Experiment 28: Action of Enzymes on starch

  • To study the action of salivary amylase on starch solution

Materials required:

  • 1% starch solution
  • 1% iodine solution
  • saliva
  • a measuring cylinder
  • test tubes
  • a dropper
  • a spatula (or spoon)


  • Collect some saliva from the mouth cavity in a test tube. Add 10 mL water to it. Label this test tube as saliva solution (S)
  • Take 2 mL of 1% starch solution in two different test tubes. Label the test tubes as A and B
  • Add 1 mL diluted saliva from S to B. Shake thoroughly. Do not add anything to A
  • After about five minutes using a dropper, take five drops of solution from A and add two drops of 1% iodine solution. Mix the solution by stirring. Observe the colour of the mixture and record your observation
  • Take five drops from B. Add two drops of 1% iodine solution to it. Record your observation
  • Repeat steps 4 and 5, after five, ten, fifteen and twenty minutes

Observations and Findings:

  • It takes less time to reach achromic point at 37°C, as the enzyme is maximum active at this temperature, while at higher and lower temperatures more time is taken to reach the achromic point.


  • Over time, salivary amylase breaks starch and converts it into sugar. We observe that starch solution turns iodine blue in the beginning but no change in color happens later, suggesting that starch has been converted to sugar


  • Saliva is one of the digestive juices secreted by salivary glands present in the mouth cavity. It contains an enzyme called salivary amylase (ptyalin) that acts on starch and converts it into simpler sugars.