I started reading the articles and “Industry Roundtables” on Wines & Vines’ website about a year ago. I like that the target audience is not me (a consumer), so much of the content avoids the condescending tone of many pop pieces on wine.
I always thought that long-chain tannins and pigments linked up to polymerize and fall out of solution in an aging bottle of wine.
I always thought that short-chain tannins were smoother in mouthfeel than longer chains - until a few months ago, when I read this…
Lots of stuff I didn’t know in there, but the bit about tannins in seeds vs skins was really interesting. My perception and understanding had always been that the tannins in seeds were mean and bad… Nice to have science point me in a different direction.
Thanks for the link. I don’t check out the website enough and since I dropped my subscription I had missed this article. Once I started with my own hobby vineyard and making wine, I realized that a lot of what I read didn’t hold true for what I was seeing in the vineyard or in the bottle.
Great post, should be in Wine Talk! This paragraph got my attention:
This makes intuitive sense: Bigger molecules have more ways to snatch proteins than smaller ones. Or, imagine the relative mouthfeel of fine beach sand and chunky gravel. (Fans of minerality in their wines can do the actual trials; for others, this is simply a thought experiment.)
Is he saying that tannin structure is responsible for the sense of minerality? Could that also be true in white wines?
I too was fascinated by the article, but the concept in the above statement about tannin molecule size is not clicking with me. Alan, you’re a chemist. Wont lots of smaller molecules have more “ends” or surface area to attach to proteins or bind to sensory receptors than a few larger molecules? If experimentation has proven that bigger molecules create a “grippier” sensation of tannins I believe it, but I’m not sure I understand why.
Other research has shown that very short chain tannins are quite bitter and increase in astringency to a certain point, then become less astringent. There are definitely more than one school of thought on this.
I still do believe that some tannins polymerize to the point that they do fall out of solution. A 50 year vertical does not tell me anything - tannin levels will be different for each and every vintage, so comparing levels in one vintage vs another really does not tell me anything . . .
It is difficult to extract the tannins INSIDE of the seeds. Most of the ‘seed tannin’ extracted during fermentation is from the outer coating, not the inside.
I have seen tannin levels decrease with extended maceration - my guess is that the solution reaches an ‘equilibrium’ and then a sort of ‘fining’ takes place.
Softening over time, at least in the early stages of a wine, is due to a number of factors, including the binding of anthocyanins onto tannins, forming color stable polymeric pigments. This pigments have been shown to possess a lower affinity to binding to salivary proteins than do tannins without the anthocyanin attached. Micro ox forms this bonds much faster, as does elevated temperatures post fermentation.
I’m no expert in this area, but the principles seem straightforward enough. The general definition from this article seems useful:
One of the most satisfactory definition of tannins was given by Horvath (1981): “Any phenolic compound of sufficiently high molecular weight containing sufficient hydroxyls and other suitable groups (i.e. carboxyls) to form effectively strong complexes with protein and other macromolecules under the particular environmental conditions being studied”
The article also states that higher molecular weight tannins are better at binding proteins, though with the later qualifier: “To have high protein affinity, tannins must be small enough to penetrate interfibrillar region of protein molecules but large enough to crosslink peptide chains at more than one point.”
But to answer your question about smaller tannins having a higher proportion of “ends”, that’s not really the case. Unlike a fatty acid chain (for example), where there might be only one carboxyl group at the end of the chain, tannins are composed of multiple phenolic groups, each of those having multiple hydroxyl (OH) groups. So a larger tannin molecule actually increases the number of “binding” sites (i.e., points where an OH could form a loose hydrogen bond with a site on a protein). An analogy might be if a bunch of people line up and hold hands, there are only free hands at the end of the chain. But if a bunch of octopuses line up and hold hands, there are still 6 hands free for every octopus.
But to a larger issue - Drew, that is why, if people are interested in what is going on, they should stop reading the likes of Kramer and various TNs and instead read the tech journals.
There continue to be so many ‘conventional wisdoms’ in wine that simply do not hold water anymore but are still believed because they always have been . . .
I think Alan’s analogy is one of the best I have ever heard for this.
My own model of what is occurring during the red vinification process deviated from conventional wisdom years ago. Besides simplifying the idea of fundamental balance as ‘angles vs rounds’ I look at red wine vitality as a function of ‘oxygen appetite.’ It’s simpler, less messy and describes what I see adequately.
I’m delighted that scientists are trying to develop better models of what is happening in this amazingly complex process, though.
Man, this brings back a few memories. It was precisely because of this article that I told University of Adelaide I wanted to study skin vs. seed tannins while I was there. Ended up coming to work for Turley instead, but it still would’ve been a hell of a lot of fun trying to figure what’s going on.
Some winery’s recent email mentioned extended maceration in their current release.
They stated that, last vintage, they did a prolonged maceration (~8-10 months). The wines were undrinkable in February, as the tannins were insane. A few months longer in contact with the skins and such, and a polished, smooth wine emerged.
I don’t know what the textbooks say, but it often seems like every winemaker has to walk the path him/herself to learn about these complicated science lessons in tannins, acids, pigmented anthocyanins, non-pigmented anthocyanins, whatever…
