prompter: 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?

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.

prompter: What chemical compounds can be found in these enzymes? Do they occur anywhere else in nature? Is is possible to isolate and harvest these enzymes at home?

assistant: The enzyme that causes browning in apples is called polyphenol oxidase (PPO). PPO is also found in many other fruits and vegetables. Isolating and harvesting PPO at home would likely be difficult as it requires laboratory equipment and expertise in enzyme extraction and purification.

assistant: The apple core turns brown due to the reaction of oxygen with the enzymes in the apple. This reaction, called oxidation, causes the apple's flesh to turn brown.

prompter: Are there fruits that do not turn brown after being cut? I will like to have explanation why if there such fruits.

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.

assistant: citrus fruits do not get brown after being cut.
their content is incapsuled and protected fron the oxygen in the environment.
btw, browning is totaly natural and is an indicator that your fruit is good to eat and did not go though a process of artificial preservation.

assistant: When you cut an apple you allow the oxygen in the air to get in touch with the pulp. All plant tissues contain enzymes that oxidize the polyphenols present in compound tissues, and the resulting compound binds to proteins causing the brownish-reddish color.

prompter: I understand. Now why do banana peels go brown so fast after you peel the banana?

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.

assistant: Banana peels turn brown so quickly after being peeled because of the process of oxidation. Oxidation occurs when the enzymes in the banana interact with the air, causing a chemical reaction that results in the discoloration of the peel.

When a banana is peeled, its flesh is exposed to the air, which triggers the enzymes in the banana to start breaking down the starch into simple sugars. This process is known as ripening and is what causes the banana to become sweeter over time.

However, as the enzymes break down the starch, they also produce hydrogen peroxide, which reacts with other substances in the banana to cause discoloration. This discoloration is what makes the banana peel turn brown so quickly after being peeled.

To slow down this process, you can try storing the banana in an airtight container or wrapping it in plastic wrap. This will reduce the amount of air that the banana is exposed to, which can slow down the oxidation process and prevent the banana peel from turning brown as quickly.

assistant: A peeled banana turns brown after some time specially during the summer and in warm temperatures. The banana skin has the enzyme polyphenol oxidase which, when the banana is peeled, comes in contact with the atmospheric oxygen and gets oxidized. A brown polymer is formed which blackens the skin.