Low-field Nuclear Magnetic Resonance Analysis Research Articles

Changes of physicochemical and functional properties of processed cheese made with natural cheddar and mozzarella cheeses during refrigerated storage

The present study aimed to investigate changes of physicochemical and functional properties of the processed cheeses (PCs) made with Cheddar (PC1), Mozzarella (PC2) and both of them at a ratio of 1:1 (PC3) during storage at 4 °C for 4 months. The results showed that the type of natural cheese used affected the composition of PCs with lower fat content in PC2 due to the lower fat content of Mozzarella cheese used. PC2 with lower fat content showed decreased meltability and oil leakage compared with PC1 and PC3. The stretchability of all the samples significantly (P < 0.05) decreased during storage, and PC1 showed lower stretchability. This was confirmed by increased protein hydrolysis of all the samples during the storage with a higher level of proteolysis in PC1, leading to decreased stretchability of PCs. Further low-field nuclear magnetic resonance analysis indicated more entrapped water in cheese due to moisture migration into the cheese matrix that might squeeze the fat globules to aggregate, causing more fat leakage during later stages of storage. This was evidenced by microstructural analysis showing different extents of increase in fat particle sizes and decrease in free serum in all the PC samples over the storage time. Therefore, the present study provides further understanding of the mechanism of quality change of PC during refrigerated storage as affected by proteolytic properties and composition of natural cheese used.

Anhydride esterification to regulate water migration and reduce ice crystal formation in κ-carrageenan gel during freezing

In this study, κ-carrageenan was chemically modified by acid anhydride esterification to produce acid anhydride-esterified κ-carrageenan, and its properties were subsequently determined. Acid anhydride-esterified κ-carrageenan can improve the water retention properties of gels and limit the deterioration of gel textural performances during the freezing process. Scanning electron microscopy results before and after freezing showed that the frozen esterified κ-carrageenans had a more regular and less fibrous network structure, which suggests that the esterified κ-carrageenans better maintained the gel network structure. These phenomena were studied in relation to intermolecular forces, water movement, and ice crystal formation. The intermolecular force analysis showed that the esterification of anhydride disrupted the hydrogen bond formed between κ-carrageenan molecules, enhanced hydrophobic interactions among κ-carrageenan molecules, and resulted in stronger electrostatic repulsion. Low-field nuclear magnetic resonance analysis showed that acid anhydride-esterified κ-carrageenan more effectively bound to water molecules during freezing. Differential scanning calorimetry results showed that acid anhydride-esterified κ-carrageenan reduced the amount of freezing water and lowered the eutectic point of the gel. The results showed that hydrogen bonding, electrostatic interactions, and hydrophobic interactions modified the structure of the acid anhydride-esterified κ-carrageenan gel network and its binding to water molecules. This phenomenon allowed acid anhydride-esterified κ-carrageenan to better maintain binding with water molecules during the freezing process, which in turn delayed and reduced the formation of ice crystals and greatly decreased the effect of ice crystals on the structure of the gel network.

Effects of starch hydration properties on the batter properties and oil absorption of fried crust and battered ham sausages

Water plays an important role in deep-frying. To assess the effects of water on oil absorption by fried crust and battered ham sausages (FCBHSs), we selected four starch types with different hydration properties: tapioca starch (TS), freeze-thawed tapioca starch (FTS), carboxymethyl tapioca starch (CMTS), and carboxymethyl freeze-thawed tapioca starch (CM-FTS). CMTS had the best hydration properties, followed by CM-FTS, FTS, and TS, respectively. CM-FTS with its medium hydration properties strengthened batter properties which reduced FCBHSs oil absorption. Low-field nuclear magnetic resonance analysis revealed that CM-FTS increased the percentages of bound and semi-bound water in the batter, thereby enhancing water retention and delaying water loss during deep-frying. Analyses of protein particle size distribution, zeta potential, disulfide bonding and microstructure revealed that CM-FTS promotes protein aggregation and the formation of a protein network structure, leading to a denser internal structure, which inhibits oil absorption. Additionally, differential scanning calorimetry analysis indicated that CM-FTS enhances the batter's thermal stability of batter, thereby rendering it more resistant to frying. However, the use of CMTS, with its strong hydration properties increased FCBHSs oil absorption. In conclusion, we propose that suitable modification of starch's hydration properties can aid in preparing deep-fried battered food characterized by low oil absorption.

Low-field, not low quality: 1D simplification, selective detection, and heteronuclear 2D experiments for improving low-field NMR spectroscopy of environmental and biological samples.

Understanding environmental change is challenging and requires molecular-level tools to explain the physicochemical phenomena behind complex processes. Nuclear magnetic resonance (NMR) spectroscopy is a key tool that provides information on both molecular structures and interactions but is underutilized in environmental research because standard "high-field" NMR is financially and physically inaccessible for many and can be overwhelming to those outside of disciplines that routinely use NMR. "Low-field" NMR is an accessible alternative but has reduced sensitivity and increased spectral overlap, which is especially problematic for natural, heterogeneous samples. Therefore, the goal of this study is to investigate and apply innovative experiments that could minimize these challenges and improve low-field NMR analysis of environmental and biological samples. Spectral simplification (JRES, PSYCHE, singlet-only, multiple quantum filters), selective detection (GEMSTONE, DREAMTIME), and heteronuclear (reverse and CH3/CH2/CH-only HSQCs) NMR experiments are tested on samples of increasing complexity (amino acids, spruce resin, and intact water fleas) at-high field (500 MHz) and at low-field (80 MHz). A novel experiment called Doubly Selective HSQC is also introduced, wherein 1H signals are selectively detected based on the 1H and 13C chemical shifts of 1H-13C J-coupled pairs. The most promising approaches identified are the selective techniques (namely for monitoring), and the reverse and CH3-only HSQCs. Findings ultimately demonstrate that low-field NMR holds great potential for biological and environmental research. The multitude of NMR experiments available makes NMR tailorable to nearly any research need, and low-field NMR is therefore anticipated to become a valuable and widely used analytical tool moving forward.

Preparation of bilayer nano-oleogel by whey protein isolate and soy lecithin for fish oil encapsulation and its application in cookies

In this study, a bilayer nano-oleogel system was designed and prepared by incorporating fish oil into varying levels of glyceryl monostearate (GMS), followed by encapsulation with soy lecithin and whey protein isolate (WPI). The formation of the nano-oleogel involved utilizing an oleogel/water nanoemulsion technique, which was followed by freeze-drying to remove water. The initial coating with lecithin yielded an average oleogel size of 144.8 nm, which increased to 561.5 nm after the second coating with WPI. Mechanical behavior analysis assessed the effect of varied GMS content on oleogel stability. The results of low-field nuclear magnetic resonance analysis exhibited a T2 relaxation time blueshift from 114.9 to 103.5 ms post fish oil encapsulation, implying reduced proton mobility in the nano-oleogel due to increased GMS within lecithin and WPI double layers. The results of differential scanning calorimetry analysis indicated enhanced thermal stability with higher GMS content in oleogels. Electronic nose analysis revealed that gelation and layer-by-layer encapsulation resulted in an off-flavor reduction from fish oil. Furthermore, the nano-oleogel was successfully used as a shortening substitution in making cookies with acceptable properties. Our findings suggested that the prepared nano-oleogel with flavor-inhibition capabilities could be used for replacing unhealthy solid fats.

Combining multi–spectroscopy analysis and interfacial properties to research the effect of ultrasonic treatment on soybean protein isolate–tannic acid complexes

In this study, ultrasonic treatment of soybean protein isolate (SPI)–tannic acid (TA) non-covalent complexes were performed. In the multi-spectroscopic analysis, it was found that the content of the α-helix decreased, the exposure of amino acid residues increased, the content of the trans-gauche-trans mode of disulfide bonds increased, and the fluorescence intensity decreased. Static quenching occurred between TA and SPI, and ultrasonic treatment promoted their combination. The SPI–TA complexes had lower surface roughness at 450 W. At this moment, the volume mean diameter and zeta potential of the complexes were 70.76 nm and −22.4 eV, respectively. The surface hydrophobicity, solubility, contact angle, emulsification activity index, and emulsion stability index were 4,355, 73.2%, 49.71°, 117 m2/g, and 63 min, respectively. The diffusion rate of the sample under ultrasonic treatment at 450 W was 0.14777. Low-field nuclear magnetic resonance analysis revealed a higher percentage of immobilized water in the SPI–TA complex at 450 W. The above findings will help to promote the improvement in various aspects of the properties of SPI and enhance its application prospects.

Effect of blanching and ultrasound pretreatment on moisture migration, uniformity, and quality attributes of dried cantaloupe.

To overcome problems of browning and crusting during the pretreatment process and provide theoretical guidance for cantaloupe convection drying at 80°C, the effects of blanching (BL) and ultrasonic (US) treatments were examined. The effects of various BL (5, 10, and 15 s) and US (10, 20, 30, and 40 min) durations on convection drying were tested. The moisture ratio, drying rate, moisture effective diffusivity, color, browning, nuclear magnetic resonance characteristics, and texture were assessed. Compared with the control group, the maximal decreases in the drying time of BL and US pretreatment groups were 40% and 33.3%, respectively. BL and US pretreatments significantly increased the effective diffusion coefficient and shortened the drying time because of the destruction of the cell structure. Low-field nuclear magnetic resonance analysis showed that free water is mainly lost during the initial drying stage, while solidified water is mainly lost during middle and late stages. According to the results of magnetic resonance imaging, the moisture distribution shows that cavitation from US acts on internal tissue, while BL disrupts the structure of external tissue. Texture data define the area enclosed by SC-D as uniform. After BL and US pretreatment, the hardness of dried cantaloupe decreased and the uniformity increased significantly. The best pretreatment process for cantaloupe at 80°C was 10 min of US. These findings provide a reference for testing in the industrial production of dried cantaloupe and are deeply relevant for practice.

Utilization of two plant polysaccharides to improve fresh goat milk cheese: Texture, rheological properties, and microstructure characterization

This study aimed to evaluate the effects of added jujube polysaccharide (JP) and Lycium barbarum polysaccharide (LBP) on the texture, rheological properties, and microstructure of goat milk cheese. Seven groups of fresh goat milk cheese were produced with 4 levels (0, 0.2, 0.6, and 1%, wt/wt) of JP and LBP. The goat milk cheese containing 1% JP showed the highest water-holding capacity, hardness, and the strongest rheological properties by creating a denser and more stable casein network structure. In addition, the yield of goat milk cheese was substantially improved as a result of JP incorporation. Cheeses containing LBP expressed lower fat content, higher moisture, and softer texture compared with the control cheese. Fourier-transform infrared spectroscopy and low-field nuclear magnetic resonance analysis demonstrated that the addition of JP improved the stability of the secondary protein structure in cheese and significantly enhanced the binding capacity of the casein matrix to water molecules due to strengthened intermolecular interactions. The current research demonstrated the potential feasibility of modifying the texture of goat milk cheese by JP or LBP, available for developing tunable goat milk cheese to satisfy consumer preferences and production needs.

Effect of cooking methods and polysaccharide addition on the cooking performance of cubic fat substitutes

This study examined the effect of two different cooking methods (grilling and frying) and konjac glucomannan (KGM) addition on the cooking yield, water distribution, color, texture, oral tribology, sensory characteristics, and thiobarbituric acid (TBA) content of cubic fat substitutes (CFS). Grilled samples displayed higher yellowness and lightness values and cooking yield. Low-field nuclear magnetic resonance analysis showed that the fixed water relaxation time gradually decreased at a higher KGM level, indicating that KGM changed the distribution and migration of internal water. The relaxation time and amplitude of the grilled samples were slightly higher, indicating a slightly lower fixed water level. The textural and sensory evaluation showed that the overall sensory score of the fried cubic fat substitutes and pork backfat exceeded that of the grilled samples. A higher KGM content improved the hardness, springiness, and chewiness of the cubic fat substitutes to improve the texture and taste. The thiobarbituric acid reactive substance (TBARS) value of all the cubic fat substitutes was significantly lower than in the pork backfat, while these values were slightly higher when fried than when grilled. Scanning electron microscopy (SEM) revealed that KGM addition rendered the network structure more compact, denser, and similar to that of pork backfat. This study provided a theoretical basis for cooking cubic fat substitutes and research involving properties such as the cooking yield and water distribution after cooking.

Correlation between Water Characteristics and Gel Strength in the Gel Formation of Golden Pompano Surimi Induced by Dense Phase Carbon Dioxide.

The relationship between the gel quality of golden pompano surimi treated with dense phase carbon dioxide (DPCD) and changes in water characteristics was evaluated. Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to monitor changes in the water status of surimi gel under different treatment conditions. Whiteness, water-holding capacity and gel strength were used as the quality indicators of the surimi gel. The results showed that DPCD treatment could significantly increase the whiteness of surimi and the strength of the gel, while the water-holding capacity decreased significantly. LF-NMR analysis showed that, as the DPCD treatment intensity increased, the relaxation component T22 shifted to the right, T23 shifted to the left, the proportion of A22 decreased significantly (p < 0.05) and the proportion of A23 increased significantly (p < 0.05). A correlation analysis of water characteristics and gel strength showed that the water-holding capacity of surimi induced by DPCD was strongly positively correlated with gel strength, while A22 and T23 were strongly negatively correlated with gel strength. This study provides helpful insights into the quality control of DPCD in surimi processing and also provides an approach for the quality evaluation and detection of surimi products.

κ-Carrageenan/konjac glucomannan composite hydrogel filled with rhamnolipid-stabilized nanostructured lipid carrier: Improvement of structure and properties

This study investigated the feasibility of applying rhamnolipid-stabilized nanostructured lipid carrier (RNLC) as a novel type of particulate filler and its impact on the structure and properties of κ-carrageenan/konjac glucomannan (KC-KGM) composite hydrogel. RNLC particles (204.87 ± 3.50 nm) were fabricated by high-pressure homogenization method. X-ray diffraction and differential scanning calorimetry results suggested that KC-KGM could regulate the crystallinity and polymorphism of RNLC. Fourier transform infrared spectroscopy analysis verified the presence of hydrogen bond and electrostatic interaction between RNLC and KC-KGM. Cryo-scanning electron microscopy and magnetic resonance imaging observation revealed that the increase of RNLC (0–0.25 wt%) led to a denser network structure with good uniformity, improving the texture profiles (hardness and cohesiveness) and rheological properties (moduli, critical strain and thermal stability) of composite hydrogels. RNLC at higher filling levels (0.5–2 wt%) made composite hydrogels more rigid and brittle. Low field-nuclear magnetic resonance analysis confirmed the decreased mobility of immobilized/free hydrogen protons in RNLC-filled composite hydrogels, and their water synthesis rates could be reduced by up to 12.26% after freeze-thawing for five repetitions. The fitting of Korsmeyer-Peppas model (R2 > 0.992) unraveled that the swelling mechanism of composite hydrogels belonged to pseudo-Fickian diffusion, and the swelling behavior could be altered by adjusting the particle filling level. Overall, the optimal synergistic effect between structure and properties could be achieved when the mass ratio of KC-KGM to RNLC reached 4:1. These findings would bring more potential for applying RNLC as a functional filler in gel foods.

Effects of κ-carrageenan gum on 3D printability and rheological properties of pork pastes

The effects of κ-carrageenan gum (KG) on the 3D printability and rheological properties of pork pastes were investigated in this study. There were five groups with different levels of KG (0, 2, 4, 6, and 8 g/kg) named as KG-0, KG-2, KG-4, KG-6, and KG-8, respectively. The addition of KG increased the yield stress, viscosity, shear stress, recovery percentage, storage modulus, loss modulus, and initial and average flow forces (P < 0.05). The results of low-field nuclear magnetic resonance analysis revealed that addition of KG reduced T21 and T22 (P < 0.05). The best printing parameters were obtained by accuracy and stability results: printing filling percent, 90%; printing speed, 35 mm⋅s−1; layer height, 2 mm; nozzle diameter, 1.55 mm, and KG addition level, 6 g/kg. KG addition improved the hardness, springiness, chewiness, cohesiveness, adhesiveness, and density, respectively (P < 0.05). The results suggested that KG addition improved the rheological properties and 3D printability of the pork pastes.

Changes in muscle quality and physicochemical characteristics of chicken breast subjected to ultrasound-assisted immersion freezing during long-term frozen storage

The influence of ultrasound-assisted immersion freezing (UF), immersion freezing (IF), and air freezing (AF) on the muscle quality and physicochemical properties of chicken breasts during frozen storage (0 –180 days) was investigated. The ice crystal size in UF samples was smaller than in IF and AF samples during frozen storage. UF significantly lowered the samples’ thawing and cooking losses during frozen storage compared to IF and AF (P < 0.05). While the cutting force values of all the samples gradually reduced with extension of storage period, the UF samples showed the least change in cutting force (P < 0.05), indicating that UF samples had the least muscle structure deterioration. UF samples also possessed the lower color deterioration and lipid oxidation compared to the IF and AF samples (P < 0.05). Low-field nuclear magnetic resonance analysis showed that UF treatment minimized water migration in samples during storage (P < 0.05). Hierarchical cluster analysis revealed that the quality of the UF samples after 180 days of storage was similar to the IF samples after 90 days and the AF samples after 60 days. In general, the UF treatment was beneficial to decrease muscle loss during frozen storage.

Polymer/organic compound high-temperature retarder used for oil and gas exploration, and development

During the process of oil and gas exploration and development, the cementing operation is the key factor to ensure oil well productivity, and the performance of additives is directly related to the success or failure of cementing. In this study, the polymer retarder PID-1 was synthesised by aqueous solution polymerisation; the chemical structure, thermal stability and microstructure of PID-1 were studied by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. In addition, the retarding effect and mechanism of PID-1 were analysed based on low-field nuclear magnetic resonance analysis, adiabatic calorimetry and scanning electron microscopy. Then, the polymer/organic compound high-temperature retarder PID-2 was constructed by adding organic compound PN with well retarding property; the retarding effect, thickening property, temperature and dosage sensitivity of PID-2 were then investigated. Combined with porosity evolution, type and content of hydration products, the internal mechanism of retarder PID-2 in relation to early mechanical strength development of the cement slurry system was revealed.

Early-Age Hydration Reaction and Strength Formation Mechanism of Solid Waste Silica Fume Modified Concrete.

Solid waste silica fume was used to replace fly ash by different ratios to study the early-age hydration reaction and strength formation mechanism of concrete. The change pattern of moisture content in different phases and micro morphological characteristics of concrete at early age were analyzed by low field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM). The results showed that the compressive strength of concrete was enhanced optimally when the replacement ratio of solid waste silica fume was 50%. The results of LF-NMR analysis showed that the water content of modified concrete increased with the increase of solid waste silica fume content. The compressive strength of concrete grew faster within the curing age of 7 d, which means the hydration process of concrete was also faster. The micro morphological characteristics obtained by SEM revealed that the concrete was densest internally when 50% fly ash was replaced by the solid waste silica fume, which was better than the other contents.

Effect of fatty acid saturation on gel properties of salt-soluble protein in pork.

The objective of this study was to evaluate the effect of fatty acid saturation (oleic acid, linoleic acid, and linolenic acid) on water distribution, migration, and gel properties of pork salt-soluble protein, by detected indicators that are Low field nuclear magnetic resonance (LF-NMR), magnetic resonance imaging (MRI), water-holding capacity (WHC), and gel strength. These results suggested that the WHC and gel strength decreased with the decrease of fatty acid saturation (p<0.05). LF-NMR analysis revealed that the relaxation time T21 and T22 decrease (p<0.05) with the decrease of fatty acid saturation. Results also showed that the T21 increased and T23 decreased in linolenic acid group compared with oleic acid group. Meanwhile, the peak area ratio of P21 and P22 decreased (p<0.05), while P23 increased (p<0.05). Therefore, the saturation of fatty acids had a great influence on the gel properties of protein. PRACTICAL APPLICATION: It provides a theoretical basis for the production of polyunsaturated fatty acids emulsified gel meat products and promotes the development of meat processing industry.

Insight into the Effect of Ice Addition on the Gel Properties of Nemipterus virgatus Surimi Gel Combined with Water Migration.

The effect of the amount of ice added (20–60%) on the gel properties and water migration of Nemipterus virgatus surimi gel obtained with two-stage heat treatment was studied. The gel strength and water-holding capability (WHC) of the surimi gel with 30% ice added were significantly higher than those of other treatment groups (p < 0.05). The addition of 30% ice was conducive to the increase of protein β-sheet proportion during heat treatment, exposing more reactive sulfhydryl groups. These promoted the combination of protein-protein through disulfide bonds and hydrophobic-hydrophobic interactions, forming an ordered three-dimensional gel network structure. Meanwhile, the increase in hydrogen bonds promoted the protein-water interaction. Low-field nuclear magnetic resonance analysis showed that more bound water was locked in the gel system, reducing the migration of immobile water to free water and finally showing better gel properties. When the amount of ice added was insufficient (20%), the gel structure lacked the support of immobile water, resulting in deterioration of gel strength. However, excessive addition of ice (>30%) was not conducive to the combination of protein-protein and protein-water, forming a large and rough gel structure, resulting in the migration of immobile water to free water and ultimately exhibited weak gel properties.

Microwave heating of dried minced pork slices with different fat content: An assessment of dielectric response and quality properties

Dried minced pork slices (DMPS) have been widely accepted owing to their unique flavor and taste, but traditional roasting (TR) process for making DMPS are time-consuming and complicated. This study presents a microwave heating (MH) method for rapid preparation of DMPS with different fat pork levels. The results indicated that DMPS size significantly affected the MH patterns. As the fat pork content increased, the complex permittivity showed a downward tendency, and the 30% fat pork content improved both the heating rate and uniformity. Fat components significantly altered the texture and color characteristics, but DMPS made by MH possessed a higher hardness and toughness values than TR. Low-field nuclear magnetic resonance analysis demonstrated that the proportion of T21 gradually decreased in MH group, while no distinct changes were observed in the TR group with the increase of fat pork content. In addition, the results of comprehensive sensory evaluation in the MH and TR groups revealed that such a convenient MH technology is alternative for the fabrication of DMPS with acceptable product quality.

Effect of extra oxygen on Apostichopus japonicus life sustainability during commercial transport

Apostichopus japonicus (A. japonicus), the main trade sea cucumber species, is one of Asia's top five luxury seafoods. Commercially, live seafood has a higher value than processed seafood products. A. japonicus can easily self-melt due to its lack of a protective exoskeleton, making it difficult to transport to the consumers living in inland markets. In this study, live A. japonicus were tested to determine this species-appropriate storage surroundings, time and temperature ranges that maintains the species' optimal quality during transport. The status score, water quality, and low field nuclear magnetic resonance (LF-NMR) analysis were used to evaluate the transportation effect on live sea cucumber species. Testing revealed that at 4 °C, an A. japonicus could stay in excellent condition for 6 days and in good condition for 8 days. The results indicated a combination of seawater with oxygen as most effective to maintain a quality product during storage and transportation. This research also demonstrated that LF-NMR analysis could be developed into a rapid and undamaged technique to monitor live seafood's health condition. Our research would help this high-value seafood sell to the markets of inland areas and benefit the commercial growth of the sea cucumber aquaculture industry.

Novel Method for Studying, the, Imbibition Production Mechanism Using NMR

Tight volcanic reservoirs, characterized by strong heterogeneity and a well-developed fracture network, are usually difficult to develop. The development of effective ways to enhance production in such reservoirs is an important task in research work for oil and gas field development. The method of enhancing production by imbibition is a promising technology for oil recovery in tight reservoirs. In this paper, based on the production data of horizontal wells in tight volcanic reservoirs, we have studied the imbibition mechanism during fracturing fluid flowback. Nuclear magnetic resonance (NMR) technology was used for analysis. First, the wire-cutting technique was used to simulate fractures generated by hydraulic fracturing in the core. Then the core was filled with quartz sand. Then the migration of fluid between small pores and macropores during the imbibition process was studied by low-field NMR analysis. The research results show that the imbibition displacement of fracturing fluid under high pressure can effectively increase the recovery rate, while the soaking time can affect the imbibition exchange of fluid between crack and matrix. Due to the small pore radius and high capillary resistance of the volcanic rock, the imbibition stability time is longer. The pore size distribution of volcanic rock was analyzed quantitatively by NMR and mercury intrusion porosimetry. The results show that the dynamic imbibition process occurs mainly in pores less than 2 im.