@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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For anyone interested in experimenting, I’m curious about results this year for hybrids especially!
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I’ll try! My only astringent persimmon that is carrying fruit is the hybrid variety, Kassandra. I’m hoping I won’t need tricks to remove the stringency, just normal ripening. We’ll see.
There’s also a single fruit of JT-02 on a graft. But that’s too little for experiments. It’s also low enough that an ambitious deer could eat it before I do.
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I’m still at least 2 years out from being able to test this myself, but I’ve put together a list of protocols to test out with hybrid and American persimmons that address some aspects that I don’t think have been properly tested yet. Note that both the times and temperatures are important. So far, I’ve seen people focus more on which chemical(s) to add, or a yes/no on CO2, immersion, etc. What I haven’t seen is paying close attention to what the temperature is and how long the treatment lasts. I also haven’t seen anyone test adding acetaldehyde directly (probably because it’s hard to get if you’re not a lab or school). Artificial green apple flavoring may be an acceptable substitute.
- Sealed container with CO2 and ethanol for 3-5 hrs at 40°C
2. Sealed container with CO2 and acetaldehyde for 3-5 hrs at 40°C
3. Sealed container with CO2, ethanol, and acetaldehyde for 3-5 hrs at 40°C - 40°C Water bath for 5 hrs
- 60°C water bath for 1 hour
- 60°C water bath for 1/2 hour
7. 40°C Water bath for 5 hrs, sealed in bag w/acetaldehyde - 40°C Water bath for 5 hrs, sealed in bag w/ethanol
9. 40°C Water bath for 5 hrs, sealed in bag w/acetaldehyde & ethanol
10. 60°C Water bath for 1 hr, sealed in bag w/acetaldehyde - 60°C Water bath for 1 hr, sealed in bag w/ethanol
12. 60°C Water bath for 1 hr, sealed in bag w/acetaldehyde & ethanol
13. 60°C Water bath for 1/2 hr, sealed in bag w/acetaldehyde - 60°C Water bath for 1/2 hr, sealed in bag w/ethanol
15. 60°C Water bath for 1/2 hr, sealed in bag w/acetaldehyde & ethanol
Edit: Upon further research, working with acetaldehyde is not something we can safely do at home. I’ve left them in the list for reference, but those tests will have to be left to research professionals.
I came up with these procedures to test based on several research articles on removing astringency. Yes, all the articles are about kaki, but they do provide some interesting clues. The water bath ones would be easy to run concurrently for a given temperature, especially if you have a sous vide circulator. If anyone wants to try these out, please let us know how it goes. If not, hopefully you’ll be hearing from me in a couple of years!
Edit: just thought of one more thing to try, based on this text from Stone Brewing about acetaldehyde in beer:
Acetaldehyde is the immediate precursor to ethanol in fermentation. Like diacetyl, acetaldehyde is found in large quantities during early fermentation as the yeast produces it en masse early in their metabolic cycle. If there is a high amount of dissolved oxygen present in the young beer, then the oxygen could react with ethanol and oxidize it back into acetaldehyde. Edit: looks like I was wrong. Some cursory searching shows that while acetaldehyde does have a green apple flavor, a different compound is actually used in artificial flavoring. Acetaldehyde treatment might have to be left to the pros.
Has anyone tried using a container of yeast in sugar water as their CO2 source in a container? It would produce CO2, acetaldehyde, and ethanol, along with a myriad of other compounds that may or may not have an impact.
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You might want to add vacuum sealing to list since it works on Saijo.
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@jcguarneri I have lots of Nikita’s Gift fruit at about the right stage to do some testing. I could try adding yeast and sugar water to my CO2 setup and see if that helps remove astringency from NG fruit.
For some of your other ideas, I don’t have a water bath, but I have an aquarium heater I could put in a tub of water, but I probably couldn’t even get to 40 deg C with that. Do you think the temp in a crock pot would be stable enough to try a small batch?
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Nice! A crock pot might get too hot, but it’s worth a try. An easier method would be to use a cooler. You’d have add water that’s a couple degrees warmer (to account for heat loss to the fruits and cooler). An average cooler should be able to hold close enough to 60C for an hour or 40C for 5 hours. I used to hold similar temps in an average cooler doing all-grain homebrewing, and people will use coolers for low-tech sous vide. A higher-end cooler (Yeti, etc). would be even better, but probably not necessary.
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@jcguarneri If I were to use green apple flavoring as an acetaldehyde substitute, what amount would be appropriate to add to, say, a quart sized ziplock of fruit?
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Beats me! I really wish I knew. I can’t even guarantee that a given green apple flavor would have any acetyldehyde in it, but my understanding is that most if not all would contain it. Acetaldehyde is the key part of that “apple” flavor. I suspect it wouldn’t take much, maybe a few drops.
Edit: looks like I was wrong. Some cursory searching shows that while acetaldehyde does have a green apple flavor, a different compound is actually used in artificial flavoring. Acetaldehyde treatment might have to be left to the pros.
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It was an original idea! Thanks for checking.
I really should read the paper to which you were referring to answer my question, but I’ll pick your brain since you’re making good suggestions -
Is your understanding that the hot water bath supposed to accelerate the reactions and result in faster removal of astringency, or are some of those reactions only likely to occur at all at a warmer temp?
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My understanding is that it speeds up the enzymatic reactions that handle the astringency removal so that they’re happening faster than the softening process. The trick is enzymes are destroyed over a given temp (different for each enzyme), so you can fly too close to the sun and accidentally remove your persimmon’s ability to become non-astringent.
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I tried the CO2 treatment with yeast for Nikita’s Gift fruit for ~48 hours. I mixed 2 teaspoons of yeast, 1 teaspoon of sugar and a quarter cup of water and put it in a dish inside the sealed container with the CO2.
I had several D. kaki fruit (Giboshi, Eureka and Giombo) in the same container, and they were all non-astringent and firm when I took them out, but the Nikita’s Gift fruit were all still astringent and firm. Now it’s a few days later, and they’re starting to soften after sitting on the counter since I took them out of my sealed CO2 container. They aren’t astringent any more, even though they are just beginning to soften. So maybe there was some effect, since I think I remember the Nikita’s Gift fruit I tasted last year off my tree needed to be quite soft before they lost all their astringency. They’re very tasty!
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Great design! Is that BTB in glass jar turning blue in presence of carbonic acid? Very cool.
Once you turned off CO2 container, did the exit tube continue to bubble from the sugar/yeast mix? Or was it an initial flush of CO2 from the bubbling yeast?
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Yes, the bromothymol blue solution turns greenish yellow when it gets to a pH of 6. The outlet tube didn’t bubble at all unless I turned on the CO2… maybe the initial flush from the yeast was gone before I sealed the container. I should have put the yeast in a larger container - it overflowed and covered one side of container.
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Very cool! Thanks for sharing your results. I’ll record that as a “maybe.” If it did have some effect, it would support the quantity of astringency being the difference. Did you have any non-treated NG at the same level of softness to compare?
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Unfortunately no. I should have left some untreated NG fruit on the counter to compare. All my untreated fruit are still on the tree and still firm. But it’s a lot warmer in the house, of course. I’m going to try it again and give them more time in CO2 to see if it makes a difference. This time I’ll leave some control fruit next to my CO2 tank.
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This article isn’t about hybrids but it seems worth reading by anyone interested in removing astringency. Maybe someone can figure a better place to file it.
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Anyone have any updated info on this? I have a lot of little Kassandra, some Nikita’s Gift and Chienting, and a few Rossyanka, and JT-02.
This Kassandra was grafted 2 years ago. I picked 10 lbs today, with maybe another 5-10 on the tree.
Chienting:
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I don’t have updated info yet. Last year, my only year with a substantial Kassandra crop, I was able to remove astringency with ethanol. I put fruits in a big plastic bin with a small cup of vodka, then closed the cover. As I recall, it took a week.
This year I will try spraying ethanol directly onto the skin.
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