Fructose INDEX

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). 

The separation was carried out on a TSKgel Amide-80 column 4.6 mm i.d. and 25 cm long with a mobile phase consisting of a 80% acetonitrile 20% water mixture. The flow rate was 1 ml/min and the column was operated at an elevated temperature of 80°C. The saccharides shown were 1/ rhamnose, 2/ fucose, 3/ xylose, 4/ fructose, 5/ mannose, 6/ glucose, 7/ sucrose and 8/ maltose. The analysis was completed in less than 20 minutes. These types of separations including other biomonomers, dimers and polymers are frequently carried out employing refractive index detection. 

Several compounds have been proposed for the measurement of the void volume, including sodium nitrate solution, water, deuterium oxide, fructose, acetonitrile, tetrahydrofuran (THF), meso-erythritol, gluconolactone, and 2,4-dinitronaphthol. The elution volume of a number of these compounds has been measured in 10-90% aqueous acetonitrile and acidic-aqueous acetonitrile. The results are given in Figure 3.9 where the volumes in A and B were measured in aqueous acetonitrile and in C and D were measured in aqueous acetonitrile containing 50 mM phosphoric acid. Methanol (a) and deuterium oxide (g) showed two peaks when monitored by a refractive index detector (Figure 3.9C). 

ICUMSA (1) has adopted tables showing the relationship between the concentration of aqueous solutions of pure sucrose, glucose, fructose, and invert sugar and refractive index at 20.0°C and 589 nm. 

Fig. 3 HPLC separation of carbohydrates in chickpeas. Column (200 X 4.6-mm ID) LiChrosorb NH2 flow rate 1 ml min-1 mobile phase 20% water in acetonitrile. Refractive index detector. Peak assignment 1, fructose 2, glucose 3, sucrose 4, rafflnose 5, maninotriose 6, stachyose 7, verbascose.

Fig. 3 Chromatogram of a red wine using Shodex S-801/S and S-802/S columns at 75°C with a mobile phase of water at a flow-rate of 1 ml/min and using a refraction index detector. Peaks A = compounds with the highest molecular mass and with an acid character 1 = glucose 2 = fructose 3 = glycerol 4 = butan-2,3-diol (= 0.8 g/L added to the initial wine) 5 = ethanol. (Reprinted from Ref. 30 with the kind permission of Elsevier Science—NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

The second method, using refractive index (RI) detection, is carried out using a resin-based polymer column. Sucrose elutes first from this column, followed by glucose, fructose and then sorbitol. This type of column is generally more robust than the amino-bonded column and if handled well will last much longer however, it is around three times more expensive. The method has been collaboratively tested for the analysis of sugars and sorbitol in fruit juices by the IFU. The HPLC conditions are given below. 

Table 21.9 Relationship of refractive index to Brix for high-fructose syrups60...

The Chi in the hairy roots and parent plant organs was extracted with a mixture of 80% acetone and 20% phosphate buffer (2.5 mol m 3,pH 7.8), and analyzed according to the method described by Porra et al. [17]. The activities of SOD and POD in the hairy roots and parent plant organs were spectrophoto-metrically determined using ferricytochrome C [18] and o-aminophenol [19], respectively. Fructose in the medium was analyzed by the Somogyi-Nelson method [20] or was determined using an HPLC with a refractive index detector. Light intensity was measured with a thermopile on the outer walls of flasks at the level of the medium surface or at the top of the Petri dish, and expressed as the mean of values determined at several positions. 

Total Solids Determine the refractive index of a sample at 20° or 45°, and use the tables in High-Fructose Com Syrup Solids, under Total Solids, Appendix X, to obtain the percent Total Solids. 

For Corn Syrups, High-Fructose Corn Syrups, Liquid Fructose, and Maltodextrin, convert the refractive index to approximate percent solids using the accompanying tables. 

Anhydrous a-maltose decomposes at about 100-120°C, and anhydrous a-lactose at 200-220 C. Note that in the case of an unknown a temperature of decomposition in one range or the other is valid as an index of identity only if the substance has been characterized as a reducing sugar. Before applying the test to an unknown, perform a comparable evaporation of a 0.1 M solution of glucose, fructose, galactose, or mannose. 

Concenlralion of aqueous fructose solurion (% w/w) Density (g/cm ) Refractive index Viscosity, dynamic (mPa s)... 

Inulin—A fructose polysaccharide that is filtered by the glomerulus its clearance is often used as an index of GER. 

Sugars Common carbohydrates are monosaccharides (glucose, fructose), disaccharides (sucrose, maltose, lactose), trisaccharides (raffinose), and polysaccharides (starch). HPLC offers a direct, quantitative method for simple sugars, which requires a specialty cationic resin-based column and refractive index or evaporative light scattering detection.7,8 UV detection at low wavelengths (195 nm) can be used but is more prone to interferences.8... 

Cmde dextransucrase was reacted with 100 mM sucrose for 1 h at 30 °C and then boiled for 5 min to terminate the enzyme reaction. One unit of dextransucrase activity was defined as that amount of enzyme releasing 1 p.M fructose per min from 100 mM sucrose. The fructose was determined by high-performance liquid chromatography (HPLC) using an Aminex FIPX 87K column (300 7.8 mm) and an HPLC analyzer coupled to a refiactive index detector. The column was maintained at 85 °C and 0.01 M K2SO4 was used as a mobile phase at a flow rate 0.6 ml/min. 

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