Starch from potatoes

In earlier times, for many people potatoes were the only food they had for some months of the year. Potatoes contain carbohydrates (starch) that supply the body with the necessary energy. Potatoes consist of water to a large extent, but also a small proportion of proteins.
In the following experiment you will try to separate the starch from a potato and show that potatoes contain proteins.


1.     Grate half a potato and place the pulp obtained into the handkerchief.

(More see below).

2.  Add some water to the pulp and squeeze the liquid out of the handkerchief into the wide mouth jar.

3.    Transfer some of the fluid into the infusion bottle.

4.     Place the bottle at an angle in the experimental tray. Let the bottle sit for quarter of an hour until a white substance has been deposited.

5.     Transfer some of the pulp from the handkerchief into the second infusion bottle and stopper it.

6.     Transfer from the first infusion bottle a drop of the white matter to the experimental tray and put the rest of the potato next to it.

7.     Add one drop of iodine - potassium iodide solution to some of the white deposit from 4 and to the potato.

8.     Allow the remaining white deposit to dry on a thick layer of paper towels.

9.     Check after one week the smell of the pulp from the sealed infusion flask.


1.     Write down your observations.

2.     What differences could you see after the addition of iodine - potassium iodide solution to the potato and to the white matter? Explain the differences.
Think about what happened to the cells of the potato when rubbed.

3.     What was the reason for adding some water to the pulp in 2 and for the squeezing of liquid out of the handkerchief?

4.     What is the smell of the pulp due to from the infusion bottle after one week?

5.     What is the dried white deposit?

6.     Read about its use as glue.

First published: 2009                                                                        Last modification: 18.07.2014