Question

You have been supplied with a sample of food. How will you perform tests for the presence of starch and proteins on it?

Answer 1

Test for starch:

1. Take the food item to be tested. Put it into a test-tube containing water and boil to make a solution.
2. Cool the solution and add 2-3 drops of dilute iodine solution to it.
3. Blue-black colour of the solution indicates the presence of starch in the food item.

Test for proteins:

1. Take the food item to be tested in a test tube.
2. Add few drops of dilute nitric acid to it.
3. Heat the test-tube gently.
4. Rinse off the acid with water and add few drops of ammonium hydroxide to it.
5. Colour change from colourless to yellow and then from yellow to orange red indicates the presence of protein in the food item.