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Magnetic resonance imaging (MRI) is the method of choice for noninvasive studies of micrometer-scale structures in biological tissues via their effects on the time- and frequency-dependent (restricted) and anisotropic self-diffusion of water. While new designs of time-dependent magnetic field gradient waveforms have enabled disambiguation between different aspects of translational motion that are convolved in traditional MRI methods relying on single pairs of field gradient pulses, data analysis for complex heterogeneous materials remains a challenge. Here, we propose and demonstrate nonparametric distributions of tensor-valued Lorentzian diffusion spectra, or "D(ω) distributions," as a general representation with sufficient flexibility to describe the MRI signal response from a wide range of model systems and biological tissues investigated with modulated gradient waveforms separating and correlating the effects of restricted and anisotropic diffusion. [ABSTRACT FROM AUTHOR]

The consumer satisfaction of lard-based bread spreads depends on a delicate balance between a liquid fat phase, allowing the spread to flow, and solid fat crystals, providing the product with substance sometimes further enhanced by crispy pork cracklings. Here we apply 13C solid-state NMR with dynamics-based spectral filtering to characterize and follow the temperature dependence of the co-existing solid and liquid triglyceride phases in commercial German Griebenschmalz and Polish smalec, both containing cracklings, as well as home-made Danish fedt and, as a chemically more pure reference, German Schweineschmalz intended for baking. The NMR method allows detection of carbon atoms representative of saturated, unsaturated, and polyunsaturated acyl chains in both solid and liquid states. The results show that the solid comprises multiple crystal forms with different melting temperatures, while the liquid is at low temperature enriched in triglycerides with shorter acyl chains and higher degree of unsaturation, which become diluted with long-chain saturated triglycerides as the solids are melting. The obtained deeper understanding of the concomitant aspects of the phase transitions may pave the way for future efforts of rational optimization of fat blend composition to extend the temperature range over which the product contains sufficient amounts of both solids and liquids to give texture properties appealing to consumers. [ABSTRACT FROM AUTHOR]

Solid-state NMR methods incorporating dynamics-based spectral editing have a remarkable versatility for resolving and separately characterizing co-existing solid and liquid phases or domains in biologically and technically relevant organic materials. While 13C spectra acquired under magic-angle spinning and 1H decoupling provide atomic resolution, the signal intensities obtained with the CP and INEPT polarization transfer techniques give qualitative information about dynamics. This mini-review covers the basics of translational and rotational motion of atoms and molecules in organic materials, theoretical aspects of the relations between C–H bond reorientation and CP and INEPT signal intensities, and applications of the methods to a broad range of heterogeneous materials comprising hydrated assemblies of surfactants, lipids, proteins, and/or carbohydrates. [ABSTRACT FROM AUTHOR]