CBSE Class 10 Science 2020 · Paper 31/4/1 · Question 15(b)

The fats and oils are slowly oxidised by the oxygen of the air and the food becomes rancid; this change is called rancidity. Two observable changes: (1) the food gives out an unpleasant smell; (2) its taste changes and becomes unpleasant. Three ways to prevent it: (1) add antioxidants, substances that prevent oxidation, to the food; (2) keep the food in airtight containers; (3) flush packets of food such as chips with nitrogen gas.