About Catechol in Bananas

Have you ever attempted to take a bite of a banana, forgotten it for a while, and then picked it up again only to notice that during the time period you had left it, it had become an unsightly shade of brown? Why exactly do bananas change color so drastically during a span of just a mere few minutes? This is because of an enzyme called catechol oxidase.

Function

• Bananas will turn brown because of the enzyme catechol oxidase. Catechol oxidase is very easily extracted from bananas. This enzyme converts catechol into a yellow pigment. Then, oxygen in the air turns the yellow colored pigment into the brown colored compound, melanin.

Expert Insight

• Browning of fruit occurs because of a chemical reaction between catechol and oxygen. The substance that this reaction produces is called benzoquinone, which is a brown compound that is toxic to bacteria. When the fruit peel is ruined, oxygen can then react with the catechol, thus defending the fruit.

Potential

• Bananas are not the only fruit that contain catechol; apples do as well. If you have noticed, apples also undergo a very similar "browning" process due to contact with oxygen. There is one way to protect fruit, and that is by using nitrogen. It can insulate bananas and apples, extending the shelf lives of the fruits by not letting oxygen come into contact with them.

Types

• Catechol oxidase has various different, alternate names. These names include diphenol oxidase, polyphenol oxidase and tyrosinase. Their reactions are catalyzed by EC 1.14.18.1, which is an enzyme nomenclature. It is rather difficult to distinguish and tell the enzymes apart after this process. It is necessary to be able to tell the enzymes apart to understand the reactions of the chemicals upon exposure to air.

Considerations

• If you do not want your bananas to turn brown rapidly, then do not keep them at the average room temperature of 78 degrees. If you maintain them in temperatures lower than 78 degrees, they will not turn brown as quickly. If you get bananas and test out this theory, you will notice that it is true and bananas in lower temperatures remain their original color much longer.