Inulin

INULIN [(C₁₀H₁₀O₅)_x + H₂O], a colloidal polysaccharide that serves as a reserve carbohydrate instead of starch in the tubers and roots of certain plants (chicory, dahlias, some varieties of artichokes). With iodine it gives only a yellow coloration. Unlike starch, which consists of glucose residues, inulin is built exclusively from fructose residues, into which it completely breaks down during hydrolysis or under the influence of the enzyme inulinase. According to the latest research, inulin consists of nine fructose residues; according to Pringsheim and Irvine (Pringsheim, Irvine), the basic structural element of inulin is anhydro-tri-fructose; three such complexes, upon polymerization, give inulin. Inulin is very difficult to dissolve in cold water, easily dissolves in hot water, not forming a paste like starch, but only an opalescent colloidal solution. It rotates the plane of polarization to the left, [a]_D ≈ -40°. The enzyme inulinase (or inulase) is found in the roots and seeds of chicory, in a number of fungi, in invertebrates; in mammals—in the spleen, placenta. In some countries, inulin, obtained from tubers of Jerusalem artichoke (Helianthus tuberosus), is used for the technical production of fructose, which is used in confectionery production and as a substitute for cane sugar. Inulin is also used in bacteriology for addition to nutrient media when differentiating certain species of bacteria.