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.
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!
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?
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.
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?
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.
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.