Why Do Apples Rot?
Moist conditions or warm environment are conditions that will cause rotting. Moist condition provides more water for the biochemical reactions to occur that lead to fruit rotting. Heat will enhance the rotting process by acting as a catalyst of all the chemical reactions. Hot water will help rotting of fruits rapidly compared to that of cool water. If any other rotten fruit is there present near the un-ripened fruit the gas ethylene will spread from the rotten fruit to the other one and makes it also to start ripen and later rot. Ethylene is the hormone that exists in the ripened fruit. Ethylene has the capacity to recreate itself in the air surrounding the ripened fruit. So a ripened fruit because of ethylene becomes rotten with the exponential influence of this hormone, as ethylene reproduces itself. Rotting of apples might occur as an advanced stage to ripening. Apples can also rot due to oxidation. Oxidation occurs in apples during which time they turn into brown color because of oxidation. This is found to be caused by an enzyme called tyrosinase. Rotting of an apple can happen due to bacteria or fungi which do not depend on light. But change in temperature will definitely show its effect on ripening and further rotting of the apple. The sunlight has its effect on the phytochrome and effectively influences the synthesis of pigment. The red pigment is more generated as the fruit ripens and indicates that it is time for the apple fruit to be eaten and gradually rot as the ripening matures. The apple rot fungi are Penicillium expansum and Monilinia fructigena. They are necrotropic pathogens which destroy the apple fruit tissue. The enzyme polygalacturonase helps in rotting by destroying the pectin layer. These fungi basically infect the apple fruit through the incisions made already by the insects on the fruit. Therefore apples rot due to any one of the above mentioned reasons.