Question

Cut surfaces of fruit and vegetables often become dark because

• A. Dirty knife makes it dark.
• B. Oxidation of tannic 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 1

Answer: (B)

Oxidation of tannic acid in the presence of trace of iron from the knife makes it dark.

Tannic acid present in vegetables and fruits will undergo chemical reaction when the knife of iron is used to cut them. This gives a blackish colour. This is very clearly observed in the case of apples.