Tartrate Crystals

So, I'm sitting with my wife and a friend (who used to selll wine) on Sunday night and my wife says "What are all those crystals in the wine (an inexpensive Loupiac)"? I say, "those are tartrate crystals, they are harmless and they precipitate out when the wine is subject to very cold temps somewhere along the way". My friend says, "Well, that's not really correct. Of course they cold stabilize some wines to remove tartrate crystals but its not ALWAYS the case that tartrate crystals form becasue of low temps". Is he correct?

It sorta seems tautological to me that if you cold stabilize to get the crystals to form so that they can be removed that cold temps cause the crystals. No?

The solubility of tartrate crystals is affected by both temperature and alcohol content. If wines are subject to cold stabilizing temperatures below about 25 degF, more tartrate crystals will form because when small ice crystals form, the alcohol content is temporarily raised. Also, during fermentation, as the alcohol content rises, tartrate crystals form as part of the lees that settle out when fermentation is complete. I'm not familiar with Loupiac, but many red wines are not cold stabilized, so, for all practical purposes, you are correct.

I don't know the science and this board is full of clever people who do know and will post the details, but based on experience tartrate crystals will form in wine over time. That's what a lot of the deposit is, albeit stained, in mature red wines.

In wineries they chill wines to below freezing (-4C) because it is a sure way to cause the crystals to form and then they can remove them. Its not that the wines will get so cold on the shelves of the supermarkets they are destined for, its to stop the crystals forming over time.

Wot Peter said! Cold temperatures increase the rate of precipitation, but do not exactly cause it.

There may well be truth in what Howie wrote too - I would not argue.

Wot Peter said! Cold temperatures increase the rate of precipitation, but do not exactly cause it.

There may well be truth in what Howie wrote too - I would not argue.

Actually, temperature does affect the solubility product of KHT. It is sparingly soluble in cold water but freely soluble in hot water. As Howie said, factors other than temperature also affect the solubility of KHT. You are correct, though, that there is also a kinetic effect. Once formed, KHT crystals may not redissolve even if the temperature of the wine is increased because of the slow rate of dissolution.

Mark Lipton

As mentioned by Howie, temperature and alcohol concentration will affect the rate of crystal precipitation. But besides these, the actual acid concentration, pH, presence of other substances, and longer aging periods could also encourage more soluble ions to become solid and precipitate in the form of “crystals”.

Salute

Thanks guys!!!!