Ice Crystals Research Articles

Double-edged effect of frequent freeze-thaw on the stability of zero-valent iron after heavy metal remediation

Freeze-thaw cycles (FTCs) cause dynamic microscale changes in ions and solvents. During freezing, heavy metals adsorbed on zero-valent iron (M-ZVI) and protons are excluded by ice crystals and concentrated in the liquid-like grain boundary region. The high proton concentration in this region leads to the dissolution of the passivation layer of ZVI. To assess the environmental risks of M-ZVI during FTCs, this study evaluated the stability of M-ZVI in this scenario from both microscale and macroscale perspectives. The results showed that the dissolution of the passivation layer had a dual effect on the stability of M-ZVI, which depends on the by-products of M-ZVI. The dissolution of the passivation layer was accompanied by the leaching of heavy metals, such as Ni-ZVI, but it also enhanced the reactivity of ZVI, causing it to re-react with desorbed heavy metals. The stability of Cr-ZVI and Cd-ZVI was improved due to frequent FTCs. Furthermore, changes in the surrounding environment (water dipole moment, ion concentration, etc.) of ZVI affected the crystallization of Fe oxides, increasing the content of amorphous Fe oxide. As low-crystallinity Fe oxides could facilitate ion doping, Ni2+ was doped into Fe3O4 lattice during FTCs, which reduced the mobility of heavy metals. Contrary to traditional views that freezing temperatures slow chemical reactions, this study provides new insights into the application of iron-based materials in cold environments.

Investigating the Interaction Between Ice-Binding Proteins and Ice Surfaces Using Microfluidic Devices and Cold Stages.

Ice-binding proteins (IBPs) protect organisms living in sub-freezing conditions by inhibiting ice growth in fish and insects, limiting ice recrystallization in plants, and assisting bacteria to adhere to ice. The mechanisms by which these proteins bind to ice and inhibit its growth have been studied both experimentally and using molecular dynamic simulations. A unique experimental technique developed to test and characterize the interactions between IBPs and ice using a combination of a microfluidic device, cold stages with millikelvin temperature resolution, fluorescence-labeled IBPs, and fluorescence microscopy is described herein. The main advantage of this technique is the ability to exchange the solution around micron-sized ice crystals and characterize their binding to and inhibition of ice.

An oscillating magnetic field suppresses ice-crystal growth during rapid freezing of muscle tissue of mice.

Regenerative medicine would benefit from a safe and efficient cryopreservation method to prevent the structural disruption caused by ice-crystal formation in cells and tissue. Various attempts have been made to overcome this problem, one of which is the use of an oscillating magnetic field (OMF). However, the underlying mechanism is unclear. In this study, to evaluate the effect of an OMF on ice-crystal formation in the leg muscles of mice, we used to use the frozen-section method with a slower freezing rate than is, usual which resulted in ice crystals forming in the tissue. We assessed the mean size and number per unit area of intracellular ice holes in sections of muscle tissue, with and without OMF. Ice-crystal growth was reduced in frozen tissue subjected to OMF. Furthermore, we evaluated the structure and function of proteins in frozen tissue subjected to OMF by immunostaining using an anti-dystrophin antibody and by enzymatic histochemistry for NADH-TR and myosin ATPase. The results imply that the ability of OMF to suppress ice-crystal growth might be related to their stabilization of bound water in biomolecules during freezing.

Effect of Cryoprotectants on Quality of Desalted Jellyfish Subjected to Multiple Freeze- Thaw Cycles

A freeze-thaw cycle in frozen products occurs when the temperature fluctuates during storage or transportation, causing drip loss, changes in ice crystal reformation, and textural protein. In practical freezing, using cryoprotectants in frozen products aids in delaying the physicochemical changes. The problem has been found in commercial frozen jellyfish with sesame oil, causing the separating oil and water derived from drip loss of thawed jellyfish protein. This study aimed to select an appropriate cryoprotectant and concentration for frozen jellyfish products. Therefore, this research compared the changes in the physical and textural properties of desalted jellyfish collagen protein soaked in inulin, sucrose, or sorbitol at 1, 5, and 10% and subjected to three freeze-thaw cycles. Results showed increased concentration of each cryoprotectant increased soaking yield. The maximum soaking yields of desalted jellyfish were 2.49 ± 0.54, 2.79 ± 0.82, and 2.78 ± 0.51%, and each cryoprotectant content was 7.18 ± 0.01, 7.54 ± 0.00, and 8.58 ± 0.32% when using static soaked in inulin, sucrose, and sorbitol at 10%. During the freeze-thaw cycle, the retardation of the denatured jellyfish protein from ice crystals increased when desalted jellyfish were immersed in inulin, sucrose, or sorbitol at the maximum concentration of 10%, displaying the drip losses at 27.88 ± 0.45, 29.45 ± 0.35, and 28.56 ± 0.73% that lowered than the control at 56.54 ± 0.64%. The increased repeated freeze-thaw cycles increased the compact structure of thawed jellyfish collagen, supported by microstructure analysis. In summary, inulin at 10% appears to have a cryoprotective effect similar to sucrose and sorbitol and will be a choice for commercial frozen jellyfish-based food menu development.

The cryoprotective effect of Guar gum co-supplemented with ethylene glycol and glycerol in Simmental bull semen

Sperm cryopreservation often reduces sperm quality by forming of intra- and extracellular ice crystals. Various compounds widely used to counteract this effect. The guar gum was considered as an extracellular cryoprotective substance. The present study evaluated the impact of the co-supplementation of guar gum with ethylene glycol or glycerol in the cryopreservation of bull sperm. Four ejaculates from 4 bulls were pooled and divided into ten groups consisting of 4 controls (glycerol 6%, ethylene glycol 6%, glycerol 3.5%, and ethylene glycol 3.5%, and six treatment groups including guar gum in 0.001% and 0.002% alone and or co-supplemented either with 3.5% glycerol or 3.5% ethylene glycol and frozen in liquid nitrogen. The sperm motility, viability, plasma membrane and DNA integrity, apoptotic-like changes, antioxidant capacity (TAC), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities evaluated. The groups contained 3.5% glycerol + 0.001% guar gum, 3.5% ethylene glycol + 0.001% guar gum, and 0.001% guar gum alone showed higher values for live sperm, antioxidant enzymes, membrane integrity, mitochondrial membrane potential (MMP), fertilization, cleavage, and blastocyst rates; and lower values for apoptotic-like changes, H2O2 level, and DNA damage than the control groups. In conclusion, adding guar gum to the bull sperm diluent either alone or combined with glycerol or ethylene glycol ameliorated sperm viability and kinematic parameters and antioxidant capacity while reducing DNA damage and apoptotic-like changes. Guar gum also has improved embryo development. Due to its cost-effectiveness and physicochemical properties, guar gum is a promising supplement for bull sperm cryopreservation.

Method of preparing unfixed ciliates for scanning electron microscopy without noticeable artifacts

Water freeze-drying of biological samples has long been considered unfeasible as a sample preparation method for scanning electron microscopy (SEM) owing to the formation of damaging ice crystals. Contrary to this assumption, however, when live ciliates in water were frozen in contact with pre-cooled copper blocks in this study, they could be freeze-dried without artifact formation, although the success rate was only about 10%. This method offers several advantages over the traditional approach of chemical fixation followed by dehydration and drying. First, the degree of sample shrinkage associated with sample preparation was much lower than with chemical fixation. Second, contractile ciliates such as Spirostomum and Lacrymaria could be sampled in their elongated state, and the metachronal waves of cilia on the cell surface were well preserved. Moreover, this method requires no special equipment and only a few hours at most for sample preparation before SEM observation. Thus, although this method needs to be improved to increase the success rate in the future, it can be used to prepare samples for SEM observation that could not be prepared by other methods.

PSVII-17 Differential Freeze/Thaw Rates Affect Water-Holding Capacity and Lipid Oxidation in Beef Rib Primal Cuts

Abstract Fresh meat is vulnerable to microbial contamination and loss of quality. Hence, freezing is used to mitigate these issues during transport and storage. However, freezing may negatively impact the same quality characteristics it was meant to preserve, resulting in products that are dissatisfying to the consumer. During the freezing process of meat, water forms ice crystals of various shapes and sizes. The degree of ice crystal growth, mainly due to the freezing rate, has been shown to affect several meat quality characteristics, including tenderness, juiciness, and color. Previous research has primarily evaluated the effect of freezing/thawing on the quality of beef retail cuts. To the best of our knowledge, however, minimal research has been devoted to examining the impact of freezing/thawing on the quality of beef primal and sub-primal cuts. Therefore, this study aimed to gain deeper insight into the histological, ultrastructural, and physiochemical changes occurring in whole beef ribs in response to different freezing/thawing treatments. To achieve our objective, we purchased 32 choice beef rib primals from a local harvest facility 24 h postmortem. Ribs were vacuum packaged and randomly divided into four groups (8 ribs/group). The first group was frozen in a −20 °C freezer (slow freezing), stored in the same freezer for 12 weeks, and thawed at 4 °C for 24 h (slow thawing). The second group was frozen in an ultralow temperature freezer (−80 °C; fast freezing), stored in the same freezer for 12 weeks, and thawed at 4 °C for 48 h. The third and fourth groups were frozen and stored in the same manner as groups one and two, respectively, but were thawed in a water bath (10 °C) for 8 h (fast thawing). Two 2.5-cm-steaks from the middle and each end were collected to represent the entire rib. One steak from each of the three areas was used for color, cook loss, and tenderness evaluation, while the other three supplied tissue for drip loss and lipid oxidation analysis. Data were analyzed using the mixed model of SAS with P ≤ 0.05 considered significant. No differences were observed in color or tenderness between the treatments (P > 0.05). However, slow thawing increased drip loss, regardless of the freezing rate (P < 0.05). Greater cook loss was observed in the fast frozen-slow thawed samples compared with fast frozen-fast thawed samples (P < 0.05). The slow frozen-fast thawed steaks had greater lipid oxidation than the slow frozen-slow thawed treatment (P < 0.05). In general, our data show that subjecting whole beef rib sections to fast freezing may reduce water loss at the expense of increased lipid oxidation. This demonstrates that additional research is needed to further optimize beef primal cut storage.

Static magnetic field improvement of the quality of rice dumpling subjected to freeze–thaw cycles: Roles of phase transition of water and changes in structural and physicochemical properties of glutinous rice flour

This study aimed to investigate the effect of static magnetic field (SMF, 0–10 mT) on the quality of rice dumplings subjected to 7, 14, 21, and 28 freeze–thaw cycles. The underlying mechanism was explored by monitoring changes in water phase transition, water distribution, and structural and physicochemical properties of rice flour. Results suggested that SMF enables the formation of small ice crystals by accelerating freezing rate, shortening phase transition time, and increasing bound water content, which attributes to reducing the mechanical damage on starch granules and thus improves the quality of frozen rice dumpling. After 7–28 freeze–thaw cycles, SMF treatment increased the whiteness by 0.08–1.58, reduced the cracking ratio by 1.67 %–8.34 %, decreased the water loss ratio by 0–0.75 %, and significantly improved the texture of cooked rice dumplings. This study confirmed the feasibility of SMF in improving the quality of rice dumpling, which contributes to expanding the applications of magnetic freezer in the preservation of starch-based foods.

The application of ice glazing containing D-sodium erythorbate combined with vacuum packaging to maintain the physicochemical quality and sweet/umami non-volatile flavor compounds of frozen stored large yellow croaker (Pseudosciaena crocea)

Ice glazing containing 0.3 % D-sodium erythorbate (DSE), combined with vacuum packaging, was used as a method to maintain the quality of large yellow croaker during frozen storage. This study aimed to assess various aspects, including water properties (water holding capacity and moisture distribution), protein-related characteristics (secondary and tertiary structure of myofibrillar protein), freshness indicators (K value and total volatile base nitrogen (TVB-N)), and non-volatile flavor compounds (free amino acids (FAAs) and nucleotides) in samples stored for 300 days at –23 °C. The results showed that vacuum packaging had a significant inhibitory effect on the growth of ice crystal. Notably, it successfully maintained the cross-sectional area of nearly all ice crystals below 20,000 μm2, effectively curtailing water loss. Simultaneously, the combination of vacuum packaging with the complex ice glaze effectively mitigated the degradation of IMP and free amino acids, maintaining low levels of K value (12.85 %) and TVB-N (11.28 mg N/100 g) throughout the 300-day frozen storage, retaining first-class freshness. Among the various treatment modalities assessed, the combined application of vacuum packaging and 0.3 % DSE-infused ice glazing emerged as the most effective in terms of preservation outcomes. This efficacious combination shows promising potential for the frozen storage of aquatic products and is therefore recommended for practical implementation.

The relationship between pore structure and strength of aeolian sand concrete under low temperature

To examine the relationship between microscopic parameters and compressive strength of aeolian sand concrete (ASC) at low temperatures, the compressive strength of ASC at different temperatures is predicted by factors such as the pore structure parameters and the ambient temperature. The experiments used 100 % replacement of river sand (RS) with aeolian sand (AS) to prepare fully ASC, and regular concrete with the same water-cement ratio as the control group. The experiment used nuclear magnetic resonance (NMR) technology and grey correlation analysis method to analyze the microscopic parameters and compressive strength of concrete specimens with three curing ages of 7d, 28d, and 60d at temperatures of 20 °C, 0 °C, −5 °C, −10 °C, −15 °C, and −20 °C. It was shown that the agglomeration between the fine particles during the mixing process results in a large number of pores in the interior of the ASC, resulting in a larger porosity compared to ordinary concrete. As a result, its compressive strength was lower than that of ordinary concrete, and the loose and porous internal structure provides room for the filling of more ice crystals. Therefore, the increase in compressive strength of ASC at different curing ages in an environment of −20 °C was greater than that of ordinary concrete. Among them, at-20 °C, the compressive strength of ASC with curing ages of 7d, 28d and 60d increased by 6.31 %, 3.59 % and 3.97 % respectively compared with ordinary concrete. Finally, a predictive model between parameters such as temperature, porosity, mean pore size distribution and gel content and compressive strength was developed, which was highly accurate.

Cryopreservation of Bovine Oocyte using Vitrification Solution and Cryotop Techniques

Cryopreservation is used to preserve biological samples over an extended period at ultra-low temperatures. This process evolved into vitrification, a more advanced and superior technology in which fluids or water molecules form a glass-like structure without forming ice crystals. Unlike fresh cells, cryopreservation is reported to reduce oocyte viability and developmental competency. This study employed two vitrification techniques, vitrification solution (VS) and Cryotop, to investigate the meiotic resumption in bovine. Oocytes were extracted from cow ovaries collected from slaughterhouses in Banting and Shah Alam, Selangor, Malaysia. The oocytes were grouped (A, B, and B’) based on cumulus morphology and matured in vitro in a culture dish (humidified 5% carbon dioxide incubator at 38.5°C) for 20 to 24 hr. Oocytes were vitrified after maturation using straws or aids of Cryotop sheets, then submerged in liquid nitrogen and stored for five days before defrosting for cryoprotectant elimination. By using Giemsa staining, the maturation state of fresh and vitrified bovine oocytes was evaluated through five parameters: zygotene, pachytene, diakinesis, metaphase I, and metaphase II. The maturation rate demonstrated only slight differences in the three groups of oocytes treated with VS (A: 44.79%; B: 30.97%; B’: 20.70%) and Cryotop (A: 39.42%; B: 37.27%; B’: 28.97%), which were significantly lower than fresh oocytes (A: 55.83%; B: 44.82%; B’: 56.17%). Both VS and Cryotop methods were viable options for cryopreserving oocytes, but the Cryotop technique was more effective in increasing the meiotic competence of poor-quality oocytes.

Seeding of Supercooled Low Stratus Clouds with a UAV to Study Microphysical Ice Processes: An Introduction to the CLOUDLAB Project

Abstract Ice formation and growth processes play a crucial role in the evolution of cloud systems and the formation of precipitation. However, the initial formation and growth of ice crystals are challenging to study in the real atmosphere resulting in uncertainties in weather forecasts and climate projections. The CLOUDLAB project tackles this problem by using supercooled stratus clouds as a natural laboratory for targeted glaciogenic cloud seeding to advance the understanding of ice processes: Ice nucleating particles are injected from an uncrewed aerial vehicle (UAV) into supercooled stratus clouds to induce ice crystal formation and subsequent growth processes. Microphysical changes induced by seeding are measured 3–15 min downstream of the seeding location using in situ and ground-based remote sensing instrumentation. The novel application of seeding with a multirotor UAV combined with the persistent nature of stratus clouds enables repeated seeding experiments under similar and well-constrained initial conditions. This article describes the scientific goals, experimental design, and first results of CLOUDLAB. First, the seeding plume is characterized by using measurements of a UAV equipped with an optical particle counter. Second, the seeding-induced microphysical changes observed by cloud radars and a tethered balloon system are presented. The seeding signatures were detected by regions of increased radar reflectivity (>−20 dBZ), which were 10–20 dBZ higher than the natural background. Simultaneously, high concentrations of seeding particles and ice crystals (up to 2,000 L−1) were observed. A cloud seeding case was simulated with the numerical weather model ICON to contextualize the findings.

Formation of advanced glycation end-products in minced pork during frozen-then-chilled storage and subsequent heating.

The influences of frozen-then-chilled storage of minced pork on the formation of advanced glycation end-products (AGEs) including Nε-carboxymethyllysine and Nε-carboxyethyllysine, and their corresponding α-dicarbonyl precursors (α-DPs; glyoxal and methylglyoxal) during storage and subsequent heating were investigated in comparison with chilled storage. During cold storage, the levels of AGEs, trichloroacetic acid-soluble peptides, and Schiff bases in minced pork continuously increased while α-DPs decreased. The 30min heating (100°C) resulted in 64-560% increase of AGEs in pork, corresponding with an increase of Schiff bases and decreases of α-DPs. Compared to the chilled storage, the frozen-then-chilled storage led to no significant difference (P>0.05) on the levels of AGEs and α-DPs in raw or heat-treated pork, implying that the formation and thawing of ice crystals in pork during the frozen-then-chilled storage had minor to no effects on the formation of AGEs and their α-DPs.

Effect of rapid freezing technology on quality changes of freshwater fish during frozen storage

The impacts of pre-frozen with −80 °C liquid nitrogen spray freezer (LNF), −80 °C refrigerator freezer (RF), and −30 °C micro-freezer (MF) on the freezing rate, physical and chemical properties and microscopic structures of freshwater fish (grass carp, tilapia and bighead carp) stored at −18 °C (14 days) were evaluated. LNF and MF were effective in shortening the entire freezing period and their muscle tissue microscopic structures were more homogeneous and thicker than the RF group, also with smaller and more regular ice crystal. Additionally, the LNF-treated samples had good water holding capacity and textural characteristics and significantly delayed changes in immobilized water content, effectively suppressing the increase in L* values in grass carp samples (p < 0.05). However, MF was not as effective as LNF and RF in inhibiting the formation of TBARS and TVBN. In conclusion, LNF played a more positive role in quality retention of freshwater fish.

Observation and Measurement of Ice Morphology in Foods: A Review.

Freezing is an effective technology with which to maintain food quality. However, the formation of ice crystals during this process can cause damage to the cellular structure, leading to food deterioration. A good understanding of the relationship between food microstructure and ice morphology, as well as the ability to effectively measure and control ice crystals, is very useful to achieve high-quality frozen foods. Hence, a brief discussion is presented on the fundamentals/principles of optical microscopic techniques (light microscopy), electronic microscopic techniques (transmission electron microscopy (TEM) and scanning electron microscopy (SEM)), as well as other non-invasive techniques (X-rays, spectroscopy, and magnetic resonance) and their application to measuring ice formation rates and characterizing ice crystals, providing insight into the freezing mechanisms as well as direct monitoring of the entire process. And, in addition, this review compares (the negative and positive aspects of) the use of simple and cheap but destructive technologies (optical microscopy) with detailed microscopic technologies at the micro/nanometer scale but with pretreatments that alter the original sample (SEM and TEM), and non-destructive technologies that do not require sample preparation but which have high acquisition and operational costs. Also included are images and examples which demonstrate how useful an analysis using these techniques can be.

Impact of supercooling storage on physical and chemical properties of yellowfin tuna (Thunnus albacares)

Seafood is highly perishable, and its spoilage begins immediately after harvesting due to the production of various metabolites. However, freezing, a conventional long-term preservation technology, causes quality degradation due to ice crystallization. Supercooling has emerged as a promising technique to prevent ice formation and quality degradation. In this study, tuna fillets were supercooled at −3.5 °C with an external pulsed electric field (PEF) and oscillating magnetic field (OMF) strengths for optimization. Quality factors such as drip loss, color, microbial analysis, texture, and total volatile basic nitrogen (TVB-N) were evaluated in comparison with refrigerated, frozen-thawed, and supercooled samples stored for 1, 4, 7, and 10 days. The results showed that supercooled samples had lower TVB-N values than refrigerated samples. The aerobic plate counts of supercooled tuna samples did not significantly vary from 1 to 7 days of storage. Moreover, supercooling preserved the textural integrity of the product and reduced drip loss compared to frozen-thawed samples. Therefore, supercooling preservation can extend the shelf-life of tuna fillets while minimizing quality degradation, indicating its potential compared to conventional refrigeration and freezing methods.

Tofukasu-derived biochar with interconnected and hierarchical pores for high efficient removal of Cr (VI)

Herein, we report the synthesis of interconnected hierarchical pore biochar (HTB) via an ice-templating strategy using bio-waste (tofukasu). The abundance of N- and O-containing functional groups in tofukasu makes it easy to form hydrogen bonds with water molecules and water clusters, resulting in nano-micro structures like ice clusters and snow crystals during freezing process. More importantly, tofukasu will be squeezed by micron-scale snow crystals to form coiled sheet-like structures, and its surface and interior will be affected by needle-like ice nanocrystals from several nanometers to tens of nanometers to form transverse groove needles and mesopores. The ice crystals are then removed by sublimation with tofukasu, leaving the interconnected pore structure intact. Therefore, the ice template synthesis strategy endowed the interconnected hierarchical pore structure of HTB with a large specific surface area (SBET, 733 m2⋅g−1) and hierarchical porosity (30.30% for mesopores/total pore volume ratio), which is significantly higher than the normal dry treated tofukasu biochar (TB), which had a SBET of 436 m2⋅g−1 and contained 1.53% mesopores. In addition, the sheet-like structure with interconnected pores of HTB favors high exposure of active sites (N- and O-containing functional groups), and a fast electron transport rate. As a result, HTB had an excellent adsorption capacity of 159.65 mg⋅g−1, which is 4.7 times that of typical block biochar of TB (33.89 mg⋅g−1) according to Langmuir model. Electrochemical characterization, FTIR and XPS analysis showed that the mechanism of Cr(VI) removal by HTB included electrostatic attraction, pore filling, reduction and surface complexation.Graphical

Advances in cryopreservation of Syzygium maire (swamp maire, maire tawake) zygotic embryos, a critically endangered tree species endemic to New Zealand

IntroductionSyzygium maire is a threatened Myrtaceae tree species endemic to New Zealand. Due to its highly recalcitrant seed, cryopreservation is the only viable long-term ex situ conservation option for this species. Our previous attempts to cryopreserve the embryonic axis (EAs) of S. maire were unsuccessful but did provide a better understanding of desiccation behavior, biochemical composition, oxidative status, and ultrastructural changes associated with desiccation in EAs.MethodsWe incorporated this knowledge with biophysical information to investigate two advanced cryopreservation technologies: a droplet vacuum infiltration vitrification (DVIV) method and a novel metal-mesh vacuum infiltration vitrification (MVIV) method using Plant Vitrification Solution 2 (PVS2) for cryopreservation of the EAs.ResultsThe PVS2 treatment at room temperature (~20°C) proved phytotoxic with extended PVS2 incubation significantly reducing EA survival. No EAs survived cryopreservation using DVIV, however MVIV resulted in post-cryopreservation survival of up to 19% following PVS2 incubation for 20 min. Biophysical thermal analysis using Differential Scanning Calorimetry revealed a 15-fold reduction in ice crystallization following incubation in PVS2 for 20 min or more, with all freezable water removed after 60 min incubation.DiscussionThese results present a significant advance in being able to successfully cryopreserve S. maire EAs. The findings from this study will aid the development of cryopreservation protocols for other extremely recalcitrant seeded species, many of which are threatened with extinction due to climate change, plant pathogens, and habitat destruction.

Designing Antifreezing Hydrogels with Enhanced Mechanical Properties Using a Simple Crosslinker

Antifreezing hydrogels are essential for materials design and practical applications, but their development and understanding have been challenging due to their high-water content. Current antifreezing hydrogels typically rely on organic solvents or the addition of antifreezing agents. In this study, we present a novel crosslinking strategy to fabricate antifreezing hydrogels without the need for additional antifreezing agents. We introduce a new crosslinker, PEGn-EGINA, which combines highly hydrophilic EGINA with polyethylene glycol (PEG) of varying molecular weights. Utilizing PEGn-EGINA as the crosslinker, we synthesize Agar/Polyacrylamide (Agar/PAAm) double-network hydrogels, alongside conventional MBAA-crosslinked hydrogels for comparison. The resulting PEGn-EGINA-crosslinked hydrogels exhibit inherent antifreezing properties and retain their mechanical integrity even at subzero temperatures for extended periods. Molecular dynamics (MD) simulations further reveal that the antifreezing behavior observed in the PEGn-EGINA-crosslinked hydrogels can be attributed to their highly hydrophilic and tightly crosslinked double-network structures. These structures enable strong bindings between water and the hydrogel network, thus effectively preventing the formation of ice crystals within the hydrogels. Notably, PEGn-EGINA-crosslinked hydrogels not only demonstrate superior mechanical performance compared to MBAA-crosslinked hydrogels, but also maintain their mechanical properties even in frozen conditions, making them suitable for a wide range of applications. This study presents a simple yet effective design concept for highlighting the role of novel crosslinker in enhancing antifreezing and mechanical properties, showcasing their potential for various applications that require both antifreezing capabilities and robust mechanical performance.

Chilling Effects: Assessing Chlorine Levels in Hawker-Served Crystal Ice Cubes in Banjarbaru City

Cold drinks served will be served along with ice cubes, one of which is crystal ice cubes. In making ice cubes must have the same quality requirements as drinking water. The provision of water quality that is suitable for drinking needs to be examined. As for drinking water quality requirements according to the Regulation of the Minister of Health of the Republic of Indonesia Number 2 of 2023 concerning drinking water quality requirements, the presence of free chlorine compounds in the allowed network distribution is 0.2-0.5 mg/l. Chlorine serves to inhibit growth and eradicate bacteria from various types of microbes, but if chlorine exceeds quality standards and reacts with water it can form hypochlorous acid which can damage cells in the body and can cause digestive disorders because it can make the stomach wall erosion and cause ulcer disease and if used in the long term can cause kidney disease and cancer. This research aims to analyze chlorine levels and crystal ice cubes of hawker sellers in Banjarbaru City and the factors that influence it. The results of the study explained that from 28 samples of crystal ice cubes, only 2 (7%) samples of crystal ice cubes met the standards, while the other 26 samples (93%) had chlorine levels above the maximum limit of 0.5 mg / L. While the behavior of ice cube sellers in washing hands before taking ice cubes only 11 people (39%), 17 other beverage sellers (61%) did not wash their hands before taking ice cubes.