Why Does a Slice of Apple Turn Brown?

When an apple is cut or bruised, an enzyme called polyphenol oxidase is released from the damaged cells. This enzyme reacts with oxygen in the air, resulting in a chemical reaction that causes the apple to turn brown. This process is known as oxidation.

Factors Affecting the Browning Process:

- Exposure to Oxygen: The main factor that triggers the browning of an apple slice is exposure to oxygen in the air. The more surface area of the apple is exposed, the faster the browning process occurs.
- Enzymatic Activity: The enzyme polyphenol oxidase present in the apple catalyzes the oxidation reaction, leading to the formation of brown pigments.
- Acid Content: Apples with higher acid content tend to brown more slowly than those with lower acid content. Acidic substances like lemon juice can help slow down the browning process by inhibiting the enzyme activity.
- Temperature: Browning occurs more rapidly at higher temperatures due to increased enzyme activity. Storing apple slices in the refrigerator can help slow down the browning process.

Preventing Apple Browning:

- Acidulated Water: Submerging apple slices in a solution of water and lemon juice or vinegar can help prevent browning by lowering the pH of the surface and inhibiting enzyme activity.
- Blanching: Briefly blanching apple slices in hot water can denature the enzyme and slow down the browning process.
- Antioxidants: Applying substances rich in antioxidants, such as honey or ascorbic acid (vitamin C), can help prevent oxidation and browning of apple slices.

By understanding the factors that contribute to apple browning and implementing preventive measures, you can enjoy fresh-looking apple slices for a longer period.