The place for all things wine, focused on serious wine discussions.

Noobie Question: What does "Volatile Acidity" taste like or do to a wine?

Moderators: Jenise, Robin Garr, David M. Bueker

no avatar
User

Brian K Miller

Rank

Passionate Arboisphile

Posts

9340

Joined

Fri Aug 25, 2006 1:05 am

Location

Northern California

Noobie Question: What does "Volatile Acidity" taste like or do to a wine?

by Brian K Miller » Tue Sep 11, 2007 2:00 pm

reading a Cellar Tracker note for Musar, the critic noted "Volatile Acidity" as a problem. Given that I usually have been drinking younger wines, how would one describe VA and its impact on a wine?
no avatar
User

Dale Williams

Rank

Compassionate Connoisseur

Posts

11757

Joined

Tue Mar 21, 2006 4:32 pm

Location

Dobbs Ferry, NY (NYC metro)

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a wine?

by Dale Williams » Tue Sep 11, 2007 2:10 pm

Sooner or later one of the people who really understand wine chemistry will answer. Until then....

Most wines I think contain volatile acids. If they reach a point where they are noticable, people start talking about VA (or terms like "lifted nose"). Some people hate any trace of VA. Other think a little enlivens a wine- pretty standard in old style Rioja for instance.

I like a little VA myself. But when it becomes too much, it reminds me of airplane glue or nail polish remover. And I really can't stand that. I find the amount of VA varies in Musar even within a vintage, but it is frequently past my threshold and is the primary reason I'll gladly taste Musar, but seldom buy it.
no avatar
User

Robin Garr

Rank

Forum Janitor

Posts

21845

Joined

Fri Feb 17, 2006 1:44 pm

Location

Louisville, KY

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Robin Garr » Tue Sep 11, 2007 2:15 pm

Dale's explanation is good. Here's a somewhat longer and more boring take on it from a <i>Wine Advisor</i> article a while back:

Volatile or vinegar?
no avatar
User

Thomas

Rank

Senior Flamethrower

Posts

3768

Joined

Wed Mar 22, 2006 4:23 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Thomas » Tue Sep 11, 2007 2:25 pm

Brian K Miller wrote:reading a Cellar Tracker note for Musar, the critic noted "Volatile Acidity" as a problem. Given that I usually have been drinking younger wines, how would one describe VA and its impact on a wine?


Put simply, volatile acidity is an attack of aceto-bacteria making acetic acid in an oxidative environment. It's the progression to vinegar, but uncontrolled it can lead to major problems.

Generally, it smells, well, volatile--shoots right up your nose and burns. As the bacteria does its work, the smell will go through stages, one of the more powerful is of nail polish or varnish.

Its taste is vinegar-like or, I suppose, varnish-like.

In the U.S. the feds allow a certain threshold level of v.a. in wine, after which the product has to be sent to the vinegar factory. Unfortunately, the feds only control what goes into the bottle...reasonably slight v.a. going in can come out worse when you pop the cork, especially if the wine isn't handled too well at the winery.
Thomas P
no avatar
User

Robin Garr

Rank

Forum Janitor

Posts

21845

Joined

Fri Feb 17, 2006 1:44 pm

Location

Louisville, KY

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Robin Garr » Tue Sep 11, 2007 2:32 pm

Thomas wrote:bacteria making acetic acid in an oxidative environment.


Make that acetic acid, ethyl acetate or a combination. Acetic acid does the vinegar thing, ethyl acetate the varnish/nail polish/airplane glue thing. In my experience, I find ethyl acetate much more common than vinegar in modern commercial wines, although I've judged some home wines that were right up there in the vinegar department. ;)
no avatar
User

Thomas

Rank

Senior Flamethrower

Posts

3768

Joined

Wed Mar 22, 2006 4:23 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Thomas » Tue Sep 11, 2007 3:23 pm

Robin Garr wrote:
Thomas wrote:bacteria making acetic acid in an oxidative environment.


Make that acetic acid, ethyl acetate or a combination. Acetic acid does the vinegar thing, ethyl acetate the varnish/nail polish/airplane glue thing. In my experience, I find ethyl acetate much more common than vinegar in modern commercial wines, although I've judged some home wines that were right up there in the vinegar department. ;)


Robin,

As I remember, ethyl acetate is formed by the combination of acetic acid and ethanol; you can't have the acetate without the acetic.

That's what I meant when I referred to acetic acid left uncontrolled will go through stages. I guess that wasn't exactly descriptive. IShouldabeen more clear!
Thomas P
no avatar
User

Paul Winalski

Rank

Wok Wielder

Posts

8872

Joined

Wed Mar 22, 2006 9:16 pm

Location

Merrimack, New Hampshire

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Paul Winalski » Tue Sep 11, 2007 10:21 pm

"Volatile acidity" is a techno-wine chemistry term that refers to various acidic compounds in wine that evaporate rather readily (hence "volatile") as opposed to other acids that stay in solution and don't evaporate off (also known as "fixed acidity").

Malic, tartaric, and lactic acids are examples of "fixed acidity". They may crystallize out (forming the white crystals or granules you sometimes find in wine), and you may be able to smell them a bit (malic acid has a tart-apples aroma), but they don't readily evaporate or fizz out.

On the other hand you have the volatile wine acids, which evaporate readily:

Carbonic acid (H2CO3), which readily bubbles off as free CO2. This is the "spritz" of young German wine and the bubbles of Champagne and other sparkling wine. In sparkling wine it's a positive feature. It's acceptable in young German wine, too. Elsewhere either fizziness or a prickly sensation of CO2 on the palate is an indication that something's gone wrong and unwanted bacteria have been at work.

Acetic acid (CH3COOH) is the acid of vinegar, with its characteristic flavor and aroma. Except perhaps in the tiniest quantities, this is an unwelcome fault in wine.

Acetone, acetoacetate, hydroxybutyrate, and related compounds (sorry, couldn't be bothered to look up the chemical formulae). Aromas of nail polish. Port seems particularly prone to this, in my experience. It is a major fault in the 1977 Ports, particularly Graham's.

Butyric acid and friends (CH3CH3CH3COOH). Aromas of rancid butter or worse. An indication that things have gone really seriously wrong.

In small quantities, these may be just aromatic nuances (nuisances?). In larger quantities, they may blow off (evaporate harmlessly) with decanting or aerating in the glass. When obvious and obtrusive, they are distinct wine faults, and symptomatic of something that's gone wrong in either the winemaking or the ageing process.

-Paul W.
no avatar
User

Oliver McCrum

Rank

Wine guru

Posts

1076

Joined

Wed Mar 22, 2006 1:08 am

Location

Oakland, CA; Cigliè, Piedmont

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Oliver McCrum » Tue Sep 11, 2007 10:29 pm

Paul Winalski wrote:Carbonic acid (H2CO3), which readily bubbles off as free CO2. This is the "spritz" of young German wine and the bubbles of Champagne and other sparkling wine. In sparkling wine it's a positive feature. It's acceptable in young German wine, too. Elsewhere either fizziness or a prickly sensation of CO2 on the palate is an indication that something's gone wrong and unwanted bacteria have been at work.

-Paul W.


Paul,

I don't think this is quite right; many unflawed white and red still wines have enough CO2 to create the prickly sensation. Many of the white wines I import do, for example, and a number of new world Pinots do.
Oliver
Oliver McCrum Wines
no avatar
User

Paul Winalski

Rank

Wok Wielder

Posts

8872

Joined

Wed Mar 22, 2006 9:16 pm

Location

Merrimack, New Hampshire

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Paul Winalski » Tue Sep 11, 2007 10:37 pm

Robin Garr wrote:Make that acetic acid, ethyl acetate or a combination. Acetic acid does the vinegar thing, ethyl acetate the varnish/nail polish/airplane glue thing. In my experience, I find ethyl acetate much more common than vinegar in modern commercial wines, although I've judged some home wines that were right up there in the vinegar department. ;)


I think varnish/nail polish remover thing is acetone (CH3COCH3), more than ethyl acetate (CH3COOCH2CH3), which has a fruity, pear-like aroma. Chemically, one would expect acetic acid present as a fault in wine to over time spontaneously combine with the ethanol to form the ester ethyl acetate.

I've found acetone aromas present occasionally in Sauternes that have a volatile acid problem, and in Ports, both good (when present in only in trace amounts) and bad (where obnoxiously present).

Thank God mercaptans rarely find their way into bottled wines (although you sometimes find them in barrel samples).

-Paul W.
no avatar
User

Mark Lipton

Rank

Oenochemist

Posts

4516

Joined

Wed Mar 22, 2006 1:18 pm

Location

Indiana

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Mark Lipton » Wed Sep 12, 2007 12:28 am

Paul Winalski wrote:
Robin Garr wrote:
I think varnish/nail polish remover thing is acetone (CH3COCH3), more than ethyl acetate (CH3COOCH2CH3), which has a fruity, pear-like aroma. Chemically, one would expect acetic acid present as a fault in wine to over time spontaneously combine with the ethanol to form the ester ethyl acetate.


Actual nail polish remover is usually either methyl ethyl ketone (2-butanone) or methyl propionate (a congener of ethyl acetate). Acetone was sometimes used, but it's too volatile and evaporates too fast. MEK is just a higher boiling version of acetone. And why do you think that acetic acid and ethanol would spontaneously combine in wine to form ethyl acetate? It's an equilibrium reaction:

CH3COOH + CH3CH2OH <-- --> CH3COOCH2CH3 + H20

The equilibrium constant for this reaction is close to 1, so whether it favors reactants or products depends mostly on the relative concentrations of water and ethanol. Guess which predominates in wine?

I've found acetone aromas present occasionally in Sauternes that have a volatile acid problem, and in Ports, both good (when present in only in trace amounts) and bad (where obnoxiously present).


Having worked around acetone, ethyl acetate and acetic acid for all of my adult life, I am thrilled to report that I have rarely, if ever, smelled the former two in a wine and only occasionally the latter. One confounding problem, though, is some people get an acetic acid smell from ethyl acetate (I know of one Professor of Chemistry who suffers that fate), apparently from hydrolysis in the nasal mucosa or something like that...

Thank God mercaptans rarely find their way into bottled wines (although you sometimes find them in barrel samples).


I've heard people say that with all the precautions now taken about excluding oxygen during elevage there are quite a few seriously reduced wines being bottled. And wouldn't you say that the well-documented "bottle stink" of older wines is often a mercaptan smell?

Mark Lipton
Oenochemist
no avatar
User

Redwinger

Rank

Wine guru

Posts

4038

Joined

Wed Mar 22, 2006 2:36 pm

Location

Way Down South In Indiana, USA

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Redwinger » Wed Sep 12, 2007 11:35 am

Dear Oenochemist,
I think my brain just exploded. :lol:
'Winger
Smile, it gives your face something to do!
no avatar
User

Bob Parsons Alberta

Rank

aka Doris

Posts

10860

Joined

Tue Mar 21, 2006 3:09 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Bob Parsons Alberta » Wed Sep 12, 2007 11:57 am

Redwinger wrote:Dear Oenochemist,
I think my brain just exploded. :lol:
'Winger


Yeah, that is all pretty impressive. I use ethyl acetate in my butterfly collecting when I want some samples. Knocks them out fast.
no avatar
User

Victorwine

Rank

Wine guru

Posts

2031

Joined

Thu May 18, 2006 9:51 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Victorwine » Wed Sep 12, 2007 8:31 pm

Question for Mark;
Do these chemical reactions depend on the presents of oxygen? It makes sense that too much exposure to air could contaminate a wine, acetic bacteria is everywhere (floating around in the air we breathe). For these organisms to survive and reproduce surely oxygen is needed. But what actually governs these chemical reactions? The living bacteria themselves or the enzymes which they posses? I would assume that for any micro-organism to be either beneficial or harmful to a given volume of wine a certain “cell-count” (or population) would have to be reached within that medium.

Salute
no avatar
User

Mark Lipton

Rank

Oenochemist

Posts

4516

Joined

Wed Mar 22, 2006 1:18 pm

Location

Indiana

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Mark Lipton » Wed Sep 12, 2007 10:25 pm

Victorwine wrote:Question for Mark;
Do these chemical reactions depend on the presents of oxygen? It makes sense that too much exposure to air could contaminate a wine, acetic bacteria is everywhere (floating around in the air we breathe). For these organisms to survive and reproduce surely oxygen is needed. But what actually governs these chemical reactions? The living bacteria themselves or the enzymes which they posses? I would assume that for any micro-organism to be either beneficial or harmful to a given volume of wine a certain “cell-count” (or population) would have to be reached within that medium.

Salute


Victor,
If you're talking about the production of acetic acid then, yes, oxygen is absolutely necessary for acetobacter to do its magic. Not all bacteria need oxygen, though, and many can't survive for long in its presence. In fact, oxygen is one of nature's best disinfectants. As for what governs the reactions, the oxidation of alcohol is carried out be enzymes related to alcohol dehydrogenase. And, yes, the cell count would have to get above a certain threshold for it to be a problem.

Mark Lipton
no avatar
User

Victorwine

Rank

Wine guru

Posts

2031

Joined

Thu May 18, 2006 9:51 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Victorwine » Wed Sep 12, 2007 11:41 pm

Thanks Mark.

Salute
no avatar
User

Howie Hart

Rank

The Hart of Buffalo

Posts

6389

Joined

Thu Mar 23, 2006 4:13 pm

Location

Niagara Falls, NY

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Howie Hart » Thu Sep 13, 2007 3:44 am

Oliver McCrum wrote:
Paul Winalski wrote:Carbonic acid (H2CO3), which readily bubbles off as free CO2. This is the "spritz" of young German wine and the bubbles of Champagne and other sparkling wine. In sparkling wine it's a positive feature. It's acceptable in young German wine, too. Elsewhere either fizziness or a prickly sensation of CO2 on the palate is an indication that something's gone wrong and unwanted bacteria have been at work.

-Paul W.


Paul,

I don't think this is quite right; many unflawed white and red still wines have enough CO2 to create the prickly sensation. Many of the white wines I import do, for example, and a number of new world Pinots do.
I agree Oliver. CO2 is produced during both normal and malo-lactic fermentation and can remain in the wine if nothing is done to remove it. "De-gassing" is how it's removed, either by violent stirring, splashing during racking operations or filtering. Wines that are handled gently - fining instead of filtering, gentle transfer methods, etc. can retain CO2. However, I don't find it appealing in most still wines.
Chico - Hey! This Bottle is empty!
Groucho - That's because it's dry Champagne.
no avatar
User

Thomas

Rank

Senior Flamethrower

Posts

3768

Joined

Wed Mar 22, 2006 4:23 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Thomas » Thu Sep 13, 2007 8:30 am

Victorwine wrote:Thanks Mark.

Salute


And Victor, acetic acid is a tiny piece of the by-products of yeast fermentation.
Thomas P
no avatar
User

Victorwine

Rank

Wine guru

Posts

2031

Joined

Thu May 18, 2006 9:51 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Victorwine » Thu Sep 13, 2007 10:07 am

Absolutely Thomas!

BTW as for CO2 production in wine I agree with Oliver and Howie. As far as “de-gassing”, if the winemaker is patient enough and the wine is properly bulk-aged, especially in oak barrels, the wine will “naturally de-gas” itself. (Just leave an opened bottle of soda with its top slightly twisted on and leave it out on the counter and see how long it takes to become “flat”). Like Howie, I agree the first couple of “wine rackings” (wine transfers) should be performed with “splashing”. But with winemakers using much more “modern” techniques (reductive winemaking) it very likely to find “more” CO2 in wines.

Salute
no avatar
User

Thomas

Rank

Senior Flamethrower

Posts

3768

Joined

Wed Mar 22, 2006 4:23 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Thomas » Thu Sep 13, 2007 10:22 am

Victorwine wrote:Absolutely Thomas!

BTW as for CO2 production in wine I agree with Oliver and Howie. As far as “de-gassing”, if the winemaker is patient enough and the wine is properly bulk-aged, especially in oak barrels, the wine will “naturally de-gas” itself. (Just leave an opened bottle of soda with its top slightly twisted on and leave it out on the counter and see how long it takes to become “flat”). Like Howie, I agree the first couple of “wine rackings” (wine transfers) should be performed with “splashing”. But with winemakers using much more “modern” techniques (reductive winemaking) it very likely to find “more” CO2 in wines.

Salute


I agree about the CO2, but I don't think splashing is necessary, not routinely. As you say, in storage, the slight CO2 levels dissipate and even a tender transfer releases CO2 in the process.

The problem with retained CO2 these days may lie in the uber-control over protection against oxygen, which likely causes more than the natural CO2 retention. I hate CO2 in what is supposed to be still wine, especially when the wine is red.

On the bright side, the CO2 will (should) prevent acetic acid from progressing much...
Thomas P
no avatar
User

Mark Lipton

Rank

Oenochemist

Posts

4516

Joined

Wed Mar 22, 2006 1:18 pm

Location

Indiana

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Mark Lipton » Thu Sep 13, 2007 2:21 pm

Thomas wrote:
Victorwine wrote:
On the bright side, the CO2 will (should) prevent acetic acid from progressing much...


No pun intended?

Mark Lipton
no avatar
User

Oliver McCrum

Rank

Wine guru

Posts

1076

Joined

Wed Mar 22, 2006 1:08 am

Location

Oakland, CA; Cigliè, Piedmont

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Oliver McCrum » Thu Sep 13, 2007 3:26 pm

Victorwine wrote:BTW as for CO2 production in wine I agree with Oliver and Howie. As far as “de-gassing”, if the winemaker is patient enough and the wine is properly bulk-aged, especially in oak barrels, the wine will “naturally de-gas” itself.


I admit I am surprised by the number of California Pinots that show CO2, the wines having presumably been aged in wood at some point (the better ones, anyway), but I am particularly referring to all-stainless whites from eg Italy, Spain, where a hint of CO2 is part of the style, absolutely intentional and in no way a defect. I think it adds freshness to the mouthfeel of the wine.
Oliver
Oliver McCrum Wines
no avatar
User

Thomas

Rank

Senior Flamethrower

Posts

3768

Joined

Wed Mar 22, 2006 4:23 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Thomas » Thu Sep 13, 2007 5:18 pm

Mark Lipton wrote:
Thomas wrote:
Victorwine wrote:
On the bright side, the CO2 will (should) prevent acetic acid from progressing much...


No pun intended?

Mark Lipton


Well, now that you mention it...
Thomas P
no avatar
User

Victorwine

Rank

Wine guru

Posts

2031

Joined

Thu May 18, 2006 9:51 pm

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Victorwine » Sat Sep 15, 2007 9:37 pm

Another question for Mark or Thomas, (sorry gang)

CH3COOH + CH3CH2OH <-- --> CH3COOCH2CH3 + H20

For this reaction to be a real problem in wine doesn’t the pH have to be close to 4.7?

Salute
no avatar
User

Mark Lipton

Rank

Oenochemist

Posts

4516

Joined

Wed Mar 22, 2006 1:18 pm

Location

Indiana

Re: Noobie Question: What does "Volatile Acidity" taste like or do to a win

by Mark Lipton » Sat Sep 15, 2007 11:06 pm

Victorwine wrote:Another question for Mark or Thomas, (sorry gang)

CH3COOH + CH3CH2OH <-- --> CH3COOCH2CH3 + H20

For this reaction to be a real problem in wine doesn’t the pH have to be close to 4.7?

Salute


That reaction is faster at lower pH. It's an acid-catalyzed process, so at lower pH you've got more acid to catalyze it. Trivia note: Organic chemists grace this reaction with a name (Fischer esterification). It's named after its purported discoverer, the legendary organic chemist Emil Fischer, who not only was a Nobel laureate but also gave the world the structures of the monosaccharides, the term "peptide" and the first explanation of enzymatic activity. Supposedly, he once got into a disagreement with Kaiser Wilhelm III, whereupon the Kaiser said "Ich bin der Kaiser" and Fischer supposedly retorted "Ich bin der Fischer." Alas, he died of cancer induced from many years of tasting every molecule he made.

Mark Lipton
Next

Who is online

Users browsing this forum: Amazonbot, ByteSpider, ClaudeBot, DotBot, Google AgentMatch and 0 guests

Powered by phpBB ® | phpBB3 Style by KomiDesign