TOPIC:

Hmm...

Anyone know how much of a vacuum you'd need to pull to get the boiling point of Ethanol down to say 50C??

It's normally 78.3C; I'm going to have to dig up the old Pressure vs. Temp formulas if Hendrix Cat doesn't know it off of the top of his head...


I wonder if you could modify a pressure cooker so that you could pull enough of a vacuum in it to get the ethanol boiling point down to around 50C and then we could experiement with trying to boil off just the Ethanol without causing too much change in the beer itself. (Now about measuring how much ethanol you actually manage to remove and therefore how much remains in the beer, I haven't the faintest idea.)

-I'm not sure that the alcohol content itself would dramatically affect the gravity of the beer so I have to think that method would be "out"...



Adam

I found these tidbits of information:

[quote:2ugg03j2]"According to the vapor pressure calculator at 30 degrees C, ethanol has vapor pressure of 78.47 mmHg, while water is at 31.82 mmHg."

"At about 6 percent of atmospheric pressure the temperature ... need only be 35° C ..."[/quote:2ugg03j2]


If you're using a vacuum pump you'd need to ensure that what gets sucked off never gets circulated back into the vessel because it would be intermingled with oils in the vacuum pump that shouldn't get involved with food.

If you drop the pressure too quickly you could cause the yeast to burst resulting in that wonderful rubbery dead yeast taste, AND you'd have to add more yeast to bottle carbonate. (Although I think bottle carbonating a low-alcohol beer defeats the whole purpose; this should be kegged to keep the alcohol to a minimum.)


I also found a reference that says that Anheiser Busch uses reverse osmosis to make their alcohol free beers...

Now we just need a reverse osmosis filter system that setup to remove Ethanol.

I think Hendrixcat is right that there's a significant possibility of some govt org considering this "distillation" as it technically is. (Although the reverse osmosis option might avoid this problem.)


Adam

Here's a GREAT paper on this subject EXACTLY.

These folks did lots of pratical experiments to reduce the alcohol content of a couple of wine using vacuum distillation. They did their testing at a temperature of 20C; obviously much less vacuum pressure would be needed at higher temperatures...

Another factor that is in favor of doing this is that their tests found that the greater volume of liquid that you use, the higher percentage of alcohol you remove. Using just a 1L sample they were able to remove up to 95.7% of the alcohol in the wine....

[url:1kdmhjx0]http://ejeafche.uvigo.es/index.php?option=com_docman&task=doc_view&gid=28[/url:1kdmhjx0]

I've got a buddy who is doing his PHD at TCD and who has access to the testing equipment to validate the before and after alcohol content if anyone gets serious about testing this.

They DID have to run the vacuum for 15 hours to get that 95.7% result and they lost a lot of other non-ethanol volume, too.

Maybe the reverse osmosis option has more merit; because the vacuum option seems fairly inefficient.

Adam

[quote:1gizdfuf]
If you're using a vacuum pump you'd need to ensure that what gets sucked off never gets circulated back into the vessel because it would be intermingled with oils in the vacuum pump that shouldn't get involved with food.
[/quote:1gizdfuf]

You can get oils that aren't toxic, we use them in scuba compressors (at my dive club) which pump to 225 bar. You can also put a filter before the pump to minimise the oils getting through (though this would neccisitate the pump working harder). I'd also say you could easily engineer a non-flow back valve that would cut the engine if it closes.