Investigation of Starch Hydration by 2D Time Domain NMR (original) (raw)
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Proton NMR relaxation of adsorbed water in gelatin and collagen
Applied Magnetic Resonance, 1995
The dependence of the water self-diffusion coefficients as well as of the proton spin-lattice and spin-spin relaxation rates on the concentration have been studied in the gelatin-water system and in hydrated native collagen. The bound and free water fractions and the corresponding spinspin and spin-lattice relaxation rates have been determined within the multi-phase water proton exchange model. Various theoretical models for the water proton cross-relaxation to the biopolymer have been studied and the results compared with the observed Larmor frequency dependence of the water proton spin-lattice relaxation rate.
Molecular Interaction in Aqueous Sugar Solutions - a Nuclear Magnetic Relaxation Study
2010
Proton Magnetic Resonance (PMR) spin-lattice relaxation times (T 1) were measured in aqueous solutions of maltose and galactose in the concentration range 0-2 molar and at a temperature of 37" C. The spin-lattice relaxation time (TI) is found to decrease with the increase of sugar concentration. On the otherhand, the relaxation time is found to be lower for maltose solutions as compared to galactose solutions. These results were discussed on the basis of molecular association between sugar and water molecules through hydrogen bonding and the two-state fast exchange model of water molecules.
Food Chemistry, 2012
Proton NMR relaxation rates (R 1 and R 2 ) were measured in aqueous solutions of sucrose, D-glucose and Dfructose with increasing concentration. The measurements were carried out using Bruker PC 20 NMR Process Analyzer. Inversion recovery and CPMG pulse sequences are used for the measurement of relaxation rates. Results show that the values of relaxation rate increase as the concentration of the sugar is increased. The relaxation rate appears to be higher for sucrose solutions as compared to glucose or D-fructose solutions. These results were discussed on the basis of molecular association between sugar and water molecules through hydrogen bonding. The water self diffusion coefficient was measured in these sugar solutions by using pulse field gradient NMR method. As expected, the water self-diffusion coefficient was reduced with increased sugar concentrations. The results of translational mobility exhibited a higher mobility for fructose than glucose or sucrose in aqueous solutions.
Proton spin relaxation study of the germination of barley grains
Archives Des Sciences Journal
The time-evolution of the spin relaxation of water protons during the germination of barley grains in-situ, supplied continuously by water, was investigated using a "home-made" permanent-magnet NMR relaxometer, working at 25 MHz. It was found that the values of the spin-lattice time, T 1 , are higher in germinating than in "killed" grains. RÉSUMÉ L'évolution dans le temps de la relaxation des spins des protons de l'eau a été examinée in-situ à l'aide d'un relaxomètre en RMN, travaillant à 25 MHz, chez la graine d'orge, alimentée en continu par de l'eau. Chez les graines qui germent normalement, le temps de relaxation spin-réseau, T 1 , est beaucoup plus élevé que chez les graines tuées.
Two-dimensional solid-state proton NMR and proton exchange
Journal of the American Chemical Society, 1993
High-resolution solid-state 'H NMR spectra were obtained by combining deuterium spin-dilution and highspeed magic-angle spinning (MAS). The effective proton relaxation time T I , which is long in these magnetically dilute samples, was reduced by reverse cross-polarization (RCP) of protons from deuterons. Two-dimensional IH NOESY spectra obtained with RCP were used to investigate proton exchange in solids, and the rapid proton exchange observed in this way was linked to hydrogen bonds. A quantitative analysis of the dependence of the 2D spectral intensities on mixing time, as a function of temperature, was employed to determine the rates, and activation energies, for proton/ deuteron exchange between the carboxyl groups of the oxalate moiety and the water of hydration in oxalic acid dihydrate. We find rate constants of 55 and 58 s-l at 17 OC and activation energies of 8.5 and 8.9 kcal/mol over the temperature range-26 to 28 "C.
Low-Field NMR Analyses of Gels and Starch-Stabilized Emulsions with Modified Potato Starches
Processes
Many different biopolymers are used to stabilize emulsions, of which starch is of particular concern. To improve the characteristics and technical utility of native starch, various types of changes can be made. This article is a report describing the molecular dynamics of water by the low-field nuclear magnetic resonance (LF NMR) of chemically (E 1412 and E 1420) and physically modified starch (LU 1432) gels and the effect of their use on the stability of oil/water emulsions obtained using bovine and porcine fats. The analysis of changes in spin–spin and spin–lattice relaxation times over time showed that the presence of the type of starch modification significantly affects the values of T1 and T2 relaxation times, as well as the correlation times. Research on time-related changes in water binding in oil-in-water emulsions showed that potato starch modified by chemical methods can be used as an emulsifier. Compared to physically modified starch, chemically modified starches have a m...
Influence of water on potato starch-lipid interactions. An electron spin resonance (ESR) probe study
Journal of the Science of Food and Agriculture, 2000
Electron spin resonance (ESR) was used in order to study the mechanism of interaction of potato starch with lipids in systems with different water contents (40, 50 and 60% w/w) during heating and cooling. Different spin probes were used, on the one hand spin-labelled stearic acids (5-DSA and 16-DSA), which limited lipids, and on the other hand the water-soluble probe 4-hydroxy-2,2,6,6tetramethylpiperidine-1-oxyl (Tempol), which was sensitive to changes in the dynamic properties of the water phase associated with the temperature-induced starch structural transformations. Whatever the water content in the hydration range considered, Tempol was observed to be relatively mobile in the presence of potato starch, whereas a strong absorption of spin-labelled stearic acids on potato starch granules took place at room temperature for all investigated starch±water systems. Spinlabelled stearic acids were expected to stick on the starch granules. The mobility of the spin-labelled stearic acid was less upon cooling than upon heating as a result of starch gelation. The mobility of spin probes decreased with increasing starch concentration. Introduction of a doxyl fragment at position 16 of the hydrocarbon chain leads to a lower degree of immobilisation of the spin probe as compared with 5-DSA. This result suggests that there is a stronger interaction of polar sites of stearic acid with starch granules.
Proton magnetic resonance relaxation studies in aqueous solutions of alkali halides and fructose
Journal of Molecular Liquids, 1990
The proton magnetic resonance (PMR) spin-lattice relaxation times (T ) were measured in aqueous solution of fructose. T1 was found to'decrease with increase of fructose concentration. This result is interpreted as due to molecular association between the fructose and water molecules. The relaxation times T were also measured in aqueous solutions of alkali halides containing the sugar fructose to study the influence of this sugar on the relaxation times. The results are interpreted in terms of structure making and breaking properties of alkali ions.