Crystalline exudate at the bottom of white wine ?

[M_Meer]

Precipitation of tartaric acid as tartrates raises pH and the wine is softer.

Thanks! Didn’t feel quite comfortable to make that assertion.

[Noah_C]

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.

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.

Sorry to be a contrarian, but you are still wrong; the solutes in a solution are not distributed differently according to gravity. The very definition of a solution is that the solute is uniformly distributed, so crystals are equally likely to form anywhere in the liquid, regardless of gravity. An easy example to understand is the childhood home experiment of making rock candy. Suspend a stick (with high surface area btw) into a sugar solution, and sugar crystals form UNIFORMLY on the stick. You don’t get more sugar precipitating onto the bottom of the stick bc of gravity.

Now, wines that are stored upright with the cork pointing up, of course will not get tartrate crystals on them bc they are not in contact with the wine. In that case, you are right, wines palletized cork down will get more crystals than cork up.

[Marcus_Goodfellow]

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.

Sorry to be a contrarian, but you are still wrong; the solutes in a solution are not distributed differently according to gravity. The very definition of a solution is that the solute is uniformly distributed, so crystals are equally likely to form anywhere in the liquid, regardless of gravity. An easy example to understand is the childhood home experiment of making rock candy. Suspend a stick (with high surface area btw) into a sugar solution, and sugar crystals form UNIFORMLY on the stick. You don’t get more sugar precipitating onto the bottom of the stick bc of gravity.

Now, wines that are stored upright with the cork pointing up, of course will not get tartrate crystals on them bc they are not in contact with the wine. In that case, you are right, wines palletized cork down will get more crystals than cork up.

I didn’t say they were distributed in the solution differently due to gravity.

I said they don’t need surface irregularity in order to form. They drop out of solution due to decreased temperature. When there isn’t surface irreularity, they form independent crystals that look similar to refined sugar crystals. With irregular surfaces, like cork or the interior of a barrel, they will form together making what could loosely be described as a crust. The gravity reference, notes that while evenly distributed in solution, when palletized with cork to the side, the crystals drop out of solution throughout the bottle, as evidenced by the fact that they are not all on the cork(there is typically a fine layer but not what I would call a crust), but there are also crystals on the low side of the bottle…having drifted down there due to gravity after precipitation.