Freezing Time Research Articles

7,8-Dihydroxyflavone ameliorates cognitive impairment induced by repeated neonatal sevoflurane exposures in mice through increasing tau O-GlcNAcylation

BackgroundSevoflurane, one of the most commonly used general anesthetics for pediatric anesthesia, has recently gained significant attention in both preclinical and clinical settings due to its potential neurotoxicity in the developing brain. Tau phosphorylation, induced by sevoflurane, is recognized as one of the major causes of neurotoxicity. 7,8-dihydroxyflavone (DHF), a TrkB receptor agonist, has been reported to exhibit potential neuroprotective effects against tauopathies. In this study, our objective was to investigate whether DHF could provide neuroprotective effects against sevoflurane-induced neurotoxicity and explore the underlying molecular mechanisms. MethodsSix-day-old mice were subjected to 2 h of anesthesia with 3 % sevoflurane, with or without pretreatment of DHF (5 mg/kg/day, i.p.) for 3 consecutive days. Autonomic motor ability was assessed by open-field test, while learning and memory abilities were evaluated by the fear conditioning test. Western blotting was conducted to measure the levels of t-TrkB, p-TrkB, tau, and phosphorylated tau. Additionally, a co-immunoprecipitation assay was performed to investigate the interaction between O-GlcNAcylation and tau. ResultsRepeated neonatal sevoflurane exposures resulted in reduced freezing time during the context and cued fear conditioning tests in adulthood. However, pretreatment with DHF restored the freezing time to the level of the control group, indicating that DHF effectively alleviated cognitive impairments induced by neonatal sevoflurane exposure. We also observed that repeated neonatal sevoflurane exposures increased tau phosphorylation while decreasing tau O-GlcNAcylation. However, DHF pretreatment rebalanced the tau O-GlcNAcylation/phosphorylation ratio by enhancing the interaction between tau and O-GlcNAcylation. ConclusionOur findings demonstrate that DHF effectively ameliorates sevoflurane-induced cognitive impairment in developing mice by restoring the balance between tau O-GlcNAcylation and phosphorylation. Therefore, this study suggests that DHF has the potential to be a therapeutic agent for treating cognitive impairment associated with anesthetics, such as sevoflurane.

Improving the practicality of recombinant Escherichia coli biosensor in detecting trace Cr(VI) by modifying the cryogenic storage conditions of biosensors and applying simple pretreatment

Hexavalent chromium (Cr(VI)) is a global environmental pollutant. To reduce the risk caused by Cr(VI), a simple, accurate, reproducible, and inexpensive method for quantifying Cr(VI) in water and soil should be developed. In this study, three types of recombinant Escherichia coli biosensors (namely T7-lux-E. coli, T3-lux-E. coli, and SP6-lux-E. coli biosensor) containing promoters (T7, T3, and SP6), chromate-sensing regulator chrB, and the reporter gene luxAB were constructed. This study investigated the effects of cryogenic freezing temperature and time on trace Cr(VI) measurement by using recombinant E. coli biosensors. The results indicated that the activity of thawed frozen SP6-lux-E. coli cells stored at −20 °C for 270 days did not differ from that of freshly prepared cells. Turbidity and conductivity in water samples and organic matter in soil interfered with Cr(VI) measurement using the biosensor. The SP6-lux-E. coli biosensor exhibited a wide measurement range and a low deviation of <5% for measuring Cr(VI) in various Cr(VI)-contaminated water and soil samples and required only a simple pretreatment or extraction process even after 270-day storage at −20 °C. To the best of our knowledge, this is the first study to report the use of recombinant biosensors for accurately measuring Cr(VI) in both water and soil.

Effect of ultimate pH on quality of aged Longissimus dorsi muscle of Zebu Nellore (Bos indicus) during long-term frozen storage

Despite the relatively high occurrence of bovine meat with intermediate to high ultimate pH (pHu), there is a lack of studies focused on the effects of long-term conventional air-blasting freezing storage on quality parameters of commercial beefs of Zebu Nellore (Bos indicus) with varying pHu ranges. The objective of this work was to evaluate the influence of pHu ranges [normal (≤5.79), intermediate (5.80 to 6.19), and high (≥6.20)] and long-term frozen storage on quality parameters of aged Longissimus dorsi beefs of Zebu Nellore (Bos indicus). The aging conditions were set at 2 °C for 14 days, while the freezing conditions were set at − 20 °C, and samples were collected after 3, 6, 9, and 12 months of storage. The results indicated that the pHu influenced meat quality parameters, as well as the chemical forms of myoglobin, which changed throughout the frozen storage, leading to a brighter red color, especially for the normal pHu beef samples, likely due to increased oxymyoglobin content. Frozen storage improved tenderness, with high pHu beef samples being the more tender after 12 months, potentially due to lower protein oxidation, as measured by the carbonyl content. Increased drip loss was observed over freezing time, with a concomitant decrease in protein solubility, especially for myofibrillar and sarcoplasmic proteins, which differed among the pHu ranges. These findings are valuable for determining freezing time as a preservation strategy to maintain beef quality within different pHu ranges.

Exploring the optimal freeze time and passes of the ultrathin cryoprobe in transbronchial cryobiopsy of peripheral pulmonary lesions.

In PPL-TBLC, quality of tissue matters more than quantity for accurate diagnosis. Comparable diagnostic yield with 1.1-mm cryoprobe can potentially be achieved in 6 s of freezing and three or more passes. https://bit.ly/49cbmbW.

An analytical framework for predicting the total freezing delay time of water droplet impact on hydrophobic solid surfaces

An analytical framework is developed to investigate the impact and freezing delay of a water droplet on solid surfaces, particularly hydrophobic ones, at subfreezing temperatures. Submodules for droplet dynamics, supercooling, nucleation and recalescence, and equilibrium solidification are developed for different droplet impact and freezing stages. These submodules are then integrated to estimate the total freezing delay time per unit mass of the water droplet. It is found that the nucleation time depends on the impact height, surface temperature, droplet impact temperature, and the droplet-substrate contact angle, while the solidification time depends on the droplet size, the nucleation temperature, and the droplet final contact diameter, which is related to the initial droplet diameter, the Weber number, the Reynolds number, and contact angle. The analytical model is validated with results from droplet freezing experiments in a subfreezing environment. By simplifying the complex droplet dynamics, nucleation, and freezing processes, the new analytical framework provides a useful way to estimate the total freezing time of impacting water droplets on hydrophobic surfaces. Its accuracy needs to be improved for practical engineering applications.

Expression of Ice Nucleation Protein in Bacillus amyloliquefaciens and Its Application in Food Freezing Process.

To produce food-grade ice nucleators, a 3.77 kb ice nucleation gene (iceE) isolated from Pantoea agglomerans (Erwinia herbicola) was introduced into the Gram-positive microorganism Bacillus amyloliquefaciens for the first time. The differential scanning calorimetry (DSC) results indicated that recombined strain B9-INP was an effective ice nucleator for controlling the supercooling point of distilled water at low concentrations. In the presence of B9-INP cells, model food systems, including sucrose solution and sodium chloride solution, different pH solutions froze at a relatively high subzero temperature, thus increasing the supercooling point by 5.8~16.7 °C. Moreover, B9-INP also facilitated model and real food systems to freeze at -6 °C. This recombinant strain not only improved the freezing temperature of food systems but also shortened the total freezing time, thus saving energy and reducing consumption. The results suggest that B9-INP has great application potential in the frozen food industry.

LIQUID NITROGEN INJECTION INTO AVIATION FUEL TO REDUCE ITS FLAMMABILITY AND POST-IMPACT FIRE EFFECTS

The finite volume method was used to study the characteristic of contaminated aviation fuel with the aim of reducing its flammability and post-impact fire. The flammability levels between pure Jet A-1 and contaminated Jet A-1 are compared using their flashpoints and fire points before and after the introduction of Liquid Nitrogen. Upon heating different mixing ratios (4:1, 3:1, and 2:1), results are analyzed to identify the best volume ratio exhibiting the highest reduction in flammability. Analysis shows that the mixing ratio of 2:1 not only froze but increased the flashpoint of the mixture from (48 ˚C–50 ˚C) to 64 ˚C. For the mixing ratio of 3:1, there was a rise in flashpoint to about 56 ˚C and partial freezing was seen at the topmost surface. At a mixing ratio of 4:1, it was observed that the effect of liquid nitrogen on Jet A-1 was minimal leading to a slight rise in its flash point (50 ˚C). Thus, liquid Nitrogen had a substantial effect on the flammability and flash point of Jet A-1 when mixed in the ratio (2:1) with a freezing time of 30 seconds and an unfreezing time of 17.5 minutes. Hence, Liquid Nitrogen can be used for the flammability reduction of Jet A-1.

Multi-functional and durable anti-corrosion coatings with hydrophobic, freeze time retardation and photothermal properties by means of a simple spraying method

In this study, a composite material consisting of perfluorinated quaternary silane-modified graphene oxide and modified CeO2 nanoparticles was prepared, and a hydrophobic, corrosion-resistant, self-cleaning and anti-icing composite coating was prepared by combining the composite material with polyphenylene sulfide (PPS) through high-temperature curing in a simple spraying method for the protection of iron sheets. The results show that the composite coating has excellent corrosion resistance, strong mechanical properties and certain photothermal properties. When the content of perfluorinated quaternary silane modified CeO2 nanoparticles with graphene oxide (P-GKC) was 10 wt%, the composite coating had a water contact angle of 145.6 ± 3° and a sliding angle of 5 ± 1°, with good hydrophobicity and low surface energy. Meanwhile, the hydrophobic modification of perfluoroquaternary silanes reduced the surface energy of the particles in the composite coatings and greatly improved the hydrophobicity. Surface temperature and laser irradiation tests of the composite coatings showed that the photothermal properties of the composite coatings were better than those of the single PPS and graphene oxide (GO) coatings, with good photothermal cycling stability.The Tafel curves and the EIS results showed that the PPS/10 wt% P-GKC composite coatings had the best corrosion resistance, with a corrosion current density of 5.01 × 10−9A cm−2. After 200 h of salt spray test in 3.5 % NaCl environment, the PPS/10 wt% P-GKC composite coating still has good substrate protection effect, which provides a practical basis for the research of composite coating anticorrosion.

The improvement of freezing time and functional quality of frozen mushrooms by application of probe-type power ultrasound

The study proposes a novel ultrasound-assisted freezing method for button mushrooms, which combines probe-type ultrasonication and immersion freezing. The effects of power ultrasound in both continuous and pulse modes (at five levels of 50, 100, 200, 300, and 400 W) on the freezing process and quality attributes of frozen mushrooms were investigated. Results showed that ultrasound-assisted freezing significantly reduced freezing time compared to immersion freezing, potentially due to the formation of abundant cavitation bubbles that enhanced heat and mass transfer rates. The lowest weight loss was achieved by the continuous mode of 200 W ultrasound (UC200), which may be attributed to the formation of smaller ice crystals during ultrasonication. Ultrasound also prevented acidification and resulted in the retention of the samples' pH and higher total solid solution than immersion freezing. The optimal ultrasound power and duty cycle for different freezing outcomes were determined using the TOPSIS method. UC200 was found to be the best treatment for total freezing time and minimizing weight loss, while a combination of UC200 and UC400 was optimal for gumminess and chewiness. The proposed ultrasound-assisted freezing method shows promise as an environmentally friendly and safe technique for commercial use in the future.

Dark matter is the new BBN

Measurements of the primordial element abundances provide us with an important probe of our universe’s early thermal history, allowing us to constrain the expansion rate and composition of our universe as early as ∼1s after the Big Bang. Prior to this time, we have essentially no empirical information on which to base any such claims. In this paper, we imagine a future time in which we have not only detected the particles that make up the dark matter, but have measured their mass and annihilation cross section with reasonable precision. In analogy to the light element abundances, the dark matter abundance in this scenario could be used to study and constrain the expansion rate and composition of our universe at the time of dark matter freeze out, which for a standard thermal relic occurs at Tf∼mχ/20, corresponding to t∼4×10−10s×(TeV/mχ)2, many orders of magnitude prior to the onset of Big Bang nucleosynthesis. As examples, we consider how such measurements could be used to constrain scenarios which feature exotic forms of radiation or matter, a ultralight scalar, or modifications to gravity, each of which have the potential to be much more powerfully probed with dark matter than with the light element abundances.

Design and Building of a Two-Stage Cascade Refrigeration System for Storage of Blood Plasma

Daily life-saving transfusions rely on the usage of blood products in clinical and research settings. With its proteins used for replacement treatment, human blood plasma serves as the main source for a variety of therapeutic transfusions. During the COVID-19 pandemic, plasma-based therapy was one of the treatment modalities used to treat infectious infections and as a source of neutralizing antibodies in patients. The specialty of transfusion medicine was adversely impacted and faced a stockpile shortage because plasma must be quickly frozen within six hours of collection in order for its proteins and coagulation components to be of the optimum quality. As a result, the cascade refrigeration system is an innovative technology that can provide the required ultra-low freezing temperature and maintain the same temperature in storage for plasma management. The paper concentrated on the design and construction analysis of a two-stage cascade refrigeration system for quick freezing time, and storing plasma proteins at extremely low temperatures to prolong their limited shelf life in a sensitive, temperature-controlled storage system. The choice of refrigerants R404A and R410A is made for high temperature and low temperature circuits which are carefully selected based on study and analysis of the characteristics of different refrigerants for short-term freezing. The ultra-low temperature evaporator is achieved using a blend of two vapour compression refrigeration cycles thermally connected by a heat exchanger to produce a freezing temperature of -35 0C. For analysis, the system was charged with various weights of plasma weighing between 1 kg and 4 kg for two hours and a half hour and kept at a temperature of -35 0C. The system's dependability and practicality for extending plasma shelf life were assessed. After 72 hours of temperature-controlled storage, the results showed 75% efficiency and a negligible (0.4) plasma quality drop.&#x0D;

Preparation of high‐hydrophobic polyvinyl alcohol‐based composite aerogel fibers containing organosilicon for effective thermal insulation

AbstractPolyvinyl alcohol (PVA) aerogel fibers exhibit encouraging potential as thermal insulation materials, but their hydrophilicity easily results in severe collapse of the aerogel pore structure. Therefore, hydrophobic modification of PVA aerogel fibers is of significance to their structural stability and durability. Here, a novel process was proposed to continuously generate high‐hydrophobic PVA‐based composite aerogel fibers containing polymethylsilsesquioxane (PMSQ) by introducing methyltrimethoxysilane (MTMS) through freeze‐thawing, freeze‐spinning, and freeze‐drying processes. With optimized freezing time and MTMS content, the PVA‐based composite solution showed good spinnability, and the resulting PVA/PMSQ (PVASi) aerogel fibers were endowed with markedly enhanced hydrophobicity and excellent weavability due to sufficient mechanical properties. Most importantly, the aerogel fibers possessed excellent hydrophobic structural stability after 12 h or 50‐cycle soaking and 50‐cycle washing. Benefiting from these superior characteristics, the aerogel fibers were demonstrated to be effective thermal insulators in high humidity (&gt;90% relative humidity) and after washing for 50 cycles.

A modeling study on freezing characteristics of sessile and pendant water droplets on cold plate surfaces

The freezing phenomena of sessile and pendant water droplets on horizontal and inverted surfaces are widespread in industrial fields, which always causes great structural destruction and energy waste. Considering the gravity effect on the droplet profile, a theoretical model is developed to calculate the freezing characteristics of sessile and pendant droplets and experimentally verified. The average deviation of the model in the droplet freezing time is 10.53 % and the determination coefficient in the droplet profile is above 98 %. Based on the model, the freezing characteristics of sessile and pendant droplets under different water droplet volumes (characterized by the Bond number, Bo), contact angles and cold plate temperatures are investigated. When Bo ≤ 1, there is almost no difference in the freezing characteristics of sessile and pendant droplets. When Bo > 1, obvious differences are observed with a pendant droplet having a higher height and a longer freezing time. For both sessile and pendant droplets, the freezing height is approximately proportional to the initial height with the sessile droplet yielding a smaller proportion coefficient. Their freezing times can be written as a function of the Bond number, contact angle and cold plate temperature. Under the same condition, the ratio of freezing time by the pendant droplet to that by the sessile one is scaled as Bo1/4 when Bo > 1. The findings in this study help better understand the freezing characteristics of the sessile and pendant droplets and thus optimize anti-icing and anti-frosting technologies.

Analysis of freezing of a sessile water droplet on surfaces over a range of wettability

HypothesisNonwetting surfaces, by virtue of their water-repelling trait, offer desirable anti-icing characteristics. Surface roughness, type and wettability are important interfacial characteristics that affect the icing dynamics that can be tailored to achieve desired anti-icing designs. Experiments and SimulationsThe present study systematically explores the effect of surface roughness on the freezing behaviour of water droplets on surfaces ranging in their wettability. Surfaces with tailored textures and wettability were fabricated using chemical etching and electrodeposition by varying the voltage. The surfaces studied include bare copper, five different dry nonwetting copper surfaces, and five different lubricant-infused copper surfaces that ranged in surface texture fractal dimension from nearly 1.0 to 1.92 and wettability measures of average water contact angle from 91° to 162° and sliding angle from less than 3° to greater than 50°. A computational model is developed to simulate the freezing dynamics on the surfaces studied. FindingsWith increasing roughness features, the freezing time increased due to the dual effects of increased contact angle and poor interfacial conductance caused by trapped air or infused liquid within the asperity textures. In general, the nonwetting surfaces increased the freezing time by a factor of at least 1.33 and up to about 3.2 compared to freezing on bare copper surfaces. The computational model shows close agreement with experimental measurements on the freeze front progression as well as freeze time. Design guidelines on the suitability of the different nonwetting surfaces for anti-icing purposes are derived from the systematic study, with the overall design recommendation favoring lubricant infused surfaces.

Photothermal and superhydrophobic composite coatings with sandwich and interlocking structure for effective anti-icing and de-icing

The accumulation of ice has brought so many troubles to our daily life and production. To achieve more efficient and environmentally friendly anti-icing and de-icing, combining active and passive methods is an effective strategy for ice prevention and removal. In this study, low-cost and widely available black carbon (BC) and versatile biomimetic adhesion polydopamine (PDA) were selected as photothermal conversion ingredient. Utilizing a simple stirring process and interfacial polymerization, the superhydrophobic photothermal fabric with sandwich structure was obtained. The presence of polydimethylsiloxane (PDMS) and BC/PDA mixed intermediate layer allows for more efficient absorption of solar radiation, facilitating rapid heat conduction and accumulation. Under about 1 Sun illumination, the coatings can reach a maximum surface temperature of 95.6 ± 2 °C. Moreover, the exceptional hydrophobicity of the coatings can help minimize the pollutants' adhesion, decrease the nucleation sites and prolong the time before ice formation. As a result, the coating exhibited a freezing time of 2.8 times slower than that of the original fabric. Under 1 Sun illumination, it took about 53 s for sliding off the surface. The de-icing time is one-eighth of that of the bare substrate. More importantly, the coating also exhibited excellent mechanical, chemical and cycling stability, making it promising for practical de-icing applications.

Cardiac AC8 Over-Expression Increases Locomotion by Altering Heart-Brain Communication

BackgroundThe central nervous system’s influence on cardiac function is well described; however, direct evidence for signaling from heart to brain remains sparse. Mice with cardiac-selective overexpression of adenylyl cyclase type 8 (TGAC8) display elevated heart rate/contractility and altered neuroautonomic surveillance. ObjectivesIn this study the authors tested whether elevated adenylyl cyclase type 8–dependent signaling at the cardiac cell level affects brain activity and behavior. MethodsA telemetry system was used to record electrocardiogram (ECG) and electroencephalogram (EEG) in TGAC8 and wild-type mice simultaneously. The Granger causality statistical approach evaluated variations in the ECG/EEG relationship. Mouse behavior was assessed via elevated plus maze, open field, light-dark box, and fear conditioning tests. Transcriptomic and proteomic analyses were performed on brain tissue lysates. ResultsBehavioral testing revealed increased locomotor activity in TGAC8 that included a greater total distance traveled (+43%; P < 0.01), a higher average speed (+38%; P < 0.01), and a reduced freezing time (–45%; P < 0.01). Dual-lead telemetry recording confirmed a persistent heart rate elevation with a corresponding reduction in ECG-R-waves interval variability and revealed increased EEG-gamma activity in TGAC8 vs wild-type. Bioinformatic assessment of hippocampal tissue indicated upregulation of dopamine 5, gamma-aminobutyric acid A, and metabotropic glutamate 1/5 receptors, major players in gamma activity generation. Granger causality analyses of ECG and EEG recordings showed a marked increase in informational flow between the TGAC8 heart and brain. ConclusionsPerturbed signals arising from the heart cause changes in brain activity, altering mouse behavior. More specifically, the brain interprets augmented myocardial humoral/functional output as a “sustained exercise-like” situation and responds by activating central nervous system output controlling locomotion.

Experimental investigation of the effect of stable magnetic field on droplet freezing

In this study, the effect of magnetic field on droplet freezing was investigated based on a visualization system. Possible influencing factors on droplet freezing, such as magnetic field intensity, cold surface temperature, and droplet volume, were considered in this study. During the two stages of droplet supercooling and freezing process, the changes of the droplet internal temperature, the formation of initial crystal nucleus, and the freezing time were observed. Experimental results show that in comparison with the non-magnetic surface, the supercooling degree of droplets was increased in the range of 150–300 mT magnetic field intensity, thereby prolonging the freezing time of droplets. Particularly, the droplet was best suppressed on a cold surface with 250 mT magnetic field intensity. The freezing time of droplets was prolonged by 132.0 %. However, the droplets were accelerated to freeze on the cold surface with magnetic field intensities of 350 mT and 400 mT. Droplet freezing on cold surfaces was also affected by surface temperature and droplet volume. As the surface temperature of magnetic cooling dropped from −10 °C to −20 °C, the ability of the magnetic field to inhibit droplet freezing would be gradually weakened. With the increase of droplet volume from 20 μL to 50 μL, the initial freezing time of droplets was shortened. These results are related to the influence of magnetic field on the nucleation process and hydrogen bond in the water molecular cluster.

Comparison of the diagnostic yield of transbronchial lung biopsies by forceps and cryoprobe in diffuse parenchymal lung disease.

Transbronchial lung cryobiopsy (TBLC) in the diagnosis of diffuse parenchymal lung disease (DPLD) has shown a promising yield in recent times, with low post-procedural mortality and morbidity. To compare the yield of TBLC and conventional transbronchial forceps lung biopsy (TBLB). A prospective study was carried out in patients with DPLD over a period of 1 year in a tertiary respiratory care institute in New Delhi, India. All 87 patients enrolled underwent both TBLB and TBLC. The procedures were performed in the bronchoscopy suite under conscious sedation and local anaesthesia, with an attempt to take a minimum of three biopsy specimens by conventional TBLB followed by TBLC. A 1.9 mm cryoprobe with a freezing time of 4 - 5 seconds was used. An Arndt endobronchial blocker was used to control bleeding along with locally administered medications. TBLB and TBLC led to a definitive diagnosis in 27 (31.0%) and 69 (79.3%) cases, respectively. The commonest diagnoses were hypersensitivity pneumonitis, sarcoidosis and pulmonary tuberculosis. TBLC led to additional diagnoses in 42 cases (48.3%). Pneumothorax was observed in 12 cases (13.8%), and moderate bleeding occurred in 63 (72.4%). There were no procedure-related deaths. TBLC had a better diagnostic yield than conventional TBLB in DPLD. It has the potential to become a safe day-care procedure in a resource-limited setting, if certain precautions are taken. What the study adds. Compared with transbronchial forceps lung biopsy, transbronchial lung cryobiopsy (TBLC) led to additional diagnoses in 42 (48.3%) of 87 patients with clinicoradiological features of diffuse parenchymal lung disease. Pneumothorax was observed in 12 cases (13.8%) and moderate bleeding in 63 (72.4%). TBLC without rigid bronchoscopy or advanced airway devices under conscious sedation had a good diagnostic yield with an acceptable adverse events profile.Implications of the findings. TBLC under conscious sedation is not resource intensive and can be carried out in settings with limited resources.

Effects of static magnetic field (SMF) and alternating magnetic field (AMF) assisted freezing on the microstructure and protein properties of channel catfish (Ictalurus punctatus) fillet

The effect of static and alternating magnetic fields assisted freezing with intensity of 1, 2, and 3 mT on the microstructure and protein properties of channel catfish fillet were investigated. The results showed that the magnetic field treatment shortened the phase transition time of freezing, and significantly reduced the size of the formed ice crystals. The changes of trichloroacetic acid-soluble peptide, Ca2+-ATPase activity, particle size, and Zeta potential, which represented solubility, denaturation and aggregation of protein, indicated that magnetic field treatment could improve the protein stability. The chemical force analysis, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and Fourier transform infrared spectroscopy (FTIR) results proved that the magnetic field could change the structure of protein. Furthermore, these changes had effects on the thermal stability of catfish meat protein which reflected by increasing of the transition temperature and enthalpy. However, the waveform and intensity of magnetic field affected the stability of protein structure.

Lyophilisation of bacterial test strains in a manifold-type apparatus: Effects of freezing and drying parameters, ampoule fill volume, and cotton filter density

Scientific relevance. Lyophilisation is the preferred method at the National Collection of Pathogenic Microorganisms (NCPM) of the Scientific Centre for Expert Evaluation of Medicinal Products of the Ministry of Health of the Russian Federation. Lyophilisation is used to provide for high standards of test-strain deposition, storage, and transportation and to ensure that test strains maintain their properties. Successful lyophilisation requires conducting experiments to establish the key parameters and critical conditions of the process.Aim. The study aimed to evaluate the effects that the speed and time of freezing, the time of drying, the fill volume of ampoules, and the density of cotton filters have on the quality of NCPM indicator microorganisms lyophilised in a manifold-type apparatus.Materials and methods. Pseudomonas aeruginosa NCTC 12924, Staphylococcus aureus NCTC 10788, and Salmonella Abony NCTC 6017 were freeze-dried using a manifold-type apparatus (M. S. R. 18, Usifroid). The authors used a low-temperature freezer at –70±2 °C for slow freezing and a mixture of dry ice and alcohol for quick freezing. The statistical analysis was performed using Microsoft Excel and Statistica 10.Results. The minimum time needed for freezing the samples in a low-temperature freezer at –70±2 °C was 4 hours. Further storage at this temperature for up to 1 month was shown possible without compromising the quality of the final product. The time needed for freezing the samples in a mixture of dry ice and alcohol was under 1 minute. No differences in quality parameters were observed between the lyophilised samples frozen slowly or quickly, except for the cake appearance. Quick freezing resulted in cakes that were non-uniform, crumbled, and pulled away from the ampoule walls, which is considered undesirable. The primary drying stage for ampoules with a fill volume of 0.2 mL took 6–8 hours. The secondary drying stage of 11, 18, 35, and 59 hours resulted in comparable lyophilisate quality: the authors observed no statistically significant differences in viable cell counts (CFU/mL) at the end of lyophilisation and at the end of stress testing. The residual moisture content after 59-hour secondary drying was less than 2%. The cotton filter density had a critical influence on the lyophilisate quality. Therefore, the authors recommend using cotton filters weighing 50 mg or less.Conclusions. The authors analysed the main stages of the lyophilisation process used for NCPM test strains and considered the effects that the speed and time of freezing, the time of drying, the fill volume of ampoules, and the density of cotton filters have on the quality of the final lyophilised product. The NCPM has implemented the results of this study in its work.