as it boils off, it'll take with it 5% additional water (hence the reason you very rarely see 100% pure ethanol).

[paulraphael]

Interesting chart here: http://homecooking.about.com/library/archive/blalcohol12.htm

←

That chart's an interesting idea, but I don't know if tells you anything besides relative values if you don't know their exact precedures. Simmering for a specific time doesn't remove a fixed percentage, it removes a fixed quantitiy (in any given pan). So simmering 4oz of booze for a minute will remove a much greater percentage of alcohohol than simmering 8oz of booze for a minute. To proove the concept, try simmering a tablespoon of booze for a minute ... you'll lose 100% of the alcohol (and water) before the time's up.

The relative values are definitely worth noticing, though. Intersting how little alcohol flaming removes compared with some methods. It makes sense; you can't flame booze that's lower than a certain alcohol percentage. It never builds up the right concentration of vapors and oxygen to ignite. So once you've burned up enough alcohol to get the percentage down to this level, the fire goes out.

[chiantiglace]

Does anyone know of a good discussion on what flaming does to the composition of booze? There's some conventional wisdom that it burns off all the alcohol but this clearly isn't the case.

I just did an experiment where I weighed some cognac, flamed it, and weighed it again (don't worry; it was cheap). It lost 30% of its mass. It was originally 40% alcohol (by volume, so we can assume it's a bit less than 40% alcohol by mass). If all the lost mass was alcohol, then we'd expect over 3/4 of the alcohol to be burned off, leaving cognac that's less than 10% alcohol.

But it tasted much stronger than this. In fact it didn't taste all that different from the unflamed cognac. Which makes me wonder it a lot of water was being evaporated in the process, leaving behind cognac that's slightly lower in alcohol, but in general more concentrated.

Thoughts?

This came up because I'm experimenting with cognac in ice creams, and I'm trying to get as much flavor as possible wiithout too much anti-freeze.

←

A lot of carbon remains

CH3-CH2-OH. You have gases (hydrogen and oxygen) burning off of the alcohol groups, as well as other gases bonding by sugar molecules of the hydroxyl group. I am not sure what remains after burning but the entire alcohol group is not burned off. Similar reactions happen when you caramelize sugar, the carbon is left behind which is what darkens the mix. The more you cook it, the less gases remain and the higher the ratio of carbon, until its one solid mass of black carbon.

I am supposing that with the release of energy the molecules rearrange and lose their flammability. Thus some molecules remain. If nothing but the carbon remained, the after tast would probably taste very bitter and flaming would never be preferred.

[Sebastian]

I am not sure what remains after burning

[/endquote]

water and co2, assuming there was enough oxygen to allow for complete combustion