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What Happens to an Apple When It Spoils?

Scientifically speaking, the sole purpose of fruit is to spread its seed and perpetuate a species. Normally, animals consume the fruit and expose the seed by excreting it in their feces. The moment a piece of fruit is pulled from its tree or vine, it no longer receives nutrients and begins to ripen and eventually rot. All fruit, including apples, will rot if they are not consumed, although the amount of time it takes depends on the type of fruit. There are a number of processes that occur both inside fruit and on the surface that contribute to it spoiling or rotting.

Ethylene Gas Emission
- Ethylene gas is a natural growth hormone produced by plant tissue. Most fruits emit ethylene gas in varying concentrations. Apples emit high levels of ethylene gas, which can speed the ripening of fruits by placing both pieces of fruit in a paper bag for a couple of days. Storing fruit and other produce close together raises the concentration of ethylene gas, thereby speeding up ripening and spoiling.
Oxidation
- Oxidation is the reaction that occurs between oxygen in the environment with any substance it comes in contact with. Examples of oxidation include metal rusting, copper turning green and apples and other fruit turning brown when cut open. Oxidation occurs in apples wherever bruising has occurred or where small punctures or cuts are made in the fruit. This damage could be the result of improper handling, or insect or animal damage. The damage caused by oxidation will spread throughout the apple if left untouched, resulting in spoilage.
Microbial Infection
- Apples are also subjected to a wide variety of microbial pathogens, including molds, yeasts and bacteria that colonize the fruit as it ripens and contribute to spoilage. Warm, moist conditions create a safe haven for these pathogens and promote spoiling. These pathogens take advantage of damage that has occurred to the apple and enter the flesh where they live and reproduce, causing the apple to rot.
Sugar Formation
- As apples and other fruits mature, enzymes in the fruit's flesh break the starches down into sugars. This provides the fruit's sweet taste and encourages animals to eat it and release the seeds. These sugars provide food for yeast, mold and bacteria that colonize the fruit and lead the way for fermentation to occur.

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