I previously asked this question in the biochemistry thread but didn’t receive any answers, so I’m reposting it here in the general chemistry
thread.
Many of you might know that as bananas overripen, dark spots develop on their skins. Around these spots, a narrow ring of chemical compounds forms,
which exhibit fluorescent properties.
I have a couple of questions regarding this phenomenon:
Could these fluorescent compounds be stabilized and stored for future use?
Based on my research, these compounds appear to form as chlorophyll decomposes. If one were to extract chlorophyll from green leaves, would they
observe a similar fluorescence effect? Additionally, would the compound be stable enough to store?
Looking forward to your insights!
-Sarinox
drakedevel - 28-1-2025 at 22:59
It's hard to say much about stability without knowing what the compound is. If it's an intermediate of the process that forms the spots, and the spots
don't fluoresce, it seems like it doesn't survive very long in musa. If you want to accumulate enough raw material to have any hope of
extracting a useful quantity (vs. just buying a truckload of bananas all at once) you'll need to find some way to inhibit that reaction because the
browning process happily proceeds in a domestic freezer. Maybe try soaking in ascorbic acid before freezing? Honestly, this seems like a
big pain
Chlorophyll is fluorescent, and you can see a photo of an extract fluorescing on that page. But I'd expect it to be red, not blue as in your
photo. As far as stability goes, it's (unsurprisingly) light-sensitive and not known for being especially stable generally, but this paper reports that it can be fairly stable if if purified, crystallized, and stored in the dark.sarinox - 29-1-2025 at 00:39
Hi drakedevel, thank you for your reply!
I was thinking that banana skins might contain a significant amount of the precursor compound that transforms into the fluorescent material during the
ripening process. If so, I wondered whether it would be possible to extract this precursor, convert it into the fluorescent substance, and then
stabilize it for future use.
Unfortunately, I don’t know the exact identity of the compound responsible for the fluorescence around the dark spots on overripe bananas. From my
research, it seems to be a product of chlorophyll breakdown. My guess is that it might be possible to extract this compound using chemical solvents,
but of course, consulting experts in the field would be the best approach!
I was hoping someone here might have more insight into what this substance is and whether it can be effectively isolated and stored.
Looking forward to hearing more thoughts on this!
I haven’t finished reading the paper you introduced yet! (I am reading it) Rainwater - 29-1-2025 at 03:09
You can try a tlc plate to seperate the compounds. And maybe identifying a few based on polarity sarinox - 29-1-2025 at 05:11
You can try a tlc plate to seperate the compounds. And maybe identifying a few based on polarity
Currently, I don’t have access to an air oven, so I’m unable to perform TLC at the moment. By the way, what solvent would you recommend for
extracting from banana skin? Should I use acetone, methanol, or dichloromethane? or what?bnull - 29-1-2025 at 06:35
A. Tiessen, The fluorescent blue glow of banana fruits is not due to symplasmic plastidial catabolism but arises from insoluble phenols
estherified to the cell wall, Plant Science (2018), (https://doi.org/10.1016/j.plantsci.2018.07.006)
The second article disagrees with some conclusions of the first and was followed by comments and a reply. This set has extensive references that are
worth checking. I'm attaching the first article.
Oh, interesting! That first paper makes it clear that the entire skin is fluorescent, not just the rings. I thought that looked like the case
from sarinox's pictures, but the post only mentioned the rings, so I figured it must have just been an artifact of the camera w/ UV light. If the
whole skin is fluorescent that sure seems more practical to extract, at least. (Though the second paper looks a bit pessimistic on the prospects of
that...)bnull - 30-1-2025 at 04:57
It's really the whole banana that fluoresces. It is a good way to know if a particular banana is ripe and palatable, although it may seem weird to
carry an UV flashlight and point it to bananas in a grocery.
Edit: I'll give it a try. I've seen weirder things being done in the grocery.