Tannins - We’ve all heard the word, here’s what they are…
“Wow, this wine is tannic”!
“…lush plummy fruit supported by a fine tannic structure…”
We’ve all heard the sentence and the phrase just above, and as the title says, the word is thrown around like a Nerf football in a college stadium parking lot, but perhaps for that very reason, my instincts tell me that many wine drinkers, if really pressed for an answer, couldn’t define the term with any real precision. Let’s have a look…
Here’s a first surprising fact about tannins: tannins have no actual TASTE (and therefore no smell) at all. What we “taste” when we come into contact with tannins is these substances reacting with the proteins from which your mouth is made, and the sensation is purely textural. And indeed this is mostly what tannins bring to the table: “mouth feel”.
We know where tannins wind up, but what is their source? The answer is an easy one. Tannins are found in the skins, seeds, and stems of grape vines (as well as in tree bark, tea leaves, etc.). And because skins must be used to produce red wines, and because skins almost never wind up in the production of white wines, red wines are tannic and white wines are not. Tannins in fact are bound up with the substances called anthocyanins (the compounds that make red wine red) which are also found in the skins. And as this bundle (most properly called proanthocyanidins) comes into contact with the acids in the juice, the acids chemically split the tannins from the anthocyanins, allowing these coloring substances as well as the tannins themselves to completely pervade the wine.
But though skins and seeds and stems are the main source of tannins in most wines, tannins can also be introduced into a wine via…OAK! Tannins are present in wood as well, though these are not chemically the same sort of tannins that one finds in grapes skins, they are tannins nonetheless. What’s more, the tannins that leach into wines as they rest in oak barrels (new ones especially) are often “finer-grained” than those present in unaged wine. Interestingly, when red wine is aged in wood barrels, there is actually a tannin EXCHANGE between the barrel and the wine with the barrel giving up it’s finer wood tannins and then absorbing the coarser grape tannins back into its grain.
So tannins give red wines their texture, but they serve an equally if not even more important function. Tannins naturally retard oxidation, and what that means in the long and the short is that tannins allow wines to AGE. So at least theoretically, the more tannic a wine is, the longer it will hold, and/or the more gracefully it will age. But to be clear, not all tannins are created equal. The family of compounds to which tannins belong are very numerous and complex, so for example, tannins that ripen slowly as the berries come to maturity are chemically different than those that have been built via a one week heat wave. Additionally, we know that both Cabernet Sauvignon and Nebbiolo are tannic varieties, but those that have drunk a few examples of both know that the CHARACTER of the tannins in these two varieties are quite different.
Another way we can encounter tannins in wine is via what are chemically called tartrates. Tartrates are those little crystals that one sometimes finds clinging to the business end of a cork, or alternately, as the sediment that one might find in the bottom of a bottle of older wine. Now strictly speaking, tartrates are NOT tannins. Tartrates are actually a potassium salt of tartaric acid, but bound up with these salts, are often a certain percentage of tannins. Therefore, the more tartrates one finds in wine the further “evolved” a wine is, which reads as less tannic. Also for the sake of clarity (pardon the pun), not all sediments are either tartrates or percipitated tannins. In wines that are unfiltered, much of what is to be found in the bottom of a bottle of wine is quite literally tiny grape skin/pulp particles. These are easily distinguished from tartrates by their color. Grape sediment is purple and opaque, while tartrates are quite clearly colored CRYSTALS. And let’s just briefly take the opportunity to make it clear to everyone that ALL of these substances are NATURAL and HARMLESS. One should still avoid ingesting them because they are at least a distraction and sometimes can be quite bitter, but they are not in any way toxic. I cannot tell you how many times people have come back into the shop claiming that a bottle was bad, and the problem to which they were referring was normal sediment…this is when these folks get the abridged version of this piece, as well as a word or two about decanting…
The final view of tannins that we’re going to take was alluded to just above, and that process is called FINING. Fining is a sort of alternate mechanical filtration process that is NOT filtering. Filtering in wine is just what it is in any other pursuit - using a sort of screen to not permit particles larger than X to pass through. Fining is done via a neutral, flavorless substance that is added to a wine that is later racked off or filtered out. The most common substances used in fining are eggs whites (no, this is not a technical term - actual egg whites) or a subtance called bentonite which a dry powdered clay that expands when mixed with water. These substances are very effective at pulling down colloidal substances like tannins, pigmented tannins, and stray proteins that winemakers may want to eliminate.
So that’s the primer on tannins in wine. There is SO much more to the chemistry of these complex compounds, but that’s well beyond this layman, but suffice it to say that tannins are absolutely inseparable from a wine’s character as well as it’s drinking future. Without tannins, wine is not “wine”.
TOM CIOCCO
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Another fine column, Tom. I’ll be the first to say I don’t know how to recognize tannins on the nose, or how to differentiate between “fine” and coarse. I only use the term when the wine is dry to the point of puckering my mouth like a green persimmon.
Comment by elbowroom — February 10, 2007 @ 12:03 am
Tom, excellent and informative column. Thanks again for sharing your substantial wine knowledge with rest of us. While I happened to know almost everything you stated in this column (I didn’t know about the bentonite), I have many friends who are desperate for knowledge so I have passed on the link to this column to them. Your writing style is also quite good - common sense, easy to digest - I enjoy these tidbits.
Comment by JayZee — February 10, 2007 @ 7:53 am
Great column, but tough to read the first part with that tongue picture visable. One of the best descriptions of tannins I’ve read comes from Jancis Robinson. She points out that they are the stuff that makes the inside of your lips feel like they are stuck to your teeth.
Comment by JimKay — February 10, 2007 @ 9:42 pm
Tom,
Good artical, but you may consider advising your readers of the formation of tartrate crystals as a result of chilling (as opposed to aging), and the preventative effects of cold stabilization. My experiences have revealed tartrates in white wines far more often than in reds.
Cheers!
Comment by Eric — February 12, 2007 @ 12:52 pm
Eric-
I’ve actually never heard anything about the formation of tartrates as a result of cooling/cold stabilzation, though there is no doubt that tartrates form in white wines as well…as I say in the article, tartrates are themselves not tannins, but in red wines, tartrates often have quantities of tannins trapped in their structures…
TOM CIOCCO
Comment by Tom C — February 12, 2007 @ 1:00 pm
Tom,
That’s an excellent article on tannins. It would be nice to see some discussion about how tannins feel in the mouth besides mouth-puckering astringency. For instance, many wine writers compare the body of wine to how skim, 1%, 2%, whole milk and cream feels in the mouth. Wines are often described as having a variety of textures (ie. silky, satiny, dusty, angular, chewy,velvety etc…). Tom I’d like to know if wines that have chalky or dusty tannins develop smoother textures with further bottle ageing?
Comment by luvgrapesqeezings — February 12, 2007 @ 2:30 pm
Luv-
Thanks for the kind words. In my experience the CHARACTER of tannins in a wine never change per se - like dusty tannins becoming spikey tannins for example, they simply fade and diminish…maybe like a photograph would do - the image will fade, change color, get dog-eared, but it’s still the same photo…
TOM CIOCCO
Comment by Tom C — February 12, 2007 @ 2:47 pm
Cold stabilization is a process used to reduce acidity in wine by chilling it to about 25 degrees F to force potassium bitartrate out of solution. It is done in white wine because there is more tartaric acid present. Also is helpful in wine made from hybrids that have a higher acid content. The wine is “cold stable” meaning bitartrate crystal won’t form latter in the bottle when it is refigerated. The crystals can be alarming to some consumers. The process is speeded up by adding some cream of tarter to the wine (seed crystals). - Modern Winemaking by Philip Jackish
Comment by JimKay — February 15, 2007 @ 9:14 pm
Interesting articel Tom.
). The texture of oak tannins is not uniform, as oak tannins are not just oak tannins. Age, growing place, subspecies, etc. have a very large influence on the eventual appearance of oak tannins. The exchange of oak tannins and grape tannins is also an issue of much controversy. Whether tannins and elagitannins exchange in a signifcant amount (that is to be noticed by the trained palate) is not certain. There is no hard biochemical evidence for that. In oaked wines they are found together. But whether the mellowing of the grape originated tannic structure is caused by oak tannin exchange or by reaction of the grape tannins with the chemeical substrate of the oak, is not really well known. Also, the different feel of oak tannins is not substantially proven. It is quite possible that the perception of lignin and lignans is automatically associated with a ‘feel’ of oak tannins, yet, when the lignin and lignans are stripped from the wine test tasters didn’t seem capable anymore of ‘feeling’ anything different.
Tannins are still a world to explore for biochemistry. Here at university of Leuven, we have smby, who already did a PhD on tannins and now for the last three years or smth is still doing research on them. He says that tannins form a molecular universe on their own (like you said: only the variety because of sudden heat or temperate periods and all).
Anthocyanins, those split offs, are also, for a large part, the compounds that make a wine red to purple (that is in its juvenile stage, the brick red colour of most aged wines is smth else). Anthocyanins colour red in an acid environment and colour blue in a alcaline environment. Do the test: when you have a considerable left over in a glass (a small sip), add some demineralized water and some colourless kitchen vinegar: the colour will be vigorously red (that is in diluted form), when you add some colourless hand soap it will turn purplishly blue. Wines are acid, so the colou will be red, that’s all. Yet, anthocyanins also have an important role in tasting patterns, etc.
Oak tannins (elagitannins) are said to have no taste. Yet, it’s still a mystery why we can ‘taste’ that a wine is oaked (without a GV-oak monster hurling it’s way through your palate
Mystery, those tannins …
There is good article on Tyler Thomas’s blog: http://www.vinesnwines.org/?p=79
Comment by TSchampaert — February 18, 2007 @ 6:39 am
Interesting piece, but what about the mouth feel? The first comment revealed more about how one *experiences* the wine than the technical description about what tannens *are.* For example, what are “integrated” or “soft” tannins that we hear so much about? And if one comes across “harsh tannens” is there something that could be done about it (the “pucker factor”)? I’ve always assumed that the the smoother a wine is, the softer the tannens–but then, I’m an inveterate philistine!!
Comment by mr. greg — February 24, 2007 @ 6:56 am
well, if by philistine, i also mean incapable of spelling: “tannins” not “tannens” — apologies! Also, sorry for not reading all the comments about mouth feel before posting mine. Okay, where’s my coffee to clear up last night’s “tastings”…?
Comment by mr. greg — February 24, 2007 @ 7:05 am
Hmmmm, someone needs to brush their tongue!
Comment by Rob — April 3, 2007 @ 3:20 pm
Tom thanks for a very enjoyable read. I have been in industrial water treating for 30 years and work in the area of settling solids and recently in Membrane separations(technologies which have found their way into the wine biz). Although I am not in the “Wine trade” I would like To add to Erics comments above. Precipitation of some solids can be enhanced via temp drop because of reduced solubility. I have always assumed this to be the case with often found tartrate crystals in whites together with or without their added presence via acidity correction
Comment by Al — August 7, 2007 @ 12:42 pm