ripening

Ripening is the series of physiological and biochemical changes that transform immature fruits and some vegetables into edible, aromatic, and flavorful produce. During ripening, colors change as pigments are synthesized or degraded, textures soften due to cell wall modification, and sugars accumulate while acids decline. Aroma compounds and volatile esters develop, contributing to characteristic flavors. In nature, ripening also affects seed dispersal by making fruit more attractive to animals.

Most fleshy fruits are climacteric, characterized by a rise in respiration and a large increase in ethylene production. Ethylene acts as a hormonal signal that coordinates many ripening reactions, including changes in color, texture, sugar/acid balance, and aroma. Non-climacteric fruits, such as grapes and citrus, do not show this respiratory peak or ethylene surge, and ripening proceeds without a marked respiratory burst.

Key biochemical changes include breakdown of starch into sugars, degradation of pectin and other cell-wall polysaccharides leading to softening, and production of volatile compounds derived from lipids and amino acids. Photosynthesis stops in many fruits; chlorophyll degrades to reveal carotenoids and anthocyanins that tint the fruit. Temperature, light exposure, and atmospheric composition influence ripening rates.

Postharvest management uses controlled atmosphere storage, low temperatures, and careful ethylene management to delay or synchronize ripening, extending shelf life. Unauthorized or premature exposure to ethylene can accelerate overripening, while refrigeration can slow ripening but may cause chilling injury in sensitive species. Ripening timing is managed in agriculture and food industries to optimize texture, flavor, and nutritional quality at the point of sale.