Sugar solutions, water relaxation

Although water relaxation in the dilute regime is now set on a firm theoretical basis, this is not the case in the more concentrated, water-poor regime appropriate to most foods. In the following we will therefore focus mainly on the concentration dependence of the water relaxation, especially the oxygen-17 data, beginning with simple sugar solutions. 

There have been a number of other papers on the hydration of biopolymers the effects of the degree of methylation of pectins on the proton relaxation times of water have been measured 50 l70 relaxation has been used to examine the hydration of bovine and caprine casein,51--54 and solid-state NMR combined with atomic force microscopy has been used to examine the influence of water on the nanomechanical behaviour of cutin.55 The effects of locust bean gum on water diffusion in sugar solutions has shown little effect,56 and the effects of gellan gum hydrogel structure on restricted diffusion has also been considered.57... 

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

C-, N-, CP MAS- and high resolution multinuclear-NMR methods have been applied to a study of ureido sugars 39. The O-NMR spectra of l-ascorbic acid recorded in aqueous solution as a function of pH have been presented under the title New spectroscopy of an old molecule , and the N- and 0-NMR spectra of doubly labelled pyrimidine nucleosides have been recorded for use as references in NMR analyses of labelled RNA fragments. Information on the hydration behaviour of several monosaccharides (Glc, Gal, Man, All, and Tag) has been obtained by measurements of water O-relaxation times. ... 

A study of the relaxational transitions and related heat capacity anomalies for galactose and fructose has been described which employs calorimetric methods. The kinetics of solution oxidation of L-ascorbic acid have been studied using an isothermal microcalorimeter. Differential scanning calorimetry (DSC) has been used to measure solid state co-crystallization of sugar alcohols (xylitol, o-sorbitol and D-mannitol), and the thermal behaviour of anticoagulant heparins. Thermal measurements indicate a role for the structural transition from hydrated P-CD to dehydrated P-CD. Calorimetry was used to establish thermodynamic parameters for (1 1) complexation equilibrium of citric acid and P-CD in water. Several thermal techniques were used to study the decomposition of p-CD inclusion complexes of ferrocene and derivatives. DSC and derivative thermogravimetric measurements have been reported for crystalline cytidine and deoxycytidine. Heats of formation have been determined for a-D-glucose esters and compared with semiempirical quantum mechanical calculations. ... 

The apparent molal volumes and compressibilities of galactose, glucose, maltose, sucrose, and dextran have been calculated fiom measurements of the density and ultrasound velocity of their aqueous solutions at 25 C. C- and H-n.m.r. lattice relaxation times T, have been used to provide information on the temperature dependence of the rotational mobility of both the sugar and the water molecules in concentrated aqueous solutions of sucrose and trehalose. ... 

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