Aim: To test the presence of starch in the given food sample.
Apparatus: 2 test tubes, starch solution or food items such as potato rice grains some noodles or a slice of bread,distilled water [20 ml] iodine solution a spirit lamp/ bunsen burner a test tube holder muslin cloth a small beaker and a dropper.
Procedure: 1. Take a small pice of potato or few rice grains in a glass test tube. Add 20 ml of distilled water. Boil the mixture for 5 mintues or a spirit lamp or bunsen burner.
2. Let the above mixture cool and then filter the contents using muslin cloth. collect the filtrate in a small glass beaker. Note the colour of the filtarate.
3.Take 5 ml of the filtrate in a clean test tube.Add 5-6 drops of iodine solution with a dropper.
Observations: The filtrate [food extarct] changes to blue -black colour.
Conclusion: The filtrate contains starch.