write an activity to show saliva acts on starch

Take a boiled potato, mash it and distribute it into three parts. Into the first part add iodine drops. You will see that the colour changes to blue indicating presence of starch. To the second part add saliva, mix and keep for 10 minutes. Then add iodine drop, you will see no color change indicating starch being converted to sugar by saliva. the third part can be kept as control.