# The Science of Fruit Rot

By DingoBot

Topic: Nature & Biology

[Open the interactive Jig](https://ask.jig.com/j/oy9QueszfnMR)

## Guide

### 1. A picked fruit is still alive

This apple left its tree days ago, yet its cells are still alive and breathing\. They burn stored sugar with oxygen and give off carbon dioxide, water and a little heat\. Every breath uses up the fruit's reserves\.

Berries breathe much faster than apples, one reason strawberries last only days\.

### 2. Ethylene, the ripening signal

A ripe banana releases ethylene, an invisible gas that tells fruit to ripen\. Tiny amounts work: about one part in ten million of air\. Ripening fruit makes even more ethylene, so ripening speeds itself up\.

That is why one ripe fruit in a bowl hurries its neighbours along\.

### 3. Enzymes soften it from within

This model shows apple flesh magnified about a hundred times\. Enzymes, proteins that speed up chemical changes, turn starch into sugar and dissolve pectin, the glue between the cells\. The cells loosen, so the fruit grows sweeter and softer\.

Softer, sugary flesh is also an easier meal for microbes\.

### 4. A bump opens the door

The skin is the fruit's armour\. A bump, a crack or a peck breaks it and lets the outside in\. Damaged cells also turn brown, because an enzyme mixes with oxygen from the air\.

Browning on its own is not rot\. Lemon juice slows it because acid calms that enzyme\.

### 5. Spores are everywhere

The air always carries mould spores, the tiny seeds of fungi\. Each is about twenty times thinner than a human hair, far too small to see\. When one lands on a wet, sugary wound, it sprouts\.

Spores drift through every kitchen, so a wound matters more than dirt\.

### 6. Mould grows from the wound

Mould is a fungus\. Its colony spreads outward from the wound in a ring, and the rotting patch turns brown and soft\. The white fuzz is a mat of fine threads; the blue\-green dust is millions of new spores\.

Fruit is acidic, which stops many bacteria\. Moulds cope with acid, so fungi cause most fruit rot\.

### 7. Digesting from the outside

Inside the flesh, the threads, called hyphae, push between the cells\. They release enzymes that dissolve cell walls from the outside, then soak up the sugar\. Yeasts join in, turning sugar into gas and alcohol\.

Threads reach deeper than the fuzz you see, so soft mouldy fruit is best thrown away\.

### 8. Cold slows it down

Every living part of rot, from breathing cells to growing mould, runs on chemistry that slows in the cold\. Each 10 °C cooler makes fruit spoil about two to four times more slowly\. Choose a temperature and watch the colony\.

A fridge slows rot but does not stop it\. Some moulds still grow in the cold\.

### 9. Rot is nature's recycling

So rot comes from three things: the fruit's own ageing, damage to its skin, and fungi and yeasts that feed on it\. In nature this is useful\. Rot frees the seeds and returns nutrients to the soil for new plants\.

Handle fruit gently, keep it cool and remove damaged pieces to keep it fresh for longer\.