Inulin like fructans are used as prebiotics as they are non digestible. Resistance to digestion in the upper GI tract results from:
High-Yield Explanation
Inulin is a dietary fibre, its a fructan with 2-60 fructose units linked a beta (1-2)bond. Due to this beta - configuration of anomeric C2 in their fructose monomers it is resistant to digestion in the GIT. Ref: Food Science and Technology Bulletin : Functional Foods By Glenn R. Gibson, Page 5; Dietary Fibre : New Frontiers for Food and Health By J. W. van der Kamp, Julie Jones, Barry Mccleary, David J. Topping, Page 177; Functional Foods : Concept to Product By Glenn R. Gibson, Christine M. Williams, Page 249.