From memory (please correct if I have this wrong), acetaldehyde is produced within the Kaki persimmon from endogenous ethanol. This is especially true in PVNAs, which produce ethanol in the seeds. So why do CO2 and ethanol remove astringency from Kakis? My assumption has been that anoxic conditions (e.g., CO2) and/or the presence of exogenous ethanol encourage the persimmon to produce endogenous acetaldehyde, which drives the removal of astringency. A further assumption (I haven’t been able to find anyone who actually states this) is that the persimmon fruit absorbs exogenous ethanol vapor and uses it to produce endogenous acetaldehyde.
So if this is remotely correct, let’s turn to DV and hybrids – Why would we expect exogenous acetaldehyde to work if exogenous ethanol does not?
Don’t misunderstand – I’m willing to try anything. I’m just trying to progress beyond magic to an understanding of mechanisms. It appears that Virginiana has somewhat different metabolism than Kaki, so CO2 and ethanol don’t work. I have no idea whether hybrid metabolism is like Kaki, like Virginiana, or some compromise. Do we know? Or is the application of methods that work for Kakis an act of faith?
I get the idea for adding acetaldehyde from the article above. Persimmons treated at 60C for more than an hour or 80C for any length of time did not respond to astringency removal except by adding acetaldehyde. In that case, I think the issue is the enzyme pathways that are creating the acetaldehyde are destroyed by the higher temps, which would also be the case in any cooked product. Also, if it’s acetaldehyde that’s doing the actual work of removing astringency, cutting out the middle man of ethanol shouldn’t matter, and I bet it’s a lot more than is produced by the ethanol/anoxic pathway. It would be like using a sledgehammer instead of a claw hammer. The claw hammer works fine for most kaki, but I suspect virginiana needs a sledgehammer. I base this not on a leap of faith, but on probabilities. Evolving a whole separate metabolic pathway to do the same thing (add/remove astringency) is way less likely, especially in the same lineage, than is evolving how active an existing pathway is and when it’s triggered. So, I can’t completely rule out a different metabolic pathway, but it’s just much less likely. Adding or dropping a step at the end of one of those pathways is also a possibility; I’d say the probability is higher than a whole new pathway, but still much lower than a difference of how active that pathway is.
I checked online and acetaldehyde seems like something I wouldn’t want to add to food…
Acetaldehyde is considered a probable human carcinogen (Group B2) based on inadequate human cancer studies and animal studies that have shown nasal tumors in rats and laryngeal tumors in hamsters. )
Acetaldehyde is a much more potent toxin than ethanol, and at least a part of ethanol toxicity is due to ethanol’s first metabolite acetaldehyde.
That’s really interesting- I remember picking Miss Kim persimmons from the tree after a freeze and didn’t notice any astringency, which was a first for me with astringent persimmons (picking off tree without astringency). I assumed it was related, but maybe they just happened to ripen by that time.
Speaking of Miss Kim, it has a lot more fruit this year. I count 14 fruit in the below pic, which is twice what the entire tree produced last year. Hopefully it is still as good.
I agree it’s probably not best for home use. I’d been mistaken, thinking that it was the ingredient in commercial green apple flavor. While it does have that flavor and smell, it turns out they use another compound instead.
This is really a case of the dose makes the poison, as it’s naturally occurring in beer, fruit, etc. But to get pure acetaldehyde and use it to remove astringency in fruits would require more precision, lab safety, etc, than most of us would be able to accomodate at home. So I think that test would be best left to the professionals.
My little 2 and a half foot tall Lehman’s Delight has held on to these 2 persimmons all season and they’re starting to get nicely colored. Of course I should have taken them off and let the tree grow, but I couldn’t bring myself to do it when my much bigger Prok dropped 100+fruit.
So I definitely want to eat these and keep them from the squirrels, but I don’t want to pick them too early if that might impact flavor. They are still rock hard and you can see one is more colored than the other and they are a little lighter on the other side which is to the north. If they were kaki I’d go ahead and pick them, but should I wait longer to pick American persimmons for best flavor?
@zendog … I went to my sisters home on oct 9 and got a large bowl full of persimmons from her trees. Some were ripe and ready… some were still firm with soft spots … all i picked were orange but many of them were still very firm.
I put them in a bowl on the counter and covered with a large glass bowl… persimmons under glass.
And since then we have been eating them a few each evening… and now there are about 10 left.
The ones we ate last night… no doubt they were orange but still very firm on oct 9… but last night they were very delicious very rich flavor… outstanding really.
Good luck with your fruit… hope you do get to enjoy them.
Just FWIW, here’s an interim update from coastal RI. These are IKKJ (left) and Kassandra (right) picked yesterday.
The IKKJ are obviously not ripe. I picked them because they were low-hanging and vulnerable to deer. I’ll ripen these indoors with no extraordinary effort, maybe just sitting in a bowl with an apple. Last year I picked this variety very orange but still firm as late as 11/15 then ripened them indoors. This year I’ve got another >100 still on the trees awaiting that treatment.
The Kassandra fruits are also not fully ripe but they are much closer. I’ve already picked and eaten a few fruit that ripened more quickly after some bird or mechanical damage. The good news is that the ripe fruit were not astringent. Not at all. This is a sharp contrast with my past experience here with Prok. I may perform a small ripening experiment with these Kassandra fruits, but honestly I don’t see the need. I expect them to ripen fully without assistance, either on the tree or on the counter. There are ~200 (at least) still on the tree.
I like the flavor of IKKJ. It has been sweeter than Prok and well (if subtlety) flavored. But it is not intensely sweet or intensely flavored, so I understand the criticism that other persimmons are better. I’ve tasted only a couple of ripe Kassandra so far, and they seem both sweeter and more richly flavored than the Jiros. As you can see, they are smaller but that may be an advantage – it may be easy to eat them without dealing with a handful of goo. And they are more numerous.
Finally, I have one JT-02 fruit (not pictured) on a graft on one of the IKKJ trees. It is just beginning to color. It’s bigger than the Kassandra but much smaller than the IKKJ. The shape is square-ish like the IKKJ but with rounder edges. Stay tuned.
Thanks for the report. I look forward to seeing the pic of your JT-02.
You are far more knowledgeable about persimmons than me. However, I wonder if your Prok is correctly labeled. If it is, how many strains of Prok are out there. My Prok, once soft ripe, lost its astringency.
@mamuang – You could be right. It won’t matter much going forward as I’m top-working the tree, mainly to the DV names such as H63A, Dollywood, and Barbra’s Blush. There’s also some good grafts of the Asian Sheng and the hybrid JT-02 but I’m not sure I’ll leave them. I’m also trying to grow all those varieties as separate trees. It’s too much fruit but a fun experiment.