ripen

Ripen is the process by which fruits and other plant organs develop the characteristics of full maturity, including enhanced flavor and aroma, color change, softening texture, and often increased sugar content. Ripening is distinct from maturation in that maturation refers to reaching full size or developmental stage, while ripening emphasizes the qualitative changes that make the produce more palatable and metabolically active.

Biology and categories. Fruits are commonly classified as climacteric or non-climacteric with respect to ripening. Climacteric fruits, such as bananas, apples, tomatoes, peaches, and avocados, exhibit a rise in respiration rate and a burst of ethylene production during ripening, which accelerates the process. Non-climacteric fruits, including grapes, citrus, strawberries, and melons, ripen gradually without a marked respiratory surge and rely less on ethylene for their changes.

Biochemical changes. Ripening involves enzymatic breakdown of starches into sugars, degradation of pectin and other cell-wall components, and the production of volatile compounds that contribute to aroma. Pigments may shift from green to yellow, orange, or red as chlorophyll degrades and carotenoids or anthocyanins accumulate. Ethylene, a plant hormone produced endogenously, acts as a key regulator in many climacteric fruits; external ethylene exposure can also induce or speed ripening.

Practical implications. Postharvest handling uses knowledge of ripening to balance shelf life and quality. Some fruits are harvested unripe and ripen during transport or at retail, while others are kept under conditions (temperature, atmosphere) that delay ripening. Temperature and gas composition, notably ethylene levels, influence the onset and rate of ripening.