Fructans examples

Polymers of D-fructose are important carbohydrate reserves in a number of plants. Inulins and levans are two major types that differ in structure. D-Fructans require only relatively mild conditions for their hydrolysis, for example, levan was qualitatively hydrolyzed by hot, dilute, aqueous oxalic acid. Permethylated fructans could be hydrolyzed with 2 M CF3CO2H for 30 min at 60°. Fructan oligosaccharides were hydrolyzed in dilute sulfuric acid (pH 2) at 70 (see Ref. 53) or 95° (0.1 M). D-Fructans from timothy haplocorm (where they comprise 63% of the water-soluble carbohydrates) could be hydrolyzed with 0.01 M hydrochloric acid at 98°. 

Fructans are polysaccharides composed of o-fructofuranose units. They are important in short-term energy reserves for grasses and some plants. Inulin, found in dahlias, and levans from grasses are examples of fructans. Levans are short linear polysaccharides composed of (3 2 1 linked fructose units as illustrated in structure 9.21. 

Fructans and fructose extracts, which can potentially be obtained from Jerusalem artichoke, have become attractive to industry for a number of food and nonfood applications because of their health benefits (e.g., Fleming and GrootWassink, 1979 Fontana et al., 1993 Fuchs, 1993 Roberfroid, 2005). Short-chain fructooligosaccharides (degree of polymerization of 2 to 5), for example, are increasingly used as low-calorie sweeteners in processed foods, and their utilization is anticipated to expand significantly in the future. 

There are five classes of fructans inulin, levan, mixed levan, inulin neoseries, and levan neoseries [26]. Inulin is a linear polysaccharide composed of (2-l)-P-D-fructosyl units (Figure 2.5a). Levan is a linear polysaccharide composed of (2-6)-P-D-fructosyl units (Figure 2.5b). Mixed levan is a branched polysaccharide composed of (2-1) and (2-6)-P-D-fructosyl units. Inulin neoseries is a linear polysaccharide composed of two inulin polymers that are connected together by a sucrose molecule. Levan neoseries is a linear polysaccharide composed of two levan polymers linked together by the glucose unit of the sucrose molecule. The type of fructan produced varies with plant species. For example, plants such as chicory (Cichorium intybus) and Jerusalem artichoke (Helianthus tuberosus) in the Asteraceae family produce inulin. Plants in the Liliaceae family such as garlic (Allium sativum) produce inulin neoseries. Plants in the Poaceae family such as wheat (Triticum spp.), barley (Hordeum vulgare), and oats (Avena sativa) produce mixed levan or levan neoseries. 

Particularly preferred polysaccharides are inulin, levans from plants, and bacterial fructans. Suitable glycol-specific oxidizing agents include sodium periodate, or lead tetra acetate. Examples of reducing agents include sodium borohydride and sodium cyano-borohydride (38). 

Another class of functional foods is prebiotics and probiotics. A prebiotic is defined as a nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth or activity of one or a limited number of bacteria in the colon. An example of a prebiotic is the inulin-type fructans. Despite the limited work done with prebiotics, studies with these inulin-type fructans have generated... 

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