Compositae fructans

Polysaccharides that exclusively contain D-fructose are known as fructans and there are two known kinds, inulin and levan. Inulin is a polysaccharide containing -D-fructofuranose linked (2 1) [118]. Inulins are found in the roots and tubers of the family of plants known as the Compositae, which includes asters, dandelions, dahlias, cosmos, burdock, goldenrod, chicory, lettuce, and Jerusalem artichokes. Other sources are from the Liliacae family, which includes lily bulbs, onion, hyacinth, and tulip bulbs. Inulins are also produced by certain species of algae [119]. Several bacterial strains of Streptococcus mutans also produce an extracellular inulin from sucrose [120]. 

Fructans occur naturally, are predominantly found in plants, fungi, and are produced extra-cellularly by bacteria such as Streptococcus mutans [13]. Plants are the most likely source of inulin for the production of material to be incorporated into foodstuffs due to its abundance in plants and also from a safety perspective. Inulin is found in the tubers and roots of the plant family Compositae which includes aster, dandelion, dahlias, comos, burdock, goldenrod, chicory, lettuce, and Jerusalem artichoke [14,15]. Van Loo et al. [16] identified the quantity of inulin in various plants as well as their degree of polymerization (O Table 3). An extensive review of occurrence and distribution of fructans in nature is provided [16,17,18]. 

Polymers of fructose are of widespread occurrence in plants, but are common only in a few orders, particularly the Compositae ind Graminae, They differ in several respects from prokaryotic fructans, especially in that they are intracellular rather than extracellular, that they are far smaller than their bacterial counterparts and that they contain relatively more glucose. Their function in plants is as storage polysaccharides and they are synthesised, ultimately from photosynthetic products. In bacteria such polymers are often assembled from exogenous, rather than endogenous disaccharides. 

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