Cold stabilization

[distancerunner]

We racked (more) today. As it turns out, we have some Merlot that did not go into cold stabilization and were able to taste both side by side.

Both are pretty good. The cold stabilized wine was less tart. The flavors are still bright. The nose is deeper. It's easier to pick out the fruit scents. I don't understand why this would be so, but that's how it tastes. Over all, the cold stabilized sample is better.

I'll test the pH on both (all) of the wine in the next few days.

In the spirit of full disclosure, all of the wines were inoculated with CH-16. According to paper chromatography, all wines completed MLF.

 

[winemaker81]

Both are pretty good. The cold stabilized wine was less tart.

This indicates higher than optimal acid, so it sounds like CS was a good choice. I suggest you keep at least a few bottles of non-CS wine so you can compare a year down the road.

 

[TurkeyHollow]

Haven't had this issue until now. I made a Grenache Blanc from grapes and after cold stabilization and racking off of the tartrates, the TA ended up a little low and pH a little high. They weren't anything ridiculously out of line but the taste was a little "flabby" and since the numbers weren't right, I figured I'd try to tweek them back in while still in bulk. What I've done in the past is dissolved the tartaric acid in a small portion of wine (along with the SO2 for protection) and then add the solution back to the bulk. This time the tartaric acid seems to resist staying in suspension. The cellar temp is around 60° F, ABV 15.49%, pH 3.45, TA 6.3 g/L (6 gal batch). Only the 2nd day of periodic stirring but I usually had better luck with it staying in solution. Anybody have a similar experience? I'm pretty confident I could get it in suspension by warming it up a little but I want it cold stabilized too.

 

[Rice_Guy]

* the freezing point of an alcohol solution is variable based on the soluble solids (salts/ ash) as well as percent alcohol or cryoprotectant as glycerol.
* rate, foods that are factory frozen are run through a blast freezer, ,, example -20 F (-40 C) with high velocity air. This is to minimize damage from crystal growth in tissues, ,, usually ice crystals but other molecules as lactose crystals in ice cream can form (called sandy ice cream defect). Once the food is frozen it will be palletized and held in a storage freezer that can be warmer.
* rate, the normal situation in a home style freezer is that the liquid/ juice will transition into a slush because the freezing rate is slower. Some clean water is removed as ice, and forming said ice lowers the freezing point of the remaining liquid. This also happens in nature with ice wine or freeze concentrated apple or orange juice.
* slow freezing is efficient at producing crystals. If I wanted to maximize the potassium bitartrate crystal growth I would hold at 30 F a few hours then drop to 28 F for a few hours then drop to 26 F. Crystal growth is a time related function. The blast freezer minimizes crystal growth.
* the solubility of potassium bitartrate is related to temperature, ie some will redissolve by raising the temp ten degrees. In the real world we ignore this because crystals are quite stable and high energy mixing would be required to actually reach the theoretical constant.
* In the Midwest 28 F (-2 C) is a safe temperature for a glass carboy which has been slowly cooled to maximize crystal growth/ slush formation. With a low dwell range temperature controller I would not worry about 26 F (-3 C), there would still be slush. With time(weeks) a dense sugar syrup can be separated from a lighter ice phase at the just sub freezing range.
* seeding with crystals is used in some food industries as producing sugar crystals. Generally speaking any nucleation site, this can be scratches on the vessel or on the lab bench Pyrex boiling beads.
* wood barrels will flex. The risk of breakage is less than a glass container. PET also flexes (Better Bottle) so if freezing happens ice would push out of the cap before breakage.

No, this is incorrect. The freezing point of wine is variable, depending on the ABV and possibly other constituents. A 10% ABV wine will freeze at 25 F, according to the U of Illinois. I've seen reports of wine freezing as high as 28 F.
Which report is believable? I don't know for sure, so I err on the side of caution. Many moons ago a friend left a case of wine in his back seat overnight, and the wine froze, . . . ..

when you get down to it the physics of running a frozen fish or an ice cream factory are similar to the physics of wine.

 

[winemaker81]

I'm pretty confident I could get it in suspension by warming it up a little but I want it cold stabilized too.

What are you trying to achieve? If your wine is flabby post-cold stabilization, you did not need cold stabilization. Your result is a yo-yo situation, adding and removing acid in turn.

As previously mentioned, cold stabilization is not an all-or-nothing situation. You can chill the wine down to any temperature between 60 F (15.5 C) and 28 F (-2 C), and get at least some effect. My cellar is 58 F (14.4 C) in the winter, and I have crystals is 2 wines at that temperature.

If crystals in the bottle are the concern, chill the wine to 50 - 55 F (10 - 13 C). However, if the wine tastes flabby afterward, you have the choice of living with a flabby wine OR risking crystals in the bottle.

 

[stickman]

It's more than just tartaric acid, it's the potassium content as well as other things that have to be considered, and unfortunately we don't usually have the information. If the wine is flabby after cold stabilization, it probably means that there wasn't enough acid to account for the potassium bitartrate dropping out. There's a fairly good explanation in the following paper.

 

[winemaker81]

It's more than just tartaric acid, it's the potassium content as well as other things that have to be considered, and unfortunately we don't usually have the information. If the wine is flabby after cold stabilization, it probably means that there wasn't enough acid to account for the potassium bitartrate dropping out. There's a fairly good explanation in the following paper.

Thanks for posting this. I learned a few new things. One of this is:

However, due to the presence of colloidal materials in wine, such as mannoproteins, pectins, and other polysaccharides, the unstable tartrate may not precipitate unless the wine is chilled or aged significantly in a tank or barrel ​

I had no idea that bulk aging would cause the crystals to precipitate. I also never considered that potassium sorbate would have an effect, due to the potassium component.

 

[TurkeyHollow]

It's more than just tartaric acid, it's the potassium content as well as other things that have to be considered, and unfortunately we don't usually have the information. If the wine is flabby after cold stabilization, it probably means that there wasn't enough acid to account for the potassium bitartrate dropping out. There's a fairly good explanation in the following paper.

That's a great paper and it explains a lot. I hadn't thought about the carbonic acid in CO2. With those saturation rates, is there a perceived effervescence? I posted because I didn't want to have a "yo-yo" effect. I just didn't think it had reached saturation and was hoping for a way to achieve a higher TA in such a dry white. Do you all "play" with the residual dissolved CO2 to tweak the flavor brightness?

 

[winemaker81]

Do you all "play" with the residual dissolved CO2 to tweak the flavor brightness?

I haven't, and I can't think of a way to control the dissolved CO2 with any accuracy.

 

[stickman]

You can achieve a higher TA by adding tartaric acid, keeping in mind a percentage will drop out as potassium bitartrate, but each time this happens there is a loss of potassium, so less tartrates will drop out after the next addition of tartaric acid. If you don't want to mess with tartaric, you can try a sample using citric acid to see if you like the results, the citric acid doesn't drop out like tartaric.

 

[sour_grapes]

Do you all "play" with the residual dissolved CO2 to tweak the flavor brightness?

I do only in the following sense: I used to extensively vacuum degas red wines, and I came to realize that they were somewhat flat. I now just "degas" by bulk aging. I just take the CO2 that I have when I think it is ready to bottle. (I once or twice bottled with higher CO2 than I wanted, just because I either needed the carboy or wanted the wine bottled to drink.)