Iodine Test

Qualitative test of carbohydrate
Qualitative test for polysaccharides
Iodine test
Iodine test is a chemical test used to distinguish mono- or disaccharides from certain polysaccharides like amylose, dextrin, and glycogen. Iodine test is based on the fact that polyiodide ions form colored adsorption complex with helical chains of glucose residue of amylase (blue-black), dextrin (black), or glycogen (reddish-brown). On heating, the blue color amylase-iodine complex dissociates but is formed again on cooling because the helical structure is disrupted; thereby amylose loses its iodine binding capacity and the blue color. The blue color reappears on cooling due to the recovery of iodine binding capacity due to regaining of the helical structure.