How can adding lemon juice prevent peeled fruits like apples from browning?

Question

Peeled apples turning brown? Learn how a little lemon juice can prevent oxidation, keeping your peeled fruits looking fresh and appetizing.

Answer 1

Adding lemon juice to peeled fruits like apples prevents browning because the citric acid in lemon juice inhibits the enzyme polyphenol oxidase (PPO) responsible for oxidation, and the low pH slows down the browning reaction.

Detailed Explanation:

When fruits like apples are peeled or cut, their cells are damaged, releasing enzymes like polyphenol oxidase (PPO). This enzyme reacts with phenolic compounds present in the fruit in the presence of oxygen, leading to oxidation. Oxidation causes the fruit to turn brown, a process known as enzymatic browning.

Lemon juice contains citric acid, which acts as a natural inhibitor of PPO. Citric acid works in two ways:

1. Enzyme Inhibition: Citric acid binds to the active site of the PPO enzyme, preventing it from reacting with the phenolic compounds. This effectively slows down or stops the oxidation process.
2. pH Reduction: Lemon juice is acidic, lowering the pH of the fruit's surface. PPO enzymes function optimally at a neutral pH. By lowering the pH, lemon juice creates an environment where the enzyme is less active, further inhibiting browning.

Therefore, coating peeled or cut fruits with lemon juice significantly reduces or prevents enzymatic browning, keeping them looking fresh and appealing for a longer period.

Pro Tip:

For the best results, dilute the lemon juice with a little water before applying it to the fruit. This prevents the lemon flavor from overpowering the fruit's natural taste, while still providing sufficient protection against browning.