Inulin and oligofructose, also called fructo-oligosaccharides (FOS), belongs to the class of fructan carbohydrates. Other synonyms for those healthy food ingredients are chicory root fiber and chicory root extract. In this explanation we refer all those alternatives to the word inulin. They occur in a large variety of plants where they have an important biological role as reserve carbohydrate. Inulin has been part of our daily diet for many hundreds of years. Since the early 1990s, inulin has been extracted from chicory roots on an industrial scale for use as a high-quality food ingredient.

The chemical composition of inulin extracted from chicory roots is GFn, where 'n' can vary between 2 and 60 (G= glucose, F= fructose). Inulin is therefore a mixture of linear oligofructose and polyfructose chains, usually terminated in a glucose molecule. The fructose molecules are linked to each other by a β(2-1) glycosidic bond. The average degree of polymerization (DP) for native inulin is 10 to 12.
Oligofructose obtained from inulin by partial enzymatic hydrolysis contains GFm and Fn chains with 'm' ranging from 2 to 10. The average degree of polymerization (DP) for oligofructose is 4 to 5.