Does artificial acidity have an aroma?

[Jenise]

A tasting note I read on Cellartracker yesterday, and I don't recall for what wine, indicated that someone out there believes it does. I had never thought so, though I believe there's a peculiar sourness of taste that I sometimes suspect is that.

Not unless some misguided winemaker is acidifying with a volatile acid. Tartaric acid, as any cook can tell you, has no smell (i.e., Cream of Tartar).

Mark Lipton

Malic acid does have the specific taste of unripe apples. But it doesn't have any aroma as far as I know.

-Paul W.

I don't know about commercial wines, but there is a product sold for home wine makers called "Acid Blend" that contains tartaric, malic and citric acids. Regarding citric acid, here's what one of my home wine making books has to say:

Sometimes, citric acid is added to finished wines specifically to increase acidity and improve acid balance. In small quantities, it provides a fresh, citric characteristic, and the citric quality is often appreciated in white table wines. Nevertheless, bench trials should always be done before making any large additions of citric acid. Significant additions of citric acid are seldom made to red wines. The citric taste does not seem appropriate in most red wines.
About half a gram of citric acid per gallon is often added to commercial wines to improve long term stability.

Not unless some misguided winemaker is acidifying with a volatile acid. Tartaric acid, as any cook can tell you, has no smell (i.e., Cream of Tartar).

Mark Lipton

yet I wonder if the addition of tartaric to any wine doesn't produce an alteration of the smell that could be what's being suggested in the title of this thread.

Not unless some misguided winemaker is acidifying with a volatile acid. Tartaric acid, as any cook can tell you, has no smell (i.e., Cream of Tartar).

Mark Lipton

yet I wonder if the addition of tartaric to any wine doesn't produce and alteration of the smell that could be what's being suggested in the title of this thread.

But, Steve, could the smell be attributed to artificial acidity as opposed to acidity in general? I know enough people who say that they can taste acidulated wines to believe them (probably related to the malic/tartaric balance, I'd guess), but in smell? How could KHT added from a bag change the smell in a way that naturally greater acidity wouldn't? I'm baffled.

Mark Lipton

I don't know what is meant by artificial acidity. Most acids for acidulation of wine are natural products and are highly refined. Some acids, notably tartaric, can be found synthetic. Those are largely racemic, as opposed to L-tartaric, found in nature. None of the normally used acidulants are volatile, but in any case, these are hardly artificial, except the racemic tartaric, which is, as I say, typically not used. I used some once from China and it did have an aroma, but I would doubt the aroma originated with the tartaric acid itself, but rather with impurities left from the manufacturing process. Needless to say, I was not pleased, and discontinued its use imediately.

"Artificial acidity" refers to the process of acidulation itself. It means acidity due to added acid, as opposed to what comes naturally out of the harvested grapes and fermentation processes.

-Paul W.

"Artificial acidity" refers to the process of acidulation itself. It means acidity due to added acid, as opposed to what comes naturally out of the harvested grapes and fermentation processes.

-Paul W.

Paul is, of course, correct. When the SWE tests for their CSW certification, part of the sensory portion is picking up the possiblity of "added acids". To that point they take a base sample and doctor it with different components. One of them is added acids.

On an entirely different note, when I was doing more consumer tastings, and when monstrously imbalanced over-oaked and over-maloed chardonnays and other whites were all the rage, some people came away from that thinking they could "smell acidity" when what they were smelling was a by-product of malolactic fermentaiton, diacetyl. Although, to be fair, diacetyl used to be a stanky tell-all of excessive malolactic, so it's not too far off the mark. It remains an artificially manipulated component that came to be accepted, if not expected, by a lot of consumers.

Hi Hoke,
Wouldn’t the amount of diacetyl (buttery component) in a wine be a function of citric acid concentration?

Salute

Hi Hoke,
Wouldn’t the amount of diacetyl (buttery component) in a wine be a function of citric acid concentration?

Salute

Would have to be, wouldn't it?

Still, there's a technical difference between smelling acid and smelling a side effect of a process (I think.)

Not that I am qualified to speak on chemistry, mind you.

...Although, to be fair, diacetyl used to be a stanky tell-all of excessive malolactic, so it's not too far off the mark...

I'm not sure what you mean by "excessive malolactic". As grapes ripen, the amount of malic acid decreases as the sugar content increases. The level of tartaric acid remains about constant during ripening. Malolactic fermentation is almost always done to completion - when all the malic acid is converted to lactic acid. Otherwise, the wine would be unstable and malolactic could continue in the bottle (CO2 and off aromas). I would say that if the grapes were picked early, when the malic acid level was much higher, then perhaps "excessive diacetyl" would be produced, but malolactic is not a relative thing, like oaking.

Hi Hoke,
Wouldn’t the amount of diacetyl (buttery component) in a wine be a function of citric acid concentration

I think you mean malic acid. Malolactic fermentation is the conversion of malic acid to lactic acid by various bacteria. Malic acid is perceived as much more sour than lactic acid by the human palate, so the net effect of malolactic fermentation is to replace the tart "green apple" malic acidity with the "creamy" lactic acidity. The malolactic bacteria also produce diacetyl and other compounds.

Malolactic fermentation usually starts up spontaneously after yeast fermentation stops, provided that the wine is at a high enough temperature. In some cellars in France, they employ special heaters to induce the start of malo. Conversely, you can block malo by chilling the wine and cold-filtering it to remove the bacteria. And I'm sure by now that somebody's figured out a way to introduce a malo bacteria culture into wines to trigger malolactic fermentation that otherwise wouldn't take place.

You'd think that since malic acid is the raw material of malolactic fermentation, the more malate you have to start with, the longer the process can go on, and so the more diacetyl you'd get. But I'm not sure it works that way. Your run-of-the-mill buttery fruit bomb California chardonnay starts out with fruit that is overripe and hence low in total acidity, particularly in malic acidity. Perhaps a low initial malic acid concentration means that the bacteria have to seek other energy sources, and end up producing more diacetyl than they would otherwise? Or maybe if the final wine has a higher acidity, you don't notice the diacetyl as much?

Any of you winemakers out there know the details of the relationship between initial malic acid concentration and presence of diacyl in the final wine?

-Paul W.

Still, there's a technical difference between smelling acid and smelling a side effect of a process (I think.).

Correct. Consider yeast fermentation in bread. The end product is CO2, which is odorless. But the yeasts produce trace amounts of a whole bunch of other compounds, too, and these collectively give the "yeasty" aroma that fresh bread has.

-Paul W.

...Although, to be fair, diacetyl used to be a stanky tell-all of excessive malolactic, so it's not too far off the mark...

I'm not sure what you mean by "excessive malolactic". As grapes ripen, the amount of malic acid decreases as the sugar content increases. The level of tartaric acid remains about constant during ripening. Malolactic fermentation is almost always done to completion - when all the malic acid is converted to lactic acid. Otherwise, the wine would be unstable and malolactic could continue in the bottle (CO2 and off aromas). I would say that if the grapes were picked early, when the malic acid level was much higher, then perhaps "excessive diacetyl" would be produced, but malolactic is not a relative thing, like oaking.

Sorry, Howie. Badly said. I meant to imply the "pushed" malo, or the spoofulated approach from manipulation, rather than the "we get what we get" attitude. Or to put it another way, some winemakers (though not as many now) chose to emphasize the diacetyl as a major part of their style.

...Conversely, you can block malo by chilling the wine and cold-filtering it to remove the bacteria. And I'm sure by now that somebody's figured out a way to introduce a malo bacteria culture into wines to trigger malolactic fermentation that otherwise wouldn't take place...

Higher levels of SO2, the addition of Lysozyme (an enzyme) or sterile filtration are employed to prevent malolactic. Also, high acid (low pH - below 3.2) will also discourage it. Commercial strains of malolactic bacteria have been around for quite a while and sold in quantities for both commercial and home use. I don't know the level of diacetyl relative to malic, but my question is "How come nobody has ever complained about buttery Pinot Noir, Cab Sauv or other reds, which routinely go through malolactic?"

Paul wrote:
I think you mean malic acid.

No, I do mean citric acid. LAB (Lactic Acid Bacteria) could metabolize citric acid into diacetyl. So I would assume the “main target” for the LAB would be malic acid (producing mainly lactic acid, CO2, and possibly other by products) and than target the citric acid (producing diacetyl and possibly other by products). Most likely however, the LAB could “target” both acids at the same time. But the amount of diacetyl would be a function of how much citric acid is present and other factors.

It’s not how much malic acid that is present that will determine “excessive diacetyl”, but how much citric acid is present while MLF is taking place.

Salute

And I'm sure by now that somebody's figured out a way to introduce a malo bacteria culture into wines to trigger malolactic fermentation that otherwise wouldn't take place.

They sure have. I'm no expert, my total winemaking experience consisting of a couple of batches of backyard Zin, but I inoculated those wines. Not to trigger an ML fermentation that wouldn't have happened but instead to make absolutely sure it happened well before it went in the bottle. Doing it near the end of primary fermentation is a good time, the high CO2/low SO2 environment at that point being favorable to the MLF.

From what I've read, Victor is correct; it's the ML bacteria's action on citric acid that gives diacetyl. Also that diacetyl binds to spent yeast. And that if the ML bugs are left in for the duration, they actually metabolize the diacetyl they'd previously generated and levels in the wine actually drop. Add that all up and if your goal is to maximize diacetyl, you'd want to avoid the sort of simultaneous primary and secondary fermentation I encouraged, instead pulling the wine off the lees before ML inoculation. Also, you'd stop the ML process when malic and citric acids were gone but before the ML bacteria started consuming diacetyl. I also wonder if some winemakers so inclined might actually add citric acid before starting MLF. Winemakers who add acid most often use straight tartaric, sometimes a tartaric/malic blend but ordinarily wouldn't add citric.

A lot of this shows up in this guidance on maximizing diacetyl.

Thanks, Victor. I wasn't aware that LAB metaboilzed citric acid into diacetyl.

-Paul W.

I don't know the level of diacetyl relative to malic, but my question is "How come nobody has ever complained about buttery Pinot Noir, Cab Sauv or other reds, which routinely go through malolactic?"

Based on the info in that "managing diacetyl" article, I would guess that we never hear complaints about buttery reds because that is considered a fault and winemakers are careful to take steps to avoid high levels of diacetyl. Things such as more lees contact, faster MLF, MLF concurrent with yeast fermentation.

-Paul W.