Inulin, acidic hydrolysis

Difructose anhydride II reacts with one mole of per-iodic acid. Hydrolysis of its methyl derivative indicates that two different trimethyl-D-fructoses are formed whose combined specific rotations in water amount to between + 20° and + 30°. If we assume that this anhydride, like the other two derived from inulin, is made up of D-fructofuranoses, the facts that have been mentioned allow only three possible structures for this anhydride. 

D-Mannitol has a diverse range of industrial applications. It is a nonhydroscopic, low-calorie, noncariogenic sweetener utilized by the food industry as well as a feedstock for the synthesis of other compounds. For example, mannitol can be oxidized at the 3 or 4 position to form two molecules of glyceraldehyde or glyceric acid, which can be used as building blocks for other compounds (Heinen et al., 2001 Makkee et al., 1985 van Bekkum and Verraest, 1996). Mannitol is formed from inulin via hydrolysis followed by catalytic hydrogenation. This yields mannitol and sorbitol from which the mannitol can be readily crystallized (Fuchs, 1987). Currently mannitol is primarily synthesized from starch. 

Inulin is measured colorimetrically, either by acid hydrolysis to generate a green product, or by a series of enzymatic reactions based on inulinase with subsequent reduction of NADH. HPLC methods are used for the remaining exogenous GFR tracers. PAH and TEA are measured colorimetrically (Newman and Price 1999). 

Inulin.— Inulin is found in certain plants, especially in the tubers of the Dahlia. It is isomeric with the other poly-saccharoses and is also a reserve food material. It is a white powder soluble in water. It is leva rotatory and gives no color with iodine. It is not hydrolyzed by diastase but by a particular enzyme known as inulase. Its peculiar characteristic is that by acid hydrolysis it yields only fructose. 

Nasab EE, Habibi-Rezaei M, Khaki A, Balvardi M (2009) Investigation on acid hydrolysis of inulin a response surface methodology approach. Int J Food Eng 5 Article 12... 

As a last example of an ultrasound application to catalytic reactions using solid catalysts, we refer to unpublished results. The hydrolysis of inuline (Eq. 12) is catalyzed by acid substances, i.e., inorganic or organic acids in aqueous solution, or acid solids or enzymes. The products of acid hydrolysis are fructose and glucose. Because of the use of the reaction in the food industry, an acid catalyst should not pollute the products at the end of the process. Therefore, solid acids, much more easily separable from the reaction products than liquid acids, must be preferred. In the present work, the employed catalyst was Amberlite IR-120-H (Carlo Erba), that is to say, a solid catalyst with a particle size from 15 to 45 mesh. The reaction was studied in a batch and in a continuous sonicated reactor. 

A kinetic study of the hydrolysis of woods and purified plant polysaccharides in 75 % sulphuric acid was monitored by electrical conductivity measurements. The coefficients of resistance of all polysaccharide substrates increased with increasing hydrolysis time. From these measurements, the degrees of polymerization of cellulose, xylan, and inulin were estimated to be 1900, 66, and 16 respectively. The polysaccharide components of various woods and pulps can be hydrolysed with trifluoracetic acid which, in contrast to sulphuric acid hydrolysis, does not require a neutralization step since trifluoracetic acid is volatile. The presence of lignin in the wood samples impeded the hydrolysis of the polysaccharides, requiring longer reaction times and correction factors to compensate for loss of monosaccharide by degradation reactions. 

Owing to its great sweetness and high utilizability in the body, D-fruc-tose has been of special interest in nutrition for many decades. In the first quarter of this century, a large demand for this ketose was predicted if economical methods could be developed for its production. In addition to sucrose, many plants store the sugar in their tubers in the form of fruc-tosans, of which inulin is the most common. Fructose can be prepared (p. 96) most conveniently from dahlia tubers and from Jerusalem artichokes, but the yield from the latter is not as favorable as from the former. Acid hydrolysis is commonly employed to liberate the fructose. 

There are several examples of one-pot reactions with bifunctional catalysts. Thus, using a bifunctional Ru/HY catalyst, water solutions of corn starch (25 wt.%) have been hydrolyzed on acidic sites of the Y-type zeolite, and glucose formed transiently was hydrogenated on ruthenium to a mixture of sorbitol (96%), mannitol (1%), and xylitol (2%) [68]. Similarly a one-pot process for the hydrolysis and hydrogenation of inulin to sorbitol and mannitol has been achieved with Ru/C catalysts where the carbon support was preoxidized to generate acidic sites [69]. Ribeiro and Schuchardt [70] have succeeded in converting fructose into furan-2,5-dicarboxylic acid with 99% selectivity at 72% conversion in a one-pot reaction... 

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°. 

Laurencin and coworkers213 have used a different approach to control the rate of bioerosion of polymers with amino acid ester side groups. They used hydrophobic 4-methylphenoxy cosubstituents ( 50%) to slow the rate of hydrolysis, and these polymers were employed to study the rate of release of inulin. Similar polymers are also being developed by the same investigators as tissue engineering substrates for bone regeneration.214"218... 

Hydrolysis of inulin has already been performed in the presence of a zeolite, namely the zeolite LZ-M-8.[11] This catalyst has been found to be extremely selective towards hydrolysis compared with fructose decomposition, thus illustrating the superiority of the zeolite over sulfuric acid or ion-exchange resins as catalysts. As an example, a 96% yield in fmctose was obtained after 15 min at 130 °C starting from 2 ml of a 0.257 mol L 1 inulin solution and 0.25 g of zeolite. 

The only dimethyl-D-fructose which has been characterized, 3,4-di-methyl-D-fructose, has been prepared by McDonald and Jackson141 from di-D-fructose anhydride I. Tritylation of this anhydride gives the 6,6 -ditrityl derivative which is methylated to 3,4,3, 4 -tetramethyl-6,6 -di-trityl-di-D-fructose anhydride I. Removal of the trityl groups followed by hydrolysis yields liquid 3,4-dimethyl-D-fructose, [ ]d —60.66° in water. It has also been obtained, with 4-methyl-D-fructose, from the hydrolysis of methylated di-D-fructose anhydride III. The structure of this dimethyl-D-fructose follows from its method of preparation from di-D-fructose anhydride I whose structure is known.10 McDonald and Jackson also prepared 3,4-dimethyl-D-fructose from inulin by the following method inulin — monotrityl inulin — monotrityl inulin diacetate — dimethyl monotrityl inulin — dimethyl isopropylidene-D-fructose — methyl dimethyl-D-fructoside —> 3,4-dimethyl-D-fructose. Its structure was confirmed by its oxidation without loss of methyl to the same lactol of the dimethyl dibasic acid obtained from 1,3,4-trimethyl-D-fructose (see page 78). The phenylosazone made from 3,4-dimethyl-D-fructose has m. p. 126° that from 3,4-dimethyl-D-glucose has not been recorded. 

---