Astringency In 1,024 Words
It’s a flavor! It’s a feeling! It’s an airplane! No, it’s astringency!
On the surface, astringency seems like pornography. It’s easy to recognize, even if it’s difficult to define. The problem is that it isn’t really all that easy to recognize. In wine, astringency is easily and often confused with bitterness and even sour sensations. Astringency is also a bit complicated, so it’s not discussed much outside of technical circles. So what is it, and why should you care? Here’s astringency, in 1024 words.
Astringency is a mouth feeling, not a flavor. Flavors are sweet, sour, salty, bitter, umami, and permutations thereupon. Flavors are registered by specialized receptors clustered in taste buds on the tongue, soft palate, and epiglottis (the flap that prevents food from going down your windpipe when you swallow), mostly. We call the resulting sensations “taste.” Mouth-feels are tactile sensations: temperature, viscosity, touch, burning, pain, prickling, and astringency. Mouth-feels are registered by mechanoreceptors specialized for touch, thermoreceptors specialized for temperature, nociceptors specialized for pain, and proprioreceptors specialized for movement and position scattered all over the mouth. And the closest we can come to a generalized word for the resulting sensations is mouth-feel, though that’s not entirely accurate. Part of our problem with feelings like astringency, then, is that we’re just not all that attuned to paying attention to and naming sensations in our mouth that aren’t flavor or temperature.
Wine’s astringency and bitterness both come principally from polyphenols—tannin—that is why red wine tends to be far more astringent than most white wine. Grape tannin is derived almost entirely from grape seeds, stems, and skin. Since red wines are made by fermenting juice in contact with skins (and some seeds, and sometimes some stems) while the juice for white wines is separated from the skins before fermentation, and since tannins are more soluble in alcoholic solutions than in plain aqueous solutions, red wines pick up much more tannin than whites. Reds are also much more likely to be aged in oak barrels than are white wines. Since oak (and many other types of wood) also contains tannin, that barrel time is another opportunity for wine to pick up additional astringency.
Tannin dissolved in water feels “dry” or “rough;” some people refer to a furry or sticky feeling on the roof of their mouths. The biochemistry here is that tannins bind to proteins in saliva—the proteins that create that nice slippery feeling—and cause them to form big agglomerates that fall out of solution, making your saliva less viscous and therefore making your mouth feel “dry.” If you’re not easily grossed out, try looking in a spittoon that has been used for spitting (not just dumping leftover) red wine; the long, red, stringy floating things you’ll see are salivary proteins that have bound to (red-colored) tannins and fallen out of solution. Tannins also interact with and disrupt the surface of the mucosal epithelial cells that line the interior of your mouth, physically making those membranes rougher. It seems that they might mimic the effect of epinephrine, a hormone that constricts blood vessels, reducing blood flow to those mucosal membranes and, again, making your mouth feel dry. (There are likely other things going on here that also contribute to rough and dry sensations, but these are the most important ones.)some
Up to this point, knowing about astringency just seems like good wine-tasting trivia: “hey, do you know why that Cabernet Sauvignon makes your mouth feel sandpapery?” But there are two useful points at the bottom of all of this. Firstly, because of its effects on salivary proteins, astringency can take several seconds to develop and the sensation builds up over repeat exposure. If you taste the same tannin solution three times, it will feel most astringent on the last sip even though it’s the same solution every time. If you taste several red wines in a row, especially without waiting in-between or “washing” your mouth with some food or water, the cumulative effect of tannins on the inside of your mouth will make the last wine feel more astringent than it would had you tasted it first or by itself. Point the first: be careful of “sequence errors” in tasting. If the last wines on your tasting list taste unpleasantly rough—and especially if you haven’t taken some water and/or food and/or time in between tastes—don’t automatically blame the wine. Consider coming back to try those wines at the beginning of another session…or, better yet, pace yourself from the get-go.
Point the second: some foods are astringent, and these foods tend to be tricky wine pairings at least in part because red wine can taste more astringent in their company. Prime examples are artichokes, cardoons (related to artichokes), walnuts, and green beans. Under-ripe persimmons are super-astringent—if you’ve ever bitten into one, you know what I mean—but if you’re using those in a recipe, you have bigger problems than the wine pairing. Chocolate is another relatively rich source of tannins, one of several reasons why it’s a tough wine pairing at best (more details on that topic here.) Astringency is only one consideration in pleasant food-wine pairing, but it’s an important one.
There’s plenty of advice on the internet about pairing astringent wine with food, some conflicting. Of course, the most useful evidence on what to serve with astringent wines comes from playing around in your kitchen to see what tastes good to you. The second most useful evidence I’ve seen thus far comes from a 2012 study by a group of Italian food scientists published in the Journal of Food Science measuring how much salivary protein wine tannins could precipitate under varying conditions. They found that the tannins were able to bind less salivary protein when the alcohol level of the wine was higher, in the presence of sugar, and at less acidic pH. These data jive with common advice that sweetness helps lessen the perception of astringency and sourness exacerbates it (but it’s nice to have some numbers behind those aphorisms.) It’s also worth noting that there’s logic to the custom of serving astringent wines with protein- and fat-rich foods. Food protein will bind to some of those protein-binding tannins and, essentially, help soak them up so that they wreak less havoc on your saliva and mucosal membranes. Fat, on the other hand, just makes your mouth feel more slippery and alleviates some of that tannin-related roughness.
And, if nothing else, you can sound erudite saying, “this wine is very astringent” instead of “gosh, this wine is really dry.” But you already know how I feel about the word “dry”…