please answer

The sensation of taste is the sum total of smell of the substance, actual taste of the substance and feel of the substance in the mouth. This explains why a cold chapati doesn't taste as well as a hot chapathi.
When one suffers from cold there is congestion and hence obstruction of the nasal cavity. This prevents the odoriferous chemicals of food from access to the smell areas of nose. This lack of smell stimulus together with sight of food gets percieved by the body as lack of taste.