Cut surface of fruits and vegatables often become dark because

Options

A. Dirty knife makes it dark
B. Oxidation of acid in the presence of trace of iron from the knife
makes it dark
C. Dust of the air makes it dark
D. None of the above

Answer

To answer the question "Cut surface of fruits and vegetables often become dark because," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components**: Understand that fruits and vegetables contain certain compounds that can react when exposed to air. One such compound is tannic acid, which is a type of polyphenol.

2. **Understand the Browning Process**: When fruits and vegetables are cut, their cells are damaged, exposing the inner tissues to oxygen in the air. This exposure triggers a chemical reaction known as oxidation.

3. **Role of the Knife**: The knife used to cut the fruits and vegetables may contain traces of iron. This iron can catalyze the oxidation process, enhancing the browning effect.

4. **Chemical Reaction**: The oxidation of tannic acid (or polyphenols) in the presence of oxygen and iron leads to the formation of dark-colored compounds, which results in the darkening of the cut surfaces.

5. **Conclusion**: Therefore, the correct explanation for the darkening of cut fruits and vegetables is that it is caused by the oxidation of acid (tannic acid) in the presence of trace amounts of iron from the knife.

### Final Answer:
Cut surfaces of fruits and vegetables often become dark because oxidation of acid in the presence of trace of iron from the knife makes it dark.

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