Even in my cool maritime climate , which does not, in some years, experience a hard freeze till January, Saijo persimmons refuse to lose astringency hanging on the tree. Even as they approach the super mushy stage on the counter, the fruit still give that fuzzy tongue aftertaste.
Determined to find a way to remove astringency, I have tried the following 4 methods with varying degrees of success (or non-success): 1) drying overnight in dehydrator, 2) drying for 2 weeks as Hoshigaki, 3) submerging for 24 hrs in a 104F warm water bath, and 4) enclosing fruit in bag filled with CO2 for 24 hours.
1.The first method, drying in a 115F dehydrator overnight definitely did not remove astringency.
2. On the other hand , drying underripe fruit (yellow with green shoulders) at 50-70F for 2 weeks (Hoshigaki) did remove astringency. Even after hanging for 1 week the fruit had lost astringency. After 2 weeks, the fruit was semi-dry, sweet, and date-like. It could then be frozen whole or sliced and frozen for later use.
3. Submerging half-ripe fruit in 104F water for 24 hrs did remove astringency and dramatically softened fruit. I placed a heating pad set on low in a cardboard box. In the box I placed a glass bowl filled with water and fruit and the probe of a digital thermometer. I placed a cover on the bowl and taped the box shut. The low setting on the heat pad kept the water temp at 102-104F. After 24 hours, the fruit was quite soft with no astringency. Could be used for jam.
4. Enclosing half-ripe fruit in bag filled with CO2 for 24 hours did remove astringency and slightly softened fruit. I used the CO2 from a soda water dispenser to fill ziplock bag and then tied bag with wire. Overnight the bags deflated somewhat. The resulting fruit still maintained some firmness and could be peeled and sliced.
When I pick persimmon all at once, I get a bounty with different degrees of ripeness. In the future the least ripe fruit I will dry as Hoshigaki and freeze, the medium-ripe fruit I will preserve with CO2 and eat fresh, and the most-ripe fruit I will warm water bath and use to make jam.
Only left 5 fruit at the top of the tree for the squirrels.
Good report !
So in #2 above , did you āpeel ā and hang them?
Which method produced the best tasting fruit? Including best texture.
These are the hanging Hoshigati, peeled with screw inserted into stem to hang. Not the traditional method of hanging from stem but straight stem didnāt always catch with line. Fruit was dipped into boiling water for 20 sec before hanging. Temperature in room is 50-70F. Humidity is 60% and fan is going. The 2 brown hanging fruit in background are Hoshigati after 2 weeks. After hanging 1 week noticed spots of mold on some of the fruit. This occurred on fruit that had started out more ripe than others. Sprayed with vodka and mold disappeared. Needed to continue spray every few days for certain ones. In retrospect I may have mistaken mold for sugar bloom. I will avoid spray on certain āmoldyā ones to see what happens.
Texture after 2 weeks is dense, quite moist, and brightly sweet, not as cloying as dates. Seems amazing since the fruit was rock hard when started! Iām considering dehydrator drying slices 
at this point to avoid having to freeze.
CO2 ripening produced fruit that was soft, very moist, and sweet. The few fruit that were still rock hard before CO2 turned out the bestā¦more like sliced non-astringent.
Hot water method produced very soft fruit. Perhaps this method, too, would work better with rock hand fruit.
My inclination for next year is to pick fruit 3 weeks earlier when most are still very hard. My aim is to avoid pudding and get firm slices.
I think the CO2 method would produce the best fruit for my taste. The best persimmon texture for me is the one of non-astringents, just when they start to soften.
I have considered building something like this, using a small CO2 tank with an on/off valve and a nozzle. That way I donāt have to use up the small CO2 cartridges from my old soda water maker. Will check out Soda Stream - perhaps that would be easier than building anything. For more large-scale CO2, this set-up (originally described on the web as a way to euthanize living animals for pet snake to eat!!) is quite intriguing. The low inlet tube is for CO2, since CO2 is heavier than room air. The high outlet tube can be submerged into a container of water so that room air does not leak into can. For chemistry lovers, BTB can be added to water to determine when 
CO2 is exiting container.
Iāve seen people use alcohol for this
(ā Iāve seen people use alcohol for thisā)
Yes. ,!
I have often ā used alcohol ā while waiting for persimmons to ripen.
If you still have some hard ones you could try storing in Fridge for 2 to 4 months in sealed zip lock bag removing air.
I have done this with American persimmons that were hard as a rock, but gathered some fruit that were falling that were soft on same tree
The Large trees were in a park, but since I couldnāt reach most of the ripe ones or shake with rope I also grabbed the unripe ones on the same tree.
I may also try this when all the simmons are not at all ripe , on same tree
and see if I get same results after storing.
By the way Thank you for the methods, and results
this may also extend your Harvest, but these were American Simmons
This thread got me interested in trying Hoshigaki. These are Maruā¦some are pollinated (brownish) and some not. Maybe not a great test since the pollinated ones arenāt all that astringent, but at least there are a couple of non-pollinated ones.
These look great! I see the cross twig is the way to go. Are these hanging outside? Whatās the temp range and humidity?
Tried the CO2 method on a store-bought Hachiya. Picked the hardest one and then put in bag for 2 days with CO2. Ended up slightly soft and sweet- sliced it like a Fuyu.
They are indoors. I was afraid the jays and mockingbirds would destroy them. Temp range is about 64 - 68 deg F. Humidity is very low - not sure of the value. Will let you know in a couple of weeks how it goes.
Just put them in the freezer overnight. Once they have frozen through, thaw them out and they should be fine.
They look great! I had to spray mine often with vodka to stop the mold. Yours are drying at a lower humidity and higher temp (mine were in cool humid greenhouse) and look good. Your temp/humidity setup may be a better way for me to go next year. No fan on yours right? I actually took mine down last night (going through too much vodka!), sliced them in half, and finished drying on rack over wood stove.
Just sampled the 3rd fruit from the left. We knew it was unpollinated. My Japanese wife says it tastes like normal hoshigaki. It is not fully dried, and is quite moist in the very center. Astringency: 99% gone. There is the slightest chalky aftertaste, not unpleasant at all. This fruit would have been inedible two weeks prior.
Great information! I am just discovering persimmons. Just have one fuyu tree now but going to add a couple of astringent varieties in 2021. Great info!
Does your Fuyu ripen outside in Vancouver? l planted Giant Fuyu and Matsumoto Wase last year but figured I would have to rig up a plastic enclosure to give them enough summer heat units. The Hoshigaki or CO2 method might be able to ripen them, even when picking them hard,
Another long shot I am going to try is Saanichton kiwi. They are being grown on (close-by) Vancouver Island, Canada!
Yes, most years my fuyu will ripen on the tree. I do watch the weather. Some years ago we had a very early very hard frost. Didnāt know it was coming so I woke up to persimmon popsicles! brought them inā¦ chunked and mashedā¦ quickly refroze. they were delicious in smoothies.