Sucrose determination

Fig. 11 Yield loci of sucrose determined using the Jenike shear cell and the simplified shear cell. Open circles Jenike shear cell open squares simplified shear cell. (Adapted from Ref. 48 with permission of the publisher.)...

J. C. Christofides and D. B. Davies, Co-operative and competitive hydrogen bonding in sucrose determined by simple 111 NMR spectroscopy, J. Chem. Soc. Chem. Common. (1985) 1533-1534. 

With an excess of invertase and GOD in the enzyme membrane the total rate of sucrose determination is limited by the spontaneous mutarotation. Therefore the sensitivity towards sucrose is only about 10% of that for glucose (Scheller and Karsten, 1983). Kinetic (dl/dt) measurement even gives only 1% of the glucose signal at the same sucrose concentration. Application of coimmobilized mutarotase gives rise to an increase of the sensitivity by a factor of 6 for stationary measurement... 

Analysis At the end of the period of reflux, cool the reaction mixture to room temperature and transfer the solution to a clean volumetric flask. Use small amounts of water to rinse the round-bottom flask and add the rinses to the flask to effect quantitative transfer fill the flask to the volumetric mark. Using the polarimeter as before, determine the specific rotation of the product mixture from the hydrolysis of sucrose. Compare this value with the specific rotation of pure sucrose determined earlier. 

Based on the above inadequacy of pH measurements and the variability in sucrose determinations by different analytical methods we stress a cautious approach in the interpretation of fundamental research data in the industrial environment. It seems likely that empirical equations for estimation of sucrose loss have little application, and obviously, the results of experimental determination of sucrose loss during evaporation will be dependent on the choice of analytical methods. 

The variability in sucrose determinations by different analytical methods is shown in Figure 6. Obviously, purity values are dependent on the choice of analytical methods. As a digression, it is interesting to note that the 880 nm pol measurement is consistently lower than the 589 nm pol, HPLC and HPIC sucrose determinations. 

An important application area of ion chromatography in the characterization of fruit juices is the analysis of carbohydrates. Traditionally, sorbitol and the main sugars such as glucose, fructose, and sucrose were determined with enzymatic methods, which are usually very sensitive and specific. Interferences caused by the matrix are rare however, they are possible when determining sucrose. The principle of the sucrose determination is based on the determination of the glucose content prior to and after enzymatic hydrolysis of sucrose. Because fixiit juices often contain large amounts of glucose in the presence of small amounts of sucrose, precise quantification of small sucrose concentrations... 

The hydrolysis of sucrose (C12H22O11) into glucose and fructose in acidic water has a rate constant of 1.8 X 10 s at 25 °C. Assuming the reaction is first order in sucrose, determine the mass of sucrose that is hydrolyzed when 2.55 L of a 0.150 M sucrose solution is allowed to react for 195 minutes. 

Sucrose determination Transfer a 1-mL aliquot of the saponified solution to a 5-mL test tube and evaporate to dryness at 90-C. Add 1 mL pyridine and 0.2 mL each of trimeth-ylchlorosilane and iV-trimethylsilylimidazole. Shake well and let stand 30 min. Add 1 mL of 100 ppm -octacosane (C28H5)j) as internal standard, dilute to 3 mL with pyridine, and analyze 5 pL aliquots by gas chromatography, comparing to a calibration curve made by treating pyridine solutions of sucrose in the same way. GC conditions 2% OV-17 on Chromosorb W (AW-DMCS), 0.3 x 225 cm, 230 C, FID. 

To determine the caloric content of sucrose, we can use the heat of combustion per gram of sucrose determined in part (a), together with a factor to convert from kilojoules to kilocalories. (Because leal = 4.184 J,lkcal = 4.184 kJ.)... 

The concentrations of nine sugars (fucose, methylglucose, arabinose, glucose, fructose, lactose, sucrose, cellobiose, and maltose) in beer, milk, and soda are determined using an... 

Sensory perception is both quaUtative and quantitative. The taste of sucrose and the smell of linalool are two different kinds of sensory perceptions and each of these sensations can have different intensities. Sweet, bitter, salty, fmity, floral, etc, are different flavor quaUties produced by different chemical compounds the intensity of a particular sensory quaUty is deterrnined by the amount of the stimulus present. The saltiness of a sodium chloride solution becomes more intense if more of the salt is added, but its quaUty does not change. However, if hydrochloric acid is substituted for sodium chloride, the flavor quahty is sour not salty. For this reason, quaUty is substitutive, and quantity, intensity, or magnitude is additive (13). The sensory properties of food are generally compHcated, consisting of many different flavor quaUties at different intensities. The first task of sensory analysis is to identify the component quahties and then to determine their various intensities. 

Polarization is the most common method for the determination of sugar in sugar-containing commodities as well as many foodstuffs. Polarimetry is apphed in sugar analysis based on the fact that the optical rotation of pure sucrose solutions is a linear function of the sucrose concentration of the solution. Saccharimeters are polarimeters in which the scales have been modified to read directiy in percent sucrose based on the normal sugar solution reading 100%. 

Polarimetric determination of the sucrose concentration of a solution is vaUd when sucrose is the only optically active constituent of the sample. In practice, sugar solutions are almost never pure, but contain other optically active substances, most notably the products of sucrose inversion, fmctose and glucose, and sometimes also the microbial polysaccharide dextran, which is dextrorotatory. Corrections can be made for the presence of impurities, such as invert, moisture, and ash. The advantage of polarization is that it is rapid, easy, and very reproducible, having a precision of 0.001°. 

Refractive Index. The refractometric value of sugar solutions is used as a rapid method for the approximate determination of the soHds content (also known as dry substance), because it is assumed that the nonsugars present have a similar influence on the refractive index as sucrose. Measurement is usually carried out on a Brix refractometer, which is graduated in percentage of sucrose on a wt/wt basis (g sucrose/100 g solution) according to ICUMSA tables of refractive index at 20.0°C and 589 nm. Tables are available that give mass fraction corrections to refractometric values at temperatures different from 20°C. 

Equations have been developed that determine the relationship of the refractive index of sucrose solutions between 0—85% concentration, 18—40°C, and 546—589 nm. 

Density. Measurement of density is widely used in the sugar industry to determine the sugar concentration of symps, Hquors, juices, and molasses. The instmment used is called a hydrometer or a spindle. When it is graduated in sucrose concentration (percent sucrose by weight), it is called a Brix hydrometer or a Brix spindle. Brix is defined as the percent of dry substance by hydrometry, using an instmment or table caUbrated in terms of percent sucrose by weight in water solution. Hydrometers are also graduated in °BaumH, stiU in use in some industries. The relationship between °BaumH and density, ing/cm, is °Baumn Baum e = 145(1 — 1/d). 

Berlin Institute Method. This method is for determination of invert sugar in products containing not more than 10% invert in the presence of sucrose. It is a copper reduction method that utilizes MbUer s solution, which contains sodium carbonate. 

Emmerich Method. This method is for determination of trace amounts of reducing sugars in pure sucrose and white and refined sugars with reducing sugar content up to 0.15%. The test is carried out in a nitrogen atmosphere and is based on the reduction of 3,6-dinitrophthahc acid. 

In the sugar industry, where the goal is to determine the exact amount of sucrose present, the analysis of other components is essential to determine purity. The most important of these, besides reducing sugars discussed, are moisture, ash, and color. Also relevant are methods used to determine particle-size distribution and insoluble matter. 

Sulfonate Esters. Sucrose sulfonates are valuable intermediates for the synthesis of epoxides and derivatives containing halogens, nitrogen, and sulfur. In addition, the sulfonation reaction has been used to determine the relative reactivity of the hydroxyl groups in sucrose. The general order of reactivity in sucrose toward the esterification reaction is OH-6 OH-6 > OH-1 > HO-2. 

The shape of the equilibrium line, or solubility curve, is important in determining the mode of crystallization to be employed in order to crystallize a particular substance. If the curve is steep, i.e. the substance exhibits a strong temperature dependence of solubility (e.g. many salts and organic substances), then a cooling crystallization might be suitable. But if the metastable zone is wide (e.g. sucrose solutions), addition of seed crystal might be necessary. This can be desirable, particularly if a uniformly sized product is required. If on the other hand, the equilibrium line is relatively flat (e.g. for aqueous common salt... 

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