How does an apple not change color after being cut

The discoloration of apples after cutting can be delayed by soaking them in salt water, lemon water, or wrapping them with plastic wrap. The oxidation of apple slices is mainly caused by the contact between polyphenol oxidase and oxygen, and the key is to adopt physical isolation or acidic environment to inhibit enzyme activity.

1. Soaking in Salt Water

Soak the cut apple slices in 3% diluted salt water for 1-2 minutes. Sodium ions can temporarily inhibit polyphenol oxidase activity. The concentration of salt water should not be too high, otherwise it will affect the original flavor of the apple. After soaking, rinse the surface salt with cold water. This method is suitable for apple chunks that require short-term preservation, such as making fruit platters or children's bento boxes.

2. Lemon water treatment

Use fresh lemon juice and water in a 1:4 ratio to prepare a solution, and soak the apple slices for 30 seconds. Citric acid can lower the pH value and create an acidic environment, while vitamin C can also act as a reducing agent to directly block oxidation reactions. This method will make the surface of the apple slightly sour, suitable for pairing with yogurt or salad, while increasing vitamin C intake.

3. Cover with honey water

Prepare a solution by mixing 1 tablespoon of honey with 200 milliliters of warm water, and immerse the sliced apples in it. The natural antioxidants and sugars contained in honey can form a protective film on the surface of apples, delaying oxidation and increasing sweetness. It should be noted that diabetes patients should control the dosage, and the soaking time should not exceed 5 minutes to avoid soft and rotten pulp.

4. Vacuum isolation

Wrap the cut surface tightly with cling film or place it in a vacuum preservation box to remove air, and physically isolate oxygen to prevent enzymatic browning. This method can maintain the original flavor of apples without adding any substances, making it suitable for people who are sensitive to taste. Ensure that the packaging is completely sealed, and it is recommended to consume it within 2 hours after opening.

5. Low temperature refrigeration

After cutting, immediately put it in a refrigerator below 4 ℃ for refrigeration. Low temperature can significantly reduce enzyme activity. The use of a covered fresh-keeping box is more effective, and the refrigeration storage time should not exceed 6 hours. If there are slight water droplets on the surface after taking it out of the refrigerator, use kitchen paper to absorb and dry it to restore its crisp taste. The essence of apple oxidation discoloration is the generation of quinone pigments by phenolic substances under enzymatic action. Although it does not affect food safety, it can reduce the appearance and some nutrient content. In addition to the above methods, it is recommended to cut and eat immediately to maximize nutrient retention. If long-term storage is required, apples can be mixed with other fruits rich in vitamin C, such as oranges and kiwis, to use synergistic antioxidant effects to delay discoloration. Use ceramic or stainless steel knives during processing to avoid iron ion catalyzed oxidation reactions. For apples that have undergone slight discoloration, it is still safe to consume after removing the surface layer by 1-2 millimeters.