Theory



Carbohydrates are one of the main components of our daily diet. This
category of foods includes sugars, starches, and fibre. Starch is the most
common carbohydrate in the human diet and is contained in many staple foods.
The word Carbohydrates Cn(H2O)n literally mean carbon (carbo) + water
(hydrate). 


            The colour of
natural starch is milky white and the pure form of starch is insoluble in water
and alcohol. Iodine reacts with starch to form starch/iodine
complex which has a blue-black colour. The appearance of blue-black colour
confirms the presence of starch in the given food sample


Material Required


Sample, Iodine solution, beaker, test tube,
tile, knife, etc.


Lab Procedure



  1. Place a potato on a tile.

  2. Grind or chop the potato into
    small pieces, using a knife.

  3. Using a spatula transfer these
    pieces of potato into a beaker.

  4. Pour some distilled water into
    the beaker.

  5. Place the beaker containing the
    mixture over a hot plate.

  6. Heat the mixture for 5 minutes
    while continuously stirring it with a glass rod.

  7. Take another beaker and cover
    its mouth with a muslin cloth.

  8. Secure the muslin cloth around
    the mouth of the beaker by tying it with a thread.

  9. Filter the solution through
    this beaker.

  10. Now take a clean test tube and
    pour some of the filtrate into it.

  11. Take a few drops of iodine
    solution using a dropper.

  12. Add a couple of these drops
    into the test solution.



Observation



The test solution turns blue-black in
colour


Precautions



  1. While using
    iodine solution, be careful, as it is toxic if swallowed or inhaled.

  2. While
    heating, care should be taken that the solution does not splash on your
    face