Why does the skin on a banana change as ripens?

As a banana ripens, several biochemical changes occur, including the breakdown of chlorophyll, the green pigment in plants. Chlorophyll degradation reveals the yellow pigments called carotenoids, which were always present in the banana peel but masked by the green color of chlorophyll.

Here's a more detailed explanation of the process:

1. Ethylene Production: Bananas produce ethylene gas as they ripen. Ethylene acts as a plant hormone responsible for triggering various ripening processes.

2. Chlorophyll Breakdown: Ethylene stimulates the activity of enzymes that break down chlorophyll molecules in the banana peel. Chlorophyll is responsible for the green color of unripe bananas. As chlorophyll breaks down, the green color fades, revealing the yellow pigments known as carotenoids.

3. Carotenoid Revelation: Carotenoids, mainly lutein and beta-carotene, are always present in banana peels but are initially masked by the dominant green color of chlorophyll. As chlorophyll breaks down, carotenoids become more visible, giving the banana its yellow color.

4. Starch Conversion: In unripe bananas, the primary carbohydrate is starch. During ripening, enzymes convert starch into simple sugars, primarily sucrose, glucose, and fructose. This conversion results in the softer texture and sweeter taste of ripe bananas.

5. Browning and Softening: As the banana continues to ripen, other complex biochemical changes occur, leading to skin browning and further softening of the fruit. These changes are driven by enzymatic reactions, the production of aroma compounds, and cell wall degradation.

Ultimately, the combination of chlorophyll degradation, carotenoid revelation, starch conversion, and other biochemical changes contributes to the changes in the skin color and overall ripening of a banana.