Starch Agar is used for cultivating microorganisms being tested for starch hydrolysis. Beef extract provides the nitrogen, vitamins, carbon and amino acids in Starch Agar. Starch reacts with Gram Iodine to give a blue colour. Organisms hydrolyzing starch through amylase Production will produce a clearing around the isolate while the remaining medium is blue. Agar is the solidifying agent.