I’ve always cut out bruised parts on a banana. They look unappealing and gross.
I’ve wondered if bruised areas have bacteria? Is it a type of rot?
Do some people ignore the bruised areas and eat them? Is it safe?
I’m going to go waay out on a limb here and say it’s safe. If it wasn’t, I and many many others would be dead many times over.
I wouldn’t want to eat a heavily blackened banana, but that’s mainly due to the gross-out factor.
Bruised bananas make perfectly fine banana bread and smoothies.
I never bother; my wife always does. We are both still alive.
I had a colleague who used to bring totally brown bananas to our brown bag lunch table and ate them. He claimed they were much sweeter than the under-ripe yellow ones. YMMV.
I’ve often thought about asking my grocery store manager to sell me their old bananas instead of tossing them. I’ll bet they are probably throwing out the exact ones I’m looking for. I’ll buy a bunch of ripe bananas, and then my wife lets them sit around until they are pretty gnarly looking before she makes banana bread and muffins. To the OP, I wouldn’t consider eating one of the horrid looking bananas that go into the bread, but they’ve never harmed us.
I buy bananas while they are still green and hard. They ripen at home and never have bruises.
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It takes a really long time for bananas to truly go bad and rot. Far beyond the stage of turning brown or black. I do notice that the bruised area of a banana does spread quicker than the non-bruised area, probably because of cellular damage. This is true of other fruits too.
Also, apple bananas aren’t truly ripe until they begin to show black spots or turn completely back. And if you put a banana in the fridge, the skin will quickly turn brown/black, but the fruit is still perfectly fine, even underripe if you put it in too early.
My local supermarkets sometimes sells bags of blackened bananas clearly marked “For banana bread”. And my Dad made a deal with a supermarket produce manager that he would happily buy all the seriously overripe persimmons for a bargain price. He tried it with our local Safeway, but the produce manager refused, saying he was required to toss them out. Note that these weren’t moldy, those were immediately tossed, but just bruised. My Dad would toss them in the freezer, peel them while still frozen and eat it like sherbert. I tried it once and it was too sweet.
A bit of trivia that I’ve talked about before. That lovely cubed and sliced fruit you see at buffets or prepacked boxes of fruit at the supermarket? Notice how lovely ripe it usually is? Most likely made with fruit that was bruised, sometimes slightly rotted on one side. Same with half or quarter fruit in the supermarket. Try to find the other quarters or halves and you’ll unlikely to find them because they’re in the dumpster.
No, your mileage doesn’t vary, Bananas become sweeter as they ripen because starches are converted to sugar during the ripening process.
Bananas are picked and packed green. They are shipped in a temperature and humidity controlled environment; onlt being allowed to ripen just before sale.
Bananas do not have to be cut off the plant green and allowed to ripen. I grow dwarf varieties at my home in Hawaii and just pick off individual fruits as they turn yellow.
While this is true … for some (a lot?) of people, well-ripened bananas acquire a hard-to-describe off-taste. It’s not a rotten taste … but neither is it merely ripe-banana+more-sweetness.
And anyone who has tasted them will know that the ones in the supermarket are just a poor relation.
I grew up in West Africa and we had banana trees on three sides of a large garden. There were several varieties, large (including plantains) and some delicious small red ones. I remember, when I was about 8 or 9, taking a whole bunch to school because there was a new teacher who had no idea how they grew. Like most people, he thought that the hands hung down. All the kids in my class took a load home and my mother was pestered for more for ages.
I too find the taste of a brown banana unpleasant. It’s more than just the additional sweetness, like you said it’s hard to define. That flavor is the flavor of ethylene, a hormone produced by the banana, which is what causes a banana to ripen and change color. Ethylene is sweet and “musky”, and I think that muskiness is what you and I find unpleasant. Ethylene is indeed safe to consume in its pure form and is only toxic when forming other compounds (such as ethylene glycol, aka antifreeze).
Ethylene is a gas and will ripen plants that come into contact with it. That’s why bananas are picked when they are green; if you wait until they ripen and store them together then the ethylene from each banana will affect nearby bananas and cause them all to ripen faster (and release their own ethylene) in a snowball effect. Just about all plants release ethylene and it’s the reason why we have the saying “one bad apple can ruin the whole bunch”; it really can. You can use ethylene to hasten the ripening/blooming of plants in a positive way too, and that practice has been done since ancient times.
Ethylene gas is also highly flammable, which makes me wonder about the plausibility of “banana bombs”… 
Brown bananas do make the best ingredients for puddings, pies, and so on. Mix that banana with other ingredients and that unpleasant muskiness is covered up.
My northern African friends always looked at me funny when I ate a ripe yellow banana. They wanted their brown and squishy with the consistency of pudding.
I think the “brown in food is bad” is still vestigial crap from the days of flour manufacturers putting down brown flour as impure. C’mon people, brown is flavor! From the maillard reaction in cooking to brown sugar to brown (and black) bread, the best part of the food is the brown part! Although I have to agree about bananas, the really brown ones aren’t really my thing.
I wonder if they’re used to the plantain-type of bananas, which in my experience are inedibly bland until they’re near-black.
When you get a bruise on a part of your body, are you rotting?
I used to order the food for the dorms at the University of Texas. I had a banana color chart next to my desk. More than once, we had to send back a truck load of bananas to be gassed because they were too green. The bananas would usually be back in about an hour. Most product companies have chambers where they can gas bananas.
My brother and I heartily disagree on when a banana is good for eating. He likes green tip bananas. I insist on no green, yellow with brown spots.
This is the Dope at its finest – thanks for the knowledge 
Now I wonder if ethylene is one of those ‘supertaster’ things, like cilantro.
When we visit Hawaii we make sure we visit a farmers’ market or two. I buy actual tree-ripened, hard-to-find local strains of bananas and we have a feast. Yes, there was a variety that wasn’t truly ripe unless it was quite blackened. I expected it to be brown and mushy under the peel, but it was perfect and barely ripe and delicious.
You can’t find anything like these on the mainland.