What Are Tannins in Wine? The Drying Feeling Explained

What are tannins in wine?

Tannins are plant compounds that make a wine feel drying, grippy and slightly rough in the mouth. In wine they come mainly from grape skins and seeds, with a smaller share from oak barrels. They are the reason a young red can leave your gums feeling as if they have been wiped with a cotton ball. Tannins can also taste bitter, but the drying feeling and the bitter taste are two separate things.

Wine Australia describes tannins as "bitter and astringent compounds found in most plant species." That names both sensations: astringency is the touch, bitterness the taste.

Tannin is not unique to wine. Strong black tea is the everyday example most people already know, and Wine Folly suggests putting a wet tea bag on your tongue to feel the effect without opening a bottle. Walnuts, dark chocolate and pomegranates appear on the same page as other familiar sources.

What do wine tannins taste like, and why does your mouth feel dry?

Mostly, they do not taste of anything; they feel like something. The technical name for the feeling is astringency. A review of the research by Jacqui McRae and James Kennedy, published in the journal Molecules in 2011, says astringency "refers to the drying and a puckering sensation in the mouth" and is "generally considered to be a tactile sensation caused by a loss of lubricity in oral saliva."

The mechanism, as that review describes it, runs like this. Saliva contains proteins that keep the inside of your mouth slippery. Tannins bind to those proteins, chiefly the proline-rich and histidine-rich proteins, and the protein and tannin clump together and drop out of solution. Saliva loses its slickness, and your tongue, gums and inner cheeks start to drag against one another. That friction is what a taster means by "grip".

Because it is a texture, astringency tends to announce itself along the gums, on the inside of the cheeks, and as a faintly furred feeling on the teeth after you swallow. It also lingers. In a study reported by Lab Manager, researchers Aude Watrelot, Hildegarde Heymann and Andrew Waterhouse found that "Trained sensory panelists perceived Cabernet as dryer, with a longer-lasting dryness, than the Pinot." The Cabernet Sauvignon in that work "contained more, larger and more highly pigmented tannins than the Pinot Noir," and those tannins "formed more protein aggregates in saliva."

If you want a way to practise noticing it, our guide on how to taste wine walks through a short exercise for separating drying texture from sweetness and acidity.

Is bitterness the same thing as tannin dryness?

No. Bitterness is one of the basic tastes, picked up by taste receptors. Astringency is a physical change in how your mouth feels. A wine can be noticeably drying with very little bitterness, and a wine can carry a bitter edge without much grip at all.

The two do share a source. The McRae and Kennedy review notes that tannins also interact "with taste receptors, particularly bitter receptors in the case of small condensed tannins." In other words, size matters: smaller tannin molecules lean toward bitterness. The same review says "The smaller molecular weight of seed tannins may be the reason for the reported bitterness of these compounds."

A practical test at the table: bitterness reads as a flavour in the finish, the way strong coffee or grapefruit pith does. Astringency reads as dryness and roughness across the mouth. Ask yourself whether the wine tastes bitter, and separately whether it makes your mouth feel dry. Two questions, two answers.

Is a "dry" wine the same as a tannic wine?

It is not, though the shared word causes endless crossed wires. On a label or a wine list, "dry" describes sugar. The labelling rules in Regulation (EU) 2019/33, in the version published on legislation.gov.uk, allow "dry" when sugar content does not exceed "4 grams per litre", or "9 grams per litre" where total acidity "is not more than 2 grams below the residual sugar content."

Tannin has nothing to do with that measurement. A crisp white wine made without much skin contact usually carries very little tannin, so it is dry without being drying. A tannic red with a touch of residual sugar can feel drying without technically being dry. When a friend asks for "a dry red", it is worth checking which one they mean: not sweet, or not grippy. The answers lead to different bottles.

Where do tannins in wine come from?

Two main places in the grape, plus the barrel.

Grape skins. Wine Australia notes that tannins appear to sit in the cell walls of the grape skin as the berry develops. According to the McRae and Kennedy review, "Condensed tannins from grape skins are extracted earlier in the fermentation process." The review reports skin tannins as long chains "ranging from 3 to 83 flavanol subunits."

Grape seeds. The review continues: "As fermentation continues, tannins begin to be extracted from grape seeds and flesh." Seed tannins are shorter, reported at between 2 and 17 subunits, and a larger share of their units carry an extra gallic acid group (a feature chemists call galloylation): 13 to 29 percent, against 3 to 6 percent for skin tannins. The review adds that "seed tannins are considered undesirable in wine."

Oak. The review states that "A small percentage of hydrolysable tannins are extracted from oak barrels or chips during aging." These belong to a different chemical family from grape tannins.

Why do red wines have more tannin than white wines?

Contact time. Wine Australia puts it plainly: "Red wines generally contain more tannin than white wine because the extended contact of the grape skins" with the juice draws more tannin out. White wines usually go the other way; Wine Folly notes that "most white wines are immediately pressed rather than macerated," so the juice spends little time with skins and seeds.

Grape variety matters as well. Wine Folly lists Tannat, Sagrantino, Petite Sirah, Nebbiolo, Cabernet Sauvignon, Petit Verdot and Monastrell among high-tannin reds, and contrasts Pinot Noir's "notoriously thin skins" with thick-skinned Syrah. For where the common grapes sit on the scale, our guide to types of red wine sets ten varieties side by side.

What does "high tannin wine" mean?

A high-tannin wine is one with a lot of tannin and, usually, a strong drying effect: firm grip on the gums, a furred feel on the teeth, and dryness that hangs on after you swallow. It is a description of structure, not a verdict on quality. Some drinkers love that firmness alongside a steak; others find it hard work without food.

Two cautions keep the phrase honest. First, the amount of tannin and the strength of the sensation are related but not identical, because other parts of the wine push the feeling up or down (more on that below). Second, "high tannin" says nothing certain about bitterness. Since bitterness is linked to the smaller tannin molecules, a wine can carry plenty of tannin and still read as firm rather than bitter.

Why can two wines with similar tannin feel so different?

Because texture and amount are separate questions. Tasters describe tannin texture with words like silky, velvety, fine-grained, chalky or coarse, and those words describe the kind of grip rather than how much of it there is. The red wine Mouth-feel Wheel, developed by Richard Gawel with researchers from the Australian Wine Research Institute, lists 53 terms for the mouth-feel sensations of red wines, which gives a sense of how many distinctions careful tasters draw.

Several things change how a given amount of tannin feels, according to the McRae and Kennedy review:

• Acidity. "Lowering the pH of wine and model wine solutions has been shown to increase the intensity of astringency." A sharper wine tends to feel grippier.
• Alcohol. Higher ethanol "concentrations have been shown to decrease the perception of astringency in model wines," though the review also notes that "one report indicated an increase in astringency with ethanol concentration."
• Polysaccharides. These large sugar-based molecules soften the feel: "All polysaccharides have been shown to reduce the perception of astringency by some degree."
• Sweetness and colour compounds. "Higher concentrations of sucrose and anthocyanins in wine have been associated with lower astringency ratings," which the review suggests may be due to increased viscosity.

Serving temperature is part of the picture as well; our guide on how cold wine should be covers sensible ranges and how temperature affects the balance of tannin, acidity and alcohol.

Do tannins soften as wine ages?

Generally, yes, though the full reason is still being worked out. The McRae and Kennedy review says ageing "is considered to render the tannins less astringent," that "Aged wine tannins have been shown to be larger than young wine tannins," and, candidly, that "The cause for the decrease in astringency of red wine over time remains uncertain." A note on health questions: tannin is sometimes blamed for wine headaches, but Wine Folly says "The jury is still out" on the link to migraines. A wine guide cannot settle that, and anyone who reacts badly to wine should raise it with a doctor. Wine is for adults of legal drinking age who choose to drink; declining a glass, or spitting at a tasting, is always fine.

Sources

• Wine Australia: Tannin
• McRae, J.M. and Kennedy, J.A. (2011). Wine and Grape Tannin Interactions with Salivary Proteins and Their Impact on Astringency: A Review of Current Research. Molecules, via PubMed Central
• Lab Manager: Why Some Red Wines Taste 'Dry'
• Wine Folly: What Are Wine Tannins?
• Commission Delegated Regulation (EU) 2019/33, Annex III Part B, on legislation.gov.uk
• Richard Gawel: the red wine Mouth-feel Wheel