Reader Gregory has been out picking persimmons and wants to know what causes the sour, pucker-y taste you get when you bite into one that isn’t quite ripe. Gregory, that’s a really great question. Tannins are responsible for that. They don’t have a taste or an aroma, rather they create a physical sensation known as “astringency”. It happens when phenolic compounds in the tannins combine with proteins in saliva. Little friction-inducing clumps of protein and other debris are created where ordinarily there is smooth lubrication. For the eater, it all adds up to a puckering feeling of dryness in the mouth, which can be downright off-putting.
Which is exactly the effect that’s intended, since fruits don’t want to be eaten before their seeds have matured. Which means that tannins are a type of chemical defense, discouraging consumption of fruit until the time is right. Consider them a warning to the taste buds, for indeed those clumping phenolic compounds can cause more serious problems if consumed in large quantities: stone-like aggregations in the stomach (known as bezoars) and potentially life-threatening intestinal blockages.
Don’t diss the plants, home boy. They’ll mess you up.