Not sure if this is the right place for this, but I found reference to some additional wrinkles. Temperature seems to matter quite a bit, and it’s possible to overdo it (at least with some treatments) such that the tannins come back! This makes me wonder if instead of needing more time than kaki persimmons, virginiana actually need a shorter treatment.
Astringency was removed from‘Triumph’persimmons by immersion in water at 40°C for 5 hr or 60°C, for 1 hr. Similar treatments at 20° and 80°C, had no effect on astringency reduction. Subsequent application of 80% CO2 for 48 hr was effective for 20°C-treated fruit but not for 80° C-treated fruit, which became nonastringent only after exposure to acetaldehyde. Extending the 60°C treatment beyond 2 hr resulted in recurrence of astringency, which was not reduced by subsequent CO2 treatment. Astringency also recurred in CO2-treated non-astringent fruit, when exposed to high temperatures. The disappearance and recurrence of astringency correlated with amount of methanol-soluble tannins.