He did mention this in the context of processing pulp for use in cooking, so I guess saltiness then can be compensated for out of the other ingredients. But for fresh eating…yeah. I guess trying much smaller amounts, and/or working through the list of other edible PH adjustors (add potassium bicarb to the list, though I hear that trades saltiness for bitterness)…
If the discoloration is from oxidation from the air and not the reaction itself, I would hope that immediately pouring the pulp into a ziplock bag and sucking most of the air out, and then tossing it in the fridge or freezer, might help…
Two assumptions: (1) Baking soda works by generating CO2. (2) Most tannins in a nearly ripe fruit are loaded in or near the skin.
If these assumptions are correct, maybe it would be way more efficient just to dump the sodium bicarbonate into a glass of lemon juice (or vinegar or whatever) inside a closed container that also holds the whole persimmons. That would generate CO2, surrounding the fruit.
Basically I’m wondering if mashing before treating shields much of the skin from any CO2 created by the bicarb.
Hmm; well…technically the CO2 comes from the base directly ripping apart acids to get at those tasty oxygen atoms. So if it’s the reaction that’s directly neutralizing the tannins, you’ll probably need to mix it in. But if most of the tannins are near the skin…yeah it’s quite possible there’d be enough osmosis and such to react and neutralize enough acids near the skin to help with the flavor, and then the resulting CO2 would help ripen the intact fruit. Though worth noting: I would absolutely not recommend leaving a low-oxygen high-PH liquid at room temperature for long without talking to someone with a degree in food safety. Straight into the fridge or freezer in my uneducated opinion…
@Itmaybejj – My understanding is that the CO2 (or alcohol vapor) produce an anaerobic environment that encourages reduction of ethanol to ethanal (aetylaldehyde), which then binds tannins. The acid-base reaction is just the source off the CO2.
Inspired by @cdamarjian 's post last year of a CO2 chamber for euthanizing rats to feed to pet snakes, I made this set-up for removing astringency in kaki persimmons using an airtight plastic container and a paintball CO2 tank.
I can refill the CO2 tank at a local paintball store much more cheaply than buying Sodastream CO2 canisters.
I pick the fruit (Giombo in these pictures) when they are just starting to turn orange and still rock hard.
I put a few drops of bromothymol blue in water with a pinch of baking soda to make a basic solution and put the outlet hose into this glass. When the water changes from blue to greenish yellow, then I know the chamber is full of CO2 and stop filling it. I remove the CO2 tank hose and cover both the inlet and outlet with saran wrap to seal the chamber. I leave it for 3 days in a dark place. The fruit comes out firm and non-astringent.
The first time I tried it last year, I tasted the fruit immediately after removing them from the CO2 chamber and they tasted carbonated, like they had been soaked in soda water. They also still had some astringency. But after leaving them overnight, they were completely non-astringent and still firm.
After this treatment, astringent kakis have a texture just like fuyu-type non-astringent kakis, but I think they are sweeter and more flavorful. Most members of my household don’t really like the gooey texture of a ripe astringent kaki, but they love the crisp crunch of the CO2 treated fruit.
I also dry astringent kakis in a dehydrator, and if you slice them when they are just starting to soften up but still astringent, drying will remove the remaining astringency. It won’t work on hard, unripe fruit, though.
I LOVE the fact that you followed up on my post from last year! This is definitely an improved set-up. The use of BTB and baking soda warms this elementary school science teacher’s heart. A++++
@cdamarjian@ncdabbler After treatment did you guys consume everything within 3 days? According to this study, CO2 treatment alone triggers the onset of post-astringency rapid softening. Persimmons lose ~60% of their firmness by day 3 after CO2 treatment (according to them). Did you notice anything (assuming they lasted that long)?
They mention treating with CO2+ 1-Methylcyclopropene to both rapidly remove astringency and prevent softening. 1-Methylcyclopropene is commercially available under the name EthylBloc and SmartFresh. It’s not an ethylene absorber. It binds to the ethylene receptor in tissue and prevents ethylene from having an effect. The study shows only a loss of ~20% firmness by day three with this treatment regiment.
@JustPeachy
I process only about 4 persimmons at a time …and end up eating all within 3 days (or maybe even all in 1 day!).
If you had access to a SmartFresh sachet, it would be interesting to include it with CO2 for a comparison test.
In this CO2 only method, persimmons are put in the bag/container in the rock-hard state and removed when they have slightly softened. Using SmartFresh might prevent this slight softening.
That may be an advantage if the intention is to refrigerate the astringent-reduced fruit for counter ripening later. In fact, maybe that’s what’s done to some specialty (astringent) persimmons that consumers just ripen on counter.
As usual, there are a lot of marketing practices to which the consumer is unaware!
Btw… “In the United States the National Organic Program does not allow the use of 1-MCP on organic produce” (Wikipedia)
I can’t find the post from last year, but I thought that was your suggestion to use the bromothymol blue! Maybe it was another responder to your post about the CO2 chamber. It wasn’t an original idea on my part. Anyway, thanks for inspiring young minds and not-so-young minds!
@JustPeachy That’s an interesting finding, and it isn’t consistent with my own limited experience with CO2 treatment up to this point. I treated 2 batches last year (I made my chamber in November 2020 at the tail-end of persimmon season), and I just started my third batch this year. So that’s not a lot to go on. But each time I’ve treated persimmons this way, I’ve picked more unripe fruit than I can fit in my CO2 chamber. The ones that don’t fit end up in an open bucket next to my CO2 chamber. And each time, a couple of the untreated persimmons have been starting to soften after three days, while the fruit in the CO2 chamber is all still quite firm when I remove it. And we don’t eat all the treated fruit within 3 days. I’ve still had firm CO2 treated persimmons more than a week after treatment, and I haven’t put them in the fridge. I keep all my picked persimmons (treated and untreated) on my kitchen counter. Some of the treated persimmons do start to soften in the second week after treatment, and some of the untreated persimmons can go longer than that before they soften. But my general impression was that the untreated persimmons generally soften sooner. I need to watch more carefully with my current batch and record exactly how long it takes for them to soften. I suspect the time required to soften them has a lot to do with how close to ripeness the fruit were when picked. They were all starting to turn orange and rock-hard, but some were likely further along than others.
Prior to the post about rapid ripening from @JustPeachy, I was going to suggest mass treatment using a 5lb CO2 bottle and placing a whole bunch of persimmons into a 5 gallon keg like those used to homebrew. Usually they are recycled Coca Cola kegs.
@disc4tw I did consider investing in a larger CO2 tank and making a bigger chamber, but I decided to experiment with this smaller version first because I don’t have enough fruit or the budget to warrant the larger scale version just yet. Refilling a 5lb CO2 tank at Airgas would be significantly cheaper per pound than at the paintball store. If my younger persimmon trees all end up producing as much as my three oldest trees do, then I will need to reconsider that idea (and get a stall at the local farmer’s market to sell them!).
I’m just speculating. Maybe it’s ethylene that’s helping them those in the bucket ripen in a semi enclosed dark space. Do the ones in the bucket which are untreated still have astringency?
Do you have any not in the bucket, just laid out? Are those post-CO2 treatment as hard as those simply laid out? That’s how I would compare firmness over the course of a few days. The paper is stating that it triggers rapid-onset of post-astringency softening. I assume this occurs for all persimmon, kaki or virginiana, but the speed of onset probably differs due to the exact transcription factors expressed in each cultivar and the environmental conditions of the test.
The untreated persimmons that start to soften are still quite astringent until they get very soft.
I have left a few untreated persimmons on the counter and not in a container, but I haven’t made careful observations. I prefer to keep my persimmons in some kind of container because sometimes they soften up and start to leak before I notice them.
I’m sure you’re right about ethylene playing the key role in ripening, but I would expect the treated fruit in the enclosed CO2 chamber would have even more exposure to ethylene than the fruit in an open bucket, right? Unless the bananas and apples in my kitchen are producing enough ethylene to affect the open bucket of untreated persimmons down the hallway and in the bedroom 30 ft away.
I’ve noticed on my trees that any fruit that has even a small bird peck will ripen long before the others on the tree. So maybe even small damage or bruising could also accelerate ripening.
Maybe the fruit in the study was much closer to fully ripe when treated with CO2 than the fruit I pick and put in my CO2 chamber. Or like you said, maybe there are differences between cultivars. Most of my treated fruit has been Giombo and Tecumseh. I’ve also treated a few fruit off my younger trees - Smith’s Best/Giboshi, Eureka and Nikita’s Gift. Interestingly, the three hybrid Nikita’s Gift fruit I tried were still too astringent to eat after 3 days of CO2 treatment, while all the kaki fruit were non-astringent. My young Nikita’s Gift tree only had three fruit on it this year, so I can’t try any more and see if a longer treatment period would remove the astringency.
If I remember correctly, ethylene formation occurs by fruits (including persimmon) on their own, so you end up with accelerated self ripening since it kind of causes a snowball effect once it starts. However, the synthesis of ethylene requires some sufficient concentration of oxygen, which is why the CO2 thing (or rather low O2) is a thing for storage of many fruits to prolong their life.
Incidentally, CO2 also is a thing that helps address astringency in persimmon, which I assume shares some but isn’t identical as the biological pathways for firmness. (Bear in mind, I didn’t read every word of all the relevant papers cause they I am really not THAT bored. I just skimmed through a few of them. At some point, tastes good is tastes good regardless how you get there.)
This could explain why you can use pure ethylene to accelerate softening of persimmon, even though the result is still astringent. Conversely, you can use CO2 to address astringency, where the result is non-astringent fruit that maintains firmness (for how long is a separate issue).
I assume the fruit is bletting when damage occurs like this exposing the flesh.
Re astringency: I didn’t read exhaustively myself either, but my take-away was that in an anaerobic environment (e.g., CO2) endogenous ethanol is reduced to ethane (acetaldehyde), which binds tannins.
The more I read and experiment, the less I think know.
I’ve been working only with the American variety Prok. I haven’t tried CO2, but I have tried alcohol. From what I’ve seen, alcohol didn’t seem to reduce astringency any faster than the mere passage of time – ~2-3 days at room temperature. But after that much time, the fruit was fairly mushy.
Often it’s better to be lucky than smart. In this case, I may have stumbled on on method that reduces astringency in American persimmons without turning the fruit to mush. The 1st piece of good luck was that the thermostat on my refrigerator broke. In that condition, it worked at one speed, which kept the box at ~60 F. The 2nd piece of good luck is that I started storing my still astringent Prok persimmons in the broken fridge – mainly hoping to keep away fruit flies.
At this temperature, it seems that the fruit took a little longer to lose astringency – maybe 3-4 days versus 2-3 at 70 F. But it was also slower to turn to mush. The resulting fruit was the best in flavor and texture that I’ve gotten from the Prok tree so far.
Take this all with a grain of salt. It’s some half-assed observations and some shaky inferences. But is there something useful here? Is it possible that the specific chemical reactions that reduce astringency may be less sensitive to low temperature than the reactions that cause softening.
