Sol-Gel transition of κ-Carrageenan as viewed through NMR

Hikichi, Kunio

doi:10.1016/0966-7822(93)90021-9

Cited by 12 publications

(7 citation statements)

References 20 publications

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“…During gelation, gellan molecules undergo a phase transition from liquid to gel, known as sol-gel transition. Up to now, various technologies have been developed to probe sol-gel transitions of food hydrocolloids, including rheometry, [9] differential scanning calorimetry, [10][11][12] electron spin resonance, [13] nuclear magnetic resonance, [14,15] and so on. In all of available methods, small deformation rheaology is preferred due to its easier performance and reproducible results without structure perturbing.…”

Section: Introductionmentioning

confidence: 99%

Rheaological behavior of high acyl gellan gum solution at gel point

Chen

Yuan

et al. 2017

International Journal of Food Properties

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The sol-gel transition temperatures of high acyl gellan gum solution were investigated using rheaological measurements. The sol-gel transition temperatures were determined from three criteria: the crossover of storage modulus G′ and loss modulus G″, the linear extrapolation method, and the Winter's criterion. The results showed that the Winter's criterion was more suitable to determine the sol-gel transition temperature. The sol-gel transition temperature increased with the increasing gellan concentration. The relaxation critical exponent n can be determined by the Winter's criterion. There is no universal n for the gelation in high acyl gellan gum solutions, indicating that this gelation belongs to the cross-linking of existing macromolecules. The values of n decreased with increasing concentration of gellan gum solution. The fractal dimension d f calculated from n without the screened hydrodynamic interaction nor the excluded volume effect suggested a denser structure in the critical gel with higher c. The gelation enthalpy (ΔH gel ) was calculated by Eldridge-Ferry model.

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Section: Introductionmentioning

confidence: 99%

Rheaological behavior of high acyl gellan gum solution at gel point

Chen

Yuan

et al. 2017

International Journal of Food Properties

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“…Encapsulation of organic dyes, coordination compounds, colloids, and proteins in tetramethyl orthosilicate (TMOS) derived sol−gels (SG) has been widely used for the study of reactions in confined spaces. − As a consequence, considerable attention has been devoted to understanding the motional dynamics of encapsulated solvent and solute molecules, notably through NMR measurements of solvent mobilities − and through solute luminescence depolarization studies of encapsulated probe molecules. ,,− A picture has emerged in which SG-encapsulated molecules reside in several regions . Those within the interior of a “cell” (free-liquid region) behave much as though they were in bulk solution, while those in an “interface region”, at or near the walls, have more restricted motions.…”

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confidence: 99%

“…Surprisingly, while magnetic resonance techniques have been extensively used to study the solid matrix that surrounds such confined spaces, and solvents or gases that fill them, rarely have they been used to study the molecular motions of solutes in confined spaces. We are aware of a diffusion NMR study of the protein ubiquitin within polyacrylamide gels, an HRMAS study of probe molecules interacting with chromatographic supports, EPR studies of paramagnetic probes in various types of gels, , and an EPR study of spin-labeled hemoglobin within a SG .…”

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confidence: 99%

Electrostatic Influence on Rotational Mobilities of Sol−Gel-Encapsulated Solutes by NMR and EPR Spectroscopies

et al. 2004

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The rotational mobilities of small solute molecules encapsulated in tetramethyl orthosilicate (TMOS) sol-gels have been investigated by EPR spectroscopy of encapsulated nitroxide probes and by high-resolution NMR spectroscopic measurements of transferred NOE's (trNOE's), of T(1)'s, and of T(1)'s in the rotating frame (T(1)rho). The two spectroscopic methods are sensitive to motions on different time scales and hence, are nicely complementary. Suites of neutral, positively, and negatively charged nitroxide probes (EPR) and of simple diamagnetic small molecules (NMR) were selected to disclose influences of electrostatic interactions with the sol-gel walls and to probe the presence of multiple populations of molecules in distinct regions of the sol-gel pores. For neutral and negatively charged solute probes, both techniques disclose a single population with a significantly increased average rotational correlation time, which we interpret at least in part as resulting from exchange between free-volume and transiently immobilized surface populations. The electrostatic attraction between cationic probes and the negatively charged sol-gel walls causes the positively charged probes to be more effectively immobilized and/or causes a greater percentage of probes to undergo this transient immobilization. The EPR spectra directly disclose a population of cationic probes which are immobilized on the X-band EPR time scale: tau(c) greater than or approximately equal 10(-7) s. However, NMR measurements of trNOE's and of T(1)rho demonstrate that this population does exchange with the free-volume probes on the slower time scale of NMR. This approach is equally applicable to the study of solutes within other types of confined spaces, as well.

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“…to R H;T o for each of the pullulan samples, which are calculated from their respective D pull;0;T o using Equation (5). The value of D pull;0;T o can be determined from M w using Equation (4).…”

Section: Estimation Of the Hydrodynamic Screening Length Q Zhao And Smentioning

confidence: 99%

“…1,2 NMR has proved to be a powerful technique for determining the dynamic and structural properties of food model systems 3 and the gelation process of polysaccharides. 4,5 NMR relaxation times give information about the tumbling motion of molecules in food hydrocolloid systems. The diffusion coefficients determined by pulsed-field-gradient NMR reflect the translational motion of molecules.…”

Section: Introductionmentioning

confidence: 99%

Estimation of the hydrodynamic screening length in κ-carrageenan solutions using NMR diffusion measurements

Zhao

Matsukawa

2012

Polym J

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We quantify the hydrodynamic screening length (n) in j-carrageenan solutions by observing restrictions on the diffusion of several pullulan probes, each with a different molecular weight (M w ). The diffusion coefficient of pullulan in a pure solvent (D pull,0 ) and a j-carrageenan solution (D pull ) were measured using a pulsed field gradient stimulated spin-echo 1 H nuclear magnetic resonance. The hydrodynamic radii (R H ) of the pullulan samples were determined using D pull,0 measured at 25 1C and the Stoke-Einstein equation. The echo signal intensity of j-carrageenan without a gradient, I kappa (0), decreased steeply at around the sol-to-gel transition temperature (T sg ), suggesting that the j-carrageenan chains formed helical aggregates at T sg diluting the solute j-carrageenan concentration. The ratio, D pull /D pull,0 , was less than 1, indicating that the mobility of pullulan was restricted by the j-carrageenan chains. Over the entire temperature range, pullulan with larger molecular size yielded more restrictions on the molecular mobility, and D pull /D pull,0 decreased as the M w of pullulan increased. Below T sg , D pull /D pull,0 increased as the temperature decreased. This behavior suggests that a decrease in the restriction degree by the j-carrageenan chains is concomitant with the formation of aggregates. To quantify the restriction degree, n was estimated at various temperatures using the relation D pull /D pull,0 ¼ exp( ÀR H /n). Polymer Journal ( Keywords: diffusion coefficient; gel; gradient NMR; hydrodynamic radius; hydrodynamic screening length; pullulan; k-carrageenan INTRODUCTIONThe diffusion of solutes in a gel matrix has an important role in applications such as the delivery of drugs and the encapsulation of fragrances. 1,2 NMR has proved to be a powerful technique for determining the dynamic and structural properties of food model systems 3 and the gelation process of polysaccharides. 4,5 NMR relaxation times give information about the tumbling motion of molecules in food hydrocolloid systems. The diffusion coefficients determined by pulsed-field-gradient NMR reflect the translational motion of molecules. The diffusion coefficient of solutes in a polymer matrix strongly depends on molecular weight, temperature, viscosity and the network structure of the diffusing matrix. Any factor that reduces the space delineated by the polymer chains will have an effect on the molecular mobility of the solute. In polysaccharide gels, the aggregation of polysaccharide chains can enlarge the diffusing space. Therefore, to understand the diffusion of molecules in a gel, it is important to understand the aggregation behavior.k-Carrageenan is a linear sulfated polysaccharide that is extracted from marine red algae. As shown in Figure 1, k-carrageenan comprises two galactose units: a-(1-3)-D-galactose-4-sulfate and b-(1-4)-3,6-anhydro-D-galactose. It is a gelling agent that has

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Sol-Gel transition of κ-Carrageenan as viewed through NMR

Cited by 12 publications

References 20 publications

Rheaological behavior of high acyl gellan gum solution at gel point

Rheaological behavior of high acyl gellan gum solution at gel point

Electrostatic Influence on Rotational Mobilities of Sol−Gel-Encapsulated Solutes by NMR and EPR Spectroscopies

Estimation of the hydrodynamic screening length in κ-carrageenan solutions using NMR diffusion measurements

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