Ethylene is a naturally occurring gaseous plant hormone that influences fruit ripening and maturation. Understanding its role is important for managing fruit freshness and optimizing storage.
How Ethylene Ripens Fruit
Ethylene initiates a series of biological changes within fruit, transforming it from an unripe to a ripe state. This gaseous hormone triggers the conversion of starches into sugars, which increases the fruit’s sweetness. It also promotes the breakdown of cell walls, leading to the softening of the fruit’s flesh and skin. Simultaneously, ethylene influences the development of characteristic aromas and flavors, enhancing the overall sensory experience.
The presence of ethylene acts as a signal, prompting not only the fruit producing it but also nearby fruits to accelerate their ripening. This self-amplifying production, known as autocatalysis, means that an initial burst of ethylene can lead to a significant increase in its own production, further speeding the process. This directly impacts fruit quality, including changes in color, firmness, and overall taste.
Fruits That Produce and React to Ethylene
Fruits are generally categorized based on their ethylene production and response during ripening. Climacteric fruits are those that continue to ripen after being picked, characterized by a significant increase in both respiration rate and ethylene production as they mature. This group includes many common fruits such as apples, bananas, avocados, peaches, pears, plums, and tomatoes. Melons like cantaloupe and honeydew also fall into this category.
Conversely, non-climacteric fruits do not ripen further once harvested and produce very little ethylene. These fruits are, however, sensitive to external ethylene and can experience accelerated spoilage in its presence. Examples include berries (strawberries, blueberries, raspberries), grapes, cherries, citrus fruits (oranges, lemons, grapefruits), pineapples, and cucumbers. Many leafy greens and most vegetables also belong to this sensitive group.
Smart Storage and Ripening Strategies
Leveraging the knowledge of ethylene production can help manage fruit ripeness and extend shelf life. To accelerate the ripening of an unripe climacteric fruit, placing it in a paper bag with an ethylene-producing fruit like an apple or banana can be effective. The enclosed space concentrates the ethylene gas, speeding ripening. This method is often used for avocados or unripe peaches.
To slow ripening and prevent premature spoilage, separate ethylene-producing fruits from ethylene-sensitive ones. Storing bananas, which produce considerable ethylene, away from other fruits extends the freshness of sensitive produce. Keeping delicate items like leafy greens, broccoli, and berries separate from apples or tomatoes in the refrigerator helps maintain their quality.