Water Migration Research Articles

Effects of slightly acidic electrolyzed water combined with ԑ-polylysine-chitooligosaccharide Maillard reaction products treatment on the quality of vacuum packaged sea bass (Lateolabrax japonicas)

In this study, a new natural preservative, ε-polylysine (ε-PL) and chitooligosaccharides (COS) Maillard reaction products (LC-MRPs), was prepared by Maillard reaction. The preservation effect of LC-MRPs combined with slightly acidic electrolyzed water (SAEW) pretreatment (SM) on vacuum-packed sea bass during refrigerated storage was evaluated. The results showed that after 16 days, SM treatment could effectively inhibit the microbial growth and prevent water migration in sea bass. In addition, the highest water holding capacity (69.79 %) and the best sensory characteristics, the lowest malonaldehyde (MDA) (58.96 nmol/g), trimethylamine (TMA) (3.35 mg/100 g), total volatile basic nitrogen (TVB-N) (16.93 mg N/100 g), myofibril fragmentation index (MFI) (92.2 %) and TCA-soluble peptides (2.16 μmol tyrosine/g meat) were related to SM group. Combined with sensory analysis, we can conclude that the combined treatment of SAEW and LC-MRPs could prolong the shelf-life of sea bass for another 11 days compared with the DW group. Results disclosed that the composite treatment of SAEW and LC-MRPs is a promising technology to improve the shelf-life of vacuum-packed sea bass during refrigerated storage.

Freeze-thaw cycles drove chemical weathering and enriched sulfates in the Burns formation at Meridiani, Mars.

Sulfate-rich sedimentary rocks explored by the Opportunity rover during its 14-year surface mission at Meridiani Planum provide an invaluable window into the thousands of sulfate deposits detected on Mars via remote sensing. Existing models explaining the formation of martian sulfates can be generally described as either bottom-up, groundwater-driven playa settings or top-down icy chemical weathering environments. Here, we propose a hybrid model involving both bottom-up and top-down processes driven by freeze-thaw cycles. Freezing leads to cryo-concentration of acidic fluids from precipitations at the surface, facilitating rapid chemical weathering despite low temperatures. Cryosuction causes the upward migration of vadose water and even groundwater with dissolved ions, resulting in the accumulation of ions in near-surface environments. Evaporation precipitates salts, but leaching separates chlorides from sulfates during the thawing period. Freeze-thaw cycles, therefore, can enrich sulfates at the surface. While freeze-thaw is more commonly understood as a mechanism of physical weathering, we suggest that it is a fundamental aspect of chemical weathering on Mars.

Effect of temperature fluctuation on the freshness, water migration and quality of cold-storage Penaeus vannamei

This study aimed to simulate cold chain sales temperatures to predict the effects of temperature fluctuations on the physicochemical properties, moisture distribution, and flavor of vacuum-packed Penaeus vannamei. The results showed that the increase in freeze-thaw cycles, the pH, total volatile base nitrogen (TVB-N) and total plate count (TPC) of shrimp increased significantly. Meanwhile, sensory evaluation scores, hardness, elasticity and chewiness decreased. Low-frequency nuclear magnetic resonance (LF-NMR) analysis showed that the water content of shrimp continued to decline during storage as the immobilized water balance fell and the free water ratio increased in the F-T groups. In addition, W1S, W1W, W2S, and W6S in the electronic nose, which were characteristic sensors of whole shrimp odor, could distinguish samples with different sensory freshness, TPC, and TVB-N contents and rapidly detect the occurrence of shrimp quality deterioration. This study provided an experimental basis for the quality control of Penaeus vannamei during storage, transportation, and sales. It can further provide a reference for studying the cold chain preservation of aquatic products.

Study on coupled heat-water-vapor transfer in buffer material based on SPH method

To study the hydrothermal evolution law in buffer materials, based on the heat balance equation of unsaturated soil and the quality control equation of water migration, a coupled heat-water-vapor model of unsaturated soil is proposed. This model comprehensively considers the transition process of water vapor, the heat transfer caused by water flow and vapor migration, as well as the influence of temperature potential on water flow and vapor migration. The smoothed particle hydrodynamics (SPH) method can be used to calculate their evolution process conveniently. In the solution, the vapor content of heat balance equation is solved first, and then the water content and temperature field are solved, so as the coupling of temperature field between water and vapor field is implemented. The rationality of the model is verified by the tested results of soil column test. According to the established theoretical model, the heat-water-vapor three-field coupling problem of the buffer material in the repository was simulated and studied, and the hydrothermal evolution law inside the buffer material was revealed. On this basis, the influence of the change of groundwater pressure and heat source temperature on the hydrothermal evolution law of buffer material was further analyzed.

BASIC METHODS OF MONITORING OF CORROSION PROCESSES OF CEMENT STRUCTURES AND THEIR IMPLEMENTATION FOR PROJECTING OF POSSIBLE MINERALOGICAL CHANGES IN MATRIX COMPOSITION: REVIEW

Long time service of concrete constructions is accompanied by continuous impact of environment on its structural integrity and capability to carry project capacity of constructions. This influences are able to change not only chemical composition of cement matrix but itself activates corrosion processes that have place to occur on the joints of metal rebar and cement matrix in reinforced concrete (RC). Chemical initiation in the reinforced concrete begins due to the migration of water with parts of molecular oxygen in the thickness of concrete via porous structure of material. The same can be said about the injected compounds of either SO4 2- or Clcomponents that both can be present either in environment or concrete itself due to the modifications of slurry. Such occurrences usually accompanied by changes of pH of the environment that is crucial for the electrolytic environment to appear. Therefore, the process of the reduction of water/ proton may begin at rebar surface wich is the cause not only of the reinforced concrete rebar corrosion but also are reason of accelerated cement matrix degradation. Also, must be noted, that steel corrosion in RC accompanied by changes in current flow. Thus, by understanding the chemical processes and changes that occur in cement matrix of concrete and basics of steel corrosion initiation under the influence of aggressive solutions, the list of non-destructive methods of monitoring (NDM) based on electrical methods of monitoring are reviewed. Different approaches using electrical methods of corrosion monitoring has shown that the use of any of the technics either measurements of the corrosion potential or concrete resistivity or polarization resistance provides different results in mapping of areas with high corrosion risks, monitoring of the heterogeneity of concrete and insights on transport phenomena (e.g. water and salts ingress) in the material. Moreover, advances in potential monitoring without connection to the rebar as non-destructive measurements have shown their effectiveness. Nevertheless, colligation of the results of both numerical and NDM methods is necessary for assortment the results to provide a better data of the worktime of RC structures.

Humidity field for unsaturated subgrade accounting for the hydro-mechanical coupling and the difference of compactness: A simulation method

The safety and stability of road structures heavily rely on the precise assessment of subgrade humidity. However, existing methods often fall short in fully considering the coupling effect between humidity and stress states, as well as variations in compactness across different subgrade areas. In this study, a new model is proposed for simulating water migration in soil subgrade, incorporating hydro-mechanical coupling and the degree of compaction. The model is implemented using a newly added physical field in the COMSOL Multiphysics platform, and a numerical method is developed for calculating subgrade humidity. Moisture migration behavior in subgrades is investigated by selecting two atmospheric environments, namely dry and wet conditions. The results demonstrate that the developed humidity calculation method, accounting for hydro-mechanical coupling and compactness variations, yields reasonable and accurate predictions. Substantial differences in subgrade humidity are observed between wet and dry conditions. Compared to the dry conditions, pronounced fluctuations in subgrade humidity are observed in areas near slopes, with the equilibrium moisture content increasing by approximately 50% compared to the initial content. Additionally, the equilibrium time for moisture migration is significantly shortened under wet conditions. Based on these findings, it is recommended that waterproof should be considered in subgrades exposed to wet atmospheric environments to avoid excessive moisture content in subgrade.

Assessment of Blue Water Migration and Efficiency in Water-Saving Irrigation Paddy Rice Fields Using the Water Flow Tracking Method

Although irrigation systems largely sustain global agricultural production, their efficiency is often alarmingly low. While irrigation water (blue water) is critical for the water-saving irrigation of rice with a high water demand, the process and efficiency of irrigation water utilization need clarification. In this study, we examined the three commonly used irrigation and drainage patterns (frequent shallow irrigation (FSI), wet and shallow irrigation (WSI), and rain-catching and controlled irrigation (RCI)) in rice fields. We developed a tracking method for irrigation water flow decomposition, which includes irrigation water evapotranspiration (IET), irrigation water drainage (IDR), irrigation water leakage (IPC), and irrigation water field residual (IRE). Using this method, we established an irrigation water efficiency evaluation index system and a comprehensive evaluation method. Our tracking method is relevant to describing the irrigation water performance under varying irrigation and drainage patterns. The results revealed that the average irrigation water input for the three irrigation and drainage patterns between 2015 and 2018 was roughly 312.5 mm, wherein IET accounted for 148 mm. However, more than 50% of the irrigation water outflow, comprising IDR, IPC, and IRE, exceeded the total amount of irrigation water input. The mean values of the gross irrigation efficiency (GIE), net irrigation efficiency (NIE), and effective consumption ratio (ECR) for all treatments in the three-year period were 0.63, 0.47, and 0.75, respectively. Additionally, the irrigation water use efficiency was significantly higher in dry years compared to wet years. The fuzzy composite rating values of the three irrigation and drainage models from 2015 to 2018 were RCI, WSI, and FSI, in descending order, under varying precipitation conditions. The RCI patterns maintained a high composite rating value (greater than 3.0) under different precipitation conditions. Previous efficiency calculations disregarded the blue–green water migration process and did not differentiate the blue–green water flow direction in agricultural fields, creating significant biases in the outcomes. This study’s method offers a new approach to evaluate the use of blue water resources in farmland.

Emulsified sausages with yeast protein as an animal fat replacer: Effects on nutritional composition, spatial structure, gel performance, and sensory quality

This paper investigated the effect of yeast protein (YP)-fat replacement on the nutritional composition, spatial structure, gel performance, and sensory quality of emulsified sausages. YP is enriched with essential amino acids (36.49 g/100 g), which improved the nutritional quality of sausages whereas reducing its fat content. Moreover, YP could absorb water and fat, thus the YP-added sausages exhibiting an amount-dependent increase in emulsion stability and water migration. The microstructure illustrated that YP acted as a filler to improve structural homogeneity and compactness of the pork gel network. And YP-fat replacement could significantly enhance the hardness, gel strength and elasticity of sausages whereas decreasing the viscosity. Additionally, at partial or full YP-fat replacement (25–100%), the YP-added sausages scored higher in odor and texture, as well as better antioxidant stability than controls. Overall, YP can be employed as a new fat substitute for the preparation of healthy and nutritional sausages, while maintaining the sensory quality.

Moisturizing and aroma-enhancing effects of low molecular weight fenugreek polysaccharides in cigarettes

Polysaccharides possess excellent moisturizing effects due to their abundance of hydrophilic groups and film-forming properties. Additionally, they can produce a refreshing aroma during the pyrolysis process. However, there is scarce research on their application in the tobacco field. Herein, we investigated the effects of low molecular weight fenugreek polysaccharide (FP) obtained through ethanol fractionation and DEAE-52 cellulose column chromatography on moisture retention and aroma enhancement in tobacco. The moisture retention test revealed that the addition of FP increased the moisture retention index (MRI) of tobacco by 11.72 %–16.69 %, indicating that the hydrophilic nature of polysaccharides facilitated the migration of free water in tobacco to bound water, resulting in reduced water activity. Moreover, the contact angle between polysaccharide and tobacco was <90°, enabling better infiltration into tobacco and slowing down tobacco shrinkage caused by water loss. Among all the components, EFP-20 and EFP-40 demonstrated superior performance. Furthermore, FP exhibited excellent thermal stability below 200 °C and can decomposed to produce aromatic substances at high temperatures. It also demonstrated the ability to adsorb ethyl heptanoate and thermally decompose to produce a substantial amount of heptanoic acid. Consequently, the incorporation of FP in tobacco demonstrated favorable effects on both moisturization and aroma enhancement.

To What Extent Do Low-Voltage Electrostatic Fields Play a Role in the Physicochemical Properties of Pork during Freezing and Storage?

Low-voltage electrostatic fields (LVEF) are recognized as a new technology that can improve the quality of frozen meat. To determine the extent to which LVEF assistance affects the quality of frozen pork for long-term storage, pork was frozen and stored at -18 and -38 °C for up to 5 months. Water-holding capacity, muscle microstructure, and protein properties were investigated after up to 5 months of frozen storage with and without LVEF assistance. In comparison to traditional -18 and -38 °C frozen storage, LVEF treatment inhibited water migration during frozen storage and thawing. As a result, thawing losses were reduced by 15.97% (-18 °C) and 3.38% (-38 °C) in LVEF-assisted compared to conventional freezing methods. LVEF helped to maintain the muscle fiber microstructure and reduce muscle protein denaturation by miniaturizing ice crystal formation by freezing. As a result of this study, LVEF is more suitable for freezing or short-term frozen storage, while a lower temperature plays a more significant role in long-term frozen storage.

Near-wall bubble migration and wake structure in viscous liquids

The migration and wake structure of a single bubble in a viscous medium near a vertical wall have been experimentally investigated using a two-camera orthogonal shadowing method combined with a particle image velocimetry system. The effects of bubble size, liquid properties, and migration modes on the motion of a near-wall bubble and its wake structure are discussed. It is shown that, unlike migration in pure water, collisions between bubbles and walls are rare in viscous liquids. As viscosity increases, the mobility of the bubble near the wall changes from 3D to 2D and finally exhibits 1D motion with only one degree of freedom. While 1D motion is dominated by viscous forces, 2D migration is influenced by both wall effects and viscous forces, while 3D migration is primarily affected by bubble size. After analyzing the wakes produced by different factors, it was found that the wakes generated by mobile bubbles in three dimensions exhibit similar shedding patterns to Karman vortex streets, while two-dimensional wakes show stronger continuity. The average topological flow field structure of the bubble wake is obtained through periodic phase averaging, and the effect of different factors on the evolution of near-wall bubble wakes is analyzed.

Octadecyl-fibrous mesoporous silica nanospheres coated 96-blade thin-film microextraction for high-throughput analysis of phthalic acid esters in food and migration from food packages

A high-throughput sample pre-treatment method combined with high-performance liquid chromatography (HPLC) was developed to analyze phthalates (PAEs) in food and food contact package samples. Thin film microextraction (TFME) in 96-blade format was used to pre-treat 96 samples simultaneously. Octadecyl groups functionalized fibrous mesoporous silica nanospheres, namely C18-FMSNs, were synthesized and used as TFME coating material. The coating was fabricated by spraying a slurry of C18-FMSNs and polyacrylontrile (PAN) mixture with a commercial portable spraypen. The prepared C18-FMSNs/PAN coatings exhibited good reproducibility, repeatability and reusability. The optimized TFME conditions for PAEs consisted of extraction at pH 4.0 for 50 min, and desorption by methanol/acetonitrile (25/75, V/V) for 40 min. The pretreatment time for each sample was approximately 1.3 min. This TFME-HPLC method showed good linearity for eight PAEs within the concentration range of 0.5–1000 ng mL−1, with the coefficients higher than 0.9972. The limits of detection and quantification were 0.096–0.26 ng mL−1 and 0.32–0.86 ng mL−1, respectively. The intra-day and inter-day RSD % were below 6.6 % and 8.4 %, respectively, indicating good precision. The PAEs analysis in real samples showed that dibutyl phthalate (DBP) of 2.3 ± 0.3 ng mL−1 and di-(2-ethylhexyl) phthalate (DEHP) of 5.5 ± 0.8 ng mL−1 in boxed milk, dimethyl phthalate (DMP) of 12.6 ± 0.8 ng mL−1, DBP of 3.2 ± 0.4 ng mL−1and DEHP of 14.3 ± 0.7 ng mL−1 in the simulated water migration of plastic box, as well as DMP of 19.0 ± 0.6 ng mL−1, DBP of 25.6 ± 0.9 ng mL−1 and DEHP of 49.5 ± 2.8 ng mL−1 in the simulated ethanol migration of plastic box were determined, respectively. In addition, the detection of PAEs in all the real samples showed good recovery ranging from 85.6 to 110 % and lower RSDs % (<7.2 %).

Effect of Direct-Contact Ultrasonic and Far Infrared Combined Drying on the Drying Characteristics and Quality of Ginger

In this study, the effects of ultrasonic power, drying temperature, and slice thickness on the drying rate, chromatism, water migration law, gingerol content, flavor, and antioxidant activity of ginger were investigated by using a direct-contact ultrasound and far infrared combined drying technology. The results showed that compared with single far infrared drying, direct-contact ultrasound and far infrared combined drying accelerated the free water migration rate of ginger (7.1~38.1%), shortened the drying time (from 280 min to 160 min), reduced the loss of volatile components in ginger, and significantly increased the antioxidant activity of ginger (p &lt; 0.05). Furthermore, after ultrasound intervention, the gingerol content decreased in slices of 4 mm thickness (0.1226 ± 0.0189 mg/g to 0.1177 ± 0.0837 mg/g) but increased in slices of 6 mm thickness (0.1104 ± 0.0162 mg/g to 0.1268 ± 0.0112 mg/g). This drying technology has a certain reference significance for the drying process of ginger slices.

Microbial communities in the fluid migration zone in the sediments of the Krasny Yar methane seep (South Baikal)

The diversity and structure of microbial communities were investigated using 16S rRNA gene barcoding in the sediments of the Krasny Yar methane seep, in the zone of near-surface occurrence of gas hydrates and the presence of oxidized and restored channels. The diversity of both bacteria and archaea along the core depth was similar to the diversity found in sediments from other areas: methylotrophic methanogens and microorganisms involved in different stages of the organic matter fermentation were detected in the sediment strata of all depths investigated. Migration flows of oxygen-rich and aerobic bacteria-rich near-bottom water influenced greatly the diversity of microbial communities in oxidized channels. Fluids migrating from the deep zone to the bottom surface provided transport from anoxygenic sediments of anaerobic archaea involved in the AOM process. The data obtained are consistent with geochemical and geothermal indicators defining the zone of active migration of near-bottom waters.

Study of Ionic Migration in Sea Water through Directional Freezing

The six most abundant ions present in seawater are chloride (Cl−), sodium (Na+), sulfate (SO42-), magnesium (Mg2+), calcium (Ca2+), and potassium (K+). By weight these ions make up almost 99 percent of the salinity of sea water. Removal of these ions or desalination makes the sea water useable. In the present work migration of these common and abundantly found ions in sea water has been studied when the water samples were subjected to directional freezing vertically as well as horizontally. Water samples collected from Arabian Sea were frozen in two partially insulated devices under different modes. The samples were placed in a freezer at different temperature conditions and all the six ions present in sea water were estimated in different fractions of ice extracted from various locations of frozen mass obtained after freezing. The fractions collected from the top of vertical device and from the periphery of the horizontal device were found to be completely decontaminated and free from the ions. Most of the ions were found concentrated at the bottom of the vertical device and in the center of horizontal device. The directional freezing method was found simple, inexpensive and free of chemicals method which can be effectively employed for the desalination of sea water particularly in the regions where cold energy is naturally available

Smart hydrogel composite for microenvironmental humidity regulation in cigar storage.

Environmental humidity profoundly influences various life activities, especially for plants that depend heavily on optimal humidity for growth. The humidity index is particularly crucial for preserving the functionality of plant leaves, notably in economically valuable plants such as cigar tobacco. This paper introduces a novel dual-layer moisturizing material, a PAS-PDMS composite, based on polyacrylamide/solketal (PAS) hydrogel and polydimethylsiloxane (PDMS). This material features a unique hierarchical water release mechanism. Comprehensive analyses, including thermogravimetric analysis, Fourier-transform infrared spectroscopy, low-field nuclear magnetic resonance, and dynamic water adsorption studies, confirm the water migration and humidity control mechanisms of the PAS-PDMS composite. This smart hydrogel composite regulates microenvironmental humidity bidirectionally. When applied to cigar boxes for storage, it stabilizes internal humidity at approximately 65%, maintaining this level for over 20 days. Furthermore, the PAS-PDMS composite exhibits superior mechanical properties and light transmittance, achieving an exceptional transmittance of 84%. In conclusion, the PAS-PDMS composite offers intelligent humidity control, providing a novel approach to the storage and preservation of cigars.

Study on gelatinization of wheat starch paste by localized heating using laser irradiation and subsequent water migration

Study on gelatinization of wheat starch paste by localized heating using laser irradiation and subsequent water migration

Experimental study on multi-scale migration characteristics of capillary water in tailings

The increase of water content in tailings is the key cause of various diseases. In order to study the microscopical mechanism of tailings capillary water transport, an online monitoring capillary water rise test system was developed by itself, which mainly includes distortionless high definition digital microscope, 3-D mobile microscopic observation frame, CAMERA/VIEW PLAY CAP wireless acquisition system and computer. The system is used to carry out the dynamic real-time observation experiment of the capillary water rising process of tailings, analyze the movement trajectory and migration characteristics of the capillary water, and clarify the evolution law of the unsaturated tailings micro-structure under the hydraulic path. The results show that: There is a power exponential relationship between the rising height of capillary water and time, and the rising process can be divided into pure inertia stage, viscosity-inertia stage and pure viscosity stage. Capillary absorption is a process of non-uniform water absorption, the water content of the capillary zone decreases with the increase of the height, and its relationship curve shows an inverse ?S? shape, the water content varies from 4.15% to 21.3%. Capillary water migration is a dynamic process in both vertical and lateral directions and the most obvious change in the microscopic structure of tailings is the occurrence of water in pores, with the change of the saturation from low to high, the occurrence shows the shape of pendulum, ring cord, capillary and serous liquid bridge. The capillarity of tailings follows the order of macropores, mesopores and micropores to absorb water, most of which occurs in mesopores, the mechanism of ?in the macropores and mesopores, capillary water increased preferentially? in tailings granular materials is proposed. The research results revealed the internal correlation mechanism of macro and micro capillary mechanics of tailings, clarified the evolution model of the micro-structure of tailings during the rise of capillary water, and further clarified the reasons for the macroscopic damage phenomenon of granular materials caused by the development process of tailings particle drying to humidification.

Research on Underground Drip Irrigation and Soil Redistribution - Take Heshan District of Yiyang City as an Example

Abstract: The drip flow and the buried depth of drip irrigation zone are not only important parameters of subsurface irrigation design and operation management, but also important factors affecting the migration and redistribution of soil water and fertilizer. Crop growth is closely related to soil water and nitrogen leaching, water and fertilizer transport patterns and redistribution characteristics. It is of great significance to study the migration and redistribution of soil water and fertilizer under subsurface drip irrigation for improving the utilization efficiency of water and fertilizer and improving the system of subsurface drip irrigation. In this paper, the migration mode and redistribution characteristics of water and nitrogen in subsurface drip irrigation were studied and analyzed by means of laboratory soil box experiment, considering the two factors of drip flow and the buried depth of drip irrigation belt. The main research conclusions are as follows: Ⅰ. Different drip flows had effects on soil moisture front, soil moisture content and soil water redistribution. If other conditions remain unchanged, increasing the drip flow can increase the moist body area of soil and increase the moisture content of soil. The distance between vertical and horizontal directions increased with the large drip flow, and the soil water content decreased with the increase of distance. Large drip flow can promote the redistribution of soil water after drip irrigation. Ⅱ. Different drip depth had effects on soil moisture content and soil water redistribution. When the drip depth was 0cm, the surface shape of the wet body was a "horizontal" semi-ellipse after drip irrigation. When the drip depth was 10cm and 20cm, the surface of the wet body was an "upright" semi-ellipse after drip irrigation. The larger the buried depth of the drip can make the distribution of soil moisture more uniform, and the larger the buried depth of the drip can promote the migration of water in the soil. Ⅲ. Different drip discharge had an effect on soil nitrogen redistribution, and large drip discharge promoted soil nitrogen redistribution after drip irrigation. The Nitrate Nitrogen (NO3--N) content in the moist body is lower than that near the edge of the wetting front. The content of Ammonium Nitrogen (NH4+-N) near the edge of the wetting peak is higher than that inside the wetting body. Ⅳ. The redistribution of soil nitrogen was affected by different buried depth of drip head, and the greater buried depth of drip head could promote the redistribution of soil nitrogen. In terms of vertical and horizontal migration of ammonium nitrogen and nitrate nitrogen, on the day after drip irrigation, the cumulative effect of Nitrate Nitrogen (NO3--N) buried at a depth of 20cm was more significant near the wetting front edge at a larger vertical downward distance, and the cumulative effect of Nitrate Nitrogen (NO3--N) buried at a depth of 20cm was more significant inside the wetting body at a larger vertical downward distance. At the same time, the drip buried depth of 20cm can spread the cumulative effect inside the wet body and near the edge of the wet front to a longer horizontal distance.

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.