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Wine does not cook out!

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Unknown

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May 17, 1993, 2:16:29 PM5/17/93
to
In one of the answers to my question about wine substitute someone brought
up that the alcohol does not cook out! (By the way, that is *supposed* to
be the title of this...ooops!) Having a vested interest (ie religious) in
finding the truth to the myth that the alcohol gets cooked out of dishes...
I researched and found that it *DOES NOT*!! So if there are Muslims,
recovering alcoholics, or just people watching their intake... be
forwarned!!

Thanks for the help, by the way!

Peace,
Kareema

TOM WAGNER, Wizzard of old Audio/Visual Equipment........Nanaimo Campus

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May 19, 1993, 11:07:15 AM5/19/93
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I have found a couple of good Dealcohized wines at my local Beer and Wine store.

They are mainly white and come from australia.

Don't know where one would draw the line between non-alcohol and dealcoholized.

I think there is a .1 % allowance on dealcoholized product in Canada. This is
certainly less than is in most drugstore products (cough syrups and mouth-
rinses).
--
73, Tom
================================================================================
Tom Wagner, Audio Visual Technician. Malaspina College Nanaimo British Columbia
(604)753-3245, Loc 2230 Fax:755-8742 Callsign:VE7GDA Weapon:.45 Kentucky Rifle
Snail mail to: Site Q4, C2. RR#4, Nanaimo, British Columbia, Canada, V9R 5X9

I do not recyle..... I keep everything! (All standard disclaimers apply)
================================================================================

David Barton

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May 19, 1993, 12:30:41 PM5/19/93
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This really is too simplistic. Wine can cook out if it is boiled (or
sauteed) almost dry. Thus, if you saute with a little wine and let
the liquid go almost dry, the alcohol will be pretty much gone.
Deglazing with some stock or water after that will get some incredibly
intense flavors for a quick sauce or something.

Alcohol does *not* tend to cook out of a sauce or pot very quickly.
Cooking for a *very* long time will probably do it. If you want to
check, a constant temperature reading will help. Wine with normal
water will boil at below normal boiling (212 F, or 100 C). If you see
a fairly sudden rise in temperature, the alcohol is gone. This can be
pretty hard to spot, as the boiling temperature of sauces tends to
vary a lot anyway (depending upon what you have added), and it can
rise gradually as the proporations change (to say nothing of the stove
cycling on and off).

In most cases, however, count on the alcohol being left behind. In
particular, flaming does not burn off all the alcohol from brandy, so
don't think it does.

Dave Barton
d...@hudson.wash.inmet.com

Betty Harvey

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May 19, 1993, 11:52:11 AM5/19/93
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Is this really true? Every Christmas my father brings a bottle of whiskey
over to my house and forgets to take it home (we don't drink whiskey, except
for medicinal purposes).

I found a great and easy recipe that uses 1 cup of whiskey. It cooks
for several hours so I thought all the alcohol evaporated
away. I thought it just tasted good, I didn't realize people might
be feeling good too :-)!!

/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Betty Harvey <har...@oasys.dt.navy.mil> | David Taylor Model Basin
ADP, Networking and Communication Assessment | Carderock Division
Branch | Naval Surface Warfare
Code 1221 | Center
Bethesda, Md. 20084-5000 | DTMB,CD,NSWC
|
(301)227-3379 FAX (301)227-3343 |
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\\/\/

Joel Offenberg

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May 19, 1993, 12:58:00 PM5/19/93
to

Kareema writes:
>>In one of the answers to my question about wine substitute someone brought
>>up that the alcohol does not cook out! (By the way, that is *supposed* to
>>be the title of this...ooops!) Having a vested interest (ie religious) in
>>finding the truth to the myth that the alcohol gets cooked out of dishes...
>>I researched and found that it *DOES NOT*!! So if there are Muslims,
>>recovering alcoholics, or just people watching their intake... be
>>forwarned!!
>>

Betty Harvey writes:
>Is this really true? Every Christmas my father brings a bottle of whiskey
>over to my house and forgets to take it home (we don't drink whiskey, except
>for medicinal purposes).

Yes, it is true. One of the great myths of alcohol in cooking is "Don't worry,
it just cooks out." Alcohol NEVER entirely cooks out. Some of it cooks out,
but you might have something like 25 - 50% (or more!) of the original alcohol
still in your final product.


Someone (I didn't save the article :( ) posted some lab results where they
actually took foods prepared with alcohol and tested them--some had surprisingly
high alcohol remnants and all had some.

For most of us, this isn't really a problem--if you add a few tablespoons of
wine to your chicken, nobody would get drunk even if none of it cooked out.
However, for people who don't consume alcohol for religious or health reasons,
even the little remnant is bad.

(PS--another form of non-alcoholic wine is grape juice. Around here, you can
find a tart white grape juice in the freezer section of your supermarket...)

-------------------------------------------------------------------------------
Joel D. Offenberg |
Hughes STX |
Offe...@uit.gsfc.nasa.gov | "There's more to this world than just
Disclaimer: I never said that. | people, you know" - Hobbes
Neither did my employers nor |
the government. |
-------------------------------------------------------------------------------

Craig_E...@transarc.com

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May 19, 1993, 12:37:32 PM5/19/93
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Excerpts from netnews.rec.food.cooking: 17-May-93 Wine does not cook out! (501)

> In one of the answers to my question about wine substitute someone brought
> up that the alcohol does not cook out! (By the way, that is *supposed* to
> be the title of this...ooops!) Having a vested interest (ie religious) in
> finding the truth to the myth that the alcohol gets cooked out of dishes...
> I researched and found that it *DOES NOT*!!

It must eventually cook out, in some kinds of cooking, or else
yeast-raised bread would be alcoholic. Instead, we assume that the
alcohol produced by bread yeast is baked out of the final bread, in the
oven.

Craig

David Casseres

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May 19, 1993, 12:32:57 PM5/19/93
to
In article <127...@netnews.upenn.edu> Kareema, writes:
>be the title of this...ooops!) Having a vested interest (ie religious) in
>finding the truth to the myth that the alcohol gets cooked out of dishes...
>I researched and found that it *DOES NOT*!! So if there are Muslims,
>recovering alcoholics, or just people watching their intake... be
>forwarned!!

*Almost all* of the alcohol is cooked out if a dish is cooked thoroughly in an
open vessel (which is what most often happens with dishes that include
alcohol). I'm sure traces are left, probably enough to detect with careful
chemical analysis, and perhaps that is enough to make a difference to someone
who avoids alcohol for religious reasons. However, recovering (or
non-recovering) alcoholics are not at risk, and neither are people just
watching their intake.

A dish that is cooked only briefly, or at very low temperature, or in a
tightly covered pot, is a different matter; under those conditions little of
the alcohol would escape. But even in these cases, it is worth considering
the total amount of alcohol in a dish, and how much of that winds up in an
individual portion. In the recipes I'm familiar with, the alcohol is
typically half a cup of wine, or less, or an ounce of spirits, in a whole pot
of food to serve 6 or 8 people. Again, it might be a problem for Muslims, but
probably not for anyone who is only concerned with the intoxicating effects of
alcohol.

-------------

David Casseres
Exclaimer: Hey!

David Serhienko

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May 19, 1993, 9:10:32 PM5/19/93
to

>
>I found a great and easy recipe that uses 1 cup of whiskey. It cooks
>for several hours so I thought all the alcohol evaporated
>away. I thought it just tasted good, I didn't realize people might
>be feeling good too :-)!!
>
>/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
>Betty Harvey <har...@oasys.dt.navy.mil> | David Taylor Model Basin
>ADP, Networking and Communication Assessment | Carderock Division
> Branch | Naval Surface Warfare
>Code 1221 | Center
>Bethesda, Md. 20084-5000 | DTMB,CD,NSWC
> |
>(301)227-3379 FAX (301)227-3343 |
>/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\\/\/

Feel like passing that recipe along??

advaTHANKSnce
David W Serhienko

Betty Harvey

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May 20, 1993, 8:48:58 AM5/20/93
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In rec.food.cooking, serh...@cobber.cord.edu (David Serhienko) writes:
>
>Feel like passing that recipe along??
>
Sure! It is very easy and it is great for a buffet party.

Whiskey Cocktail Hotdogs

1 cup Whiskey
1 cup Catsup
1 cup Brown Sugar
1 lb Hot Dogs (Sliced in 1" diagonal slices) or Cocktail Hotdogs

Mix whiskey, catsup and brown sugar in pan or crock pot. Add hot
dogs. Cook on very low heat for 4-5 hours until a it reaches
the consistency of barbeque sauce.

Michael J. Edelman

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May 21, 1993, 2:30:56 PM5/21/93
to
In article j...@meaddata.meaddata.com, ja...@meaddata.com (Jack Eddington) writes:
...>
>I don't want to start a flame war on this, but please give references for
>this finding. This contradicts the laws of physics. If you heat a mixture
>of alcohol and anything else, it should boil away at something like 160-170
>degrees F

Reference? Our resident food chemist, Shankar. He ran some samples through the
gas chromatagraph, as I recall, and found a large portion of the alchohol remianed
in the dishes he sampled. (Shankar, where are you?)

The problem is that it is not all that easy to seperate water and alchohol
via distillation when the boiling points are that close...and when you've got
so many other ingredients, etc.

--mike

Tom Moser

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May 21, 1993, 4:23:40 PM5/21/93
to

This reminds me of the fish I cooked last year. I went fishing a caught
several nice bluefish. I have _The Bluefish Cookbook_ and I decided to
make _Bluefish in Gin_ which is basically 2 fillets of Bluefish, 1 cup of
gin, some onions, peppers and spices. I put the fish in the baking dish
added the ingredients and put it in my electric oven. When the time was up
I opened up the oven door and WHOOSH a large sheet of blue flame exploded
from the door burning off my eyebrows and quite a bit of my hair!!!!


I figure that the alchol evaporated from the dish but did not ignite because
there was not enough oxygen in the oven --- until I opened the door.


After the shock subsided and I cleaned up the burned hair from the floor I
did eat the fish - it was quite good. However, I have not made this dish
since then.

-Tom

Jack Eddington

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May 21, 1993, 12:30:30 PM5/21/93
to
(Kareema) writes:

>In one of the answers to my question about wine substitute someone brought
>up that the alcohol does not cook out! (By the way, that is *supposed* to

>be the title of this...ooops!) Having a vested interest (ie religious) in
>finding the truth to the myth that the alcohol gets cooked out of dishes...
>I researched and found that it *DOES NOT*!! So if there are Muslims,

^^^^^^^^^^^^


>recovering alcoholics, or just people watching their intake... be
>forwarned!!

I don't want to start a flame war on this, but please give references for

this finding. This contradicts the laws of physics. If you heat a mixture
of alcohol and anything else, it should boil away at something like 160-170

degrees F (I don't have a chemistry book available, just estimating based
on memory). If there was a chemical reaction, then that would change the
temperature but you wouldn't have alcohol because of the reaction. In
either case, no alcohol. Please enlighten me.

--
Jack Eddington -- ja...@meaddata.com -- uunet!meaddata!jacke

Gary Heston

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May 23, 1993, 9:16:56 PM5/23/93
to
ja...@meaddata.com (Jack Eddington) writes:

First, delete the assumption that a kitchen is a theoretically perfect
chemistry lab. Second, remember that permeability of the alcohol-
containing mixture affects the amount of time for all of it to be
heated and work its' way to the surface to be released as vapor.

It is *theoretically* possible to evaporate all the alcohol out
of a mixture, but *in practice* you can't. It'd require a very long,
carefully controlled heating process to come close.

It's not so easy that all the alcohol flashes into vapor once the
temp reaches 162F or so. That'd be more of an explosion....

Gary Heston, at home....
ga...@cdthq.uucp

tha...@rhea.arc.ab.ca

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May 26, 1993, 6:37:09 PM5/26/93
to
>> >In one of the answers to my question about wine substitute someone brought
>> >up that the alcohol does not cook out! (By the way, that is *supposed* to
>> >be the title of this...ooops!) Having a vested interest (ie religious) in
>> >finding the truth to the myth that the alcohol gets cooked out of dishes...
>> >I researched and found that it *DOES NOT*!! So if there are Muslims,
>> >recovering alcoholics, or just people watching their intake... be
>> >forwarned!!

This has certainly generated a lot of discussion lately, so I may as
well throw in my two cents worth...

Just how much alcohol are we talking about? Some dishes may retain
a moderate amount after cooking if a lot of alcohol has been added,
but if wine or sherry is used to flavour food in small amounts
then surely anything remaining after cooking must be in trace
amounts. If we want to take this to extremes then the yeast
used to make bread rise produces alcohol, and some trace
of this probably remains after baking bread. Does this mean that
people who want to avoid alcohol (for religious or other reasons)
should avoid bread?

The point I'm trying to make is that in most dishes that call for
a bit of liquor for flavouring the amount remaining after cooking
will be negligible, and I don't think that eating those
dishes would be considered to be imbibing alcohol. Maybe I'm
ignorant or misguided, but that's my two cents worth.

Don

Michael D. Galloway

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May 27, 1993, 9:13:59 AM5/27/93
to
anyone who's ever 'flamed' a dish knows that the alcohol is boiling off.

michael

Michael J. Edelman

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May 27, 1993, 10:26:39 AM5/27/93
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In article s...@suntan.eng.usf.edu, Michael D. Galloway <m...@solid.ssd.ornl.gov> writes:
>anyone who's ever 'flamed' a dish knows that the alcohol is boiling off.
>
>michael

This misses the point. Yes, you can boil off some of the alchohol, especially
in a dish in which a high-alchohol content liquor is heated and then poured
over the dish, which is how one usually does a flambe. We're talking about
alchohol boiling out of a dish in which wine (typically) has been incorporated.

There's really nothing to argue about. Shankar has done the empirical work, and
posted results here (see what you missed while relaxing at your Mom's table,
Shankar?). Others have done similar research. The hard facts are that wine does
not completely cook out; a *significant* portion remains.

--another michael


Julie Kangas

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May 27, 1993, 10:32:51 AM5/27/93
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In article <1993May26...@rhea.arc.ab.ca> tha...@rhea.arc.ab.ca writes:
>>> >In one of the answers to my question about wine substitute someone brought
>>> >up that the alcohol does not cook out] (By the way, that is *supposed* to
>>> >be the title of this...ooops]) Having a vested interest (ie religious) in

>>> >finding the truth to the myth that the alcohol gets cooked out of dishes...
>>> >I researched and found that it *DOES NOT*]] So if there are Muslims,

>>> >recovering alcoholics, or just people watching their intake... be
>>> >forwarned]]

>
>This has certainly generated a lot of discussion lately, so I may as
>well throw in my two cents worth...
>
İ...¨

>
>The point I'm trying to make is that in most dishes that call for
>a bit of liquor for flavouring the amount remaining after cooking
>will be negligible, and I don't think that eating those
>dishes would be considered to be imbibing alcohol. Maybe I'm
>ignorant or misguided, but that's my two cents worth.

I've had cherry liquor flavored chocolates that have given me
quite a buzz (and I didn't need to eat the whole box...) I think
you need to approach each dish flavored with alcohol as a potential
source of alcohol.

Julie
DISCLAIMER: All opinions here belong to my cat and no one else

Michael Panayiotakis

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May 28, 1993, 12:36:37 AM5/28/93
to

Well, now, let me carry this thread a bit further.

HOW MUCH ALCOHOL do you put in a dish? If you don't flambe' it, typical
is a wine glass MAX. say 60% of it cooks out (which is a very high
estimate...the highest amount of alcohol remaining in the dish is less
than half the ammount of alcohol in a glass of wine, which (wine) in
itself doesn't have a high alcohol content. Now divide that into
servings....say four servings. You get one fourth of 60% which remains.
this *is* a miniscule ammount of alcohol, and I'm using the highest
numbers impossible here. Usually wine is added and it comes in contact
with the pan, which is the hottest part of the whole damned ordeal, and
then you usually leave the meat (usually) with the wine only (vefore
adding anything else to cool it off) inthe pan for at least 2-3 minutes.
I'd say that'd kill at least 30% of the alcohol right there. then you
simmer it for a while more...and then you divide it into servings....

As I see it, alcohol may not all burn off, but it's a miniscule ammount
that remains. Even in layer cakes where I sometimes add brandy or
what-have-I to the layers to moisten a bit before the frosting, which is
not cooked and therefore doesn't evaporate, there's still a miniscule
ammount of alcohol (I'd say about 30 TBspn inthe whole cake. Now divide
that into servings...)

Now if your religion (or whatever other ethical reasons) forbid you to
consume alcohol, well, then whether you eat these food or not strictly
depends on how strict you are. As for the law, I personally don't think
it applies. If so, what abou all the medicines w/ alcohol? what about
lemon extract??? that's 90% alcohol. Almond extract is high-alcohol,
too.

that's my few bucks' worth.

peace,
Mickey

Shankar Bhattacharyya

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May 28, 1993, 8:42:31 AM5/28/93
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In article <1u2j2v$p...@vela.acs.oakland.edu> m...@pookie.pass.wayne.edu writes:
>In article s...@suntan.eng.usf.edu, Michael D. Galloway <m...@solid.ssd.ornl.gov> writes:
>>anyone who's ever 'flamed' a dish knows that the alcohol is boiling off.

>There's really nothing to argue about. Shankar has done the empirical work, and


>posted results here (see what you missed while relaxing at your Mom's table,
>Shankar?). Others have done similar research. The hard facts are that wine does
>not completely cook out; a *significant* portion remains.

Well, Michael, I see that you and Gary Heston are still fighting the good
fight on this subject. I arrived at what looked like the tail end of this
thread, so I was planning to let this be. I have no idea what portion
of the usual cycle this has already been through. Besides, I'm tired of
batting down this particular idea. But, since you mention my little
experiment, what the hell, I'll roll up my sleeves and join the cause.

I offer a meta-post alert. Much of this is repetition, of course. And I
include an offer of a copy of the Augustin paper, with strings attached.
Also, there is an explanation of evaporation rates that I wrote up a long
time ago, but don't think I've posted.

Anyway ....

There are two separate issues in the matter of how much alcohol remains in
dishes which use alcohol.

First is the issue of just how much alcohol there is in a serving of a
dish cooked with alcohol. In most such dishes, if the proportion of alcohol
initially added is small, the actual amount of alcohol in a serving can be
fairly trivial, largely as a matter of dilution. I have no argument with
that.

Nor do I have any argument to offer on the subject of who should worry
about those amounts, and who should not. Actually, I do, but I will refrain
from expressing it. That's simply opinion, anyway.

The second issue, which is what most people talk about when they talk about
how much alcohol remains, is this: What fraction of the added alcohol is
left at the end? To the food chemist, this is the interesting question.
The answer to that question, it turns out, is: it varies a lot, and is
almost always wildly more than people seem to expect.

As Michael Edelman mentions, I've done an experiment to test this. A
couple of years ago this subject came up on the net. I decided to check
it out for myself. It's pretty trivial to check for oneself, so what the
hell. What's a modern kitchen without a gas chromatograph, anyway?

I found, to my immense surprise, that a beef burgundy I made, precisely
to Child, Bertholle and Beck's recipe in "Mastering the Art of French
Cooking", retained about 25% of the added alcohol. However, I did just
a single experiment, not a substantial study. I can pretty much guarantee
that this 25% retention number is an underestimate. I will refrain from
going into that in any greater detail. I've done that before.

This was a single measurement on a single preparation, of a single (if
classic) dish. I reached no global conclusions, but it does suggest that
the common wisdon is wrong. The alcohol is not all gone.

The analysis was reliable - industry standard conditions, and so on. I
could comfortably defend the experiment in any scientific forum.

I was quite surprised by the result. I had expected to see some alcohol,
but not a whole lot. However, if you think reasonably carefully about
this, it is easy to understand. In fact, it is wildly obvious. So now I
wonder why anyone would expect the alcohol to be all gone. 20/20 technical
hindsight, of course.

Anyway, at about the same time, Evelyn and Jorg Augustin, of Washington
State University and the University of Idaho, were completing a systematic
study of this exact issue for the USDA nutrient retention studies. I assume
that it was at about the same time, anyway, since their paper was published
a few months later. Their paper came as a considerable surprise to me. In
fact, Martin Golding had suggested to me that this sort of work was
publishable, and I said, "Oh, come on. This has almost certainly been done
already. It's just not widely known." Well, Martin, your judgment was
better than mine. It had never been done.

The Augustins studied several dishes, prepared by different cooking
techniques, and tried to reach some understanding of what determines
the retention of the alcohol. Interesting paper. Nice work.

Wes Voss has, on a couple of occasions, posted an account of the Augustins'
results, based on an article by Karola Saekel in the San Francisco
Chronicle. I'll leave it to Wes to repost that very informative post, if
he hasn't already done so.

From Wes's quote from the Chronicle article I gather that Saekel was
startled by the very high alcohol retention in flambees. This, in
particular, is not at all surprising. No chemist would expect that
flambeeing a dish would get rid of the alcohol. That is simply too silly an
idea. Saekel is probably not a chemist, so it would be unreasonable to hold
this against her.

Now, here's the offer. I have a copy of the Augustin paper. I'll send a
copy to anyone who asks for one. However, if I get swamped with requests, I
will attach strings. I will divide the list of people in half, and start a
binary tree for distribution. That should work very quickly. So, if you ask
for a copy, be prepared to send out two copies yourself. That seems fair
enough. So, if you want a copy, send me a mailing address, and you'll get
one in a bit. This is just in case I get swamped. It comes up often enough
here that I don't want to commit myself to a job that gets out of hand.

Those who have been on the side of truth, light, and gas chromatography in
this thread get their copies without strings.

OK, on to an explanation. I'm not going to argue about this explanation.
Some of it you will have to take on faith. It's a mite simple, but it is
defensible.

[If you want to argue about it, make sure that you can pop a physical
chemistry book open and read, preferably fluently, the section on the
colligative properties of solutions. A phase diagram, such as that for
the alcohol-water system, will also have to make complete sense to you.

It would help if you understood hydrogen bonding, not because you need it
to be able to figure this out, but because if you don't you will not be
sure that you have figured it out.

I don't want to come off as arrogant about this, but I really think that
is what you need to know to have any serious undersatanding of what
happens, certainly if you want to fight with a chemist about it.]

OK, first the flambeeing affair. That is actually fairly simple.

The success or failure of an attempt to light up a dish is not even a good
guide to whether there is alcohol left in the dish. It is a good guide to
whether there is a *great deal* of alcohol left.

An alcohol-water mixture will allow a flame above it if, at the
temperature in question, the vapour pressure of alcohol above the surface
is high enough. This actually requires rather a lot of alcohol in the
mixture, since it requires quite a lot of alcohol in the vapour to allow a
steady-state, persistent reaction, i.e. a persistent flame.

Even allowing for elevated temperatures, beer will not sustain a flame. I
have not tested this out, but I am fairly confident in that assertion.
Wine may, although I doubt that, and I may test that out, but the flame
will go out while the alcohol concentration in the liquid is quite high.

The flame goes out when the vapour phase runs out of meaningful amounts of
alcohol, not when the liquid runs out of it. So the flame will burn only so
long as the rate at which alcohol evaporates from the liquid under the
temperature conditions is sufficiently high that the alcohol in the vapour
can be replaced pretty much as fast as it is consumed by the flame. A
considerable amount of alcohol will still be left in the liquid at that
point. You are likely to be able to relight the flame a few times, but in
the end there will still be a lot of alcohol left. This is controlled by
the kinetics of evaporation.

That is not a nitpicking residual level, either, Flambeed dishes contain
very substantial amounts of residual alcohol.

I do hope that makes sense. It is completely obvious if you understand how
"liquids" burn. Red Adair would understand.

Now, on to the more complicated business of what happens when you cook
stuff that contains alcohol.

People, including chemists, have historically assumed that when they cook
with wine, essentially all the alcohol goes away, as long as you do, in
fact, cook the stuff for some time.

People offer naive chemical and physical justifications for their
expectation that most of the alcohol will be gone, but that simply ain't
so. The recent experimental evidence clearly shows this.

Once you know the idea to be false, and you spend a few minutes thinking
about it, it is fairly obvious that this is a silly idea. It is interesting
that people, trained chemists included, have cheerfully gone along with
this silliness for a very long time. We have been handed this piece of
conventional wisdom for a century or so, and we have simply accepted it,
without thinking about it.

If you take a mixture of two miscible liquids, the equilibrium vapour
pressure above the surface at any temperature is the sum of the
contributions from the individual liquids. Each liquid contributes the
vapour pressure that it would contribute by itself, weighted by the
fraction of the molecules in the mixture that are of that liquid, i.e.

total vapour pressure = M1 * SVP1 + M2 * SVP1

where M1 and M2 are the molar ratios, and the SVP's are the saturated
vapour pressures for the pure liquids at the temperature. The boiling point
is the temperature at which that total vapour pressure is equal to the
ambient pressure.

[Things are different for immiscible liquids, and that is left as an
exercise for the reader. That's the basis of steam distillation, by the
way.]

Those three little paragraphs are actually quite information dense.

This assumes that the two liquids do not interact, i.e. that the solution
behaves ideally. In practice, alcohol water systems are not at all ideal.
After all, alcohol and water form an azeotrope, which is very non-ideal
behaviour indeed. This behaviour makes it much harder to examine the
problem in very simple ways.

Anyway, assume ideal behaviour. It's close enough for current purposes.

When you bring a solution of two liquids to the boil, the one with the
lower boiling point will occur in the vapour at a concentration higher than
its concentration in the liquid phase, but it will not be the only thing in
the vapour. In fact, what fraction of the total vapour consists of the
lower boiling component depends both on the SVP values, and the molar
ratios.

At any temperature upto the boiling point of a pure liquid, the lower the
boiling point of a substance, the higher its SVP. [Those are approximately
equivalent statements, given some understanding of the thermodynamics of
evaporation.]

If there is a very large difference in boiling points, the composition of
the vapour will be dominated by the SVP values, and the lower boiling
component will get blown off very efficiently, in preference to the higher
boiling component.

However, if there is not a very large difference in boiling points - and
the 22 degree Celsius difference in boiling points between water and
ethanol is really not wildly large - the relative concentrations play a
larger role. In fact, towards the end, while a few percent of the lower
boiling component is still left in the liquid, the vapour will have almost
the same composition as the liquid (not exactly, of course, but you
probably get the idea), and the concentration of the lower boiling
component in the residual liquid simply does not change very much.

As Gary Heston correctly points out at the slightest indication that anyone
is about to ignore this, all this stuff assumes that you have equilibrium
conditions, at one theoretical plate. In a kitchen, as he points out, you
sure as hell don't. In order for kitchen conditions to work this well, I am
fairly sure that the second law of thermodynamics would have to be untrue,
and perpetual motion machines would be possible. So, before anyone gets all
excited about arguing with him about whether you can do as well in the
typical kitchen, do be prepared for that argument. Make an argument that
violates the second law and you will be picking your teeth off the
sidewalk. We in the nerd community get all excited about that. You can be a
murderer. That's OK. You can be a traitor. That's OK. You can even have bad
taste in food. That's OK, too. But you can't be on the worng side of the
second law. That's immoral.

If you think about it, it is really quite unreasonable to expect that all
the alcohol will go away, but we chemists have historically just accepted
this without argument. We should have known better. We did not. There is a
lesson in humility in there.

- Shankar

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