Lab 4: Polysaccharides. IUG, Spring 2014 Dr. Tarek Zaida. Iodine Test for Polysaccharides. Iodine forms colored adsorption complexes with polysaccharides Blue color with starch Red-blue or purple color with dextrin Red color with glycogen With cellulose it gives no color. Reagents.
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IUG, Spring 2014
1. In a suitable plate place a small amount of the tested solution
2. Add 1 to 3 drops of a dilute solution of Iodine solution.
3. Compare the color obtained with that of water and iodine solution.
4. As the test proceeds, the reaction with iodine should become weaker & finally be negative.
5. At this point place all test tubes containing Benedict’s solution in a boiling water-bath for 3 min.
6. Remove the tubes then allow to cool.
7. Note the degree of reduction in each case compare with the rate of the disappearance of iodine reaction.
7. Note the insoluble mucic acid crystals from the oxidation of galactose.
8. Transfer one drop of the liquid plus crystals to a clean microscope slide, examine with a low power microscope (10X).
Note the gritty crystals of mucic acid.