Autumn is barely underway, but reader Gregory has been out picking persimmons. He wants to know what causes the sour, dry taste you get when you bite into one that isn’t quite ripe. Gregory, that’s a really great question. Chemical compounds called tannins are responsible for that. They don’t have any taste or aroma themselves, though they do create a physical sensation known as “astringency” which happens when phenols in the tannins combine with proteins in saliva to create a mass of friction-inducing protein clumps. These clumps spread over the surfaces of the mouth — which are ordinarily slick with lubrication — putting the smooth interaction of tongue, cheek and gum to a halt. The result a puckery, dry sensation which can be downright off-putting.
Which is exactly the effect the persimmon intends, since a fruit generally doesn’t want to be eaten until such time as its seeds have matured. So tannins like these are a type of chemical defense, discouraging consumption until the time is right. The effects are generally harmless, though tannins can cause more serious health problems if they’re consumed in very large quantities: stone-like aggregations in the stomach (known as bezoars) and potentially life-threatening intestinal blockages.
All of which is to say that persimmon season is long, reader Gregory. No need to go jumping the gun here. About another month or so and the pickings should be much more to your liking!