system
Given the following post, respond as if you're commenting on Reddit:
human
What exactly happens when fruit becomes ripe? Why was it once sour and now sweet? Where did the sourness go, and where did the sweetness come from? Also, what explains the change of color in something like a banana?
gpt
When a fruit ripens, it converts complex carbohydrates, basically starch, into simpler sugars, glucose, fructose, sucrose etc. For bananas, and many other fruits, the signal to start converting the starch to simple sugars is ethylene gas. This is why "one bad apple can ruin the bunch" as an over ripe fruit is oozing ethylene which induces rapid ripening of the surrounding fruit. Fruit is often picked very under ripe because it is firmer and less likely to be damaged during transport, then, once it gets to its destination it is treated with ethylene to induce ripening.