(Chemistry for ages 5+)
Have you ever sliced up an apple to pack in your lunch box, only to pull it out at lunch time and see it’s turned brown? That doesn’t seem very appetizing! What even makes your apple turn brown, and how can you keep it looking fresh longer?
The video above shows one way to experiment with different liquids that might protect your apples. Here’s how you can try it at home:
4 pipettes or spoons
Napkins or paper towels
Adult supervision (Adult supervision at all times please)
- Start by cutting your apple into slices and placing the slices on your napkins or paper towels. Place a label near each slice to remember which kind of liquid you are going to test on it.
- Using a pipette or spoon, cover one apple slice in water. You do not need a ton of liquid, but you want enough to coat the apple slice.
- Next, repeat step 3 but with the lemon juice.
- Again, repeat step 3 with vinegar.
- Finally, repeat step 3 with a mixture of 1 tablespoon of baking soda in 1 cup of water.
- Leave your apple slices undisturbed for 1 hour.
- After the hour is over, check to see how your apple slices fared with the different liquid coatings. What do you notice? With which liquid did the apple slice turn the most brown? What about the least brown?
Apples turn brown when they are exposed to the air because of a process called oxidation. Apples, and some other foods like pears, bananas, and potatoes, have an enzyme called polyphenol oxidase.
When this enzyme encounters oxygen, like when you cut it up and the fleshy inside is exposed to fresh air, they go through the oxidation reaction which releases melanin and turns the apple brown.