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Salivary Amylase and Starch Digestion

Introduction

Salivary amylase, an enzyme found in human saliva, is involved in the digestion of starch molecules. This technique shows how the action of this enzyme can be investigated.

Materials

• Clear test tubes.
• 1% starch solution (add one gram of soluble starch to
• 100ml of boiling water).
• Rubber bands.
• Iodine test solution.

WARNING HAZARD

Iodine is toxic,an irritant and will stain clothes. Wear rubber or medical gloves and use protective eyeware. Avoid contact with skin and eyes.

Method

Obtain a sample of saliva. Some people naturally produce a lot of saliva others need to be stimulated. An easy way to generate saliva is to chew on a clean rubber band (take extra care with young children).

Saliva is collected by drooling in to a test tube. Do not spit as this alters the sample.

Add 10 drops of saliva to a clean test tube then add 10 drops of the 1% starch solution.

The presence of starch can be detected by adding 2 drops of the iodine solution. If starch is present a black/dark blue color is formed. If there is a yellow color (caused by the iodine) no starch is present.

Material used in this proceedure can be diposed of down the sink.

Background Information

There are many enzymes involved in digestion of food. Probably the most accessible is Salivary Amylase which we all produce when eating. Amylase hydrolyses starch to form a sugar called maltose.

We can detect the presence of starch because the iodine forms a dark blue complex with the starch molecule.

Experiment Ideas

• Investigate the effect temperature has on starch digestion.
• Does the pH of the solution alter starch digestion? How does this relate to enzyme activity in the stomach?
• Is there a difference between enzyme activity in children and adults? What about smokers?