How do you prevent a cut apple from turning brown?
Things Required:
An apple
Lemon juice
Directions:
Cut the apple into quarters. Let one of the quarters remain on the kitchen table. Place another in the refrigerator. Sprinkle lemon juice on the other two quarters. Place one of these on the table and the other in the refrigerator.
This Is What Happens:
The untreated apple on the table turns brown first. The apple with the lemon juice in the refrigerator stays fresh longest.
Science Behind It:
When you cut into an apple, you tear its cells, releasing an enzyme called polyphenoloxidase. The enzyme speeds up the process by which compounds in the apple (phenols) combine with oxygen from the air. This is what produces the brownish pigment that darkens the fruit and makes it taste bad.
The enzyme works more slowly at cold temperatures than at room temperatures. It works even more slowly in an acid like lemon juice, which completely inactivates it.
If you don’t have any lemons around, you can use orange juice, but lemon juice is better because it contains more acid.