They will ripen on the counter. The freezer should also work. Not sure about a dehydrator or any of the other Kaki methods.
I gave my very first girl friend on our first date a mostly ripe persimon and apon the first bite she puckered up and we nailed down my first kiss.
@cousinfloyd I don’t see any reason why the methods that work for kaki wouldn’t work for virginiana. The astringency is from the same compound and removed via the same metabolic process, so it should respond to the same treatment processes. The biggest difference may be quantity of the astringent compounds. As far as I can tell, if anyone has tried it, they haven’t reported back on their findings. I have read on this forum that CO2 will work on hybrid Nikita’s Gift.
@jrd51 you could be a trailblazer. Take a handful of hard ripe Prok and stick them in a sealed container with some vodka. Also try a handful submerged in water for a few days. If I don’t get a definitive answer by the time my trees are producing, I plan to try these tests.
If you have a SodaStream (often found for $10 at thrift stores), take a few Prok and place them in a 1 gallon freezer bag filled with CO2 from the Sodastream. Ziplock and/or twist tie the top. It works great on Hachiya. When put in bag hard, after 2-3 days, they soften and can be sliced like a Fuyu!
Does the CO2 (a) ripen, (b) remove astringency, or © both (e.g., a leads to b)?
CO2 both (a) ripens and (b) removes astringency.
I have tried the drying, freezing, water soak, and vodka techniques. Not good for me with Saijo.
CO2 works the very best and you end up with a sweet, non-astringent, firm, sliceable product from an astringent-variety persimmon.
Thanks for the added info. I’m definitely not surprised about the freezing. That’s well documented that it doesn’t work for virginiana, and I find it marginally effective at best for astringent kaki. At least for the odd store-bought Hachiya I fail to soften properly every year or two, that is! I also haven’t seen anyone try a slow dehydration, hoshigaki-style, with virginiana. Probably because the American persimmons are too small for all that fuss. But I’m not surprised putting them in the dehydrator doesn’t get rid of it. Does that actually work for kaki? That’s pretty cool if it does. Have you tried, or do you have written account of, trialing CO2, submersion, or alcohol? I’ve really been looking for evidence one way or another. I hope to have some fruits in a couple years so I can try it for myself. I’ll have to rely on the experience of yourself and others in the meantime.
Just a thought here. If you have a lot of persimmons to treat with CO2, how about trying a 55 gallon drum with removable lid and locking ring. Get a welding CO2 tank with the right fittings and fill the tank up with it. Have a exhaust valve t o let out some air as you are filling it up. CO2 is heavier than air so if you do it slowly it should displace the air. This is a plan I may try in the future but my trees are all seedlings now.
I’ll have to see if I can find the full text for these articles, but the abstracts are interesting.They’re looking at removing tannins from kaki persimmons, but I think they illustrate the key to understanding this whole thing. First, the tannins don’t actually go away, they just become insoluble. Second, they don’t dissipate right away, regardless of treatment type, but rather go down over time. So, if there’s more tannin to become insoluble, it should take longer to work through. I’m still trying to find some numbers on this, but I’d bet money that D. virginiana fruits are starting with a higher tannin concentration than kaki fruits. If that’s the case, it follows that any treatments that work for kaki should work for virginiana, but I would expect it to take longer. @cousinfloyd does that seem plausible to you? It certainly explains why I have limited luck freezing out the tannins from Hachiya; I’ve probably never left them in long enough. Also, the dehydrator probably just happens too quickly for the tannins to become insoluble for virginiana.
It sounds like ethanol, CO2, and submerging in water are all working on the same principle: creating anaerobic conditions that make the fruit accumulate acetaldehyde (green apple smell), which then reacts with tannins. So find a way that works for you to make an anoxic environment. Or maybe toss them in a bag with a green Jolly Rancher…
@jrd51 if my general thesis holds water, your frozen pulp should reduce in tannins the longer it sits in the freezer. Also, since it’s about concentration of soluble tannins rather than simply presence or absence, there’s probably a ratio of fully ripe to underripe persimmons where the concentration stays low and your batch isn’t ruined. The trick is if we’re talking 10:1, 100:1, or 1,000:1.
Comparatively, higher soluble tannin content 11.68 (mg/g DW) and lower insoluble tannin content 10.02 (mg/g DW) was observed in control (day 0). Therefore, the astringency of persimmon fruits incubated at − 20 °C and − 80 °C was markedly reduced and after 15 up to 60 days of storage, the astringent taste virtually disappeared.
In the last century, several postharvest treatments including ethanol vapour, carbon dioxide gas, nitrogen gas or warm water treatment have been assayed to remove astringency without fruit softening. Under anaerobic conditions, fruit accumulate acetaldehyde, which reacts with soluble tannins transforming them into an insoluble and non-astringent form. Persimmon tannins, mechanism of astringency loss, deastringency treatments, and factors affecting the process of astringency removal are examined.
The evidence would seem to support your recommendation re freezing. At least, one article showed very good results but the period of freezing was long. From memory, something like 70-90 days.
Alcohol works, maybe especially in combination with an added source of ethylene (e.g., a banana). We just need a strong vapor, which we’d get with a small amount in cups inside a closed or mostly closed container. This seems easier to me than CO2.
Most interesting, given my interesting in processing fruits to a puree, one article shows great results from added soy protein. The protein binds and neutralizes the tannins, with no adverse impact on flavor.
Some of this is repeated from the other thread. I can find and post links, if needed.
Edit: I no longer believe that the extra exogenous source of ethylene (e.g., an apple or banana) is necessary.
I’ve tried drying (no good), freezing (no good), and Sodastream CO2 in freezer bag (yes!) for hard, store-bought Hachiya.
Below is an internet pic of a janky(!) intermediate set-up for using CO2. Instead of metal can, you could use a large styrofoam freezer box with inserted inlet and outlet tubes.
Instead of CO2 canister with on/off fitting, you could attach inlet hose to outlet of Sodastream. Place outlet hose in bottle of water to prevent room air intake.
I’m curious – how long did you keep the persimmons frozen?
Probably 12 hours. Maybe not long enough? The change in texture is not too appealing to me. The fact that CO2 ripened ones remain firm enough to be sliced is a plus for me.
One research article that I remember reported success but after a much longer time. From memory it was 70-90 days.
I agree with you about the impact on the texture of fruit. I’m also very interested in the impact on processed pulp, e.g., a puree.
If you try this, I’d be Interested in your results.
I’ve taken the astringency out of Hachiyas that were mostly ripe, but still a bit astringent, with just 24 hours in the freezer. But these were basically fruit I thought might be ripe enough, but could tell from the first bite I made a mistake. So these weren’t fruit that were still firm and quite astringent.
At the end of last season, I did buy a few dozen Hachiya that were colored and starting to go soft and put them in the deep freeze. I took the first one out a bit over a month after going in and it was clear of astringency, so a month was enough but I have no idea if a week or even just a few days would have been. The rest I’ve been enjoying occasionally throughout the year since then and still have a couple to eat before they show up at reasonable prices in the Asian markets around here. I cut them all in half before freezing and enjoy them still partially frozen but soft enough to dig out and eat with a spoon.
For hard but fully colored fruit I’ve found the alcohol treatment to be very easy and reliable.
Turns out the answer is YES.
<< The most frequently used technique to measure the soluble tannins is the Folin-Denis method (Taira, 1996) but there is an easier method called “Tannin print method” (Eaks, 1967) where a solution of ferric-chloride at 5% reacts on the cut surface of the fruit after an immersion of 30 s and produces an ion complex tannin-Fe of blue-black colour; the intensity of the colour is correlated with the soluble tannins content and this colour is evaluated on a scale of 1 to 9. >>
Nice! I’m really digging your deep dive on this matter.
Thanks. But on reflection, I’m not sure that this particular issue – a test – is more than academic. The test is useful to scientists as an objective method for measuring astringency. But would I ever use it?
With apples, I feel that I can “starch test” a few apples and then, if the starch is low, pick the whole tree. It won’t matter if one apple is 2% starch and another is 5%. I wouldn’t notice the difference and a cider combining the apples would be quite acceptable.
With astringent American persimmons, I may test one that is low in tannins while its untested neighbor is just high enough in tannins to be inedible. After all, the taste threshold for astringency is low, and the fruit don’t become fully ripe all at once.
Also, there’s a version of the “uncertainty principle” at work. I can only eat the fruits that are untested. Once I test a fruit, whether it’s ripe for not, I have to discard it. How many good persimmons do I want to throw away?
Bottom line: I may end up using some treatment (probably alcohol or CO2) on all my whole American fruit. And I will almost certainly end up using some treatment (alcohol, protein) on any puree or paste that I make.
Continuing, it occurred to me that if acetaldehyde is the “active ingredient” that binds “kaki tannin” then maybe I should simply add it directly to any puree.
The problem is that while acetaldehyde is produced naturally in fruit and is rapidly metabolized by the human liver, it can be toxic. It is, for example, one of the substances responsible for a hangover.
It might also work to add small amounts of ethanol directly to a puree, then rely on still active enzymes to dehydrogenate the ethanol to produce acetaldehyde. But I don’t want the persimmon paste to taste like alcohol; and I don’t want more acetaldehyde than would be necessary to bind the tannins. The precise method would be to titrate the doses, but that’s just not practical.
I’m left thinking that the easiest and safest approach might be to find a tasteless, harmless protein (like the soy milk discussed above) that will bind the tannins. Probably I could use a combination of crude arithmetic and trial-and-error to derive some appropriate dosages.