Inulins

Inulin is soluble in water (maximum 10% at room temperature) and forms a gel-type structure. It does hydrolyse in acid conditions over time to produce fructose. It is heat stable. In soft drinks it can produce similar mouthfeel and technical properties to glucose syrup. 

Inulin has no sweetness and possesses a bland taste. Physiologically, inulin behaves as a dietary fibre. At relatively high dose levels (15-40 g/day) it can have a prebiotic effect (i.e. it can selectively promote the growth of beneficial bacteria in the colon) and at high dose levels it may also have a laxative effect (Kolida el al., 2002). This is dependent on the specific composition of the product and the degree of polymerisation, which can vary. The caloric value for inulin is 1 kcal/g. Its use in soft drinks is as a fibre source, prebiotic and partial sugar replacer. 

FOS and oligofuctose are fructose oligomers that are either produced by enzymic conversion of sugar or extracted from chicory, as inulin, and then hydrolysed. These products behave as soluble fibres and prebiotics. In acid conditions, they can hydrolyse, but are usually sufficiently stable for short-shelf-life juices, near-water products with low acid levels or powdered soft drinks. Prebiotic activity varies with preparation and required daily dose can be as low as 2.5-5.0 g/day for shorter chain FOS preparations (DP 2 1). Some positive effects on magnesium absorption and calcium absorption (in some populations) have also been shown (Beghin Meiji, 2001). 

Products are available in dry or syrup form. They have a lower sweetness than sucrose, RS = 0.3-0.6. The caloric value in the EU is 2 kcal/g. They are relatively hygroscopic and have good solubility. Use in soft drinks and juice products is as a sugar replacer, soluble fibre and prebiotic. 

Inulin is not biosynthesised by a Leloir pathway involving a nucleotide mono- or diphospho sugar, but by transglyeosylating enzymes of GH 32 and GH 68 acting on sucrose. Only two enzymes are involved, a sucrose-sucrose 1-fructosyl transferase (1-SST), whieh produees the primer trisaccharide 1-kestose, and fructan 1-fruetosyltransferase (1-FFT), whieh exchanges 

The thermodynamic driving force for fructan biosynthesis is the sterically strained nature of the crowded glycosidic linkage in sucrose. 

Crosslinked inulin-divinyl sulfone (DVS) microparticles synthesized by water-in-oil microemulsion polymerization were reported to be noncytotoxic in fibroblast cell culture, and degradable xmder acidic and basic conditions. They were found to be potential carriers for controlled release applications [14]. 

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D-fructose, C HijOo. Crystallizes in large needles m.p. 102-104 C. The most eommon ketose sugar. Combined with glucose it occurs as sucrose and rafftnose mixed with glucose it is present in fruit juices, honey and other products inulin and levan are built of fructose residues only. In natural products it is always in the furanose form, but it crystallizes in the pyranose form. It is very soluble in... 

Inulin. This polysaccharide melts with decomposition at about 178°. It is insoluble in cold but dissolves readily in hot water giving a clear solution which tends to remain supersaturated. It does not reduce Fehling s solution. Inulin gives no colouration with iodine solution. 

In nature, fmctose (levulose, fmit sugar) is the main sugar in many fmits and vegetables. Honey contains ca 50 wt % fmctose on a dry basis. Sucrose is composed of one unit each of fmctose and dextrose combined to form the disaccharide. Fmctose exists in polymeric form as inulin in plants such as Jemsalem artichokes, chicory, dahlias, and dandeHons, and is Hberated by treatment with acid or enzyme. 

Fig. 6. Solute transport in hemodialysis. Clearance vs solute mol wt for dialy2ers prepared from the two different membranes illustrated in Figure 5. Numbers next to points represent in min /cm calculated from equations 10 and 5. Data is in vitro at 37°C with saline as the perfusion fluid. Lumen flow, dialysate flow, and transmembrane pressure were 200 ml,/min, 500 mL/min, and 13.3 kPa (100 mm Hg) area = 1.6. Inulin clearance of the SPAN...

FIGURE 2.7 SEC elution profiles of dextran in clinical samples, serum ( ) and urine ( ). The first peak represent dextran and the second peak inulin (used as a reference for clearance). The content of carbohydrates was determined in collected fractions with the anthrone method. [Reproduced from Hagel ef of. (1993), with permission.]... 

Degree of polymerization distribution of a plant fructan (inulin) at increasing physiological age of the source remarkable performance of S-200 in the low dp range degree of polymerization distribution obtained from bad (P-6) and good (S-200 / P-6) resolution of high dp components... 

Bio-Gel P-6 and a combined system of P-6/S-200 were utilized for investigations of inulin-type /3(2- l)-linked nb fructans. With a flow rate of 0.33 mP min, each separation of a sample volume of 1 ml of a 20- to 30-mg/ml concentrated solution typically lasted 20 hr, i.e., one run per day. Both systems (P-6 and P-6/S-200) maintained stability for approximately 1 year, equivalent to approximately 100 runs. 

FIGURE 16.23 Inulln isolated from small (—). medium ( ) and large (A) tubers separated on P-6 (140 X 1.5 cm) flow rate 0.33 ml/min eluenf. H20(dest) + 0.002% NaNa mass detection Waters 403 R differential refractive index detector, sensitivity 8X applied sample solution volume I ml of a 20-mg/ml aqueous inulin solution. 

As an illustration for the improved performance of P-6/S-200 compared to P-6 solely, highly purified inulin was separated on both systems. Obviously, the high dp inulin components could not be resolved on P-6 (Fig. 16.25), whereas all of the inulin components were eluted within the selective separation range of the P-6/S-200 system (Fig. 16.26). 

Well established names such as cellulose, starch, inulin, chitin, amylose and amylopectin are retained. Carrageenan and laminaran are now often used rather than the older names ending in -in . 

In 1952, Wolfrom and Hilton demonstrated that L-sorbose was also capable of forming dimeric dianhydrides,22 and they postulated sorbofuranosyl and pyra-nosyl cationic intermediates. In 1955, Boggs and Smith23 postulated a fructofu-ranosyl cationic intermediate in the formation of per-O-acetyl ot-D-Fru/-1,2 2,l -p-D-Fru/[di-D-fructose anhydride I (5)] from inulin triacetate. They indicated that three adjacent P-2,l -linked fructofuranosyl units would be required for formation of the dianhydride. 

In 1933, Schlubach and Knoop32 isolated a di-D-fructose dianhydride from Jerusalem artichoke and tentatively identified it as difructose anhydride I [a-D-Fru/-1,2 2,1 - 3-D-Fn / (5)]. Alliuminoside ( -D-fructofuranose- -D-fructofura-nose 2,6 6,2 -dianhydride) was isolated from tubers of Allium sewertzowi by Strepkov33 in 1958. Uchiyama34 has demonstrated the enzymic formation of a-D-Fru/-1,2 2,3 -(3-D-Fru/ [di-D-fructose anhydride III (6)] from inulin by a homogenate of the roots of Lycoris radiata Herbert. 

The biosynthesis and degradation of fructans by microbial organisms has been reviewed in detail recently.35 Additionally, a review of the production of di-D-fructose dianhydrides from inulin and levan by enzymes has been published in Japanese.36 This account is therefore limited to a general overview. 

An extracellular inulin fructotransferase that results in the formation of a-D-Fru/-1,2 2,1 -(3-D-Fru/ [difructose anhydride I (5)] has been purified from Arthrobacter globiformis S14-3,65,66 from Arthrobacter sp. MCI-249367 and from Streptomyces sp. MCI-2524.68... 

A mechanism was proposed31 for the formation of di-D-fructose dianhydrides from inulin and fructose. It was suggested that a-D-Fru/-1,2 2,1 - 3-D-Fru/ [difructose anhydride I (5)] formed first and then isomerized via ionic intermediates to produce the remaining products. Important support for the concept of the reversibility of the isomerization was the observation that ot-D-Frup-1,2 2,1 - 3-D-Frup (4) and p-D-Frup-1,2 2,1 - 3-D-Frup produced, upon treatment with HF, the same product mixture as did D-fructose. 

The new compounds were assigned structures by examination of their 13C NMR spectra and of the H NMR spectra of the peracetates. A similar mechanism to that previously postulated for fructose and inulin,31 and involving a sor-bofuranosyl fluoride was suggested for the formation of these isomers. In both Refs. 31 and 80, formation of the 2,3-linkage was associated with more-rigorous conditions. 

Thermal activation of sucrose and inulin in the presence of citric acid,93 and sucrose in the presence of acetic94 acid, yields caramels containing, among other products, di-D-fructose dianhydrides and glycosylated difructose dianhydrides, as described in Section V.6). Similarly, the thermal treatment of 6-0-ot-D-glu-copyranosyl-D-fructofuranose (palatinose) in the presence of citric acid87 has been shown to produce appreciable proportions of glucosylated di-D-fructose dianhydrides. 

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