Physiological disorders in tropical and sub-tropical fruits are non-pathogenic abnormalities caused by environmental, nutritional, or handling factors rather than by pests or pathogens. These disorders significantly affect the quality, appearance, shelf life, and marketability of fruits, leading to considerable post-harvest losses. Understanding these disorders from the perspectives of food chemistry and physiology helps in developing better handling and storage practices to minimize the damage.

One of the common physiological disorders is chilling injury, which occurs when tropical fruits are exposed to temperatures lower than their optimal storage range. Tropical fruits like mango, papaya, banana, and avocado are sensitive to chilling because their metabolism is adapted to warmer climates. When chilled, their cell membranes lose fluidity due to changes in lipid composition, leading to increased permeability and ion leakage. This causes symptoms such as surface pitting, uneven ripening, browning, and increased susceptibility to decay. From a biochemical standpoint, chilling stress causes oxidative damage due to the accumulation of reactive oxygen species (ROS), which damage cell membranes, proteins, and nucleic acids. Enzymatic activities such as polyphenol oxidase (PPO) increase, resulting in enzymatic browning.

Another disorder common in these fruits is internal