What causes wines to “shut down”?

[David_Patte]

This question has been addressed “scientifically” a couple times before… Mind you, not sure how well these explanations stand up to scientific scrutiny, but I’ve heard this particular explanation about polymerization of phenolic compounds from multiple people. And it seems to make sense.

Most recently from Doug Hein here: https://www.wineberserkers.com/forum/viewtopic.php?p=3153685#p3153685

Regarding the shutdown, much of it has to do with chemistry. Many of the phenolic compounds in wine, like tannins, can and do polymerize. They also bind with other aromatic compounds that effect taste and aroma. The polymerization process is the start of the shutdown. These polymer chains continue to grow and link, binding up much of the flavor of the wine. At some point, they become to long to remain in suspension and start falling out as sediment. They also become unstable and weak and start breaking apart, releasing the other compounds that have been bound up. When this occurs, the wine starts opening up. It seems to happen fairly rapidly at both ends.

After the wine reawakens, then it’s really a matter of continuing evolution of the aging process and all of the slow reduction reactions ongoing in the bottle. The first phase is prominent primary fruit, integrated tannins and the lovely earthy nose of Bordeaux. Beyond that is the shift to more of the interest tertiary flavors and the gradual fading of primary fruit. Of course, all this and the timeframe is dependent on the structure of the wine. For example, that 2005 Leoville Barton that is drinking so well now, doesn’t have what it takes to be the wine at 35 years old that the 1982 Montrose was I recently had was. But it’s a wonderful Bordeaux to drink now and for another 10 years.

I think this makes a lot of sense but that we need to give more emphasis to the wine’s redox chemistry. Especially if we want to offer an account for why white wines shut down. To do this, we really need to factor in closure too, as different closures have different oxygen transmission profiles over time. But I think it’s clear that the higher a wine’s redox potential, i.e. the stronger its tendency to move in a reductive direction, the longer it will tend to shut down, all things being equal (which, thanks to closures, they seldom are!). So a low pH white with appreciable dry extract from the skins (flavenols and other antioxidants) will have a higher redox potential and tend to shut down harder and longer.

On wine chemistry, good points about redox points and tannin polymerization. I’ll just add that there are entire wine chemistry textbooks : ) full many more flavor compounds and species that change over time, some affecting or masking fruit and floral aromatics and flavors. Hard to summarize all of this but I’ll give it a shot on the main issues that I have experienced and have had drilled in me.

I currently have a Pinot that after month 6 started to show di- and tri-sulfides, masking the fruit. Perhaps the most well know is mercaptans, but there are more than a dozen of these compounds and they are unstable, changing with time based on the wine’s redox (which can change with an initial after-bottling bump (6mo.) and also includes slow in-bottle oxygen intake via the cork/closure). Volatile sulphuric compounds bring “swampy”, sulfurous vegetable (onion, cabbage, etc), burnt rubber, earthy, fecal, etc., etc., type odors. Keep in mind that at low levels they can be barely, or not very perceptible, BUT nevertheless mask fruit and floral aromatics and flavors.

Same is true for Brett.-caused phenols.

Other compounds that change during bottle aging include fruity and floral esters (branched fatty acid ethyl esters (soapy, oily, candle-like) increase over time; straight-chained (fruity/floral) ethyl esters decrease); terpenes (floral, progressive release over time due to mild acid hydrolysis); glycosylated compounds such as ketones (due to hydrolysis; a bunch of these from buttery, butterscotch, to exotic floral and fruit…); and lactones (oak lactones not only persist, but increase over time; there are also grape-derived lactones that do the same, e.g. in Gerwurztraminer which like Riesling significantly changes over time).

So… like Larry said, this is Holy Grail stuff because all of this chemistry can be happening more or less significantly depending on the grape varietal, how many of these compounds (or their precursors) were released during fermentation (juice YAN?, native yeast? cultured yeast? Daily, twice daily or rare punch downs? Pump overs or délestage? Total skin contact, or gross lees time, Etc), cellar maturation style (reductive or a bit more oxidative with battonage and rackings prior to bottling?), bottle storage conditions, and a host of other reasons.