isnt it true that different chemical reactions are happening, some which are more or less effected than others by temperature? Like the tannic structure will last much longer with the cold, but the rate of change with sugars wont be impacted as much? Essentially changing not just when the peak is, but what the peak is?
Also, colder temperatures are more difficult to maintain humidity
I have an underground passive cellar in my Utah residence that gets that cold in the winter. What I have noticed over the last 10+ years is that my wines age slowly. Crappy supermarket wines I found last year buried in the corner from 2007 vintage were fine and youthful. Some wines will precipitate tartaric ccid crystals at these temps so I often see some extra crystals on wines that werenāt cold crashed at the winery. Overall, I feel none of these are worth being excited about.
My cellar is passive and ranges between low 60ās in the peak of summer to low 40ās in the dead of winter. Wines from this cellar seem no different than wines from my active cooler which is at 55 degrees.
I donāt want to postulate which reactions are faster in wine, but an important thing to consider is that the slower ones will be more affected by temperature. The general rule that reaction rates double with every 10 degrees (C) is only true in the relatively narrow band of common activation energies. But a very slow reaction (implying a high activation energy) might increase by a factor of 10, or even 20, with every 10 degrees; while a fast reaction (implying low activation energy) might increase by only a factor of 2 or less with every 10 degrees. There are no hard and fast rules for what happens to wine with temperature.
I conducted an experiment on this once for my own education. I took samples of the same high-tannin red wine and stored them at 55 F (wine fridge) and at 40 F (fridge fridge) for one month. The one stored at 55 F experienced almost no precipitation. The one at 40 F precipitated both tannins and tartrates. The resulting wine stored at 40 F was actually visually less intense in color (makes sense, since in wine older than a few years most of the anthocyanin is bound to tannin). They both tasted like shit because the environment they were stored in was sealed but had some headspace so they had died an oxidative death. The oxidation could have contributed to the precipitation of tannin - it certainly promotes increased polymerization - but bear in mind that the oxidation should have occurred more rapidly in the warmer sample. So, these polymerized tannins were either (1) less soluble at low temperature and so precipitated out more, or (2) adsorbed onto or co-precipitated with tartrate, or both.
Thatās not to say that the enhanced precipitation of tannin or tartrates will negatively impact your wine - Iām not sure any of us can really comment on that in a fully informed way but would be interested to hear any information others may have. Anyway itās something to bear in mind.
I think the difficult thing is that the improvement or damage could be wine dependent as well. It would be very interesting to buy 4 cases of a wine that has 20+ years of life in it and to put 24 at 38 degrees and 24 at 55, and try 1 of each sbs each year for 24 years. But I dont think that would really give anything close to a definitive answer on wine in general, more just that specific wine with those specific levels of tannins, tartratesā¦
I was thinking this. It seems like colder than 55 preserves fruit better while still allowing for tertiary development, maybe more slowly. If I could live to be 150 and still appreciate wine, Iād probably want to store everything at 45 degrees.
There are a number of temp controllers used for home brewing. I used to use one on a chest freezer for controlled fermentation temps for lager beer. Since they can fail, I would probably not trust one on a freezer with thousands of dollars of wine in it, but it could be used on a spare refrigerator to maintain 55 degrees. I expect that the freezer would no longer be freezing, but the if thatās not important to you, this might be a solution. Iām planning to try it out on my spare refrigerator once the freezer is empty.
Iām not following that. As the air cools, it has a harder time absorbing the existing humidity, so you reach 100%. I had that problem in a friendās very damp passive cellar.
Normally a standard air conditioner would dehumidify a space. Guessing this refers to actively cooled spaces. In parts of the country that already have dry air like Arizona, air conditioned cellars are likely to struggle maintaining humidity. In Florida this isnāt as big of an issue because youāre starting from a much higher baseline.
Iām not sure about the cellar in the restaurant but I would guess the warehouse across the street to be about 50 degrees. Just a guess based on numerous 30 minute excursions.
Cold air actually canāt sustain as much vapor. You reach 100% relative humidity, not because their is actually more humidity in the air, but because it is relative to the maximum at that temperature which is less when it is cold. So thatās why the reading may go up with less or the same amount of absolute humidity, just as temperature drops.
I personally donāt know if relative humidity is the important measure for wine storage in general or it is only useful at roughly 55 degrees, because it correlates with some specific absolute humidity.
Curious - how do you know that both tartrates and tannins were precipitated? Did you do a tannin analysis? Just really curious . . .
I can say that when I was at UC Davis, part of my masterās thesis was looking at tannin development in the same wines at different temperatures. Granted, these were freshly pressed wines but I had them stored at 41, 50, 68 and 86 degrees an a temperature controlled lab. I took samples from each sample bottle over an 8 month or so period to note changes in color intensity, anthocyanin presence, tannin development, etc (this was NOT meant to be used for taste or olfactory analysis).
The data showed what one might expect - the development of polymeric pigments (tannin-anthocyanin complexes that are color and SO2 stable) increased with increased temperature, with the type of polymeric pigment created (short or long chain) depending upon āstarting materialsā. But there was no decrease in total tannins whatsoever, regardless of the temperature.
Exactly. Itās a misunderstanding that tannins āprecipitate outā. They do not. They polymerize (thatās my understanding), which is a chemical reaction that benefits from higher temperature (as Larry said), and also takes significant time under normal bottle conditions. Precipitation is essentially a solid salt being formed because the solution reaches its saturation point at lower temperature.
Fascinating! Did you publish that thesis or is it available through Davis? Would love to see the data on that. Did the increase in polymeric pigments plateau during the 8 months or was it still increasing at the end?
To answer your question, yes. Tannin and polymeric anthocyanin in the 40 F sample were measurably lower at the end of the month than in the 55 F sample. As you and others mention, Iām sure the phenolic make-up of the wine strongly impacts these behaviors.
Iām not the worldās expert on this topic, and I know that much of the following will be familiar to yourself and other people on here - Iām just including it all so anyone reading can (hopefully, if Iām doing it right) follow along.
All dissolved solids in wine have solubility limits and will precipitate out of an ethanol-water solution if (a) those limits are exceeded and (b) the kinetics of the precipitation reaction are sufficiently rapid to allow it to happen on the timescale of interest. I explain this to tasters by observing what happens to the last drops of wine left behind in a finished glass. As it dries out, it leaves behind a solid residue, but that solid residue starts to form before the liquid has totally vanished, because the evaporation of the liquid is concentrating these dissolved solid compounds in the residue until their concentration exceeds their saturation point. Because the solubility of solids in liquids is, as a general rule, higher a higher temperature, you can also sometimes achieve this saturation by lowering the temperature. Compounds that are near their saturation point at 55 F may precipitate at lower temperatures. Of course, at lower temperatures, the kinetics are slower, so it can take a longer time for this precipitation to happen. This principle is indeed used for the cold stabilization of white wines by precipitating out tartrates at ~0 C prior to bottling, but the same principle can also apply to other dissolved solids.
Some dissolved solids are present in wines at concentrations far below their solubility limits and so never precipitate out of most wines under reasonable conditions. These include things like sugars, most acids (except tartaric), and most salts (chlorides, sulfates, phosphates, etc). However, tannins are present in many red wines at concentrations quite close to their saturation point. In fact, during extended maceration it is not uncommon for tannins to start precipitating out of the wine, even as they continue to be extracted into the wine from the skins. The controls on tannin extraction and solubility in wine are still not very well understood.
The reason tannins precipitate out of wine when they polymerize is that highly polymerized tannins are less soluble in water than less polymerized tannins. Their large size increases their hydrophobic character and makes them more likely to clump together than to remain complexed by water molecules. The resulting solid is not a nicely ordered ionic salt like potassium hydrogen tartrate but is a pretty unstructured glob of tannins and other tannin-bound molecules that help to link tannins together. This mushy, unappetizing structure is common in organic precipitates, and is also observed in other phenolic precipitates such as the slimy green quercetin precipitates that can occur in Sangiovese. The disordered structure of these precipitates is reflected in their macroscopic properties: organic precipitates donāt usually form nice crystals.
One of the fun details of this topic is that most high-tannin wines actually already contain tannin precipitates suspended in the wine. They are prevented from settling out by gravity by being very small - and so having a very very slow settling velocity in a fairly viscous wine - and by being juuust loosely held in solution, probably by some kind of colloidal structure. If you stick them in a centrifuge you can agitate them out of suspension. I have not explored the sensory effects of this but it would be fun to do one day.
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