Also called persimmon, this edible fruit has different interesting properties for health. Normally tannin levels are pretty high if the fruit is not mature and this could provide a noxious sensation. Tannins are polyphenols with the ability to coagulate proteins like the mucin of the buccal mucosa, and thus that sense of asperity if it's not mature enough.
A technique like this allows keep away herbivorous and other animals, until the seeds are ready for dispersion or at least, that's the theory behind it. Pests are not usually affecting this variety.
Some individuals try to get ride of tannins using alcohol because some quantity could enter in the fruit after evaporation. For the purpose, it might be better using a drinkable potion than other kind of alcohol with possible chemicals. Anyway, the method works by scientific reasons.
Other method is to use a paper to wrap it since the air content could gain ethylene content, a simple hydrocarbon. After some days, the khaki would be ready for enjoyment.
The fruit was called Diospyros and pyros, something similar to “divine fruit”, probably for its complex taste and texture.