Fructose aqueous solution

Fructose aqueous solution or solid 8 exp, lamp, ts max, tecero. Atochem Kynar... 

Fructose—Dextrose Separation. Emctose—dextrose separation is an example of the appHcation of adsorption to nonhydrocarbon systems. An aqueous solution of the isomeric monosaccharide sugars, C H 2Dg, fmctose and dextrose (glucose), accompanied by minor quantities of polysaccharides, is produced commercially under the designation of "high" fmctose com symp by the enzymatic conversion of cornstarch. Because fmctose has about double the sweetness index of dextrose, the separation of fmctose from this mixture and the recycling of dextrose for further enzymatic conversion to fmctose is of commercial interest (see Sugar Sweeteners). 

Alkaline Degradation. At high pH, sucrose is relatively stable however, prolonged exposure to strong alkaU and heat converts sucrose to a mixture of organic acids (mainly lactate), ketones, and cycHc condensation products. The mechanism of alkaline degradation is uncertain however, initial formation of glucose and fructose apparendy does not occur (31). In aqueous solutions, sucrose is most stable at —pH 9.0. 

In a similar manner, ketones can react with alcohols to form hemiketals. The analogous intramolecular reaction of a ketose sugar such as fructose yields a cyclic hemiketal (Figure 7.6). The five-membered ring thus formed is reminiscent of furan and is referred to as a furanose. The cyclic pyranose and fura-nose forms are the preferred structures for monosaccharides in aqueous solution. At equilibrium, the linear aldehyde or ketone structure is only a minor component of the mixture (generally much less than 1%). 

Figure 25.5 Pyranose and furanose forms of fructose in aqueous solution. The two pyra-nose anomers result from addition of the C6 -OH group to the C2 carbonyl the two furanose anomers result from addition of the C5 -OH group to the C2 carbonyl.

Similar anomalous distributions are observed in other thermal product mixtures. A commercial soft caramel made by heating sucrose and 0.1% acetic acid to 160°C contained 18% of a mixture of di-D-fructose dianhydrides.94 fi-D-Fru/-1,2 2,1 - 3-D-Fru/(now assigned as a-D-Fru/-l,2 2,l -a-D-Fru/83), ot-D-Fru/-1,2 2,1 -p-D-Fru/(5), ot-D-Frup-1,2 2,l -0-D-Fnjp (4), ot-D-Fru/-l,2 2,1 - 3-D-Frup (1), and p-D-Fru/-l,2 2,3 - 3-D-Fru/ (2) were found in the ratio 4 12 1 6 2. The first three of these, constituting 68% of the mixture, are considered to be kinetic products. The authors commented on this, but did not offer any explanation. Notice, however, that the preparation of such commercial caramels commences with heating of an acidic aqueous solution of sucrose, which almost certainly results in hydrolysis. Hence, the final dianhydrides are probably derived from the reaction of fructose, rather than sucrose. 

By application of first-order, kinetic equations, B. Anderson and Degn claimed that an equilibrated (25°) aqueous solution of D-fructose contains 31.56% of jS-D-fructofuranose and 68.44% of -D-fructopyranose. N.m.r. studies, however, showed that, at equilibrium, a solution of D-fructose contains /3-D-fructopyranose, -D-fructofuranose, a-D-fructofuranose, and a trace of a-D-fructopyranose the distribution of these isomers was shown by gas-liquid chromatography to be 76,19.5, and 4%, respectively. Based on Anderson and Degn s result, Shallenberger reasoned that, as 0.68 X 1.8 = 1.22 (which approximates the reported sweetness of mutarotated D-fructose ), the furanose form(s) must possess very little sweetness. 

A long-wavelength probe 29 signaling carbohydrates in aqueous solutions by increasing of fluorescence was developed by Akkaya and Kukre on the basis of a symmetrical squaraine dye containing two phenylboronic acid functions [89]. The emission maximum of this probe is at 645 nm. A maximal response of about 25% was found for fructose. 

A large number of polyfructosans that have been reported from time to time by different authors have been investigated by Schlubach and his associates. In order to obtain polysaccharides of constant optical rotation, 100 to 300 precipitations from aqueous solution by the addition of alcohol were necessary. Fifty to 150 precipitations from chloroform solution with petroleum ether were required for purification of the acetate derivatives. These were methylated according to the procedure of Haworth and Straight,24 and upon hydrolysis partially methylated fructoses were obtained. 

The rotations were measured in chloroform solution, a fact which is not stated in the original article. The hydrolysis curves for aqueous solution of difructose anhydride III indicate that the rotation in water of the resulting trimethyl-D-fructose is also within this range. 

Evans, Nicoll, Strause and Waring46 oxidized D-glucose and D-fructose in aqueous solution with excess cupric acetate at 50° for the purpose of ascertaining whether the general principles underlying the mechanism of carbohydrate oxidation in alkaline solutions are sufficient to explain the course of such oxidations in acid solutions. D-Glucosone was claimed to be one of the first products of oxidation the osone was not isolated, and,... 

Following a report60 that D-fructose, but not D-glucose, is oxidized by selenious acid, Dixon and Harrison61 used this reagent to prepare D-glucosone from D-fructose in aqueous solution isolation and purification were carried out after the manner of Fischer,4 but no yield was given. By this... 

The substantial amounts of this ketohexose are mainly prepared by base-catalyzed isomerization of starch-derived glucose, yet may also are generated by hydrolysis of inulin, a fructooligosaccharide. An aqueous solution of fructose—consisting of a mixture of all four cyclic tautomers (Figure 2.5), of which only the (3-D-pyranose ((3-p) form present to about 73% at room temperature is sweet — about 1.5 times sweeter than an equimolar solution of sucrose hence, it is widely used as a sweetener for beverages ( high fructose syrup ). 

A good example of using adsorptive separation in a non-refining/petrochemical application is the separation of fructose from an aqueous solution of mixed sugars. This process allows the production of high concentration fructose which has a much higher sweetness to calorie ratio than simple glucose or sucrose. As in fine chemical and pharmaceutical applications we can often use adsorption when distillation is not possible or feasible or when the material is thermally sensitive. 

This enzyme [EC 2.4.1.7], also known as sucrose gluco-syltransferase, catalyzes the reaction of sucrose with orthophosphate to produce D-fructose and a-D-glucose 1-phosphate. In the forward reaction, arsenate may replace phosphate as the substrate. However, the resulting product is unstable in aqueous solutions. In the reverse reaction, various ketoses and L-arabinose may replace D-fructose. See Arsenolysis... 

Two methods are employed industrially to produce crystalline fructose, aqueous crystallization and alcoholic crystallization. Yields of fructose crystallized from water syrups are only of the order of 50%, due to the very high water solubility of the sugar, while the high viscosity of the concentrated solution results in long crystallization times, typically 50 hours or more (2). The second process requires the addition of lower alcohols (eg. ethanol) to a concentrated fructose syrup, generally 90% total solids or more, at temperatures of 50 C to 80""c and then cooling to cause crystallization. Fructose yields are from 70 to 80% and the total time involved is 8 to 12 hours (3). However, large quantities of... 

Figure 5. Growth rate vs C for fructose crystallizing from aqueous ethanol. Also shown are the results of Shiau and Berglund (10) for aqueous solution.

Figure 9. Growth spread standard deviation vs mean growth rate from Shlau and Berglund (10) for fructose grown from aqueous solution.

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