Fitting of the beat pattern observed in NMR free-induction decay signals of concentrated carbohydrate-water solutions

Superradiant Detection of Microscopic Optical Dipolar Interactions

The interaction between light and cold atoms is a complex phenomenon potentially featuring many-body resonant dipole interactions. A major obstacle toward exploring these quantum resources of the system is macroscopic light propagation effects, which not only limit the available time for the microscopic correlations to locally build up, but also create a directional, superradiant emission background whose variations can overwhelm the microscopic effects. In this Letter, we demonstrate a method to perform "background-free" detection of the microscopic optical dynamics in a laser-cooled atomic ensemble. This is made possible by transiently suppressing the macroscopic optical propagation over a substantial time, before a recall of superradiance that imprints the effect of the accumulated microscopic dynamics onto an efficiently detectable outgoing field. We apply this technique to unveil and precisely characterize a density-dependent, microscopic dipolar dephasing effect that generally limits the lifetime of optical spin-wave order in ensemble-based atom-light interfaces.

In situ monitoring of mechanochemical MOF formation by NMR relaxation time correlation

In this paper, we present a new approach to monitoring mechanochemical transformations, based on a magnetic resonance (MR) method in which relaxation time correlation maps are used to track the formation of the popular metal-organic framework (MOF) materials Zn-MOF-74 and ZIF-8. The two-dimensional (2D) relaxation correlation measurement employed yields a spectrum which visually and analytically identifies different 1H environments in the sample of interest. The measurement is well-suited to analyzing solid mixtures, and liquids, in complex systems. Application in this work to monitoring MOF formation shows changes in signal amplitudes, and their MR lifetime coordinates, within the 2D plots as the reaction progresses, confirming reaction completion. This new measurement provides a simple way to analyse solid-state reactions without dissolution, and there is a logical pathway to benchtop measurement with a new generation of permanent magnet-based MR instruments. The methodology described permits measurement in an MR compatible milling container, which may be directly transferred from the shaker assembly to the MR magnet for in situ measurement of the entire reaction mixture.

Development of a method to determine the SFC in the fat phase of emulsions using TD-NMR FID-CPMG deconvolution

Fat crystallisation in emulsions is a complex process. One of the important parameters is the solid fat content (SFC). Up to now, there is no standardised method to measure the SFC in emulsions, let alone to determine the SFC of the fat inside droplets, thus avoiding the signal of the aqueous phase. This work evaluates the capabilities of deconvolution of the free induction decay (FID)-Carr-Purcell-Meiboom-Gill (CPMG) signal of emulsions. Three models were evaluated. The first model was a combination of a Gaussian function and a bi-exponential function (GBE model). The second model combined a Gaussian function with multiple exponential functions (GME model). The last model contained multiple Gaussian functions and multiple exponential functions (MGME model). The latter two models used a simplified CONTIN analysis. Based on the analysis of the determination coefficient R² , the calculated water content and the estimated SFC of nonemulsified two-phase systems, the GBE model was selected to analyse the FID-CPMG signal of emulsified systems. However, the results obtained with the other models did not differ substantially, and hence, they could be used to obtain a full relaxation time distribution. When the GBE model was applied on different emulsion systems, no significant differences in estimated SFC of the fat phase were found, thus indicating that the emulsion formulation (i.e. water-in-oil [W/O], oil-in-water [O/W] or water-in-oil-in-water [W/O/W]) only had a minor effect on the SFC in the systems considered here.

Physicochemical and Morphological Study of the Saccharomyces cerevisiae Cell-Based Microcapsules with Novel Cold-Pressed Oil Blends

Vegetable oils rich in polyunsaturated fatty acids are a valuable component of the human diet. Properly composed oil blends are characterized by a 5:1 ratio of ω6/ω3 fatty acids, which is favorable from a nutritional point of view. Unfortunately, their composition makes them difficult to use in food production, as they are susceptible to oxidation and are often characterized by a strong smell. Encapsulation in yeast cells is a possible solution to these problems. This paper is a report on the use of native and autolyzed yeast in the encapsulation of oils. The fatty acid profile, encapsulation efficiency, morphology of the capsules obtained, and thermal behavior were assessed. Fourier transform infrared analysis and low-field nuclear magnetic resonance relaxation time measurements were also performed. The process of yeast autolysis changed the structure of the yeast cell membranes and improved the loading capacity. Lower encapsulation yield was recorded for capsules made from native yeast; the autolysis process significantly increased the value of this parameter. It was observed that NY-based YBMCs are characterized by a high degree of aggregation, which may adversely affect their stability. The average size of the AY capsules for each of the three oil blends was two times smaller than the NY-based capsules. The encapsulation of oils in yeast cells, especially those subjected to the autolysis process, ensured better oxidative stability, as determined by DSC, compared to fresh blends of vegetable oils. From LF NMR analysis of the relaxation times, it was shown that the encapsulation process affects both spin-lattice T1 and spin-spin T2* relaxation times. The T1 time values of the YBMCs decreased relative to the yeast empty cells, and the T2* time was significantly extended. On the basis of the obtained results, it has been proven that highly unsaturated oils can be used as an ingredient in the preparation of functional food via protection through yeast cell encapsulation.

Glass Transition in Rice Pasta as Observed by Combined Neutron Scattering and Time-Domain NMR

Experimental protocols aiming at the characterisation of glass transition often suffer from ambiguity. The ambition of the present study is to describe the glass transition in a complex, micro heterogeneous system, the dry rice pasta, in a most unambiguous manner, minimising the influence of technique-specific bias. To this end, we apply an unprecedented combination of experimental techniques. Apart from the usually used NMR and DSC, we employ, in a concurrent manner, neutron transmission, diffraction, and Compton scattering. This enables us to investigate the glass transition over a range of spatio-temporal scales that stretches over seven orders of magnitude. The results obtained by neutron diffraction and DSC reveal that dry rice pasta is almost entirely amorphous. Moreover, the glass transition is evidenced by neutron transmission and diffraction data and manifested as a significant decrease of the average sample number density in the temperature range between 40 and 60 °C. At the microscopic level, our NMR, neutron transmission and Compton scattering results provide evidence of changes in the secondary structure of the starch within the dry rice pasta accompanying the glass transition, whereby the long-range order provided by the polymer structure within the starch present in the dry rice pasta is partially lost.

Magnetic resonance T1-T2* and T1ρ-T2* relaxation correlation measurements in solid-like materials with non-exponential decays

Magnetic resonance T₁-T₂* relaxation correlation is a newly emerging and powerful tool to study the structure and dynamics of materials. However, the T₁-T₂* of solid-like materials may consist of a linear combination of exponential decays and non-exponential decays, and the traditional methods for processing T₁-T₂ data would be not applicable. In this paper, a method of processing T₁-T₂* data with non-exponential decays was proposed. The critical idea is to decompose the data into two sub-datasets, exponential decays and non-exponential decays, employing a non-linear fitting method, and then to invert the sub-datasets and to combine the inversion results. We also introduce a related relaxation correlation measurement, T_1ρ-T₂*, for examination of solid-like materials. The same data processing strategy as for T₁-T₂* was implemented. The effectiveness of the proposed method for processing non-exponential data, Sinc Gaussian and Gaussian decay, was validated with simulation and experiment. The results showed that the proposed method recovers T₁-T₂* and T_1ρ-T₂* spectra with accurate relative signal intensities. The proposed method provides a platform for further development of MR methods applied to solid-like materials. These relaxation correlations are well suited to measuring composition of mixtures, with solid components in the mixture.

A comparative analysis of gaseous phase hydration properties of two lichenized fungi: Niebla tigrina (Follman) Rundel & Bowler from Atacama Desert and Umbilicaria antarctica Frey & I. M. Lamb from Robert Island, Southern Shetlands Archipelago, maritime Antarctica

Gaseous phase hydration properties for thalli of Niebla tigrina from Atacama Desert, and for Umbilicaria antarctica from Isla Robert, maritime Antarctica, were analyzed using ¹H-NMR relaxometry, spectroscopy, and sorption isotherm analysis. The molecular dynamics of residual water was monitored to distinguish the sequential binding very tightly, tightly, and loosely bound water fractions. These two species differ in hydration kinetics faster for Desert N. tigrina [A₁ = 0.51(4); t₁ = 0.51(5) h, t₂ = 15.0(1.9) h; total 0.7 for p/p₀ = 100%], compared to Antarctic U. antarctica [A₁ = 0.082(6), t₁ = 2.4(2) h, t₂ = [26.9(2.7)] h, total 0.6 for p/p₀ = 100%] from humid polar area. The ¹H-NMR measurements distinguish signal from tightly bound water, and two signals from loosely bound water, with different chemical shifts higher for U. antarctica than for N. tigrina. Both lichen species contain different amounts of water-soluble solid fraction. For U. antarctica, the saturation concentration of water soluble solid fraction, c_s = 0.55(9), and the dissolution effect is detected at least up to Δm/m₀ = 0.7, whereas for N. tigrina with the similar saturation concentration, c_s = 053(4), this fraction is detected up to the threshold hydration level equal to ΔM/m₀ = 0.3 only.

Fast-forward approach of time-domain NMR relaxometry for solid-state chemistry of chitosan

Chitosans with different average degrees of acetylation and weight molecular weight were analyzed by time-domain NMR relaxometry using the recently proposed pulse sequence named Rhim and Kessemeier - Radiofrequency Optimized Solid-Echo (RK-ROSE) to acquire ¹H NMR signal of solid-state materials. The NMR signal decay was composed of faster (tenths of μs) and longer components, where the mobile-part fraction exhibited an effective relaxation transverse time assigned to methyl hydrogens from N-acetyl-d-glucosamine (GlcNAc) units. The higher intrinsic mobility of methyl groups was confirmed via DIPSHIFT experiments by probing the ¹H-¹³C dipolar interaction. RK-ROSE data were modeled by using Partial Least Square (PLS) multivariate regression, which showed a high coefficient of determination (R² > 0.93) between RK-ROSE signal profile and average degrees of acetylation and crystallinity index, thus indicating that time-domain NMR consists in a promising tool for structural and morphological characterization of chitosan.

Characterisation of Fat Crystal Polymorphism in Cocoa Butter by Time-Domain NMR and DSC Deconvolution

The polymorphic state of edible fats is an important quality parameter in fat research as well as in industrial applications. Nowadays, X-ray diffraction (XRD) is the most commonly used method to determine the polymorphic state. However, quantification of the different polymorphic forms present in a sample is not straightforward. Differential Scanning Calorimetry (DSC) is another method which provides information about fat crystallization processes: the different peaks in the DSC spectrum can be coupled to the melting/crystallisation of certain polymorphs. During the last decade, nuclear magnetic resonance (NMR) has been proposed as a method to determine, qualitatively and/or quantitatively, the polymorphic forms present in fat samples. In this work, DSC- and NMR-deconvolution methods were evaluated on their ability to determine the polymorphic state of cocoa butter, with XRD as a reference method. Cocoa butter was subjected to two different temperature profiles, which enforced cocoa butter crystallization in different polymorphic forms. It was found that XRD remains the best method to qualitatively determine the polymorphic state of the fat. Whereas the quantitative NMR and DSC deconvolution results were not fully in line with the XRD results in all cases, NMR deconvolution showed great promise both in a qualitative and quantitative way.

Power-optimized, time-reversal pulse sequence for a robust recovery of signals from rigid segments using time domain NMR

Time domain NMR (TD-NMR) has been widely used on the analysis of liquids or liquid components in heterogeneous materials such as food, biological tissues, synthetic and bio polymers, oil-bearing rocks, biomasses and cement-based materials. The use of TD-NMR for studying solid and soft mater has been growing in number and variety of applications, mostly for organic systems where the detection of ¹H signals is highly advantageous. However, the strong ¹H-¹H dipolar interactions in solids make the ¹H FID to decay in the same order of the dead time of most commercially available NMR probe heads. Thus, solid echoes are often used for recovering signals from solid components. In this article we reinvestigate the time-reversal solid-echo pulse sequence proposed by Rhim and Kessemeier, seeking for optimal pulse power and timing conditions that maximize its efficiency on recovering ¹H signals from rigid segments. We show that under these optimized conditions, which we denote as Rhim and Kessemeier - Radiofrequency Optimized Solid-Echo (RK-ROSE), the experiment can be more efficient than its most popular counterparts Solid-Echo (SE) and mixed-Magic Sandwich Echoes (mixed-MSE). Our results also suggest that, despite the finite pulse power, with current probe technology the RK-ROSE experiment is potentially able to provide an accurate estimation of rigid components, without relying on an external calibration using multiple standard samples, as usually done in SFC analysis of the FID signal. At last, we demonstrate that RK-ROSE can be adapted as a simple filter to supress signals from mobile segments in heterogeneous materials.

Exploring the crystallinity of different powder sugars through solid echo and magic sandwich echo sequences

Time-domain nuclear magnetic resonance techniques are frequently used in polymer, pharmaceutical, and food industries as they offer rapid experimentation and generally do not require any considerable preliminary sample preparation. Detection of solid and liquid fractions in a sample is possible with the free induction decay (FID). However, for the classical FID sequence that consists of a single pulse followed by relaxation decay acquisition, the dead time of the probe (ring out of resonance circuitry) occurs and varies between 5 and 15 μs for standard 10-mm tubes. In such a case, there arises a risk that the signal from the solid fraction cannot be detected correctly. To obtain quantitative measurement on crystalline and more mobile amorphous fractions, alternative sequences to the classical FID in the solid-state nuclear magnetic resonance were developed. Solid echo and magic sandwich echo sequences perform the relaxation decay refocusing somehow excluding the dead time problem and allow detection of the signal from the solid fraction. In this study, knowledge of amorphous/crystal fraction, which is obtained through solid echo and magic sandwich echo, has been explored on powder sugar samples for the purpose of developing a groundwork for a reliable quality control method. Different sugars were examined for the utilization of the sequences. What is important to add and make this study unique is that the method proposed did not involve multiparameter fitting of the "bead" pattern FID signal that normally suffers from ambiguity; just the integration of the fast Fourier transform of the solid echo was needed to calculate the second moment, (M₂ ).

A high-pressure metallic core holder for magnetic resonance based on Hastelloy-C

A metallic core holder, fabricated from non-magnetic Hastelloy-C276, has been designed for Magnetic Resonance (MR) and Magnetic Resonance Imaging (MRI) of core plug samples at high pressures and temperatures. Core plug samples, 1.5″ in diameter and 2″ in length, can be tested in the core holder at elevated pressures and temperatures, up to 5000 psi and 80 °C. These are conditions commonly found in petroleum reservoirs. A radio frequency probe, which excites and detects magnetic resonance signals, was placed inside the metal vessel. Proximity to the sample improves the signal to noise ratio of the resulting measurements. The metallic core holder is positioned between the poles of a 0.2 T permanent magnet and subjected to rapidly switched magnetic field gradients as part of the imaging process. This switching induces eddy currents on the conductive core holder, which degrades the magnetic field gradient waveform in the sample space. The low electrical-conductivity of Hastelloy-C276 minimizes the duration and the magnitude of such eddy currents. A recently developed pre-equalization technique was employed to ensure that magnetic field gradient pulses, required for MRI, are near ideal in the sample space. A representative core flooding experiment was undertaken in conjunction with MR/MRI measurements.

A method of water-soluble solid fraction saturation concentration evaluation in dry thalli of Antarctic lichenized fungi, in vivo

Background

At initial steps of rehydration from cryptobiosis of anhydrobiotic organisms or at rehydration of dry tissues the liquid ¹H NMR signal increased anomaly. The surplus in liquid signal may appear if some solid constituents dissolved, or if they were decomposed by enzymatic action.

Methods

Hydration kinetics, sorption isotherm, ¹H NMR spectra and high power relaxometry were applied to monitor gaseous phase rehydration of Antarctic lichen Cetraria aculeata. Tightly and loosely bound water signal were distinguished, and the upper hydration limit for dissolution of water soluble solid fraction was not observed. A simple theoretical model was proposed.

Results

The hydration courses showed a very tightly bound water fraction, a tightly bound water, and a loosely bound water fraction. Sigmoidal in form sorption isotherm was fitted well by multilayer sorption model. ¹H NMR showed one Gaussian signal component from solid matrix of thallus and one or two Lorentzian line components from tightly bound, and from loosely bound water. The hydration dependency of liquid signal was fitted by rational function.

Conclusions

Although in dehydrated C.aculeata the level of carbohydrates and polyols was low, the lichenase action during rehydration process increased it; the averaged saturation concentration c_s=(57.3±12.0)%, which resembled that for sucrose.

General significance

The proposed method of water soluble solid fraction saturation concentration, c_s, calculation from ¹H NMR data may be applied for other organisms experiencing extreme dehydration or for dry tissues. We recalculated the published elsewhere data for horse chestnut (Aesculus hippocastanum) bast [water-soluble solid fraction recognized as sucrose, c_s=(74.5±5.1)%]; and for Usnea antarctica, where c_s=0.81±0.04.

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Hydration kinetics show three fractions of bound water in lichen thallus.

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Sorption isotherm yields water fraction saturating primary water binding sites.

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¹H NMR spectra distinguish solid thallus and mobile and immobilized water fractions.

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Signal intensities supply saturation concentration, c_s, of water-soluble solid fraction.

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A simple theoretical model is proposed and applied also to already published NMR data.

Two dimensional IR-FID-CPMG acquisition and adaptation of a maximum entropy reconstruction

By acquiring the FID signal in two-dimensional TD-NMR spectroscopy, it is possible to characterize mixtures or complex samples composed of solid and liquid phases. We have developed a new sequence for this purpose, called IR-FID-CPMG, making it possible to correlate spin-lattice T1 and spin-spin T2 relaxation times, including both liquid and solid phases in samples. We demonstrate here the potential of a new algorithm for the 2D inverse Laplace transformation of IR-FID-CPMG data based on an adapted reconstruction of the maximum entropy method, combining the standard decreasing exponential decay function with an additional term drawn from Abragam's FID function. The results show that the proposed IR-FID-CPMG sequence and its related inversion model allow accurate characterization and quantification of both solid and liquid phases in multiphasic and compartmentalized systems. Moreover, it permits to distinguish between solid phases having different T1 relaxation times or to highlight cross-relaxation phenomena.

Basic principles of static proton low-resolution spin diffusion NMR in nanophase-separated materials with mobility contrast

We review basic principles of low-resolution proton NMR spin diffusion experiments, relying on mobility differences in nm-sized phases of inhomogeneous organic materials such as block-co- or semicrystalline polymers. They are of use for estimates of domain sizes and insights into nanometric dynamic inhomogeneities. Experimental procedures and limitations of mobility-based signal decomposition/filtering prior to spin diffusion are addressed on the example of as yet unpublished data on semicrystalline poly(ϵ-caprolactone), PCL. Specifically, we discuss technical aspects of the quantitative, dead-time free detection of rigid-domain signals by aid of the magic-sandwich echo (MSE), and magic-and-polarization-echo (MAPE) and double-quantum (DQ) magnetization filters to select rigid and mobile components, respectively. Such filters are of general use in reliable fitting approaches for phase composition determinations. Spin diffusion studies at low field using benchtop instruments are challenged by rather short (1)H T1 relaxation times, which calls for simulation-based analyses. Applying these, in combination with domain sizes as determined by small-angle X-ray scattering, we have determined spin diffusion coefficients D for PCL (0.34, 0.19 and 0.032nm(2)/ms for crystalline, interphase and amorphous parts, respectively). We further address thermal-history effects related to secondary crystallization. Finally, the state of knowledge concerning the connection between D values determined locally at the atomic level, using (13)C detection and CP- or REDOR-based "(1)H hole burning" procedures, and those obtained by calibration experiments, is summarized. Specifically, the non-trivial dependence of D on the magic-angle spinning (MAS) frequency, with a minimum under static and a local maximum under moderate-MAS conditions, is highlighted.

Hydrogen skeleton, mobility and protein architecture

The mobility of the proton-proton radial vectors is introduced as a quantitative measure for the structural dynamics of organic materials, especially protein molecules. As defined for the entire molecule, the hydrogen mobility (HM) is proposed as an "order parameter," which describes the effect of motional narrowing on inter-proton dipole-dipole interactions. HM satisfies all requirements of an order parameter in the Landau molecular field theory of phase transitions. The wide-line NMR second moments needed to obtain HM are exactly defined and measurable physical quantities, which are not produced by mathematical fitting and do not carry the limitations and restrictions of any model (theoretical formalism). We first demonstrate the usefulness of HM on small organic molecules with data taken form the literature. We outline its link with structural and functional characteristics on a range of proteins: HM provides a model-free parameter based on first principles that can clearly distinguish between globular and intrinsically disordered proteins, and can also provide insight into the behavior of disease-related mutants.

Structure and organization within films of arabinoxylans extracted from wheat flour as revealed by various NMR spectroscopic methods

Arabinoxylans (AXs) extracted from wheat flour were characterized by using three different techniques of NMR spectroscopy. Liquid-state (1)H NMR and solid-state (13)C NMR allowed the investigation of the fine structure of the three specific fractions of AXs representative of the structural heterogeneity of AX in wheat tissues. Three pure AX fractions exhibiting an arabinose to xylose ratio of 0.33, 0.53, and 0.73 were compared relative to their substitution feature and also to their assembly into thin films. Measurements of M(2), i.e. the second moment of proton dipolar interactions between the polysaccharide chains, were achieved using time-domain (TD) (1)H NMR at different water contents and temperatures. Transitions of the M(2) values were observed at a certain temperature close to the glass transition temperature T(g) values of AXs in films. Comparison of the different AX films containing various water contents pointed out stronger dipolar interactions for lowly substituted AX. This indicated that, in films, contiguous unsubstituted xylan chains can interact together through hydrogen bonding resulting in a compact structure with small nanopores because of the lower chain motions and the shorter average distances between the lowly substituted AX chains.

¹H Nuclear Magnetic Resonance of Lodgepole Pine Wood Chips Affected by the Mountain Pine Beetle

In this study, wood-water interactions of mountain pine beetle affected lodgepole pine were found to vary with time since death. Based on an analysis of magnetization components and spin-spin relaxation times from 1H NMR, it was determined that the mountain pine beetle attack does not affect the crystalline structure of the wood. Both the amorphous structure and the water components vary with time since death, which could be due to the fungi present after a mountain pine beetle attack, as well as the fact that wood from the grey-stage of attack cycles seasonally through adsorption and desorption in the stand.

Quantitative single point imaging with compressed sensing

A novel approach with respect to single point imaging (SPI), compressed sensing, is presented here that is shown to significantly reduce the loss of accuracy of reconstructed images from under-sampled acquisition data. SPI complements compressed sensing extremely well as it allows unconstrained selection of sampling trajectories. Dynamic processes featuring short T2* NMR signal can thus be more rapidly imaged, in our case the absorption of moisture by a cereal-based wafer material, with minimal loss of image quantification. The absolute moisture content distribution is recovered via a series of images acquired with variable phase encoding times allowing extrapolation to time zero for each image pixel and the effective removal of T2* contrast.

Study of triacylglycerol polymorphs by nuclear magnetic resonance: effects of temperature and chain length on relaxation parameters

It is very important to monitor the characteristics of triacylglycerol crystal network in fats, as these crystals have an impact on many food properties such as texture, sensory taste, and extended shelf life. Although time-domain NMR (TD-NMR) is now the reference technique to determine the solid fat index in food, the entire possibilities of this technique are not used. Some NMR studies have been performed to determine its power for the discrimination of polymorphism. In this study, extended investigations proved that TD-NMR could evaluate triacylglycerol (TA) polymorphism, independently from temperature and chain length. Study of the dipolar interactions through second moment M(2), which is characteristic of proton mobility in solid-state samples, provided a new understanding of the structural organization of crystal molecules. Proton spin-lattice relaxation, which has been proved to be a true probe of polymorphism, has provided information on crystal networks. Combination of the two techniques revealed two very interesting kinds of results, i.e. the presence of a minimum spin-lattice relaxation time T(1) for tristearin alpha, which is a characteristic of a dynamic molecular process, and differences in behavior between long and short chain lengths, both at a molecular and a crystal level.

Using Low-Field NMR To Infer the Physical Properties of Glassy Oligosaccharide/Water Mixtures

Low-field NMR (LF-NMR) is usually used as an analytical technique, for instance, to determine water and oil contents. For this application, no attempt is made to understand the physical origin of the data. Here we build a physical model to explain the five fit parameters of the conventional free induction decay (FID) for glassy oligosaccharide/water mixtures. The amplitudes of the signals from low-mobility and high-mobility protons correspond to the density of oligosaccharide protons and water protons, respectively. The relaxation time of the high-mobility protons is described using a statistical model for the probability that oligosaccharide hydroxyl groups form multiple hydrogen bonds. The variation of energy of the hydrogen bond is calculated from the average bond distance and the average angle contribution. Applying the model to experimental data shows that hydrogen atoms screen the water oxygen atoms when two water molecules solvate a single hydroxyl group. Furthermore, the relaxation time of the oligosaccharide protons is independent of its molecular weight and the water content. Finally, inversion of the FID using the inverse Laplace transform gives the continuous spectrum of relaxation times, which is a fingerprint of the oligosaccharide.

Rapid phase-compositional assessment of lipid-based food products by time domain NMR

In food science and technology, assessment of phase-compositional behaviour of lipids is critical for understanding many product properties and for effective process control. Time Domain NMR is a rapid and easy-to-handle technique, and is already well appreciated as a tool for phase-compositional assessment in foods. The phase-compositional detail that can be obtained with the established methodology is limited, however. In this work, we set out to obtain more phase-compositional details of lipids as currently feasible with the already established 'classical' NMR methods. We deployed a combined FID-CPMG experiment, and analyzed the Transversal Relaxation Decays by Deconvolution (TRDD) with semi-empirical mathematical functions for solid, semi-solid and liquid components. Within the solid component, different lipid crystal polymorphs can be discerned in a quantitative manner, i.e. alpha, beta and beta'. The TRDD method was validated against established NMR SFC methods, in terms of accuracy ('trueness') and precision. The solid fat content (SFC) of a large collection of fat blends was measured by the commonly employed NMR Direct and Indirect SFC methods and a good correlation with the results of the TRDD was observed, thereby demonstrating accuracy. Furthermore, TRDD was found to be equally precise as the established NMR SFC methods.