Whole Lemons in Water at Room Temp
I put a bag of whole washed lemons in a mason jar filled with RO water and left it room temp to try to get some more life out of the lemons. When I remembered and opened it 2 weeks later the water was all bubbly. I put the lid back on and left it because I wanted to do some research to see if they were still good. I forgot and it now 2 months-ish later and the water is still bubbly. It’s smells great too. I did finally take a lemon out and cut it. It also smells wonderful and is just softer than it normally would be. Are these lemons still good? Did they ferment themselves? I’m very curious and know almost nothing about this kind of thing.
Recommended by Food52
I keep a jar of drinking water on the table, loaded with a cut up lemon and some orange peel trimmings. After about a week with the sane citrus, it gets a natural slight natural and pleasant fermentation.
If you want more info on fermentation, check out Sandor Katz abd Brad Leone (books, videos).
The tip for storing-citrus-longer-in-water (up to about 3 months) works at fridge temperatures. See article here by Valerio Ferris, 2020.
BTW, Katz and Leone are separate authors/presenters. Though they've done at least one video together.
Submerged under water, this was inaerobic, most likely a lactic acid fermentation. The citric acid in the lemons probably prevented other unwanted microorganisms from developing by creating an unsuitable acidic environment.
As for whether or not they are good, no one here can say authoritatively. Generally speaking good-smelling fermentations are edible. White is generally good, green or black is generally bad.
Over millennia humans have discovered that they can increase the chances of a good lactic acid fermentation by creating an environment that favors LAB (lactic acid bacteria).
Salt does a particularly good job and 2% salt by weight is a commonly accepted threshold that discourages the growth of most undesirable microorganisms. This is something humans have done for thousands of years (sauerkraut, kimchi, etc.) to provide more reliable, repeatable results rather than hope for sheer luck.
It is your call whether to taste or toss. Since I have been making my own sauerkraut for years, I'd probably taste a small amount if the scent is clean.
Best of luck.