Why do fruit go really soft over time, like when they over-ripe?


Why do fruit go really soft over time, like when they over-ripe?

In: Biology

Rotting. Or [Decomposition “ the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts.](https://en.m.wikipedia.org/wiki/Decomposition)

Fungi and bacteria slowly eat the fruit. Eating breaks down the structural proteins just like digestion in your stomach. Less proteins = less structure = less rigidity = more softening

Close answers, but not quite.

Fruit is full of sugar molecules that have been linked together into long, branching chains. These long sugar chains are called “starch” or “carbohydrates”, and they provide rigidity and structure to the fruit. Think of a green banana, raw potatoes or fresh corn, they are full of starch and are extremely stiff. Even though it’s made of sugar, starch are different enough molecules that our taste buds no longer recognize them as sweet.

In response to a variety of factors, those starches are slowly broken down into simple sugars. One example is Ethene gas. Ethene gas is produced by ripening bananas and promotes the breakdown of starch into sugars. If you place ripe bananas in a sealed container with unripe fruit, like apples, the apples will rapidly ripen.

Since sugars aren’t structural, like starches, the fruits will become softer.

Starches are also really difficult to metabolize, no organism can obtain energy directly from starch. They will first need to break it down into it’s constituent simple sugars. Humans do this with enzymes in our saliva and digestive system, but bacteria and fungi have limited ability to do this since they are so simple. Once the starch has become the process of turning into simple sugars the fruit comes a prime feeding ground for microorganisms and the decomposition process can start in earnest.