Cut fruit turns brown fast, and it happens for a specific chemical reason, not because you did something wrong when you sliced it. In case you have been wondering why your fruit turns on you this quickly, you are not alone, and it is not just your imagination. According to a Penn State Extension fact sheet, that browning can be slowed with something most people already have on hand: vitamin C.
Why cut fruit turns into a sad brown mess so fast and the fix
When you cut open an apple, pear, peach, or banana, the flesh inside comes into contact with oxygen for the first time, and things spiral out of control practically immediately. According to a peer-reviewed study titled “Browning inhibition mechanisms by cysteine, ascorbic acid and citric acid, and identifying PPO-catechol-cysteine reaction products,” published in the Journal of Food Science and Technology, this reaction is caused by an enzyme named polyphenol oxidase, which reacts with some natural compounds in the fruit when oxygen enters, leading to the formation of brown pigments. No bacterial spoilage; it's an enzyme at work too zealously. However, no one would want to eat a plain old banana slice, even if it was "technically fine."
