Ripe bananas release ethylene gas, which speeds up ripening in nearby fruit.

The longer version

Ethylene acts as a plant hormone, a small gaseous molecule that many fruits produce as they mature. Once a fruit begins making it, the gas diffuses into the air and binds to receptors in neighboring produce, triggering a cascade that softens cell walls, converts starch into sugar, and breaks down chlorophyll. This is why a ripe fruit sealed in a bag with firm ones hurries them along.

Commercial shippers manage the process by controlling temperature and ventilation, and some storage rooms scrub ethylene from the air. Cold slows both the production of the gas and the response to it. The same mechanism explains why one damaged apple in a bowl can spoil the rest fairly quickly, since wounding tissue releases a burst of the hormone.

Where this entry sits

Everyday ingredients turn out to be full of quiet chemistry and long history. This collection gathers short, plain explanations of how bread rises, why onions sting, where common spices originate, and how coffee, tea, and chocolate reached the modern kitchen. The full list sits on the Food and Drink page, where every entry is listed in order.