Device an activity to prove that saliva helps in. digestion of starch.

Activity to show action of saliva on starch
Procedure:
(i) 1 mL of 1% starch solution is taken in two test tubes and labelled as A and B.
(ii) 1 mL of saliva is added to test tube A. Nothing is added to test tube B (control).
(iii) The test tubes are left undisturbed in safe place and similar conditions for about 30 minutes.
(iv) After about 30 minutes, a few drops of dilute iodine solution is added to each test tube.
Observations:
(a) In test tube A there no change in iodine solution i.e., solution remain brownish that is the colour of iodine solution. It means that starch is not present.
(b) In test tube B, the solution turns blue black. It proves presence of starch.
Conclusion:
Saliva has enzyme which can digest starch and convert into other carbohydrate (sugars).
Conclusion
In test tube A the saliva acts on the starch and break them down. whereas in test tube  B where no saliva is present the starch is not broken down.