Can the black garlic process 70°C, 85% humidity, 30+ days, apply to bananas? Will alkaline PH help?
You cannot make up your own fermentation recipes.
If you hold your bananas at these conditions, you won't get the same bacteria to grow on them that grow on garlic. And as you don't know which bacteria have grown, you don't know if they are pathogenic or not. One thing is for sure - the amount of bacteria you ingest will be sufficient to give you severe food poisoning, if they turn out to be pathogenic.
Bottom line, when doing fermentation, stick to proven recipes, and don't change them.