| Abstract
| - Inulin (general formulas GFn and Fm, with G = anhydroglucose and F = anhydrofructose) naturallyoccurs as a homologous series of oligo- and polysaccharides with different chain lengths. For reasonsof growing interest in the food and pet food industries, the short chain inulins have to be separatedfrom their long chain analogues because their properties (digestibility, prebiotic activity and healthpromoting potential, caloric value, sweetening power, water binding capacity, etc.) differ substantially.To study these properties in relation to the number average degree of polymerization (DPn),ultrafiltration, specific crystallization from aqueous solution, and precipitation from solvent/watermixtures were used to enrich native chicory and dahlia inulin in the higher molecular weight fractions.Depending on the membrane module used, the DPn of chicory inulin (DPn = 8.1) and dahlia inulin(DPn = 29) could be increased by ultrafiltration to a maximum value of, respectively, 22 and 43. Withcrystallization from aqueous solutions (25 °C), similar results were obtained but at a much higheryield. Finally, long chain inulin could be precipitated from aqueous solutions in the presence of highconcentrations of methanol, ethanol, and acetone. Acetone demonstrated to be the best solvent systemto increase the DPn, followed by ethanol and methanol. However, for safety reasons and foodpurposes, ethanol was evaluated to be the best choice. With ethanol, the DPn could be raised to 25for chicory inulin and up to 40 for dahlia inulin. Keywords: Inulin; chicory; dahlia; number average degree of polymerization; DPn; ultrafiltration;crystallization; solvent precipitation
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