Sugar estimation

Reducing Sugars. Estimation of total reducing sugars (RS) as... 

A tripeptide containing a sulphydryl group which has a role in maintaining the integrity of erythrocytes by virtue of it being an important regulator of oxidation-reduction reactions. It is known to interfere in some methods of blood sugar estimation. 

A method of blood sugar estimation based on the ability of glucose to reduce ferricyanide to ferrocyanide. The ferricyanide remaining is determined iodometrically. 

Saccharification is never complete. A residue of amylopectin, phosphates, and hemi-cellulose remains, its composition depending on the nature of the starch. Hydrolysis may be traced by means of the iodine test or by sugar estimation. 

Benedict s qualitative reagent must not be confused with his quantitative reagent, which is used only for sugar estimation. 

Important examples are (i.) The use of methylene blue as a hydrogen acceptor in dehydrogenase systems, (ii.) The nadi reagent, which led to the elucidation of the Warburg-Keilin system, (ui.) The application of methylene blue as an internal indicator in sugar estimation by Lane and Eynon. (iv.) The estimation of ascorbic acid by titration with dichlor-indophenol. 

Methylene Blue, 0-1 per cent. Redox indicator used in determining the end-point in Fehling s sugar estimation. 

Fehling s solution A solution of copper sulphate, sodium potassium tartrate and NaOH used for estimating and detecting reducing sugars. 

The third method is of limited application and is used only in special cases, The second is the most accurate and rapid method, and is of considerable technical importance. The chemical method (described below), although less accurate than the polarimetric method, is of great value for the estimation of sugars in biological fluids. In fact, for such purposes, it is often to be preferred to the polarimetric method owing to the probable presence of other substances having high optical rotations. 

This is done by estimating the reducing power of the sugar after hydrolysis (or inversion ) by acid, the glucose and fructose thus formed having very nearly the same reducing power. 

Breslow studied the dimerisation of cyclopentadiene and the reaction between substituted maleimides and 9-(hydroxymethyl)anthracene in alcohol-water mixtures. He successfully correlated the rate constant with the solubility of the starting materials for each Diels-Alder reaction. From these relations he estimated the change in solvent accessible surface between initial state and activated complex " . Again, Breslow completely neglects hydrogen bonding interactions, but since he only studied alcohol-water mixtures, the enforced hydrophobic interactions will dominate the behaviour. Recently, also Diels-Alder reactions in dilute salt solutions in aqueous ethanol have been studied and minor rate increases have been observed Lubineau has demonstrated that addition of sugars can induce an extra acceleration of the aqueous Diels-Alder reaction . Also the effect of surfactants on Diels-Alder reactions has been studied. This topic will be extensively reviewed in Chapter 4. 

Fehling s solution (sugar detection and estimation) (a) Copper sulfate solution dissolve 34.639 g of CUSO4 5H2O in water and dilute to 500 mL. (b) Alkaline tartrate solution dissolve 173 g of rochelle salts (KNaC40g dHjO) and 125 g of KOH in water and dilute to 500 mL. Equal volumes of the two solutions are mixed just prior to use. The Methods of the Assoc, of Official Agricultural Chemists give 50 g of NaOH in place of the 125 g KOH. 

Fig. 7. U.S. production of beet sugar from molasses desugarization processes. Values for 1995 are estimated.

The 1995 Canadian and United States sugar alcohol (polyol) production is shown in Table 2. The market share of each is also given. Liquids comprise 48% crystalline product comprises 39% and mannitol comprises 13% of the polyol market. An estimate of total U.S. sorbitol capacity for 1995 on a 70% solution basis was 498,000 t. ADM, Decatur, lU., produced 68,200 t Ethichem, Easton, Pa., 13,600 t Lon2a, Mapleton, lU., 45,400 t Roquette America, Gurnee, lU., 68,200 t and SPI Polyols, New Castle, Del., 75,000 t (204). Hoffman-LaRoche, which produces sorbitol for captive usage in the manufacture of Vitamin C (see Vitamins), produced about 27,300 t in 1995. 

Uses. High fmctose symp is used as a partial or complete replacement for sucrose or invert sugar in food appHcations to provide sweetness, flavor enhancement, fermentables, or humectant properties. It is used in beverages, baking, confections, processed foods, dairy products, and other apphcations. Worldwide HES production in the 1994—1995 fiscal year was estimated at about 8.6 x 10 t (dry basis) (18). About 75% of total world production is in the United States. 

Quantitative Estimation of Deoxy Sugars and Related Compounds with Special Reference to Periodate Oxidation. 

In as far as other analytical methods are concerned, many specific reactions have been elaborated for the quantitative determination of 2-deoxy aldoses. 2-Deoxy-D-ribose (2-deoxy-D-erythro-pentose), a compound which was recognized early as playing an important role in biological systems, has been of particular interest. Overend and Stacey (43) have given a critical review of the methods available until 1952 for the estimation of 2-deoxy pentoses. A recent summary of specific methods for the identification and quantitative estimation of the different classes of deoxy sugars has been prepared by Dische (13). 

To obtain reliable, accurate, and reproducible methods for quantitative estimation of deoxy sugars, certain conditions must be fulfilled. Thus, it is necessary that the chromogen be formed quantitatively from the sugar. The chromogen must then react quantitatively with the compound used for color formation, and lastly, the dye, once formed, should be stable and have a well defined molar extinction coefficient. In methods in which all of these conditions are not or cannot be fulfilled, recourse must be had to simultaneous determinations with suitable standard substances, a requirement not always easy to fulfil. 

Despite the above-mentioned short-comings, this approach to the estimation of those deoxy sugars which yield malonaldehyde when oxidized with periodate, seemed promising, since, as has been seen (58,59), the dye is formed quantitatively in the reaction of malonaldehyde with 2-thiobarbituric acid also, more recently, its constitution (49,57) and molar extinction coefficient (36) have been established. Thus, if conditions could be found in which malonaldehyde, while being formed quantitatively from the deoxy sugars, would be stable, an ideal method, independent of standard compounds, would be available for the quantitative determination of all of these sugars. 

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