Removing astringency from hybrid persimmons -- Collating observations

In a separate thread – https://growingfruit.org/t/persimmons-2021 – I asked whether CO2 or alcohol work equally well in Asian and American persimmons. Personally, I had very disappointing results with the American Prok. @Harbin responded with his observation that CO2 works with astringent Asians but does not work with Americans while hybrids are hit-or-miss, depending on genetics.

It would seem useful to compile results for various hybrid persimmons so growers can know when CO2 (or alcohol) might work. So if you have experience trying to reduce astringency in Asian-American hy bred persimmons, pease report your results.

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I’ll do my part with Gora Goverla (aka Hoverla) and Gora Roman Kosh. Both these hybrids are very large (up to 300g) and are descendants of Nikita’s Gift backcrossed with kaki. So my rough estimate is that they are about 80 to 90 % kaki and 10 to 20 % virginiana. While Roman Kosh is very nice and juicy when soft. Hoverla turns into a mushy stuff which I don’t like.
So when I pick ripe and hard fruits of Hoverla I place them into a small cooler box. On the bottom of a cooler box is a small dish with 70% persimmon brandy (any spirits would do, I guess) covered with wire mesh. Fruits are loaded up to the rim covered with a lid and left there for 5 days.
After that they can be eaten while still firm, astringency gone whatsoever: crunchy, juicy nearly as good as the store bought Rojo Brillante.

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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.

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The possibility of the disappearance and recurrence of astringency did occur to me. Since Saijo is rendered non-astringent in an anoxic environment, would it reverse itself and return to astringency in open air?
The Saijo that I vacuumed for 4 days has remained non-astringent 2 days later in room air. Perhaps hybrids will react differently.
Perhaps someone with a hybrid can test the vacuum method.

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And another article I need to track down:

Shimomura and Subhadrabandhu (1997) proposed a rapid astringency removal system by which the removal was achieved by treatment of 0.62-2.5 ml of 99.5% ethanol/kg fresh fruit and above 95% CO2 for 3-5 h at 40°C. The author suggested a sealed incubation of 12 h at 40°C after a temporary opening and chemical removing, and the fruits were stored at 20°C. The treated fruits remained unripe and had a “crisp” texture for a long period.

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As I understand it, Triumph is an astringent Asian type, developed in Israel and sold commercially after treatment with CO2 under the name Sharon. So while this article is interesting, it doesn’t move the ball forward re American fruit.

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I agree it doesn’t have the answer for American and hybrid persimmons, but it does suggest some factors that I don’t think have been adequately tested. In particular, the fact that it can be overdone is very interesting.

This thread didn’t seem to get much traction, but I’ll try to post whatever relevant observations I find.

@ncdabbler reports (link below) that 3 days of CO2 did not remove astringency from Nikita’s Gift (but did work on some Asians).

NG has thicker skin than most persimmon, at least that was the case from those I have tried. @PharmerDrewee How about yours?

It would be interesting to see @ncdabbler retry with a different hybrid like Rossey, Kassandra, and a 100% D. virginiana.

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@JustPeachy, maybe next year… I didn’t have any other hybrids or 100% D. virginiana fruit to work with this year, but I have trees that should start fruiting soon.

I’ve had no real luck trying to remove astringency from Nikita’s Gift with CO2 this year.
Did 24hrs of CO2 in a sealed homebrew keg at room temp followed by 3 days in normal air, still astringent. Then repeated that process and they do seem less astringent but still not really edible and who knows if that is the CO2 or just the time.

After the first CO2 treatment I also took a few fruits and put them in a bag with an apple and one of those has softened and fully reddened to a usual edible state at least.

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