You should peel certain fruits like persimmons before cooking because the skin can be bitter, tough, and negatively impact the texture and flavor of the final dish. Peeling ensures a smoother, sweeter, and more palatable result.
The skin of some fruits, like persimmons, contains high levels of tannins. Tannins are naturally occurring compounds that can impart a bitter or astringent taste. While some people might not mind a slight bitterness, in many cooked preparations, this bitterness can become overpowering and unpleasant. Furthermore, the skin of certain persimmon varieties, especially when unripe, can be quite thick and tough. Cooking doesn't always soften it sufficiently, leading to an undesirable texture in your final product. Peeling removes these undesirable elements, allowing the fruit's natural sweetness and smooth texture to shine through. The peeling process also helps the fruit cook more evenly, as the skin can sometimes act as a barrier to heat penetration. This is particularly important when baking or making jams and preserves.
To easily peel ripe persimmons, try blanching them briefly in boiling water for about 30-60 seconds, then immediately transferring them to an ice bath. This will loosen the skin, making it much easier to peel with a paring knife.