Digestive System — Question 5

The following tests can be carried out:

Test for starch:

Aim — To detect the presence of starch in the sample

Procedure and Inference —

1. Add some starch powder to a test tube containing water, shake well. Boil well to make a solution.
2. Add some drops of iodine solutions when the solution cools down.
3. Iodine solution can be prepared by dissolving 1g iodine with 1g potassium iodide in 100ml of distilled water, dilute this solution before using.
4. The solution in the test tube would turn blur-black indicating the presence of starch.

Test for proteins:

Aim — To detect the presence of proteins in the given sample

Procedure and Inference—

1. In a test tube add a few pieces of the sample (hard-boiled egg)
2. Add a few drops of dilute nitric acid so as to seal the food
3. Gently heat the test tube, rinsing off the acid with water, to this add ammonium hydroxide
4. Observe the changes – from the initial white, color changes to yellow
5. After adding ammonium hydroxide – the color changes from yellow to orange.