Test for Starch

What is Starch?

In simple words, starch can be defined as the most important complex carbohydrate compounds. It is a polysaccharide and glucoside reserve of plants. It is a renewable and biodegradable product, so it can act as a perfect raw material and a substitute for fossil-fuel components in making detergents, glues, plastics, etc.

The starch molecules comprise a large number of glucose units that are bound together by glycosidic bonds and are produced by all vegetables and other plant sources through the process of photosynthesis. The starch molecules function as energy storage in plant cells, which is necessary for their growth, development, and reproduction. Barley, potatoes, maize, rice, wheat are a few examples of plant products from which starch are extracted and distributed to different industries.

Also Refer: Carbohydrates

Why do we perform Test for Starch?

The iodine test for starch is mainly performed to test the presence of carbohydrates. The food products which we eat include different types of carbohydrates, among which starch and sugars are the main carbohydrates found in our food products.

Also Read: Sources of Carbohydrates

Test for Starch in Plants Source

Materials Required

  • Knife
  • Spatula
  • Porcelain tile.
  • Iodine solution
  • Food sample – Potato or any other vegetables or fruits.


  • Take a fresh Potato which is washed, cleaned and dried.
  • Peel off the skin of the potato.
  • Cut the potato into small cubes or slices.
  • With the help of clean and dried Spatula, place the potato samples on the clean and dried porcelain tile.
  • Add 2 to 3 drops of dilute iodine solution on the potato samples.
  • Keep the slide undisturbed and observe the changes.


There will be a change in colour. A blue-black colour develops on the slice or cubes of the potato samples.


The result is positive.

According to the observation the food sample or the potato slice turned to blue-black on adding the iodine solution. This proves the presence of starch in the given plant source.

This was a simple experiment which is used to check for the presence of starch. This Iodine Test for Starch can be performed for both the liquid and solid food samples.

For more additional information about starch, carbohydrates, sources, its types or other related biological concepts and experiments, visit us @ BYJU’S Biology.

Test Your Knowledge On Test For Starch!

1 Comment

  1. Hi I did not understand how the Iodene solution is made and how is it blue and black

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