Probing structural features in potato starch granules at moderate hydration through the modelling of 1H->13C polarization transfer kinetics.

The structural arrangement of starch polymers in presence of water is known to impact the functional properties of starchy products. In this study, the hydration of potato starch granules was investigated at the molecular level through various 1H->13C polarization transfer solid-state Nuclear Magnetic Resonance (ss-NMR) experiments. The impact of increasing the water content from 12.3 % to 45.9 % was assessed using 13C Cross Polarization Magic Angle Spinning (CPMAS), Variable Contact Time (VCT-CPMAS), Variable Spin Lock (VSL-CPMAS), and T One Rho QUEnching (TORQUE) NMR sequences. Of these, VCT-CPMAS proved to be the most promising. When applied with an optimal number of contact times, it enabled the application of several mathematical models that provided detailed insights into the structuring of protons in the hydrated potato starch granules. At low hydration (12.3 %), the models enabled various structural domains to be distinguished, which we suggest are associated with helical and amorphous structures. At moderate hydration (45.9 %), we tested two fitting models. Two pools of protons were revealed, corresponding to loosely ordered structures on the scale of tens of nanometers. These findings suggest varying water distribution during starch hydration and are likely to indicate variable hydration levels in the multilamellar amorphous structures of starch granules.

Polysaccharide-water interactions: NMR and DVS data.

The data provided here relate to the research paper "Assessing the complementarity of TD-NMR, solid-state NMR and Dynamic Vapor Sorption in the characterization of polysaccharide-water interactions". The original data from TD-NMR, ss-NMR and DVS is provided in .dps, topspin and .xls formats respectively, allowing other authors to repeat our processing protocols using different parameters. We also include results obtained by varying the signal treatments. The analysis of these multimodal data have highlighted a variation in polysaccharide-water interactions depending on the type of assembly. These datasets are very useful for discriminating between water bound to polysaccharides and water absorbed or adsorbed into polysaccharide network, a key element in understanding interactions in these assemblies and an essential approach for developing tailor-made polysaccharides-based products.

Assessing the complementarity of time domain NMR, solid-state NMR and dynamic vapor sorption in the characterization of polysaccharide-water interactions.

Characterizing the hygroscopic behavior of macromolecular assemblies is crucial for understanding biological processes as well as to develop tailor-made polysaccharides-based products. In this work, assemblies consisting of nanocelluloses (CNC or CNF) and/or glucomannan in different ratio were studied at different water activity levels, using a multi-analytical approach that combined Dynamic Vapor Sorption (DVS), Time-Domain Nuclear Magnetic Resonance (TD-NMR) and solid-state NMR (ss-NMR). The water retention capacity of the films, as a function of their composition, showed that an enrichment in konjac glucomannan in association with cellulose increased the water absorption capacity but decreased the water retention capacity. In addition, the combination of CNC and glucomannan appears to reduce the water absorption capacity of each polymer. Correlating the findings from the various methods allowed us to propose the use of TD-NMR data for predicting the water retention capacity. These results, summarized in a schematic representation, offer new insights into the organization of water molecules in polysaccharide assemblies in various humidity conditions.

Optimization of acquisition and processing times for the measurement of 1H to 13C polarization transfer kinetics.

Solid-state NMR (ssNMR) is a unique technique allowing the study of macromolecular assemblies in their native state without prior modification. The proposed method simplifies the current long and tedious data-acquisition and processing protocols for Variable Contact Time (VCT) ssNMR experiments used in dynamic studies of macromolecular assemblies. Using cellulose nanocrystals as a model for polysaccharide assembly, the acquisition time was reduced by decreasing the number of scans and shortening the recycling time required for the 1H to 13C polarization transfers.•A tenfold reduction in the acquisition time for each kinetic point was achieved while maintaining a good signal to noise ratio.•The processing time for the pseudo-2D solid-state NMR data was also shortened by using signal intensities derived from peak picking rather than the classically-used spectral deconvolution method.•These optimizations enabled the molecular dynamic parameters T1ρ H, THH, TCH to be accessed within a day.

Assessment of cellulose interactions with water by ssNMR: 1H->13C transfer kinetics revisited.

To evaluate cellulose interactions with water, 1H->13C polarization transfer kinetics during Variable Contact Time CP-MAS NMR spectroscopy were studied and modelled using cellulose of different origins. The increase in the temporal resolution of the plot relating signal intensity to contact-time made it possible to compare different physical models for use in fitting the kinetic curve. These models involve combinations of variables, such as proton spin diffusions, that require a better understanding of their physicochemical and structural bases. To that end, hydrogen interactions were modulated by adding water, first by varying cellulose water content, second by exchanging hydroxyl protons with D2O, and last by varying the spinning rate. The results demonstrate that this approach makes it possible to probe interactions of polysaccharides with structural water, as well as to follow the evolution of the proton-proton interactions during hydration through spin diffusion times.