Tartaric crystals

J

Jeff Grossman

Jeff Grossman
I just drank a wine that had shed tartaric crystals all over the place: on the cork, in the neck, on the bottom, in my glass. Sheesh.

Why do they fall out of the wine? How did they stay in solution in the first place? Should the wine taste softer once they've all fallen out?
 
I'll let Steve or Bruce or someone answer in detail. They stay in solution until the wine gets cold--industrial winemakers chill the wine way down to precipitate and remove them.

The precipitate is monopotassium tartrate, and whether the wine softens or not depends on the pH. Winemakers please correct me, but it seems that it should move the wine away from the 2nd pKa. So in a low pH wine, you're losing the conjugate base by precipitation, leaving proportionately more tartaric acid. A high pH wine loses the acid, leaving more dibasic tartrate.

Or am I nuts?
 
originally posted by Jeff Grossman:
Tartaric crystalsI just drank a wine that had shed tartaric crystals all over the place: on the cork, in the neck, on the bottom, in my glass. Sheesh.

Why do they fall out of the wine? How did they stay in solution in the first place? Should the wine taste softer once they've all fallen out?
Click to expand...

Wine is quite concentrated in tartaric acid, often to the limit of its solubility. If the wine is bottled at, say, 70F and then later cooled to 50F in someone's cellar, the solubility of tartrate is decreased and some of it falls out of solution as crystals. In Germany, it was considered the sign of a quality wine to have such crystal deposits, which were referred to as "weinstein." In modern times, winemakers can prevent this by "cold stabilizing" the wine, cooling to 40F or so and filtering out the tartrate crystals -- but why bother? They don't hurt the wine in any way. You're right, however, when you suggest that the wine will be softer when tartrate falls out of solution. Fortunately, however, the wine by default will still be saturated with tartrate so unlikely seem too soft (unless it was acidulated with tartrate, in which case it could be deficient in malate and possibly lactate and taste weird, unbalanced and possibly soft).

Mark Lipton
 
originally posted by SFJoe:
I'll let Steve or Bruce or someone answer in detail. They stay in solution until the wine gets cold--industrial winemakers chill the wine way down to precipitate and remove them.

The precipitate is monopotassium tartrate, and whether the wine softens or not depends on the pH. Winemakers please correct me, but it seems that it should move the wine away from the 2nd pKa. So in a low pH wine, you're losing the conjugate base by precipitation, leaving proportionately more tartaric acid. A high pH wine loses the acid, leaving more dibasic tartrate.

Or am I nuts?
Click to expand...

You're right about pH, but you're also decreasing TA. I don't know how to interrelate those two effects.

Mark Lipton
 
Thank you. This was a rose that was technically fine the first year, even after being chilled (a likely fate for rose, I'd say). I kept a couple bottles for a year, just to see what would happen. I may hold the last one for another year.

[ It was, of course, yummy at the winery. It was a bit stern when I tried it at home later that first year. This bottle was more pleasurable and hid its Californiated alcohol level very well. ]
 
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