Erythro-dextrin

Solubility.— The poly-saccharoses differ from the sugars in the absence of a sweet taste, in their non-crystalline character and in their general insolubility. Inulin and dextrin are soluble in water, glycogen is soluble to an opalescent liquid, while starch and cellulose are insoluble. In hot water starch forms a colloidal solution or emulsion, known as starch paste. Starch reacts with a solution of iodine and gives a beutifiul blue color. This is a characteristic reaction for starch and is used as a qualitative test, especially in microscopic examination. Dextrin exists in several forms, one of which known as erythro-dextrin, gives a red color with iodine. 

Neither inulin, a polysaccharide of fructose, nor achroo-dextrin gives a colour with iodine. The first is detected by hydrolysis, when it only liberates fructose (distinction from the non-reducing sugar, sucrose), the second is rarely met with free from erythro-dextrin. 

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