Low-field Nuclear Magnetic Resonance Technology Research Articles

Modification mechanism of calcium lignosulfonate on cementing cement

During the construction of coalbed methane extraction wells, cementing cement sheath is crucial for the stability and sealing of surface wells. One effective method to enhance these properties is the addition of lignosulfonate. However, the mechanism of the effect of calcium lignosulfonate on the whole process of cement hydration is still unclear. In this paper, the water distribution and variation characteristics of calcium lignosulfonate modified cement paste were revealed by low-field nuclear magnetic resonance technology, and the hydration ion experiment of modified cement was carried out to obtain the variation characteristics of hydration ions of modified cementing cement. Finally, the formation mechanism of hydration products was clarified by analyzing the phase change of modified cement stone. The results indicate that the cement paste’s hydration process can be divided into four stages: dissolution, crystallization, acceleration, and decline. During the dissolution stage, calcium lignosulfonate’s air entraining effect maintains the cement paste in a stable suspension state. In the crystallization stage, calcium lignosulfonate’s electro-repulsion delays the formation of hydration products and the hydration process. During the acceleration stage, the addition of calcium lignosulfonate reduces bound water formation in the cement slurry’s flocculation structure, and the released filled water participates more in the hydration reaction, reducing the total relaxation signal’s increasing trend. In the decline stage, the cement paste has solidified, and the system’s water is primarily in the porous medium. The research results have practical guiding significance for the addition of calcium lignosulfonate in cementing operations.

Investigation of the soybean infiltration process utilizing low-field nuclear magnetic resonance technology.

This paper employs low-field nuclear magnetic resonance (LF-NMR) technology to meticulously analyze and explore the intricate soybean infiltration process. The methodology involves immersing soybeans in distilled water, with periodic implementation of Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence experiments conducted at intervals of 20 to 30 minutes to determine the relaxation time T2. Currently, magnetic resonance imaging (MRI) is conducted every 30 minutes. The analysis uncovers the existence of three distinct water phases during the soybean infiltration process: bound water denoted as T21, sub-bound water represented by T22, and free water indicated as T23. The evolution of these phases unfolds as follows: bound water T21 displays a steady oscillation within the timeframe of 0 to 400 minutes; sub-bound water T22 and free water T23 exhibit a progressive pattern characterized by a rise-stable-rise trajectory. Upon scrutinizing the magnetic resonance images, it is discerned that the soybean infiltration commences at a gradual pace from the seed umbilicus. The employment of LF-NMR technology contributes significantly by affording an expeditious, non-destructive, and dynamic vantage point to observe the intricate motion of water migration during soybean infiltration. This dynamic insight into the movement of water elucidates the intricate mass transfer pathway within the soybean-water system, thus furnishing a robust scientific foundation for the optimization of processing techniques.

Experimental Study on the Evolution Law of the Mechanical and Pore Characteristic Parameters of Set Cement under High- and Ultra-High-Temperature Treatments

Cement has been widely used as a structural material in many underground projects, and these projects often face high- or ultra-high-temperature environments, leading to the deterioration of the mechanical, porosity, and permeability properties of set cement, thereby increasing the risk of instability of underground structures. In response to this, two new temperature-resistant cement slurry systems were designed. Experiments were conducted on the changes in porosity and permeability of set cement after thermal treatment using low-field nuclear magnetic resonance technology (NMR), visual studies of pore and crack development were carried out using the argon-ion polishing field emission scanning electron microscopy (FE-SEM) and computed tomography (CT) methods. The research results show that as the thermal treatment temperature continued to rise, the compressive strength first increased (25 °C–200 °C) and then decreased (200 °C–600 °C). The porosity of the set cement first decreased (25 °C–115 °C) and then increased (115 °C–600 °C), and the penetration first slowly increased (25 °C–400 °C) and then rapidly increased (400 °C–600 °C). Visualization experiments were conducted on micro-cracks and the pore distribution of the set cement under high- and ultra-high-temperatures, which proved the evolution law of these characteristic parameters. The research results have vital reference significance for the protection of the structural stability of cement components when encountering high-temperature environments.

Permeability mechanism of PVC-P geomembranes based on low-field NMR technology

The permeability of plasticized polyvinyl chloride (PVC-P) geomembranes (GMBs) is of significant importance to the safe operation of the impermeable structures and even the project. To avoid the drawbacks of adopting the permeability coefficient to characterize permeability traditionally, this paper presents a mathematical model of porosity and seepage discharge based on the results of the vertical permeability test and porosity obtained from low-field nuclear magnetic resonance (NMR) test, and the applicability of porosity to evaluate the permeability was explored combined with the dynamic distribution of pores and pore radius. The results show that the low-field NMR technology with 1H atoms as the probe can accurately measure the distribution of pores and pore radius in the PVC-P GMB. The proportion of micropores (Mic), mesopores (Mes) and macropores (Mac) and the shrinkage or development of pore radius are primarily responsible for the variation of the porosity. The porosity is closely correlated with the seepage discharge, and the constructed model can accurately predict the seepage discharge. Furthermore, the porosity can provide technical support for the evaluation of the permeability of PVC-P GMBs and the selection of appropriate GMBs for engineering design.

Insights into the effect of CNTs on cement hydration from the perspective of water evolution

The addition of carbon nanotubes (CNTs) into cement can remarkably enhance the mechanical properties of concrete. To investigate the impact of CNTs addition on the early-stage hydration of cement paste, low-field nuclear magnetic resonance (NMR) was employed to monitor the water evolution and microstructure of cement paste. The relaxation signals obtained from low-field NMR can provide valuable information regarding the state and content of water molecules, thereby indirectly characterizing the microstructural change of cement. Based on the correlation of characteristic transverse relaxation T 2 and water confinement state, low-field NMR can be used to predict the setting time of cement in the early stage. The findings indicated that the addition of CNTs can expedite the initial hydration process of cement, leading to a denser microstructure and shorter setting time. The results of Vicat needle test validated the efficacy of low-field NMR in predicting the setting time of cement. The non-destructive and non-invasive nature of low-field NMR technology renders it particularly advantageous in assessing the impact of CNTs on the early-stage behavior of cement paste.

Perspectives on Novel Technologies of Processing and Monitoring the Safety and Quality of Prepared Food Products.

With the changes of lifestyles and rapid growth of prepared food industry, prepared fried rice that meets the consumption patterns of contemporary young people has become popular in China. Although prepared fried rice is convenient and nutritious, it has the following concerns in the supply chain: (1) susceptible to contamination by microorganisms; (2) rich in starch and prone to stall; and (3) vegetables in the ingredients have the issues of water loss and discoloration, and meat substances are vulnerable to oxidation and deterioration. As different ingredients are used in prepared fried rice, their food processing and quality monitoring techniques are also different. This paper reviews the key factors that cause changes in the quality of prepared fried rice, and the advantages and limitations of technologies in the processing and monitoring processes. The processing technologies for prepared fried rice include irradiation, high-voltage electric field, microwave, radio frequency, and ohmic heating, while the quality monitoring technologies include Raman spectral imaging, near-infrared spectral imaging, and low-field nuclear magnetic resonance technology. These technologies will serve as the foundation for enhancing the quality and safety of prepared fried rice and are essential to the further development of prepared fried rice in the emerging market.

Wettability alteration and dynamic wetting behavior of coal during geologic CO2 sequestration using LF-NMR technology

As CO2 has a strong affinity to coal surface, coal seams are considered as an attractive geological formation for CO2 sequestration. Naturally occurring coal seams are often saturated with free water in the cleats as well as moisture. Hence, the wetting behavior of coal by water is an important aspect in the study of coal properties. However, carbon dioxide, which replaces methane on the surface of coal, interacts with water and coal for a long time. Geochemical reactions of CO2-H2O-coal system can change the surface properties and pore structure of coal. Studies on wettability of coal altered by CO2-H2O-coal interaction are rare. This paper explored the wettability alteration and wetting dynamic behavior of two bituminous coals in Huainan and Huaibei coalfield using low-field nuclear magnetic resonance (LF-NMR) combined with CO2-H2O-coal interaction experiments. The results show that dynamic wetting of water in the coal mainly depends on the pores structure. The geochemical reaction changed the pore structure of coal reservoir, further promoted the hydrophobicity of coal surface, and thereby affected the dynamic wetting process of water. Moreover, the wetting of large pores in coal is not significantly affected by the weakening of hydrophilicity, whereas wetting in small pores is obviously affected by the enhanced hydrophobicity, which may be beneficial to the adsorption and storage of CO2 in the coal.

Effect of Fines Content on Pore Distribution of Sand/Clay Composite Soil

Plant sand fixation is the most durable and environmentally friendly sand mitigation measure for windblown sand hazards. For aeolian–sand composite soil, the fines content is the main factor affecting the pore size distribution characteristics and determines the soil water retention characteristics. Sandy soil with uniform particle size was used as the material, low-plasticity clay as a fine particle, and composite soils with different fines content were prepared. The evolution of the pore size distribution of composite soils was quantitatively determined using low-field nuclear magnetic resonance technology, and the influence of the fines content on the pore size distribution was obtained. The results show that as the fines content increases, the pore size first increases and then decreases. The pore size distribution curve gradually changes from a single-peak structure to a double-peak structure and becomes a unimodal structure again. The corresponding dominant pore size of composite soils increases first and then decreases with the increase in the fines content. A critical fine particle content is identified to control the strong local honeycomb pore structure of composite soils, which provides a theoretical basis for the material selection and design of plant sand fixation measures.

New insights into determining the “time zero” of autogenous shrinkage in low water/binder cement-based composites (LW/B-CC) system based on relaxation theory

This study proposes a novel insight to accurately determine the time zero of autogenous shrinkage in low water/binder cement-based composites (LW/B-CC) based on relaxation theory. Firstly, low-field nuclear magnetic resonance (NMR) technology is used to study the process of water consumption inside the LW/B-CC and clarify the evolution of capillary tension to determine the time zero of autogenous shrinkage. Then, the Laplace equation is used to establish the relationship between water consumption, capillary tension, and autogenous shrinkage in LW/B-CC. The results show that the time corresponding to the development of capillary tension and water consumption in pores is considered as “time zero” of autogenous shrinkage. Furthermore, the capillary tension generated by internal water consumption, about 100 KPa ∼200 KPa, can cause enormous autogenous shrinkage, which easily leads to cracking. In addition, expansion products produced by calcium sulfoaluminate cement (CSA) hydration facilitate the formation of the matrix skeleton and reduce autogenous shrinkage in LW/B-CC. In general, low-field NMR technology is an effective tool to determine the time zero of autogenous shrinkage.

Heterogeneous structural responses of high-rank coal pores to hydraulic fracturing based on low-field nuclear magnetic resonance

Pores in coal are not only the main space for coalbed methane (CBM) occurrence but also the space to be opened during CBM recovery. Therefore, the analysis of the impact of hydraulic fracturing on coal pores, especially the change of adsorption pores before and after hydraulic fracturing, is of great significance to the evaluation of the hydraulic fracturing effect and CBM recovery. Hydraulic fracturing experiments and low-field nuclear magnetic resonance technology were used to analyze changes in the T2 curve, adsorption pore, and the effects of distance and in situ stresses on pore modification in coal samples of the Sihe (SH) and the Chengzhuang (CZ) mines before and after hydraulic fracturing. The results show that hydraulic fracturing can affect pores <10 nm. The CZ coal samples exhibit stronger heterogeneity than the SH coal samples after hydraulic fracturing, and the pore size distribution (PSD) anisotropy of the CZ samples is increased. For the SH coal samples with poor heterogeneity, the effect of hydraulic fracturing on pore transformation depends more on in situ stresses. The smaller horizontal in situ stresses difference facilitates the establishment of complex pore networks. After hydraulic fracturing, when the pore diameter is 30–100 nm, the pore volume proportions of the SH samples in the directions of maximum horizontal principal stress (σH), minimum horizontal principal stress (σh), and vertical stress (σV) increase from 43.73% to 64.84%, 59.79%, and 60.16%, respectively. Hydraulic fracturing increases the anisotropy of the PSD of the CZ samples.

Review on the Application of Low-Field Nuclear Magnetic Resonance Technology in Coalbed Methane Production Simulation.

Low-field nuclear magnetic resonance has become one of the main methods to characterize static parameters and dynamic changes in unconventional reservoirs. The research focus of this paper is process simulation of coalbed methane (CBM) production. The dynamic variation of pore volume with different pore sizes during pressure drop, methane desorption–diffusion process, and methane–water interaction during migration is discussed. Moreover, the calculation principles of NMR single and multifractal models are systematically described, and the applicability of NMR fractal models within different research contexts is discussed. Four aspects need urgent attention in the application of this technology in CBM production: (1) overburden NMR technology has limitations in characterizing the stress sensitivity of shale and high-rank coal reservoirs with micropores developed, and we should aim to enable an accurate description of micropore pore stress sensitivity; (2) dynamic NMR physical simulation of reservoir gas and water production based on in-situ and actual geological development conditions should become one of the key aspects of follow-up research; (3) low-temperature freeze–thaw NMR technology, as a new pore–fracture characterization method, needs to be further applied in characterizing the distribution characteristics of pores and fractures; and (4) NMR fractal model should be used as the main theoretical method to expand the simulation results. The applicability of different fractal models in characterizing pore–fracture structure (static) and CBM production process (dynamic) needs to be clarified.

Concrete Durability after Load Damage and Salt Freeze-Thaw Cycles.

To determine how the performance of concrete changes after initial load damage and salt freezing, concrete samples were first subjected to loading and unloading, and were then put into salt solutions to carry out rapid freeze–thaw cycle (FTC) experiments. Salt solutions were created based on the saline soil of western Jilin, China, for use in salt freeze–thaw testing. This determined the change law of the compressive strength and the dynamic elastic modulus (DEM). Additionally, low-field nuclear magnetic resonance technology and a scanning electron microscope were applied to investigate the pore characteristics and microstructure of concrete samples after FTCs. This study found that when the concrete specimens were subjected to an initial load of 0.3f under 50 FTCs, the loss in the compressive strength increased by 24% when the concrete was subjected to freeze–thaw cycles in freshwater and increased by 24% when concrete was subjected to freeze–thaw cycles in a 6.8% composite salt solution compared with the specimens without the initial load. When the concrete was subjected to FTCs in a 6.8% composite salt solution 50 times, the loss in the compressive strength increased by 110% for concrete without an initial load and increased by 109% when the concrete was subjected to an initial load of 0.3f compared with the specimens under FTCs in freshwater. The persistent effect of the FTCs also aggravated chloride ion erosion in the concrete, which gradually reduced the concrete’s permeability resistance. Internal pores in the concrete, especially the proportion of above-medium-sized pores, gradually increased along with the increase in the number of FTCs. There is a good linear correlation between the change rule of compressive mechanical properties and the change rules of mass, DEM, and pore characteristics inside the concrete under rapid FTCs in different salt solutions.

Experimental study on pore fluid characteristics of fractured sandstone based on nuclear magnetic resonance technology

The groundwater seepage in the fractured rock mass affects the stability of the surrounding rock of the roadway. To understand the fluid seepage characteristics and the change law of the microscopic pore structure of the fractured rock mass under different loading conditions, the low-field nuclear magnetic resonance technology (LF-NMR) was used to conduct a visual experimental study. The T2 spectrum distribution curve tested by nuclear magnetic resonance indicated that the pore structure of the fractured sandstone sample had three peaks (namely micropores, mesopores, and macropores) with medium and large pores distributed from 0.63 μm to 100 μm. Quantitative analysis of nuclear magnetic resonance imaging signals during water flooding of fractured sandstones revealed the characteristics of fluid migration and distribution at different times and locations at different flow rates in the core. The height of the fractured core at 23 mm had small water content and low porosity. The water content at the position of 25–40 mm was higher, and the porosity was large. Under the effect of flow velocity, there were obvious differences in the state of fractured core displacement. That is, the greater the flow velocity, the shorter the water flooding time and the more concentrated the fluid sweep area. The dominant channel for seepage was formed quickly. The research results can provide a reference for preventing the erosion of roadway surrounding rock caused by groundwater fluid.

Pore wetting process characterization of Equal-Sized granular coals by using LF-NMR technology

Understanding the pore wetting process is of great significance for determining fluid wetting behavior in porous media such as coal, and for the development and utilization of natural gas reservoirs, however, most studies on the process simplify porous media as glass capillaries, which may lack practical application. To better understand and quantitatively characterize the actual pore wetting process of coals, a new, low-field nuclear magnetic resonance (LF-NMR) experimental characterization method was developed. The experiment used equal grain sizes of glass beads and coals to yield porous media with variable pores of specific size ranges. LF-NMR was then used to characterize the pore wetting process of a given amount of water in the porous media at different times. Six groups of high-rank coals were also characterized by contact angle experiments to analyze the role of the surface contact angle on pore wetting. The results show that the pore wetting process can be divided into three ideal physical phases: a first touch state, a semi-free water state and an inter-granular diffusion or quasi-static state. The wetting pore size distribution (W-PSD) spectrum obtained by measurement of the transverse relaxation time and the transformation coefficient reflected change in pore size during wetting, with the location of the W-PSD quantified by the equivalent wetting pore size. The equivalent wetting pore size obtained at a final time of 24 h was used to characterize the pore wettability, it was significantly correlated with the surface contact angle with a linearity of up to 0.99. However, the W-PSD or the equivalent wetting pore size is dependent on the surface relaxivity. Overall, the experimental characterization method used in this study is an effective way to study the “black box problem” of the wetting process in porous media, as it is simple and has low sample requirements.

Effect of partial substitution of sodium salt on the quality of salted quail eggs.

To improve the quality of salted quail eggs and solve the problem of excessive sodium content in salted eggs, we selected substitutes (K2 CO3 , CaCl2 , MgCl2 , ZnCl2 , and FeC6 H5 O7 ) to partially replace NaCl and study its effect on water migration, physicochemical properties, and textural characteristics. The low-field nuclear magnetic resonance technology (LF-NMR) was used to qualitatively analyze the moisture and proton content of quail eggs during the pickling process. The results showed that the relaxation curves of ZnCl2 and FeC6 H5 O7 groups were significantly different from those of other groups. The bound water content of the ZnCl2 group increased significantly, and FeC6 H5 O7 made the binding degree of water closer. The Na+ of different substitute groups was determined by atomic absorption spectrometry; it was found that the permeation rate of NaCl in the curing process was in the following order: K2 CO3 > control group > MgCl2 > FeC6 H5 O7 > CaCl2 > ZnCl2 . Through the electronic tongue study and comparing the ripening period of salted quail eggs, it was found that the flavor and ripening time of salted quail eggs cured by ZnCl2 and FeC6 H5 O7 were not suitable for low-sodium pickling preparation. At the same time, CaCl2 and MgCl2 were suitable for low-sodium pickling and could improve the product quality. When using K2 CO3 , the substitution ratio can be reduced and two or more compound-curing agents can be formed with CaCl2 and MgCl2 , thus reducing the content of sodium salt in salted eggs. PRACTICAL APPLICATIONS: We simulated the metallic elements contained in the traditional black ash-salted eggs and salt mud coatings. By partial substitution of sodium chloride (NaCl) with different metal salts (K2 CO3 , CaCl2 , MgCl2 , ZnCl2 , and FeC6 H5 O7 ), we studied the effects of these metal salts on the physical and chemical properties, texture, and microstructure of quail eggs during the pickling process. Several suitable low-sodium substitutes were screened out to provide a theoretical foundation for the process optimization of low-sodium-salted quail eggs.

Investigation of hydration and setting process in nanosilica-cement blended pastes: In situ characterization using low field nuclear magnetic resonance

In order to characterize the effect of nano-SiO2 addition on early properties of Portland cement paste, low-field nuclear magnetic resonance (NMR) was used to monitor the hydration process and microstructure evolution. The relaxation signals of low-field NMR can provide the information about the water molecules status and corresponding content, thus indirectly revealing the microstructure evolution of cement paste. Based on the relaxation signals, new applications of low-field NMR in predicting the strength and setting time of cement were developed. The results indicate that the increasing nano-SiO2 addition as well as decreasing water-to-cement ratio can accelerate the early hydration process of cement and densify its microstructure, thus shortening the setting time and enhancing the early compressive strength. The effectiveness of low-field NMR in predicting the strength and setting time of cement was confirmed by the results of compression test and Vicat needle test, respectively. Due to the non-destructive and non-invasive characteristics of low-field nuclear magnetic resonance technology, this method shows special advantages in characterizing the influence of nano-silica on the early performance of cement paste.

Experimental study on the influence of aerated gas pressure and confining pressure on low-rank coal gas adsorption process

To deeply study the variation characteristics of the gas content in the process of gas adsorption for coal samples under different gas pressures and confining pressures, low-field nuclear magnetic resonance technology was used to carry out experimental research on the gas adsorption of coal. The relationship between the T2 spectrum amplitude integral and the gas quantity was analyzed. The results show the following: (1) When the samples were inflated for 11 h at each gas pressure point (0.31, 0.74, 1.11, and 1.46 MPa), after ∼5 h of adsorption, the amount of adsorbed gas exceeded 85.0% of the total adsorption capacity; additionally, as the adsorption time increased, the amount of adsorbed gas gradually tended to stabilize. When the gas pressure was >1 MPa, the amount of adsorbed gas exceeded 90.0% of the total adsorption capacity; Higher the pressure of aerated gas, greater the gas pressure gradient or concentration gradient on the surface of the coal sample and the greater the driving force for gas molecules to seep or diffuse into the coal sample. (2) When the samples were inflated for 11 h at each confining pressure point (3, 4, 5, and 7 MPa), the adsorbed gas increased by ∼85.0% of the total adsorbed gas in the first 5 h. When the pressure was <5 MPa, the amount of adsorbed gas exceeded 85.0% of the total amount of adsorption; that is, the increase in adsorbed gas was the largest at ∼5 h in the adsorption process for the columnar coal sample under different confining pressures, and the increase was ∼5.0% from 7–11 h. When the large pores in the coal sample closed, the amount of gas that seeped into the deep part of the coal sample within the same aeration time was reduced.

Fracturing fluid retention in shale gas reservoir from the perspective of pore size based on nuclear magnetic resonance

Shale gas development requires large-scale hydraulic fracturing, but a large amount of the slickwater fracturing fluid injected into the reservoir cannot be brought back to the surface. In this study, spontaneous imbibition and reverse displacement experiments were carried out on shale core to simulate fracturing fluid imbibition into the matrix during the fracturing stage of a shale gas reservoir and the displacement of fracturing fluid by reservoir gas during the flowback stage. With the help of low-field nuclear magnetic resonance technology to dynamically monitor the volume change in the liquid in the shale core throughout the entire process, the volume distribution of the liquid in the pores of the different scales were calculated at each time. The reason for the low flowback efficiency of shale gas reservoirs from the perspective of pore size was studied, and the influence of the fracturing fluid’s salinity on the flowback process was analyzed. The research results show that there is a certain pore size threshold in the shale gas reservoir. When the fracturing fluid enters pores smaller than this size threshold, it is difficult to displace it during flowback. The relative volume of the fracturing fluid entering the pores smaller than the size threshold determines the flowback efficiency. The higher the proportion of this part of the fracturing fluid to the total volume, the lower the flowback efficiency. Using a fracturing fluid with a higher salinity can reduce the volume of liquid entering the pores less than the pore threshold to a certain extent, thereby increasing the flowback efficiency. This research is important for gaining a better understanding the low flowback efficiency in shale gas reservoirs and for evaluating the safety of groundwater resources.

Quality changes of Pleurotus eryngii during vacuum frying

Quick and accurate determination of oil content is extremely important to control the oil content of vacuum fried fruit and vegetable chips. This article uses fresh Pleurotus eryngii as raw materials to explore the influence of different vacuum frying times (0–14 min) on the moisture distribution, oil changes and quality of Pleurotus eryngii strips. The results show that as the frying time increases, the lateral relaxation time required for the taro strips to drop from the highest point of the signal amplitude to smooth becomes shorter and shorter, and the decay rate becomes faster and faster, that is, when the frying time is 14 minutes, The attenuation curvature and velocity are the largest. The oil content and brittleness of Pleurotus eryngii strips are significantly increased (P < 0.05); the water content is significantly reduced (P < 0.05); the hardness first decreases and then increases (P < 0.05); the brightness L* value does not change much, and the color is not Significant change (P > 0.05). At the same time, low-field NMR shows that the high-degree-of-freedom water in the pleurotus eryngii strips migrates to the low-degree-of-freedom water during the vacuum frying process. Among them, the free water in the pleurotus eryngii strips has a large degree of freedom. It has been removed, resulting in poor mobility and increased inability to flow. Part of the free water migrates to the semi-bound water, and most of the semi-bound water migrates outward as free water and then is removed. From this, all peaks are gradually removed. Moving to the left, the total peak area decreases. During the frying process, the T2 relaxation time of Pleurotus eryngii strips all shifted to the left, the total peak area is continuously reduced, the water content is getting less and less, the fat content is getting higher and higher, and the fat content distributed in the edge shell is always higher than Other locations. Low-field nuclear magnetic resonance technology can provide a fast, accurate, and non-destructive method for detecting moisture and grease for the vacuum-fried fruit and vegetable chips. As the frying time increases, the inner contour of the MRI image of Pleurotus eryngii strips gradually becomes blurred, the brightness gradually decreases, the volume shrinks, the less water, and the image interior is close to the background color (blue), indicating that the sample has reached the end of drying; and The grease content is distributed in the edge shell layer higher than other positions. Therefore, the water is continuously removed, the oil signal becomes stronger and stronger, and the oil content of the sample becomes higher and higher.

Rapid and non-destructive detection method for water status and water distribution of rice seeds with different vigor

In this study, newly harvested and aged rice seeds were analyzed to determine their aging process, identify the difference between artificially and naturally aged seeds, and to develop a rapid, accurate, and non-destructive detection method for water status and water distribution of rice seed with different vigor. To this end, an artificially accelerated aging test was conducted on the newly harvested rice seeds. Then, low-field nuclear magnetic resonance (LF-NMR) technology was applied to test the new (Shennong No. 9816, 2018), old (Shennong No. 9816, 2017), and artificially aged seeds (Shennong No. 9816, 2018). A standard germination test was conducted for three types of seeds. Finally, the differences of water status and distribution between rice seeds of different vigor were analyzed based on the standard germination test results and wave spectrometry information collected using LF-NMR. The results indicated that new seeds, old seeds, and the artificially accelerated aging rice seeds all exhibited two water phases, and the vigor of rice seeds after the artificial accelerated aging test was lower than that of new seeds. There were significant differences between the frequencies of bound water at the time of the peak and the time at the end of the peak for the three types of seeds. The two times showed an increasing trend for rice seeds with poor vigor, indicating that the ability of the water in the rice seeds having poor vigor to combine with other substances was weakened. There were significant differences between the distributions of free water peak end time for the three types of seeds. All the rice seeds with poor vigor exhibited a decreasing trend at this time, indicating that the freedom of free water inside the rice seed samples with poor vigor was weakened. The total water content of the artificially aged seeds and the aged seeds was higher than that of the new seeds, but the free water content increased from artificially aged seeds to new seeds to aged seeds. This indicates that LF-NMR technology is an effective detection method that can simply compare the differences in seed vitality with respect to water distribution as well as differentiate the seed internal water content of artificially aged and naturally aged seeds. Keywords: low-field nuclear magnetic resonance, rice seed, water status detection, water distribution detection, seed vigor DOI: 10.25165/j.ijabe.20211402.5780 Citation: Song P, Kim G, Song P, yang T, Yue X, Gu Y. Rapid and non-destructive detection method for water status and water distribution of rice seeds with different vigor. Int J Agric & Biol Eng, 2021; 14(2): 231–238.