Ethene: the ripening gas

Have you ever wondered what makes your fruits ripen? How does it know to ripen and change appearance? And how can you make this process faster so you can enjoy your fruits?

The mysterious agent behind this chemical reaction is the gas ethene!

Ethene (also known as ethylene) is a simple hydrocarbon from the alkene family. Under standard conditions it is a colourless gas with a sweet odour and is highly flammable. In the ripening process in fruits, it works alongside other hormones and signals as the fruit matures.

In comparison to the simple gaseous hydrocarbon ethene, most other hormones are complex organic molecules such as lipids, proteins and steroids.

Ethene is a volatile signalling molecule which easily diffuses through the air and can trigger effect such as fruit ripening and leaf senescence (natural aging process of leaves) within and between plants/fruits.

There are 2 groups of fruits: climacteric and non-climacteric fruits.

Climacteric fruits such apples and bananas can ripen after harvest, they produce ethene in an autocatalysis reaction. As respiration increases so does ethene production in the fruit; this catalyses the production of more ethene and accelerates ripening.

This is why putting a ripening banana next to unripe fruits will speed up their ripening process!

It triggers a change in colour, softening of the fruits as well as secretion of aromatic compounds that give fruits their appealing scents

 

Non-climacteric fruits such as strawberries and grapes don't respond to ethene for ripening and instead ripen while still attached to the plant. These fruits' ripening is more dependent on external factors like light and temperature.

Ethene is not only released in fruit ripening but can be released as a stress response to help the plant survive and adapt to various environmental changes. For example when there is physical damage to the plant a spike in ethene production induces healing and can trigger formation of protective barriers. Release of ethene can close stomata to reduce water loss when the plant experiences drought and water stress.

Transport of globally sourced fruits means that harvesters pick fruits while they are still unripe and then artificially ripen them using ethene gas once they reach their destination. This triggers natural ripening and currently has no harmful effects on consumers.

Ethene is a gaseous plant hormone that plays a large role in our eating habits. Without it we wouldn't be able to enjoy fruits such as apples and bananas or globally sourced fruits like mangoes.

Next time you eat a sweet, ripe banana you can appreciate the work of ethene!