Crystalline exudate at the bottom of white wine ?

This evening, I finished up the “last glass in the bottle” of two different 2019 Chablis. One of these wines showed a tan to clear crystalline exudate, and the other was clean. I assume this is harmless, but what does it tell me about how the wine was made? Pros/Cons of decisions made by the winemaker to allow this or to prevent it?
exudate.jpg

Tartaric Acid crystals, aka wine diamonds. Present in most wine, particularly whites that have been cold stabilized during the final stages before bottling. Filtration removes it, so does enough racking after cold stabilization. It’s harmless, and generally tells whether a wine is filtered or not.

Here’s a more detailed article Tartaric Crystals in Wine: the "Wine Diamonds" of Quality

1 Like

What Chris said. When I was at Martinelli Winery, this was probably the most frequent question asked of me. Convincing customers that their wine wasn’t ‘corked’ led me to create a PDF that described what the crystals are. I lost count of how many times I sent it. Fundamentally, the less that is done to wine before it is put in the bottle can result in tartaric acid precipitating out when it gets cold.

The tartrates in your glass probably mean it was not cold stabilized. When that happens, I sometimes get the impression that the wine is softer than when first opened the day before.

To clarify, these are crystals of potassium bitartrate (cream of tartar) and they are typically found in wines that have not been cold stabilised.

The precipitation of these crystals depends mostly on the amount of tartaric acid in the wine, the amount of potassium, and the temperature. Potassium mostly comes from the grape skins so red wines have higher potassium content, but red wine grapes are also harvested riper and tend to have lower tartaric acid contents. These crystals are found in both reds and whites, but they are more overtly obvious in whites because in reds they are “just part of the sediment” - tartrate crystals bind to tannins and so pull a small amount of tannin out of red wine when they precipitate - that’s why these crystals almost always look red in red wines, even though naturally they are white/colorless.

Potassium content is also related to vintage - I might be misremembering here but I think that high rainfall in spring and a resulting wet subsoil can lead to high potassium in the grapes…

Aside from cold stabilization followed by racking or filtration, there is also now a product on the market that inhibits the nucleation and growth of potassium bitartrate and so keeps it in the wine. The compound used is potassium polyaspartate.

Some people will also seed their wine with potassium bitartrate crystals to overcome the nucleation energy barrier and allow any crystals that would naturally form to precipitate out and be removed under controlled conditions before bottling.

7 Likes

Great summary, Ben!

Is potassium polyaspartate terroir?

A Burgundy producer’s answer for tartaric crystals: “We had a soft winter in our cellars.”

[rofl.gif]

These crystals can also occasionally be seen crusted onto the underside of a cork. This is usually the best way to find them in red wine. In my opinion, crystal presence is usually a good thing because it typically indicates a less manipulated wine.

My most striking experience with tartrate crystals was in a 2015 Le Rocher des Violettes Pétillant Naturel. The gentle carbonation made these very fine tartrate crystals dance around throughout this lovely golden colored wine- holding the glass up to the light was very beautiful. Big crystals at the bottom of the glass can be an unpleasant experience if you get a mouthful of them, but these were so tiny that they were imperceptible on the palate. Gorgeous!

My 2001 d’Yquem looks like a snow globe in my very cold cellar. This pic is 5 years old, I should take a new one.
Yquem.jpg

Another tartrate related question: why do tartrate crystals tend to accumulate around the cork and not elsewhere in the bottle?

My guess is the crystal precipitation/growth starts more easily on the relatively rough cork surface as opposed to smoother glass.

I figured that’s the case. Curious to how the crystals would develop under different closures like a glass stoppers

That’s not just an impression. Precipitation of tartaric acid as tartrates raises pH and the wine is softer.

My guess would be that many wines are stored neck down when palletized. Much of the time precipitation starts before the wine goes into a refrigerator. And the presence of tartrate crystals will help with further precipitation.

1 Like

Incorrect. It has nothing to do with the position of the bottle because the crystals are formed from tartrate that is in solution. Solutes are uniformly distributed throughout the volume of the liquid. That is what makes it a solute. As long as the cork is touching wine (upside down, sideways, whatever), crystals will grow there.

There are two reasons you find crystals on the cork. 1- Cork is rough. The probability of a crystal to form on any given surface is proportional to its surface area. The cork is rough and therefore has a much high surface area relative to the glass. Hence, more crystals. 2. Crystals can adhere to the cork. If a crystal forms on the side of the glass, but doesn’t stick, they form to the bottle of the bottle. Crystals that form on the cork stay there.

I don’t know the relative contribution of these two factors, but my guess is that the roughness of the cork has a large role to play. It is similar to the Mentos in Coke trick. The CO2 gas is dissolved in the soda, but doesn’t all come flying out because the smooth inside of the Coke bottle is not conducive to precipitation of the solute. On a microscopic level, Mentos are apparently very rough and therefore have a high surface area. One Mentos in the Coke, and all the gas nucleates on the rough surface and the result is a large amount of gas precipitating all at once and causing a fountain. The CO2 gas in Coke is supersaturated, and the tartrate in wine is not, so the analogy isn’t perfect.

Even so, let’s bottle some wine with a Mento (is that the singular?) and see what kind of tartrate crystals we get!

So Noah, in my experience wine is in contact with the cork when bottles are palletized upside down. Wine is not in contact with the cork when they are palletized neck up…so no crystals will grow on corks then.

Some wines in lay down boxes are palletized and with those some crystals may form on the cork surface but, it in my experience, it does not form across the entire surface of the cork. Tatrates crystals do encourage the precipitation of more tatrate crystals, but like most things they also feel the pull of gravity and seed on the low point leaving a small bit on the cork and the rest of the crystals will wind up dispersed in the wine.

The only time that I have consistently seen the tartrate crystals form across the top, almost like a seal is when the wines are stored upside down. I have two wines that we make that are too small for us to cold stabilize any way other than a cold winter, so formation of tartrate crystals is something I have some regular practical experience with.

It’s also important to remember that tartrate crystals form according to temperature, not surface area irregularities. Wines not in contact with the cork still precipitate tatrates, they just drop to the bottom of the bottle.

Question: Why the tan color? I have seen this, but rarely. Tartrates in white wine are clear a very high percentage of the time.

Dan Kravitz

Ben Mandler noted in his excellent post, tartrates will bind up a bit of tannin in red wines. If there are any lees in the wine when the tartrates precipitate, even very small amounts, the tartrates will have bound up some of the solids, and take on the tan color of the lees.

That’s speculative since I don’t know the wine here, but unfined and unfiltered wines would have a possibility of this.

Marcus and others, FYI the wine with the precipitate was a Jean-Marc Brocard 2019 Les Vieilles Vignes de Sainte Claire

Yes, I asked because it was a white wine. Actually a red wine with that color of tartrates would also be puzzing, as the tartrates I see in red wine tend to be just about as red as the wine itself. And a 2019 Chablis obviously is not (should not be) tan-orange.

Dan Kravitz