Freezing Of Water Research Articles

Ultralow-freezing-point (−70 °C), organic solvent-free aqueous electrolyte with superior ionic conductivity and thermodynamics stability

Water-in-salt and organic solvent-additive strategies have significantly improved the electrochemical stability window of aqueous electrolyte, while it still faces poor low-temperature thermodynamics stability and unsatisfied transport kinetics, as well as flammability risks caused by organic solvent. Herein we report a novel “cation-water-urea ternary interaction strategy” via environmental-friendly and non-flammable urea (CO(NH2)2) to solve the above dilemma. The cation-water-urea ternary interaction strategy preferentially develops CO(NH2)2-cation solvation structures for weakened cation-anion associations, improved anti-salt-precipitation capability, and thus enhanced ionic conductivity, meanwhile it improves the low-temperature thermodynamics stability via the stronger CO(NH2)2-water hydrogen-bond interactions to suppress the freezing and electrolysis of water. The optimum ternary aqueous electrolyte exhibits an ultralow freezing point (−70 °C), wide electrochemical stability window (2.9 V) and outstanding ionic conductivity (135 mS cm−1@25 °C and 5.3 mS cm−1@−50 °C), demonstrating superior performance compared to traditional organic solvent-additive and water-in-salt electrolytes. Finally, to demonstrate its potential for practical applications, ternary aqueous electrolyte-based supercapacitors are fabricated using commercial activated carbon electrodes, which exhibit outstanding capacitance retention (71.4 %) and much lower ion transport resistance even at ultralow temperature of −40 °C. This work proposes a novel ternary aqueous electrolyte with improved thermodynamics stability and kinetics for safe, low-temperature energy storage applications.

Microstructure and durability of rapid repair mortar with self-emulsifying waterborne epoxy polymer

Due to the low hydration rate of ordinary Portland cement (OPC), it cannot meet the requirements of rapid repair, especially in negative temperature environments. Simultaneously, facing the harsh marine environment, repair materials urgently need high durability. In this paper, a self-emulsifying waterborne epoxy polymer (WEP) suitable for cement systems was combined with sulfoaluminate cement (SAC) to prepare repair materials. The effect of the WEP on the development of microstructure, auto-drying shrinkage and durability was investigated by nuclear magnetic resonance, XRD and SEM methods. Results showed that a continuous interpenetration polymer network (IPN) was intricately woven within the multiphase composites, using the macromolecular network structure formed by —OH groups in WEP and Ca2+ and Al3+ in cement as a bridge. The resistance to chloride migration and water absorption exhibited an increase followed by a decrease. In particular, the resistance to chloride migration was improved by 45 %. Similar trends were observed for the carbonation resistance. Due to the lower porosity and capillary pressure caused by IPN, leading to a decrease in auto-drying shrinkage. Nevertheless, the larger percentage of capillary pores in a mortar with a P/C of 15 % increased the auto-drying shrinkage. The WEP decreased the availability of pores of critical diameter (14 nm) of mortar exposed to water freezing, leading to an increase in the freeze-thaw resistance. The change in P/C hardly affected the resistance to sulfate attack. Under −10°C, at 2 hours, the compressive strength of CSA-based mortar satisfied the load requirements for vehicular operations. This research provides theoretical and practical implications for the repair work of large-scale projects serving in harsh environments.

Alternative material recommendation for facade cladding: High silica-containing stonepaste ceramics

This study investigated the potential of using stonepaste ceramics, which were widely preferred as a coating and decoration material on the facades of architectural buildings in ancient times and continues to be produced on a workshop scale today as a cladding material on building facades. Stonepaste ceramics, made from a mixture prepared with a high amount of crystalline quartz as well as frit, plastic clay, and bentonite raw materials, were hand-shaped and sintered at 930 °C after glazing. The physico-mechanical properties of stonepaste ceramics, their behaviour under various environmental conditions (resistance to chemicals, frost, and thermal shock), and their microstructures have been characterized. The characterization results were compared with the properties of commonly used facade cladding materials. It was determined that stonepaste ceramics had a very low firing shrinkage value (2.84 %) compared to that of other ceramic cladding materials, a higher water absorption value (11.79 %) than that of porcelain tiles and floor tiles, and close to wall tiles, and a flexural strength value (33.64MPa) higher than wall tiles and close to porcelain tiles despite the high-water absorption value. Ten cycles of thermal shock resistance showed that the body and glaze layer of the stonepaste ceramic material are well bonded to each other, and there is no significant thermal expansion mismatch between them. One hundred cycles of freeze-thaw conditions indicated that the stonepaste ceramic had good adhesion and thermal expansion compatibility between the glaze and the body but only chipping damage under the action of tensile forces caused by the freezing of water entering the pores of the body. In terms of behaviour against various chemicals, stonepaste ceramics were found to be highly resistant to high and low concentrations of household chemicals, swimming pool salts, and alkalis but less resistant to low concentrations of HCl and citric acid and high concentrations of HCl and lactic acid compared to other chemicals. The results show that stonepaste ceramics, despite their high-water absorption potential, have properties close to those of traditional ceramic tiles and, like these materials, can serve for significant periods in various environmental conditions when used as facade cladding. Consequently, it has been revealed that stonepaste ceramics can be used as a facade cladding material in sustainable, long-lasting, contemporary architectural facades thanks to their technical and protective properties.

Peridynamic simulation of micro-internal damage and macro-mechanical properties of cement paste under freeze-thaw cycles

Concrete is a multi-phase, multi-component, heterogeneous composite material and a typical porous medium with a complex microstructure. Under freeze-thaw cycles (FTCs), pressures from the freezing and migration of water within the pores of the concrete cause freeze-thaw damage, which is influenced by its microstructure. To effectively simulate and understand the freeze-thaw damage mechanism, it is crucial to use a geometric structure that reflects the actual pore distribution. This study employs the μic model to create a geometric structure of hardened cement paste, capturing the spatial distribution of pores. The study utilizes the peridynamics (PD) method based on ice formation and crystallization thermodynamics to investigate the freeze-thaw damage evolution and the deterioration of mechanical properties in cement paste under FTCs. The simulations revealed the entire freeze-thaw damage process of cement paste, including internal crack initiation and propagation, as well as surface freeze-thaw spalling. The freeze-thaw damage of cement paste intensifies with increasing FTCs, and the extension of cracks diminishes the interconnection among the skeletons constituting the cement paste microstructure, leading to decreased tensile strength and elastic modulus. Additionally, the stress-strain evolution behavior of freeze-thaw cement paste under uniaxial tensile loads was obtained. The tensile strength and elastic modulus of cement paste decrease with increasing FTCs, and the higher the water-cement (w/c) ratio, the greater the reduction in strength and modulus.

On water freezing in slag-blended cementitious materials at early ages

Concretes casted in cold climate can be threatened by frost action from the initial stages of maturing. Hence, to secure their long-term functionality, it is essential to be acquainted with the material's early response to sub-zero temperatures. Addressing this challenge, the article concerned the resistance of young slag-blended cementitious materials against the early frost attack. An extensive experimental analysis covering both macro- and microscales was designed for this purpose. At first, development of the pore size distribution and ice content profile of the 100 % Portland cement and slag-blended pastes were evaluated from the early ages until maturing via mercury intrusion porosimetry and differential scanning calorimetry. It was reported that the distinction between gel pore and capillary pore is created after 3rd day for OPC and after 21st day for slag-blended paste. Next, the destructive impacts of a single freezing-thawing cycle on the mechanical properties of the young Portland cement and slag-blended mortars were measured. Subsequently, the strength development of the Portland cement and slag-blended concretes that experienced the frost exposure were evaluated and compared with each other. It was observed that the early freezing strengthen (up to 15 %) the OPC based concrete and weaken (up to 13 %) the slag-blended concrete. Additionally, the analysis was proposed to simulate the winter conditions at the building sites. The strength development of the Portland cement and slag-blended concretes that were cured at low temperatures and experienced an early freezing episode were assessed. The decrease of curing temperature caused the reduction of compressive strength of OPC-based concrete around 25 % and slag-blended concrete around 50 %. As a result, micro- and macrostructural requirements were proposed to secure the proper resistance of the slag-blended cementitious materials against the possible early frost damage.

Gelatin hydrolysate in freeze–thawed shrimp model system: retardation of weight loss and muscle protein denaturation

SummaryThis research explores the cryoprotective potential of gelatin hydrolysate by determining weight loss and physicochemical changes in the muscle protein of freeze–thawed shrimp. Shrimp treated with gelatin hydrolysate exhibited significantly higher and lower weight gain (9.20%) than those treated with distilled water (0.93%) and mixed phosphates (16.99%), respectively. Gelatin hydrolysate could lower the increasing rate of thawing and cooking loss and freezable water content in freeze–thawed shrimp (P < 0.05) and comparable to those of mixed phosphates treated shrimp (P > 0.05). As the shrimp were subjected to freeze–thawing, gelatin hydrolysate slowed the decline of protein solubility and Ca2+‐ATPase activity and mitigated the rise of surface hydrophobicity and disulfide bond content. It also delayed the shear force increase. These findings suggest that gelatin hydrolysate could be an effective alternative to traditional cryoprotectants, retarding weight loss and protein denaturation to preserve shrimp quality during freezing and frozen storage.

Microbial preference for chlorate over perchlorate under simulated shallow subsurface Mars-like conditions

The Martian surface and shallow subsurface lacks stable liquid water, yet hygroscopic salts in the regolith may enable the transient formation of liquid brines. This study investigated the combined impact of water scarcity, UV exposure, and regolith depth on microbial survival under Mars-like environmental conditions. Both vegetative cells of Debaryomyces hansenii and Planococcus halocryophilus, alongside with spores of Aspergillus niger, were exposed to an experimental chamber simulating Martian environmental conditions (constant temperatures of about − 11 °C, low pressure of approximately 6 mbar, a CO2 atmosphere, and 2 h of daily UV irradiation). We evaluated colony-forming units (CFU) and water content at three different regolith depths before and after exposure periods of 3 and 7 days, respectively. Each organism was tested under three conditions: one without the addition of salts to the regolith, one containing sodium chlorate, and one with sodium perchlorate. Our results reveal that the residual water content after the exposure experiments increased with regolith depth, along with the organism survival rates in chlorate-containing and salt-free samples. The survival rates of the three organisms in perchlorate-containing regolith were consistently lower for all organisms and depths compared to chlorate, with the most significant difference being observed at a depth of 10–12 cm, which corresponds to the depth with the highest residual water content. The postulated reason for this is an increase in the salt concentration at this depth due to the freezing of water, showing that for these organisms, perchlorate brines are more toxic than chlorate brines under the experimental conditions. This underscores the significance of chlorate salts when considering the habitability of Martian environments.

Lattice Boltzmann study of liquid water flow and freezing in the gas diffusion layer

The flow and freezing process of liquid water in the gas diffusion layer (GDL) is studied using a proposed lattice Boltzmann method that integrates the multi-component pseudo-potential model and the enthalpy-based method. The evolution of liquid water, ice, and temperature distributions inside the GDL during this process is specifically analyzed, and the effect of GDL porous structure, such as porosity and carbon fiber diameter, is discussed. Results indicate that liquid water exhibits a propensity to break through the GDL through the regions characterized by larger pores, subsequently forming a liquid droplet on the GDL surface and beginning to freeze. The freezing process extends from the droplets to the CL side through the liquid pathways within the GDL. In addition, liquid water is more prone to freezing around carbon fibers. Due to the released latent heat during freezing, the temperature at the liquid water/ice interface stabilizes at 273 K. Moreover, it is also demonstrated that a large porosity and coarse carbon fibers both facilitate the flow of liquid water into the GDL where it then freezes, leading to more serious blockage of pores by ice and liquid water.

First insights into the age of the giant ice deposits in the Eisriesenwelt cave (Austria)

Frozen water is the most widespread type of ice present in ice caves and forms ice stalagmites and stalactites as well as floor ice, which is often several meters thick. Organic macroremains are commonly rare in this type of cave ice, which makes it difficult to establish a chronology and severely limits the use of such ice deposits as paleoenvironmental archives. Here, the chronology of such ice deposits in the inner part of the glaciated Eisriesenwelt, one of the world’s largest ice caves located in the European Alps of Austria, is determined by a combination of radiocarbon and 230Th dating of cryogenic calcite. The data suggest that this cave ice has formed over the last three millennia, with a marked increase in the average accumulation rate during the thirteenth century, coinciding with the onset of the Little Ice Age in the Alps. Data from a second site closer to the entrance suggests that large parts of this tourist cave were likely ice-free during the Medieval Warm Period and that a substantial part of the ice is probably a relic of the Little Ice Age. The current warming has already penetrated deeper into the cave than during the Medieval Warm Period, although air exchange during the warm season is restricted by a door at the cave entrance.

An improved model for discrete element method simulation of spatial gradient distributions of freeze-thaw-induced damage to sandstone

The investigation into the freeze-thaw (F-T) damage holds paramount theoretical significance in comprehending the mechanisms underlying F-T disasters, predicting catastrophes, and devising engineering protection systems. F-T damage in rock evolves progressively from the surface towards the interior, however, current models exhibit conspicuous deficiencies in simulating such progressive damage. Drawing upon experimental findings concerning the evolution of F-T damage in water-saturated rock, an improved discrete element model (DEM) for rock F-T damage is developed. In this model, thermal conduction model and volume expansion theory are integrated to describe the volumetric expansion characteristics during the freezing of internal pore water, thus effectively simulating the initiation and progression characteristics of frost heave cracks. We validated this model through comparisons with theoretical analyses and experiments, exploring the effects of model parameters. Employing moment tensor, the spatial gradient distribution patterns of F-T damage in water-saturated rock from the vantage point of fracture energy was analyzed. The results reveal that at −20 °C, 20 F-T cycles are requisite for the propagation of damage from the outer layer to the center of the Sichuan sandstone samples. The extent of damage in the outer layer exceeds that of the center, with the maximum fracture energy density of the outer layer being approximately 38.7 times that of the center. This model aptly delineates the progressive development of F-T damage characteristics and holds promise for further applications in identifying and delineating F-T damage zones in cold region rock engineering.

High-performance and frost-resistance MXene co-ionic liquid conductive hydrogel printed by electrohydrodynamic for flexible strain sensor

Conductive hydrogels with high performance and frost resistance are essential for flexible electronics, electronic skin, and soft robots. Nonetheless, the preparation of hydrogel-based flexible strain sensors with rapid response, wide strain detection range, and high sensitivity remains a considerable challenge. Furthermore, the inevitable freezing and evaporation of water in sub-zero temperatures and dry environments lead to the loss of flexibility and conductivity in hydrogels, which seriously limits their practical application. In this work, ionic liquids (ILs) and MXene are introduced into gelatin/polyacrylamide (PAM) precursor solution, and a PAM/gelatin/ILs/MXene/glycerol (PGIMG) hydrogel-based flexible strain sensor with MXene co-ILs ion–electron composite conductive network is prepared by combining the electrohydrodynamic (EHD) printing method and in-situ photopolymerization. The introduction of ILs provides an ionic conductive channel for the hydrogel. The introduction of MXene nanosheets forms an interpenetrating network with gelatin and PAM, which not only provides a conductive channel, but also improves the mechanical and sensing properties of the hydrogel-based flexible strain sensor. The prepared PGIMG hydrogel with the MXene co-ILs ion–electron composite conductive network demonstrates a tensile strength of 0.21 MPa at 602.82 % strain, the conductivity of 1.636 × 10−3 S/cm, high sensitivity (Gauge Factor, GF = 4.17), a wide strain detection range (1–600 %), and the response/recovery times (73 ms and 74 ms). In addition, glycerol endows the hydrogel with excellent freezing (−60 °C) and water retention properties. The application of the hydrogel-based flexible strain sensor in the field of human motion detection and information transmission shows the great potential of wearable devices, electronic skin, and information encryption transmission.

Dynamic response of ultra-high performance engineered cementitious composites (UHP-ECC) under low-velocity impact: Effect of waste rubber incorporation and low temperatures

This study aims to explore the dynamic response of ultra-high performance engineered cementitious composites (UHP-ECC) incorporating waste crumb rubber (CR) at various temperatures, focusing on its potential to enhance the resilience and sustainability of civil infrastructures against low-velocity impacts. To date, the impact behaviour of UHP-ECC under low temperatures has rarely been explored. Firstly, natural river sand and waste tyre CR was utilized to prepare the UHP-ECC. Then, a series of mechanical tests, including compression test, flexural test and uniaxial tensile test were carried out to investigate the static mechanical properties of rubberised UHP-ECCs. In addition, the effects of different waste CR incorporations (0%, 5%, 10%, and 15%) and various temperatures (25 °C, −5 °C, −30 °C, −50 °C, −100 °C and −196 °C) were comprehensively investigated by low-velocity impact tests with constant impact energy. Lastly, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) model was introduced to evaluate the overall performance of UHP-ECC. It was found that the use of river sand and CR significantly enhanced the tensile ductility and impact toughness of UHP-ECC. Impact energy primarily dissipates through damage such as matrix crack initiation, propagation, and fibre pull-out/rupture within the specimen. Adding CR notably decreased stress fluctuations during impact at room temperature, facilitating steady state energy absorption. Moreover, the time to reach peak impact force decreased with decreasing temperature across all UHP-ECC groups. At room temperature during impact process, fibre failure mode is dominated by pull-out failure, while lower temperatures lead to increased fibre rupture at the cracking surface. In low-temperature conditions, the impact response of rubberised UHP-ECC necessitates a comprehensive consideration of the synergistic effects, including material contraction, fibre bridging capacity, rubber phase transition, and water freezing.

Inulin with different degrees of polymerization as a functional ingredient: Evaluation of flour, dough, and steamed bread characteristics during freezing

In the study, the effects of short-chain inulin (OP), natural inulin (OH), and long-chain inulin (OHP) at substitution levels of 3%, 6%, and 9%, as well as freezing of 0, 15, and 30 days, on the farinograph and extensograph characteristics of flour, the rheological properties, water distribution, and microstructure of dough, as well as the quality of the final steamed bread, were investigated. The findings revealed that inulin led to a reduction in the water absorption of the dough while increasing its stable time. Furthermore, inulin delayed the alteration of freezable water within the frozen dough. Notably, the addition of inulin resulted in a more cohesive and evenly arranged network structure within the frozen dough. Steamed bread supplemented with 6% OP, 6% OH, and 3% OHP consistently dislayed a higher specific volume and spread ratio. These findings offer valuable insights into the utilization of inulin in frozen wheat foods.

A multivariable control strategy based on fuzzy logic interference rule for a solar-driven, direct air-cooled H[formula omitted]O-LiBr absorption chiller

The operation of a solar-driven H2O-LiBr Absorption Chiller (AbC) is subjected to various limitations regarding its ability to satisfy efficiently the required cooling demand while avoiding certain internal conditions, such as H2O-LiBr solution crystallization and water freezing. These circumstances would lead to problematic situations and jeopardize the continuous operation of the system. Thus, the development of accurate control strategies is an issue of interest. A new operational control strategy approach is introduced and tested through simulation studies, by employing a transient model of the entire solar cooling application. A prototype under development is used for the parametrization of the direct air-cooled AbC model used in the simulations. The developed control strategy aims to minimize the electrical consumption of the auxiliary components of the AbC (i.e., fan, pumps) during the partial load operation period, by using a fuzzy logic interference rule for determining the cooling capacity demand and then applying an optimization algorithm for determining the velocity of the auxiliary components. Within the proposed control strategy, a fast-calculation model is embedded, which predicts the chiller’s capacity under variable external conditions and partial load operation. The electrical COP is increased up to 2.2 times with respect to a baseline case, based on a basic two-step control strategy, while allowing the chiller to operate smoother, minimizing the crystallization and freezing risk.

Chickpea peptide as a plant-based cryoprotectant in frozen dough: Insight into the water states, gluten structures, and storage stabilities

The potentials of pulse peptides as cryoprotectants remain less exploited than other well-known applications, e.g., nutrient supplements, stabilizers, antioxidants etc. Thus, for the first time, this study screened a number of widely-used pulse peptides (pea, chickpea, lentil, mung bean, and white kidney bean) by evaluating their ice recrystallization inhibition (IRI) and thermal hysteresis (TH) activities. Then, chickpea peptide (CP) with the most prominent anti-freezing performance was selected for systematical evaluation of its cryoprotective effects on frozen dough in terms of water state, gluten structure, and storage stability. CP reduced the content of freezable water to 60% and unified the water distributions of frozen dough in a dose-dependent manner (0–6 g peptide per 100 g wheat flour). Freezing-induced changes on gluten disulfide bonds, secondary structures, and dough microstructures were also restrained. Accordingly, dumpling wrappers prepared from CP-added frozen dough manifested the reduced cracking rates (31%–5%), increased toughness (68%–79%), extensibility (82%–92%), and cooking stabilities. CP was rich in basic amino acids (arginine, lysine, and histidine), accounting for 27% of total amino acids, which were responsible for its outstanding cryoprotective activity. Chickpea peptide might therefore be a good candidate for development of high-performance dough cryoprotectants.

Monitoring the Dough Properties, Quality Characteristics and Volatile Compounds of Whole Wheat Bread Made by Different Sourdough Types during Frozen Storage.

There is a need to increase the consumption of whole wheat bread (WWB) due to its health benefits by overcoming its poor technological quality and improving its sensory characteristics. In this study, sourdough bread-making and frozen dough technology were combined to provide fresh WWB at any time with better quality. Also, it was aimed to investigate the effects of three types of sourdough (type I, II, and IV) on the final quality of WWB during frozen storage (-30 °C, 14 and 28 days). The tan δ of WWB with type I sourdough was highest at the end of the frozen storage. Freezable water content was lower on day 0 for WWB with type II and IV sourdough than other bread types. No significant effect of frozen storage was observed in bread types in terms of an α helix structure, except for WWB with type I sourdough. A lower hardness increment was shown in WWB with baker's yeast and WWB with type II sourdough over 14 days of frozen storage when compared to other bread types. WWB with type I sourdough and WWB with type IV sourdough were differentiated from other bread samples in volatile compound (VC) analysis on frozen storage days 28 and 0, respectively. The frozen storage of WWB with baker's yeast and WWB with type II sourdough caused no notable changes in the VCs profile. These results suggest that a less detrimental effect of frozen storage was observed in WWB with type II sourdough, indicating a more favorable choice for producing WWB with sourdough.

Gelatin hydrolyzed by papaya latex enzymes as an alternative cryoprotectant for frozen raw Pacific white shrimp (Penaeus vannamei)

The cryoprotective activity of gelatin hydrolyzed by papaya latex enzymes at degrees of hydrolysis (DH) of 5%, 10%, 15%, and 20% were determined. The thermal hysteresis of gelati hydrolysate increased as DH increased up to 15% (2.31–4.19 °C) and decreased at DH of 20% (2.94 °C). The gelatin hydrolysate with 15%DH (G15), showing the highest thermal hysteresis, was subjected to fractionation and cryoprotective effect study in Pacific white shrimp. The fractionated peptide with the highest thermal hysteresis (5.19 °C) had a molecular weight of 1.7–4.2 kDa. After the soaking, G15-treated shrimp showed significantly lower and higher weight gain (7.33%) than those treated with mixed phosphates (16.12%) and distilled water (0.82%), respectively. Mixed phosphates- and G15-treated shrimp had lower α-glucosidase (AG) and β-N-acetyl-glucosaminidase (NAG) activities in exudate and lower thawing loss than distilled water-treated shrimp. G15-and mixed phosphates-treated shrimp also reduced freezable water content and maintained Ca2+-ATPase activity and protein solubility more effectively than distilled water-treated shrimp. Therefore, gelatin hydrolysate could be a potential alternative cryoprotectant in frozen raw shrimp.

Effect of bovine hide gelatin antifreeze peptides on the quality of frozen dough treated with freeze-thaw cycles and its steamed bread

The structure of frozen dough was damaged due to the recrystallization of ice crystals during freeze-thawing. Therefore, the effect of bovine hide gelatin antifreeze peptides (BgAFPs) on the quality of frozen dough treated with freeze-thaw cycles and its steamed bread was investigated. The results showed that BgAFPs exhibited a high thermal hysteresis activity at 1.64 °C and possessed the significant ability to inhibit ice crystals growth due to its -Gly-X-Y- (where X was mostly proline or hydroxyproline, Y was any amino acid) repeating sequences. The decrease in gassing rate of frozen dough without BgAFPs (41.31%) was significantly greater than those of frozen dough with BgAFPs (36.32%, 27.74% and 24.30%), revealing that the BgAFPs had cryoprotective effect on yeast cells. Additionally, BgAFPs maintained a continuous apparent morphology of the frozen dough by inhibiting water migration. Specifically, the freezable water content in the frozen dough with 0% and 1.0% BgAFPs increased from 63.35% and 59.41% to 73.74% and 64.36%, respectively. Furthermore, BgAFPs increased the specific volume and springiness, decreased the hardness of the steamed bread. These results suggested that BgAFPs effectively attenuated the freeze-thaw induced damage to frozen dough and improved the quality of steamed bread.

Optimization of method for cross-section hydrogels preparation using high-pressure freezing.

High-pressure water freeze fracturing is a method for preparing water-containing samples such as hydrogels for scanning electron microscopy (SEM), in which a sample is placed in a divisible pressure vessel, filled with water, sealed, frozen with liquid nitrogen and then vacuum dried after the vessel is divided. The pressure (∼200 MPa) generated by the phase transition from water to ice is expected to inhibit ice crystal formation that causes large deformation of microstructure in the sample. To maximize the useable sample size, where SEM observation is not affected by ice crystal growth, preparation conditions including the size of pressure vessel were examined in this work. Using pressure vessels 8.0 mm, 5.5 mm and 4.5 mm in diameter, agarose gel, gelatin gel, wheat starch hydrogel, wheat flour noodle and cellulose hydrogel were used to prepare SEM samples. With agarose gel, an area of 3.6 mm in diameter in the 5.5 mm vessel was achieved as the maximum size of the area observable without ice crystal growth. The observable size of other samples was comparable, except for gelatin gel. As a result, observation of the three-dimensional network structure of hydrogels could be performed over a wider range than with the conventional method without shredding or chemical treatment of the samples. Additionally, usability of agarose gel for sample support matrix in high-pressure water freeze fracturing was demonstrated.

Quantification of Residual Water in Pharmaceutical Frozen Solutions Via 1H Solid-State NMR

Freezing is essential for the stability of biological drug substances and products, particularly in frozen solution formulations and during the primary drying of lyophilized preparations. However, the unfrozen segment within the frozen matrix can alter solute concentration, ionic strength, and stabilizer crystallization, posing risks of increased biophysical instability and faster chemical degradation. While quantifying the unfrozen water content is important for designing stable biopharmaceuticals, there is a lack of analytical techniques for in situ quantitative measurements. In this study, we introduce a 1H magic angle spinning NMR technique to identify the freezing point (Tice) and quantify mobile water content in frozen biologics, applying this method to analyze the freezing of a commercial high-concentration drug product, Dupixent®. Our results demonstrate that water freezing is influenced by buffer salt properties and formulation composition, including the presence of sugar cryoprotectants and protein concentration. Additionally, the 1H chemical shift can probe pH in the unfrozen phase, potentially predicting the microenvironmental acidity in the frozen state. Our proposed methodology provides fresh insights into the analysis of freeze-concentrated solutions, enhancing our understanding of the stability of frozen and lyophilized biopharmaceuticals.