[hevi_jos]

It is more complex than that.

Japan is not a producer of fruits. They come from far away. This means they have to transport it economically, that means they are transported by sea.

That means bananas are green when collected and sent to Japan, because transporting it by sea takes a long time.

Bananas naturally release CH4 that actually makes the fruit mature and spoils it. So they have to absorb it or diffuse during transport, then add it in Japan.

But if they add it in Japan, the fruit does not mature entirely, only the external side, so it is a good idea to add an artificial atmosphere of some kind.

[m0xte]

In the UK they come in large boxes by ship unwrapped. They are green when they arrive. I’m sure japan can manage that.

I suspect it’s a social thing rather than a necessity.

[twic]

Nitpick: it's C2H4, ethene. CH4 is methane. You can power rockets with that, but not ripen bananas.

[elhudy]

Thank you for this info - very interesting.