Action of Salivary Amylase on Starch

This demonstration shows how salivary amylase breaks down starch in cooked rice into simpler sugars like maltose. Students use chemical tests to identify starch and reducing sugars while learning about enzyme activity and its dependence on conditions such as temperature.

1. Cook some white rice until soft and allow it to cool slightly.
2. Place a small portion of rice into two test tubes, or just use starch power.
3. Add a few milliliters of water to each tube and mash the rice into a suspension.
4. To one test tube, add a small amount of fresh saliva and mix. Leave the other tube as a control without saliva.
5. Incubate both tubes at room temperature for several minutes.
6. Test samples from both tubes with iodine solution to check for the presence of starch (a blue-black color indicates starch).
7. Test samples with Benedict’s solution and heat in a water bath to check for reducing sugars (a green to red color indicates the presence of glucose or maltose).
8. Compare results from the saliva-treated sample with the control sample.

Action of saliva on starch | Digestion | Biology - KClassScienceChannel:

The starch & amylase experiment - Paul Scott:

📄 Salivary amylase and starch - Science Learning Hub: https://www.sciencelearn.org.nz/resources/1846-salivary-amylase-and-starch

• Repeat the experiment using cooked potato or bread instead of rice.
• Compare results when saliva is boiled first to demonstrate enzyme denaturation.
• Test the effect of different incubation temperatures (e.g., chilled, room temperature, and warm water bath).

• Safety glasses should be worn when handling iodine and Benedict’s solution.
• Use caution with hot water baths to prevent burns.
• Use only your own saliva and do not share samples to avoid cross-contamination. The use of saliva may not be allowed at your site.
• Dispose of biological material safely after the experiment.

• What happens to the starch in the saliva-treated sample compared with the control? (The starch breaks down into sugars in the saliva-treated sample, while starch remains in the control.)
• Why does iodine change color in the presence of starch? (It forms a complex with the helical structure of starch molecules.)
• What does the color change in Benedict’s solution indicate? (The presence of reducing sugars like maltose or glucose.)
• Why is temperature important for enzyme activity? (Enzymes work best at their optimal temperature; high heat can denature them, while low temperatures slow their activity.)
• Why is it important to control variables in this experiment? (To ensure changes in results are due to enzyme activity and not other factors.)