Learn why apples turn brown after cutting and discover simple tricks for apple browning prevention. Keep your apple slices fresh for hours.
1 Answer
Apples brown after slicing due to an enzyme called polyphenol oxidase (PPO) reacting with oxygen in the air. You can prevent this by inhibiting the enzyme or creating a barrier to oxygen.
Detailed Explanation:
When an apple is cut, cells are damaged, releasing enzymes and compounds within the apple tissue. One of these enzymes, polyphenol oxidase (PPO), reacts with phenolic compounds (naturally present in the apple) in the presence of oxygen. This reaction, known as enzymatic browning, results in the formation of melanins, which are brown pigments. The browning is a natural oxidation process, similar to rust forming on iron. To prevent browning, you need to either slow down or stop the enzymatic reaction or prevent the apple from being exposed to oxygen. Here are several methods:
Acidic Juices: Soaking apple slices in lemon juice, lime juice, orange juice, or pineapple juice lowers the pH, inhibiting the PPO enzyme. The citric acid in these juices is particularly effective.
Salt Water: A mild salt water solution (about 1/2 teaspoon of salt per cup of water) can also slow down browning. Rinse the apple slices after soaking to remove the salty taste.
Honey Solution: Dissolving honey in water creates a solution that contains peptides that can inhibit the PPO enzyme.
Sugar Syrup: Coating the apple slices in a sugar syrup creates a barrier that prevents oxygen from reaching the apple tissue.
Blanching: Briefly immersing apple slices in boiling water (blanching) deactivates the PPO enzyme. However, this will slightly soften the apple.
Proper Storage: Storing sliced apples in an airtight container or bag in the refrigerator slows down the oxidation process.
Pro Tip:
When using lemon juice, dilute it slightly with water to avoid making the apple slices too tart. A ratio of 1 part lemon juice to 3 parts water is usually sufficient.