Fructans are built up of fructose residues, normally with a sucrose unit (i.e. a glucose-fructose disaccharide) at what would otherwise be the reducing terminus. The linkage position of the fructose residues determine the type of the fructan. Linkage normally occurs at one of the two primary hydroxyls (OH-1 or OH-6), and there are two basic types of simple fructan:
1-linked: In Inulin, the fructosyl residues are linked by β-2,1-linkages.
6-linked: In Levan (or Phlein), the fructosyl residues are linked by β-2,6-linkages.
Fructans are important storage polysaccharides in the stems of many species of grasses and confer a degree of freezing tolerance. A notable exception is rice, which is unable to synthesise fructans.
^Kawakami, A.; Sato, Y.; Yoshida, M. (2008). "Genetic engineering of rice capable of synthesizing fructans and enhancing chilling tolerance". Journal of Experimental Botany59 (4): 793–802. doi:10.1093/jxb/erm367. PMID18319240.edit
^ abcdefSUSAN J. SHEPHERD, M Nut Diet, APD*; PETER R. GIBSON, MD, MB, FRACP, "Fructose Malabsorption and Symptoms of Irritable Bowel Syndrome: Guidelines for Effective Dietary Management," J Am Diet Assoc 2006:106:1631-1639.
^ abDepartment of Food Science and Nutrition, University of Minnesota, Joanne L. Slavin, PhD, RD, "Mechanisms for the Impact of Whole Grain Foods on Cancer Risk," Journal of the American College of Nutrition, Vol. 19, No. 90003, 300S-307S (2000)
^Muir, J.G., et al. (2007). "Fructan and Free Fructose Content of Common Australian Vegetables and Fruit". Journal of Agricultural and Food Chemistry55: 6619–6627. doi:10.1021/jf070623x.
^ abKarppinen, Sirpa. Dietary fibre components of rye bran and their fermentation in vitro. Espoo 2003. VTT Publications 500. 96 p. + app. 52 p.