Field Nuclear Magnetic Resonance Research Articles

Effect of pectin addition on the drying characteristics of freeze-dried restructured strawberry blocks

Pectin is a commonly used food additive, however, the freeze-drying characteristics of restructured strawberries with pectin addition are currently unclear. This study investigated the effects of 0, 3, 6, and 9 g/kg pectin addition on moisture content, drying date, moisture ratio, water state distribution during the freeze-drying process, as well as water uptake and volatile compounds of freeze-dried restructured strawberry blocks (FRSB). The drying rates at the four levels of pectin addition presented similar early acceleration and later deceleration trends. Moisture content in FRSB was linearly predicted by peak area of low field nuclear magnetic resonance with R2 higher than 0.90 for all the four groups. High pectin addition resulted in higher sulfides response values. Compared with the control group, the water uptake of FRSB samples in 0, 3, 6, and 9 g/kg group decreased by 12, 22, and 31%, respectively, which can be reasoned that pectin addition shielded hydrophilic functional groups from external water molecules. These results provide guidance for improving the drying characteristics, volatile compounds, and water uptake of FRSB by adding pectin.

Effect of targeted acetylation on wood–water interactions at high moisture states

Acetylation is a wood modification used to increase the durability. Although it is known that the wood moisture content is lowered, the exact mechanisms behind the increased durability are not known. However, since fungi need water in different locations for different purposes the location and state of water is most probably of importance in addition to the total moisture content. In a previous study, we used targeted acetylation to alter the wood–water interactions in different parts of the wood structure in water saturated and hygroscopic moisture states. The main range for fungal degradation is, however, between these moisture ranges. This study investigated the effect of targeted acetylation on location, state and amount of water at non-saturated, high moisture states using the pressure plate technique. Specimens were modified using acetic anhydride by two approaches: (1) uniform modification (2) interface modification acting on the cell wall-lumen interface. They were then conditioned to eight moisture states between 99.64 and 99.98% relative humidity in both absorption and desorption and the location and state of water was studied using Low Field Nuclear Magnetic Resonance, X-ray computed tomography and Differential Scanning Calorimetry. Capillary water was present at all the included moisture states for all specimen types, but the amounts of capillary water in absorption were small. Increasing degree of interface modification increased the amount of capillary water compared to untreated wood. In addition, the uniformly modified wood often had higher amounts of capillary water than the untreated wood. The amount of cell wall water was decreased by uniform modification, but slightly or not reduced by the interface modification. The combination of targeted modification and conditioning to high well-defined moisture states thus gave very different amounts of capillary water and cell wall water depending on the conditioning history (absorption or desorption) and choice of modification. This opens new possibilities for designing materials and moisture states for fungal degradation experiments of wood.

Reducing water activity and softening texture of Areca catechu L. by phosphates and Maillard peptides and their improvement on flavor

Many studies have focused on reducing Aw to prevent the growth of spoilage bacteria. The effects of complex phosphates (CP) and Maillard peptide complexes (MPCs) on water activity (Aw), water status, sensory attributes, flavor, and hardness of the areca nuts were studied to extend their shelf life and improve their eating quality. The results showed that the addition of 1.6% CP and 0.6% MPCs significantly reduced the Aw of areca nuts (Aw = 0.8116). Low field nuclear magnetic resonance indicated that it was due to that the CP and MPCs promoted the conversion of free water to bound water through hydrogen bonding or electrostatic interaction. In addition, CP combined with MPCs reduced the extrusion hardness and puncture hardness of areca nuts, accompanied with a significant increase in softness and pulpiness as assessed through sensory analysis, which might be due to the improved water binding capacity of areca nuts. Moreover, MPCs increased the content of N, S heterocyclic compounds of the areca nuts and contributed to an increased “kokumi” attribute compared with CP.

Neurometabolism and brain morphometry in an adolescent female with an extra-hepatic congenital portosystemic shunt.

Chronic hepatic encephalopathy (CHE) has been reported both in patients with congenital porto-systemic shunts (CPSS) and chronic liver disease. CHE is difficult to recognize in children as there is no clear definition and its manifestations are highly variable. CHE is associated with variations in brain volumes and metabolites that have already been demonstrated using 1.5-3T MRI systems. However, the in-depth study of brain metabolism requires the high spectral resolution of high magnetic fields. We analyzed the neurometabolic profile, brain volumes and T1 relaxation times of a child with a CPSS using high field proton magnetic resonance spectroscopy (1H MRS, 7T) combined with MRI and compared it to an age-matched control group. We also evaluated the impact of shunt closure on neurocognitive symptoms using adapted neuropsychological tests. 7T MRS revealed a significant increase in glutamine compared to controls, a decrease in brain osmolytes, and a slight elevation in NAA concentrations. 7T MRI scans showed morphological abnormalities but no changes in the signal intensity of the globus pallidus. Neurocognitive testing revealed attention deficit disorder, language difficulties, and mild intellectual disability. Most of these areas improved after shunt closure. In this paediatric case of type B HE with normal fasting ammonia, neurometabolic profile was compatible with what has been previously shown in chronic liver disease, while also demonstrating an isolated glutamine peak. In addition, neurocognitive function partially improved after shunt closure, arguing strongly for shunt closure in both presymptomatic and symptomatic patients.

Effect of ultrasound combined with psyllium husk powder on the structure and gel properties of goose myofibrillar protein

In this study, we aimed to investigate the effect of ultrasound (US) combined with different amounts of psyllium husk powder (PHP) (0 %, 0.5 %, 1 %, 2 %, 3 %) on the gelation and structure of goose myofibrillar protein (GMP). The analysis of circular dichroism, surface hydrophobicity and fluorescence spectroscopy showed that the combination of US and 2 % PHP could promote the development of myofibrillar protein (MP) secondary and tertiary structure, which could facilitate the exposure of active site and enhance the interaction between GMP and PHP. Meanwhile, the thermal stability was enhanced with US and PHP treatment. In addition, the analysis of rheology, Low field nuclear magnetic resonance (LF-NMR), Fourier transform infrared (FT-IR) spectroscopy and microstructure showed that US combined with 2 % PHP addition could make the gel network structure denser. Thus, these results suggested that the combination of US and 2 % PHP could promote the unfolding of GMP structure and improve its gel properties. This study provides new insights for the interaction of GMP and PHP under US treatment, improving the application of goose meat in practical production.

Alleviative effects of carboxymethyl chitosan on the quality deterioration of frozen rice dough during freeze thaw cycles

The objective of this study was to examine the impact of carboxymethyl chitosan (CMCh) on rice dough quality during freeze–thaw cycles (FTCs). We conducted a comprehensive analysis of frozen rice dough using various techniques, including scanning electron microscopy (SEM), low–field nuclear magnetic resonance (LF–NMR), confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FT–IR), size–exclusion high–performance liquid chromatography (SE–HPLC), small–angle X–ray scattering (SAXS), X–ray diffraction (X–RD), differential scanning calorimetry (DSC), and rapid visco–analysis (RVA). Our results revealed that adding carboxymethyl chitosan (CMCh) to frozen rice dough reduced damage to starch granules and gluten proteins during FTCs compared to dough without CMCh. This resulted in the deceleration of the modification of the ordered protein structure. Furthermore, the inclusion of CMCh resulted in increased cross–linking with the large protein polymer, impairing the capacity of bound water to transition into free water within the frozen rice dough. Consequently, this led to an elevation in the storage modulus (G′), effectively retarding the textural transformation of the frozen rice dough. Introducing CMCh to frozen rice dough subsequently decelerated the alterations in the short-range order and crystal structures of starch, consequently modifying the pasting and thermal properties of the frozen rice dough. Based on the results obtained from our experiments, CMCh has a decelerating effect on the impact of frozen rice dough on FTCs.

The anti-digestibility mechanism of soy protein isolate hydrolysate on natural starches with different crystal types

The effects of soy protein isolate hydrolysate (SPIH) on the physicochemical properties and digestive characteristics of three starch types (wheat, potato, and pea) were investigated. Fourier-transform infrared spectroscopy and molecular dynamics simulations showed that hydrogen bonds were the driving force of the interaction between SPIH and starch. Furthermore, the SPIH was predicted to preferentially bind to the terminal region of starch using molecular dynamics simulations. Compared to pure starch, adding 20 % SPIH to wheat starch, potato starch, and pea starch, the content of resistant starch increased by 39.71 %, 125.66 % and 37.83 %, respectively. Both the radial distribution function (RDF) and low field-nuclear magnetic resonance (LF-NMR) showed that SPIH reduced the flow of water molecules in starch, indicating that SPIH competed with starch for water molecules. Multiple characterization experiments and molecular dynamics simulations confirmed that the anti-digestibility mechanism of SPIH on natural starches with different crystal types could be attributed to the interaction between starch and SPIH, which decreased the catalytic efficiency of amylase. This study clarified the anti-digestibility mechanism of SPIH on natural starches, which provides new insights into the production of low-glycemic index foods for the diabetic population.

Geophysical signatures of soil AFFF contamination from spectral induced polarization and low field nuclear magnetic resonance methods

Few field methods are available for characterizing source zones impacted with aqueous film forming foam (AFFF). Non-invasive geophysical characterization of AFFF source zone contamination in situ could assist with the delineation and characterization of these sites, allowing for more informed sampling regimes aimed at quantifying subsurface poly- and perfluoroalkyl substances (PFAS) contamination. We present initial results from the investigation of the sensitivity of two existing surface and borehole-deployable geophysical technologies, spectral induced polarization (SIP), and low field nuclear magnetic resonance (NMR), to soils impacted with AFFF. To investigate the sensitivity of these methods to AFFF-impacted soil, bench-scale column experiments were conducted on samples consisting of natural and synthetic soils and groundwater. While our findings do not show strong evidence of NMR sensitivity to soil PFAS contamination, we do find evidence that SIP has sufficient sensitivity to detect sorption of AFFF constituents (including PFAS) to soils. This finding is based on evidence that AFFF constituents associated with the pore surface produce a measurable polarization response in both freshly impacted synthetic soils and in soils historically impacted with AFFF. Our findings encourage further exploration of the SIP method as a technology for characterizing contaminant concentrations across AFFF source zones.

Insights into the adsorption of perfluoroalkyl substances (PFASs) on excess sludge from an on-site leachate treatment plant

The disposal and reduction of excess sludge is one of the most challenging aspects of wastewater treatment. Recycling excess sludge as functional materials is an innovative approach that has garnered broad attention, as it can address environmental concerns and reduce the consumption of valuable materials. However, this approach is still challenging due to the low mixed liquor suspended solids in sewage treatment plants and the high synthesis costs involved. In this study, we proposed the application of excess sludge from an on-site leachate treatment plant for the efficient removal of perfluoroalkyl substances (PFASs) from wastewater. A simple thermal treatment was conducted and the obtained sludge-based adsorbents enable effective PFASs removal. Through the use of low field nuclear magnetic resonance and structural characterizations, results demonstrated that denitrifying sludge had higher hydrophobicity and specific surface area (30.85 m2/g) than nitrifying sludge, resulting in enhanced PFASs adsorption capacity and initial adsorption rates. Kinetic and isotherm simulations indicated that the adsorption was efficient and controlled by surface and intraparticle diffusion. Characterization and regulation results showed that the adsorption was dominated by hydrophobic and electrostatic interactions. These findings suggest a promising recycling approach of excess sludge while elucidating the dominant mechanisms involved.

Pore and permeability changes in coal induced by true triaxial supercritical carbon dioxide fracturing based on low-field nuclear magnetic resonance

Supercritical carbon dioxide (ScCO2) fracturing is a green, clean, waterless extraction technique that has gained widespread attention. Coal pore properties, such as porosity, pore size distribution, connectivity, and permeability, are critical for fracturing and efficient coalbed methane production. This study examines the effects of ScCO2 fracturing on coal reservoir pore modification by conducting true triaxial ScCO2 fracturing experiments on high-rank coal samples under various stresses and injection rates. Low field nuclear magnetic resonance technique was used to compare and analyse the pore permeability characteristics of the samples before and after ScCO2 fracturing. The research discusses the influence of stress and ScCO2 fracturing fluid injection rate on coal pore modification and its controlling mechanisms. The results show a significant impact on coal pore modification, with a 59.85 % increase in porosity, 60 % increase in pore volume, 56 % increase in pore throat volume, and 47.5 % increase in permeability. Under the same injection rate and fixed temperature (40 °C), higher stress differences (8 MPa) benefit large pore modification and connectivity, while lower stress differences (4 MPa) are more favourable for micropore and transition pore modification and connectivity. These findings contribute to a deeper understanding of the microscopic mechanisms of ScCO2 fracturing in modifying coal pores.

Artificial intelligence-driven shimming for parallel high field nuclear magnetic resonance

Rapid drug development requires a high throughput screening technology. NMR could benefit from parallel detection but is hampered by technical obstacles. Detection sites must be magnetically shimmed to ppb uniformity, which for parallel detection is precluded by commercial shimming technology. Here we show that, by centering a separate shim system over each detector and employing deep learning to cope with overlapping non-orthogonal shimming fields, parallel detectors can be rapidly calibrated. Our implementation also reports the smallest NMR stripline detectors to date, based on an origami technique, facilitating further upscaling in the number of detection sites within the magnet bore.

An LF-NMR homogeneous immunoassay for Vibrio parahaemolyticus based on superparamagnetic 2D nanomaterials

In this work, a sensitive low field nuclear magnetic resonance (LF-NMR) homogeneous immunoassay, also called magnetic resonance switch (MRSw) sensor, for Vibrio parahaemolyticus (VP) was developed. Superparamagnetic 2D nanomaterial was designed and used as the magnetic probe of MRSw sensor. It was GO@SPIONs&Ab, a composite nanomaterial with many superparamagnetic Fe3O4 nanoparticles (SPIONs) providing a magnetic signal and VP antibody (Ab) specifically recognizing the target VP evenly distributed on the surface of GO. The presence of VP controllably changed the aggregation state of the probe, eliminating the uncertainty of MRSw sensor type, and thus then achieving a regular variation of transverse relaxation time T2 and ensuing quantitative detection of VP. Triple signal enhancement of the MRSw sensor was obtained due to the application of the designed 2D probe, by increasing the number of SPIONs, improving the magnetic intensity and susceptibility, and forming a synergistic effect. Under optimized experimental conditions, VP could be detected with satisfied sensitivity, selectivity, precision, accuracy, and stability, even in turbid real samples. LOQ for VP was 10 CFU/mL. This detection principle is widely applicable, providing an idea for the construction of highly sensitive MRSw sensors.

Completion of 25.2 T ultrahigh magnetic field NMR user facility in China

Significant scientific breakthroughs often arise from research conducted under extreme conditions, such as ultrahigh magnetic fields. Ultrahigh field nuclear magnetic resonance (NMR) provides a cutting-edge platform for studying material properties under extreme conditions. However, pursuing ultrahigh NMR presents considerable challenges, with only a few institutions worldwide having the requisite technical capabilities. After several years of research and development, we have successfully created the world’s first high-temperature superconducting (HTS) NMR experimental instrument under low-temperature measurement with a field strength exceeding 25 T using the Bi-2223 HTS double-pancake winding technique. The instrument has demonstrated exceptional performance, and stable operation, fully satisfying the demands of the user facility. The open operation of this experimental facility will significantly support basic scientific research in China and around the world.

Rheological and physicochemical properties of heat-induced ovalbumin gels in presence of sodium carboxymethyl cellulose.

In this study, the effect of sodium carboxymethylcellulose (CMC-Na) on the rheological and physicochemical properties of heat-induced ovalbumin (OVA) gels was evaluated. The OVA/CMC-Na composite gels were prepared by heat-induced (85 °C, pH 7.0) a mixture of CMC-Na (0, 0.2, 0.4, 0.8 and 1%) and OVA. The results revealed that the addition of CMC-Na dramatically reduced the springiness and hardness of the composite gels, while slightly enhancing the intermolecular hydrogen bonding interactions, which facilitated the improvement of the softness of the gels. It can be observed by SEM that the added CMC-Na was stacked on the surface of the OVA, resulting in visible "linear bumps". All gel samples exhibited shear-thinning behavior. The apparent viscosity of the composite gels increased with the addition of CMC-Na, and the OVA gel with 1% CMC-Na showed the highest apparent viscosity and the lowest storage modulus (G'). Additionally, low field nuclear magnetic resonance (LF-NMR) measurements indicated that the increasing CMC-Na boosted the water mobility of the composite gel. This study offers a novel approach to the development of ovalbumin-based soft gel foods, especially for certain populations with swallowing difficulties.

Pore structure characteristics and mechanical property of engineered cementitious composites (ECC) incorporating recycled sand

The mechanical properties of recycled sand (RS) modified ECC are intimately linked to its pore structure characteristics, but the internal pore size and distribution of RS modified ECC and its impact mechanism on the mechanical properties are still unclear. This study employed mercury intrusion porosimetry (MIP) and low field nuclear magnetic resonance (LF-NMR) techniques to analyze the pore structure of ECC incorporating RS. Furthermore, compression and tension mechanical experiments were conducted to investigate the correlation between the evolution of pore structure and mechanical properties of ECC incorporating RS. The findings demonstrate that the addition of RS increases the porosity of ECC. When replacement ratio of RS is 100 %, the volume fraction of pores decreases within the range of 10 nm to 100 nm, whereas it exhibits an increasing trend within a ranging from 100 nm to 1 μm. The incorporation of RS results in a decrease of the volume fraction of gel pores and the increase of capillary pores in ECC owing to its high-water absorption and porous, as well as the reduction of calcium-silicate-hydrate (C-S-H) due to the surface attached old mortar. Therefore, addition of RS lead to a reduction in both the compressive strength and tensile strength of ECC. However, as a result of the pore structural flaw inherent in the recycled fine aggregate, the occurrence of multi-crack cracking, induced by interfacial imperfections between the recycled fine aggregate and matrix, contributing to development of cracks in ECC and thus enhancing its tensile strain capacity.

Tracking transformation behavior of soluble to insoluble components in liquid egg yolk under heat treatment and the intervention effect of xylitol

The heat sensitivity of egg yolk limits its application, and xylitol can improve its thermal stability. The soluble and insoluble components of egg yolk and egg yolk containing xylitol treated at different temperatures were explored from the aspects of thermal instability behavior characterization and structure property. Magnetic resonance imaging and low field nuclear magnetic resonance showed that increased temperature induced liberation and transfer of hydrogen protons. Meanwhile, the apparent viscosity of soluble components increased, while that of insoluble components decreased. Microstructure showed that heat treatment induced aggregation and lipid transfer. SDS-PAGE showed that heat treatment induced aggregation and transformation of γ-livetin and apo-LDL. The change in crystal structure, Raman spectroscopy, and 3D fluorescence spectra showed that heat treatment resulted in the unfolding of yolk proteins, especially plasma proteins. Xylitol could alleviate transformation of components by stabilizing protein structure, alleviating the damage in protein integrity and elevation in aggregation size.

Rational biodiesel production by screening different long-term stored plant oils via nuclear magnetic resonance spectroscopic measurement

Screening the raw materials for biodiesel production has normally concentrated on the triglyceride (TAG) content and fatty acid profile without considering the oxidation stability, a crucial restriction factor for commercial life of biodiesel. The traditional screening methods had complex procedures by characterizing the raw material’ and the prepared biodiesel’ properties, which was not applicable for large sets of raw materials. These factors propelled the development of a simple and efficient screening method for potential biodiesel feedstock. Herein, we compared two kinds of spectroscopic measurements, the three-dimensional fluorescence (3D-FL) and high field nuclear magnetic resonance (NMR), for screening special and differential raw materials by investigating 19 plant oil species with one-year storage for biodiesel production. Among these samples, 13 kinds of plant oils contained TAGs, and the other 6 were free of TAGs. The results showed that 3D-FL measurements improperly assigned citronella oil as a TAG-containing plant oil and determined limited information about their chemical composition, suggesting unsatisfactory screening performance. In contrast, 1H NMR measurements screened 3 kinds of differential oils out of those 19 plant oil species, including coconut oil (Cocos nucifera L.), cotton seed oil (Gossypium barbadense L.), palm oil (Elaeis guineensis). Hierarchical clustering analysis (HCA) and partial least square discriminant analysis (PLS-DA) presented that the statistically significant NMR spectral bins for their differential compositions were signals at 3.6 ppm (–OCH3), 2.31 ppm (–OCH2–COOH), 4.29 ppm (TAG skeleton), and 5.27 ppm (TAG skeleton), representing the oxidation products, unsaturated fatty acids, and TAGs. Finally, the converted methyl and ethyl esters (biodiesel) from those three differential plant oil samples were subjected to Rancimat tests. They showed quite different oxidation stabilities from Rancimat tests, which was relevant to the composition differences in the NMR analysis. Our results suggested that the rapid, simple, and reliable NMR measurement combined with HCA and PLS-DA can serve as an efficient tool for potential biodiesel feedstock screening.

Improvement of the quality of frozen dough for fried flour products by electrostatic field assisted freezing.

With the continuous development of the food industry, frozen dough technology has gradually become an indispensable part of dough processing, but its quality is often reduced due to freezing during the production process. Electrostatic field assisted freezing (EF) technology, as a key research project in recent years, reduces the physical damage of food materials by reducing or changing the size of ice crystals in frozen products. In this study, different intensities of electrostatic fields were used to assist in the repeated freezing and thawing process of dough. The effects of electrostatic fields on the freezing nucleation process were evaluated by measuring dough freezing curves, low field nuclear magnetic resonance, and melting enthalpy. Finally, it was found that the freezing time of frozen dough added with electrostatic field assisted freezing processing was shortened, the decrease rate of hardness, viscosity, and elasticity was reduced, and the indicators of water distribution and protein secondary structure components were closer to those of fresh dough. This experiment used electrostatic field assisted freezing to reduce the damage to the dough structure during the freezing process, improve the quality of frozen dough and fried products, and improve the freezing efficiency of frozen dough. It provides a new idea for the study of frozen dough. This article is protected by copyright. All rights reserved.

Analysis of the mechanical behavior of polyurethane thermoset elastomers based on hydrogen bonding between different crosslinking point structures

To reveal the effect of polyurethane crosslinking point structures on the mechanical properties of polyurethane thermoset elastomers, using amorphous prepolymer poly (azide glycidyl ether) (GAP) as a binder, polyisocyanate cross-linker N100 and hexamethylene diisocyanate (HDI) as curing agents, trimethylolpropane (TMP) as a crosslinking agent, two GAP polyurethane thermoset elastomers that have similar chemical crosslinking network density, elastomer S0 prepared from GAP and N100 and elastomer S4 prepared from GAP and HDI/TMP, were selected to study in detail. DSC and XRD analysis indicated that two GAP polyurethane thermoset elastomers both exhibit stable amorphous aggregation structure below 80 °C. Mechanical properties test showed that thermoset elastomer S0 gives higher tensile modulus, lower tensile strength and elongation rate, while thermoset elastomer S4 gives lower tensile modulus, higher tensile strength and elongation rate. In-situ FTIR and low field nuclear magnetic resonance (LF-NMR) analysis suggested that there exists stronger urea carbonyl hydrogen bonding structure within thermoset elastomer S0, while weaker urethane carbonyl hydrogen bonding structure within thermoset elastomer S4. The different strength of the hydrogen bonding between crosslinking points imparts different segment mobility to S0 and S4. Dynamic thermodynamic analysis (DMA) indicated that, stronger urea carbonyl hydrogen bonding has suppressed segments mobility and thermoset elastomer S0 present lower loss modulus and loss factor, while thermoset elastomer S4 present higher loss modulus and loss factor because there just exist weaker urethane carbonyl hydrogen bonding interaction between crosslinking points.

Measurement of physicochemical and dough pasting properties of fresh potato instant noodles as influenced by addition of emulsifiers

Effects of different types and concentrations of emulsifiers on physicochemical properties of fresh potato added instant noodles and its dough pasting properties were analyzed. The Rapid visco-analyzer (RVA) data showed that noodle sample at 30 % polysorbate-40 (P40) exhibited significantly high pasting properties compared to control sample and changed slightly at added distilled monoglycerides (DMGs) and diacetyl tartaric acid esters of mono-glycerides (DATEM) levels. Rheological analysis exhibited comparable storage modulus (Gʹ) to loss modulus (Gʹʹ) and tanδ higher than control sample. The fresh potato instant noodles added with DMGs and DATEM exhibited low textural parameters, enhanced color parameters and loose microstructures. Fourier transform infrared spectroscopy (FT-IR) analysis revealed that molecular structure of the noodles was not affected by the added emulsifiers. Low field nuclear magnetic resonance (LF-NMR) analysis indicated that distribution of water fraction in fresh potato noodles was slightly affected by the added emulsifiers.