Does a ripe banana make others ripe faster?

Have you ever noticed that one ripe banana in a bag will make the others ripen faster? That’s chemistry! Ripening fruit releases ethylene gas (), a plant hormone that signals to nearby fruits to start ripening, too. This process breaks down starches into sugars (making the fruit sweeter) and changes its color. This process is a classic example of a positive feedback loop in biology.

Here’s a more detailed look at the chemical cascade that happens inside the fruit once it gets that ethylene signal.

💨 The Signal: Ethylene’s “Chain Reaction”

The process you mentioned is technically called “climacteric” ripening, which applies to fruits like bananas, apples, tomatoes, and avocados.

1. The Trigger: As a fruit like a banana begins to mature (or if it’s bruised or stressed), it starts to produce small amounts of ethylene gas.
2. The Signal: This ethylene gas diffuses out of the fruit and travels through the air to its neighbors.
3. The Reception: The nearby, unripe fruits have receptors that detect this ethylene.
4. The Cascade: Receiving this signal triggers a massive internal response in the unripe fruit. Crucially, it not only starts the ripening process but also causes the fruit to produce its own ethylene.

This creates a chain reaction: a little ethylene triggers more ethylene, which triggers even more ethylene, leading to a rapid, coordinated ripening of the whole bunch. This is why sealing a banana in a paper bag makes it ripen faster—it’s trapping and concentrating its own ethylene gas.

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🔬 The Internal Chemistry: What Ethylene Tells the Fruit to Do

When a fruit cell receives the ethylene signal, it activates specific genes. These genes tell the cell to start producing a variety of enzymes, which are the chemical “workers” that do the actual job of ripening.

Here are the three main changes they cause:

1. 🍌 Sweetness (Starch-to-Sugar Conversion)

• The Problem: Unripe fruit is bland and starchy. It’s filled with large, complex polysaccharides (starches), which are just long chains of glucose that our tongues can’t taste as sweet.
• The Enzyme: Ethylene activates enzymes like amylase.
• The Chemistry (Hydrolysis): Amylase breaks down those long starch chains (hydrolysis) into simple sugars, primarily fructose and glucose. These small, simple sugars are what taste sweet, dramatically changing the fruit’s flavor profile.

2. 🎨 Color Change (Chlorophyll Breakdown)

• The Problem: Unripe fruit is green because its skin is full of chlorophyll, the pigment used for photosynthesis.
• The Enzyme: Ethylene signals for enzymes like chlorophyllase to start breaking down the chlorophyll molecule.
• The Chemistry (Unmasking): As the green chlorophyll disappears, it “unmasks” other pigments that were already there but were simply hidden.
  • Carotenoids: These are responsible for the orange color
  • Anthocyanins: These are synthesized during ripening and create the reds

So, that one “bad influence” banana isn’t just releasing a gas; it’s initiating a complete, enzyme-driven chemical transformation in its neighbors, turning them from hard, bland, and green into the soft, sweet, and colorful fruits we love to eat.