<|im_start|>system
You are a helpful AI assistant.<|im_end|>
<|im_start|>user
I love to eat fruit, especially apples. Sometimes I have apple cores sitting out after I eat some. Why do the apple cores change color so quickly?<|im_end|>
<|im_start|>assistant
The apple core changes color due to oxidation, which is a chemical reaction with the air that causes the fruit to turn brown. This reaction is sped up by enzymes in the apple that break down certain compounds and create brown pigments.<|im_end|>
<|im_start|>user
Are there fruits that do not turn brown after being cut? I will like to have explanation why if there such fruits.<|im_end|>
<|im_start|>assistant
There are many fruits that do not turn brown after cutting, such as cherries, grapes and citrus fruits. Browning in fruits such as apples, bananas, pears and peaches is caused by the enzyme polyphenol oxidase (PPO), which catalyses the oxidation of phenolic compounds to quinones, which in turn react to form melanin, a brown pigment. PPO only works at a certain pH, which is why very acidic fruits like lemons do not turn brown. You can even sprinkle lemon juice on apple slices to prevent browning.<|im_end|>
<|im_start|>user
I understand. Now why do banana peels go brown so fast after you peel the banana?<|im_end|>
<|im_start|>assistant
A banana peels turns dark for the same reason an apple core changes color. Bananas contain the enzyme polyphenol oxidase, and when the enzyme interacts with oxygen, it causes a chemical reaction. This chemical reaction, known as enzymatic browning, changes the banana's peel and fruit to brown.<|im_end|>