I don't have a scientific answer, but I do remember what my Grandma used to tell me about persimmons... she said that they won't be ready to eat till after the first one ot two frosts. Till then they can be real bitter.

I have heard the same. I ate a japanese persimmon before frost once. I won't do that again. Harriet

I've got a large wild persimmon in my backyard, and it's been dropping ripe fruit for almost a month. Standard procedure is to scan the grass for windfall before mowing, splitting the winnings w/the 5year old.