Fructans are built up of fructose residues, normally with asucrose unit (i.e. aglucose–fructosedisaccharide) at what would otherwise be the reducing terminus. The linkage position of the fructose residues determine the type of the fructan. There are five types of fructans.[2]
Linkage normally occurs at one of the two primaryhydroxyls (OH-1 orOH-6), and there are two basic types of simple fructan:
1-linked: ininulin, the fructosyl residues are linked by β-2,1-linkages
6-linked: inlevan andphlein, the fructosyl residues are linked by β-2,6-linkages
A third type of fructans, the graminin type,[2] contains both β-2,1-linkages and β-2,6-linkages.[3]
Two more types of fructans are more complex: they are formed on a 6G-kestotriose backbone where elongations occur on both sides of the molecule. Again two types are discerned:
neo-inulin type (also called "inulin neoseries"[2]): predominant β-2,1-linkages
neo-levan type (also called "levan neoseries"[2]): predominant β-2,6-linkages
In barley, fructan accumulates in the cellvacuoles and acts as acarbon sink within the cell to facilitate photosynthesis. Fructan reserves are transported to the reproductive tissue during grain filling, and to the vegetative tissues during periods of growth.[citation needed]
Chicoryinulin-type fructans are used mainly as the raw materials for industrial production of fructans as food ingredients. Use in the food industry is based on the nutritional and technological properties of fructans as aprebioticdietary fiber.[7][8]
^abcdChibbar, R. N.; Jaiswal, S.; Gangola, M.; Båga, M. (2016)."Carbohydrate Metabolism".Reference Module in Food Science.doi:10.1016/B978-0-08-100596-5.00089-5.ISBN9780081005965.Fructans, on the basis of glycosidic linkage, are categorized into five groups: (a) inulin having β(2 → 1) linkage, (b) levan/phlein having β(2 → 6) linkage, (c) graminin (having inulin or levan backbone with ≥ 1 short branch), (d) inulin neoseries (like inulin but one glucose unit between two fructose moieties), and (e) levan neoseries (like levan but one glucose unit between two fructose moieties) (Figure 1).
^Pollock, C. J.; Cairns, A. J. (1991). "Fructan Metabolism in Grasses and Cereals".Annual Review of Plant Physiology and Plant Molecular Biology.42:77–101.doi:10.1146/annurev.pp.42.060191.000453.
^Meyer, D.; Bayarri, S.; Tárrega, A.; Costell, E. (2011-12-01). "Inulin as texture modifier in dairy products".Food Hydrocolloids. 25 years of Advances in Food Hydrocolloid Research.25 (8):1881–1890.doi:10.1016/j.foodhyd.2011.04.012.ISSN0268-005X.
^abTungland, Bryan (1 June 2018), Tungland, Bryan (ed.), "Chapter 8 - Nondigestible Fructans as Prebiotics",Human Microbiota in Health and Disease, Academic Press, pp. 349–379,doi:10.1016/b978-0-12-814649-1.00008-9,ISBN9780128146491{{citation}}: CS1 maint: work parameter with ISBN (link)
^Muir, J.G.; et al. (2007). "Fructan and Free Fructose Content of Common Australian Vegetables and Fruit".Journal of Agricultural and Food Chemistry.55 (16):6619–6627.doi:10.1021/jf070623x.PMID17625872.
^abKarppinen, Sirpa. Dietary fibre components of rye bran and their fermentation in vitro. Espoo 2003. VTT Publications 500. 96 p. + app. 52 p.[1]
Sugar – Chemical, Biological and Nutritional Aspects of Sucrose. John Yudkin, Jack Edelman and Leslie Hough (1971, 1973). The Butterworth Group.ISBN0-408-70172-2
