Describe an activity saliva in starch

Experiment to show the effect of saliva on starch

• Two test tubes were taken and were labeled A and B.
• In test tube A one teaspoon full of boiled rice was kept.
• In test tube B one teaspoon full of boiled rice which were chewed for 3-5 minutes were kept.
• 3-4 ml of water was added to both the tubes.
• Then 2-3 drops of iodine solution was added to both test tubes A and B.

Observation:

• The test tube A shows blue – black colour whereas test tube B does not show this colour.

Conclusion:

• Since test tube B has boiled rice which were chewed for 3-5 minutes, the saliva present in mouth has acted upon starch to break down into sugars. So it does not show any colour in presence of iodine solution.
• Boiled rice in test tube A has not been exposed to saliva, so starch is present which is indicated by blue-black colour on addition of iodine solution.