“Nicely integrated tannins” is a phrase frequently used in this column to describe a pleasant characteristic of red wine.

Used less frequently to describe tannic traits are the words “gripping,” “silky” (a synonym for nicely integrated), “mature,” “well-rounded” or “balanced.”

But what are tannins?

Tannins are naturally occurring substances found in plants. When it comes to wine grapes, tannins are found in the skins, seeds and stems. Tannins give red wine its structure.

Tannins in their natural state are very astringent. We do not eat or harvest green grapes, because in their unripened state, they are bitterly tannic.

See for yourself: Pop the sweet pulp out of a thick-skinned native muscadine. Then chew the tough skin. The grape flavor dissipates, leaving a harshly bitter, mouth-drawing, gripping tannic experience.

Cinnamon is a tannin extract from the bark of a Southeast Asian tree. The astringent bark, like the green grape and the tough muscadine skin, is the plant’s defense against predators.

Though I would not try this at home, a video featuring an individual trying to win a bet by swallowing a teaspoon of cinnamon has apparently gone viral and was featured this past Sunday night on ABC’s “America’s Funniest Home Videos.” No, gentle readers, I do not watch this show, but this ridiculous human exercise caught my attention as I was looking for more worthy viewing like “Desperate Housewives.”

No animal can swallow a teaspoon of ground cinnamon. There is a physiological reason for this extreme reaction.

Tannins are polyphenols. I cannot find a definition for this substance that I am capable of putting in my own words. It is a complex substance, but one of its known properties is that it attaches to protein. When ground cinnamon is placed in the mouth, polyphenols find proteins contained in human saliva and attach themselves, rendering swallowing impossible — turning the mouth inside out, or so it would seem.

To a much lesser degree, this is how the human mouth reacts to tannins in wine.

If the wine has gripping tannins, for some it may be too bitter and astringent to drink.

Wines with insufficient tannins may seem too light and diluted.

Wines with integrated, silky smooth tannins are like Goldilocks’ experience with Baby Bear’s porridge: “Just right!”

Tannins occur in white wine, but to a much lesser extent because white wines spend less time in contact with skins and seeds than do red wines. White wines are fermented from free-run juice.

Tannins in white wines are usually found in those spending time in new oak. Pricey new oak barrels are a source of tannins, as well.

Besides supplying structure to wine, tannins also act as a preservative. Because white wines generally have lower tannins, they therefore have a shorter lifespan.

Red wines such as cabernet in California and France, sangiovese in Italy and tempranillo in Spain generally have longer lifespans.

Tannins do change. A young, harsh wine can, over time, become smooth and approachable, while other young, harsh wines remain harsh into their dotage. With wines, like humans, some age well and some do not.

Tannins are perhaps the most misunderstood and underappreciated component of wine. Scientific study of this component is in its infancy.

Currently, tannic structure is determined by the winemaker, who controls the length of time that fermenting juice remains in contact with skins, seeds and stems; time spent in new oak; speed of fermentation by controlling fermentation tank temperature; timing harvest when grapes are at optimum ripeness with less hash tannins present; and a host of other interventions.

The next time you have a glass of spectacularly fruity, balanced, slightly gripping, gently aging red wine, raise your glass to the tannin provider, Mother Nature, and to your quaff’s winemaker.