Question

1 mL of very dilute starch solution (1% starch solution) is taken in a test-tube and 1 mL of saliva is added to it. After keeping this mixture for half an hour, a few drops of dilute iodine solution are added to the test-tube. There is no change in colour on adding iodine solution. What does this tell you about the action of saliva on starch?

Answer 1

When a mixture of dilute starch solution and saliva is kept in a test tube for half an hour, it does not produce a blue-black colour on adding iodine solution. This shows that no starch is left in the test tube. It indicates that the saliva has broken down the starch into another substance that does not react with iodine solution. Saliva contains the enzyme amylase, which converts starch into sugar.