Because my company website is read by both consumers and produce managers, I list the ethylene production and sensitivity for each fruit and vegetable. No matter how well I spell it out, I always get a consumer demanding to knowing what the strange sounding word means and why we put it on our produce.
Ethylene, the word itself conjures up smoke belching chemical plants. But that's the furthest from the truth. Ethylene is a nature gas that fruits emit during their ripening process. Ethylene triggers the fruit's ripening process.
Produce managers want to know how ethylene sensitive their produce is so that they don't overripen something. That's why you don't see avocados right next to bananas, unless the store wants to sell guacamole (produce joke). And that's why you put an unripe piece of fruit in a paper bag with an apple or banana (both emit high levels of ethylene). The ethylene gas emitted by the apple or banana helps the unripe fruit to ripen.
So ethylene is our friend. Sorry, I always wanted to say something like that.
Humans and plants have some things in common. A harvested fruit and vegetable is constantly breathing, using its energy reserves to take in oxygen and release carbon dioxide.
Plants also have hormones that regulate growth and development. Ethylene is one of these plant hormones and triggers the ripening process. Certain fruits continue to ripen after they are harvested. Like humans, plants can convert complex carbohydrates into simple sugars. Unlike humans, plants becoming sweeter in this process.
Papayas are a great example of this type of fruit. On the outside, the papaya is not the most cosmetically beautiful of fruit as it ages. But truly beauty is only skin deep; as it ages papayas get sweeter and sweeter. The grocery store cash register gal always looks askance at me as she rings up what has to be the ugliest fruit in the store. I don't care; once the skin comes off, it's the sweetest.
Avocados are another fruit that continues to ripen after harvesting. Avocados, like mangos and bananas, need to mature on the tree. They grow as big as they're going to get on the tree but only start to ripen when it's picked. So you never really eat 'just picked' avocados. Or I should say you'll never really enjoy eating 'just picked' avocados. You can barely cut them with a knife.
That's why Florida avocados, all 70+ types, aren't picked unless they have reached the optimum size for their type. Pickers go into the field with an avocado diameter measuring device. They only pick if the fruit measures beyond a certain size.