Ethylene is a simple, naturally occurring gaseous compound that acts as a plant hormone, serving as the primary internal signal for fruit maturation. This colorless and odorless gas regulates the final stages of a fruit’s development, triggering the complex changes associated with ripening. The production rate of this compound varies dramatically among different fruit types, which directly impacts their post-harvest life and how they should be handled.
Ethylene’s Role in Fruit Ripening
Ethylene initiates a cascade of biochemical reactions that transform a hard, unpalatable fruit into a soft, sweet, and aromatic food source. The gas triggers the breakdown of chlorophyll, causing the familiar shift in color from green to vibrant reds, yellows, or oranges. Simultaneously, ethylene activates enzymes, such as pectinase and cellulase, that soften the cell walls, giving the fruit its tender texture. Furthermore, ethylene promotes the conversion of complex starches into simple, sweet-tasting sugars like glucose and fructose. This process is a self-amplifying system in many fruits, where ethylene production stimulates the fruit to create even more of the gas.
Classifying Fruits by Ethylene Production
To manage fruit quality, produce is grouped into two distinct categories based on its physiological response to and production of ethylene. The first group, known as climacteric fruits, is characterized by a dramatic surge in both respiration and ethylene production during the ripening phase. This autocatalytic burst allows these fruits to continue and complete their ripening process after they have been harvested. The second category is non-climacteric fruits, which exhibit a different ripening pattern. Consequently, they must be allowed to ripen fully while still attached to the plant, as they will only slowly deteriorate once they are picked.
High Ethylene Producers The Top Sources
The fruits that produce the largest volumes of ethylene are overwhelmingly those classified as climacteric, with certain varieties standing out as the most prolific emitters. Apples and bananas are consistently cited as the highest producers, often releasing the gas at rates far exceeding other common climacteric fruits. Bananas are also extremely high producers, generating significant amounts of ethylene as they transition from green to yellow. Other major sources of the gas include avocados, peaches, and cantaloupe melons. For long-term storage, the concentration of ethylene in the fruit’s atmosphere must be kept below one part per million to prevent premature softening.
Practical Storage Strategies
To maximize the shelf life of ethylene-sensitive produce, it is necessary to store it physically separated from high-producing fruits. Ethylene-sensitive items include many vegetables, which can suffer from premature yellowing, softening, or sprouting when exposed to the gas:
- Leafy greens
- Broccoli
- Carrots
- Potatoes
Conversely, this knowledge can be used to accelerate the ripening of an underripe climacteric fruit, such as an avocado or pear. Placing the hard fruit in a brown paper bag along with a ripe, high-emitting fruit, like an apple or banana, traps the gas and concentrates its effect, rapidly triggering maturation.