A science teacher wrote 3 statements about rancidity:
(i)When fats and oils are reduced, they become rancid
(ii) In chips packet, rancidity is prevented by oxygen
(iii) Rancidity is prevented by adding antioxidants.
Select the correct option.
A.(i)
B. (ii) and (iii)
C. (iii)
D. (i), (ii) and (iii)

Hint: Food items are perishable and get spoiled when exposed for a longer time to the atmosphere. Foods contain nutrients in the form of carbohydrates, proteins and fats. Among them fats are responsible for spoiling the food due to their reaction in the atmospheric oxygen. This results in food being rancid.

Complete answer:
When food is kept for a long time, it is exposed to the atmosphere having oxygen and moisture. The unsaturated fats and oils that are present in the preparation of food, then react with the oxygen and get oxidized to saturated fats. This results in the rancidity of food that creates foul smell and taste with discoloration.
So, rancidity happens when the fats are oxidized, so statement (i) is incorrect.
The rancidity happens when oxidation occurs in presence of oxygen, so adding oxygen in food items cannot prevent rancidity. So, statement (ii) is incorrect.
On the contrary, rancidity can be prevented by adding antioxidants that reduce the oxygen activity and prevent oxidation.
Hence, the correct statement about rancidity is statement (iii).

So, option C is correct.

Note:
To prevent rancidity for chips, nitrogen gas is filled in the chips packets that preserve them and make them last longer. In the presence of nitrogen, the food does not reduce or oxidize. Antioxidants have the capability to prevent the free radical conversion of oxygen atoms that makes oxygen more reactive, hence preventing rancidity.