Initial Freezing Research Articles

Impacts of Aging Sequence and Freezing Rate on Quality Attributes and Oxidative Stability of Frozen/Thawed Pork Loins

ObjectivesAging is known to improve quality attributes of frozen/thawed meat by minimizing quality defects, such as purge/drip loss, texture and/or color. In frozen/thawed meat, the extent of quality deterioration is considerably influenced by freezing rate, as it impacts on the size, distribution, and/or location of ice crystals. This, in turn, results in the physicochemical and structural damages to muscle tissue. However, there have been no available literatures on the effect of aging sequence (between aging and freezing/thawing) and freezing rate on frozen/thawed meat quality attributes. Therefore, the objective of this study was to evaluate the combined effects of aging sequence and freezing rate on quality attribute and oxidative stability of frozen/thawed pork loins.Materials and MethodsAt 1 d postmortem, pork loins (M. longissimus dorsi) were removed from 1 side of 6 carcasses. Each loin was cut into 6 equal-length sections and vacuum-packaged. Then, 6 treatments, comprised of 3 aging/freezing sequences (freezing/thawing without aging, aging prior to freezing/thawing, or freezing before thaw/aging) and 2 freezing rates (slow vs. fast), were randomly assigned to the loin sections. Slow-freezing was conducted in a commercial –20°C blast freezer, whereas fast-freezing was performed in a liquid nitrogen cabinet (–80°C). Aging of the loin section in a vacuum bag was conducted in a 1°C cooler for 19 d. Once assigned initial freezing was completed (either slow or fast), the loin section were stored in the –20°C freezer for 6 wk, and thawed in the 1°C chilling cooler for 2 d. Purge/thaw loss, cooking loss, shear force, color (CIE L*, a* and b*), 2-thiobarbituric acid reactive substances (TBARS), carbonyl content and histology of thawed pork loins were determined. The PROC MIXED of SAS (SAS Inst. Inc., Cary, NC) was used for data analysis (P < 0.05) by using least significant differences.ResultsNo interactions between aging sequence and freezing rate on purge/thaw loss and cooking loss were observed (P > 0.05). The highest purge/thaw loss was found in the loin section assigned to frozen first then thaw/aged (12.4%) compared to frozen/thawed only (8.5%) or aged/frozen/thawed (7.8%) samples (P = 0.0003). This result indicates the importance of aging and aging sequence for WHC of frozen/thawed meat. No difference in cooking loss of pork loins between treatments was found (P > 0.05). Aged/frozen/thawed pork loins had a lower shear force than frozen/thawed only pork loins (P = 0.0223). Further, slow-frozen then thaw/aged loin had the lowest shear force among treatments (P < 0.0001). Aging tended to increase initial L* (lightness), regardless of its combination sequence with freezing/thawing (P < 0.05). No differences in the TBARS value and carbonyl content of frozen/thawed pork loins were found between treatments (P > 0.05). Based on histological analysis, severe structural damages were observed in the slow-frozen then thaw/aged loin section.ConclusionThe results of the current study found that the sequence of aging prior to freezing play a significant role in affecting the WHC and texture of frozen/thawed pork loins. Moreover, this study confirms that fast-freezing could be an effective process to improve WHC of frozen/thawed meat products, regardless of aging combination and/or its sequence.

Measurement of adsorption energy between a solid adsorbent and a liquid adsorbate using differential scanning calorimetry

We report on a novel method involving the use of differential scanning calorimetry (DSC) in evaluation of adsorption energy between a liquid adsorbate and a solid adsorbent. The proof of concept is demonstrated by measuring the exothermic heat release due to the adsorption of automotive transmission fluid (ATF), the adsorbate, to a paper-based friction material used in automotive torque converters, the adsorbent. The novelty of the measurement technique involves initial freezing of the liquid adsorbate so that the initiation of the adsorption process can be identified. Our experimental results and theoretical calculations reveal that the adsorption energy of the friction paper and the summation of adsorption energies of each friction paper ingredient are in good agreement.

Effect of hydrocolloids blends on frozen dessert “popsicles” made with whey concentrated

The present study aim to investigate the physical and sensorial parameters of frozen dessert made with concentrated whey obtained through a nanofiltration process in total replacement of water and an ideal combination of hydrocolloids. The hydrocolloid mixtures were: T1 (guar/xanthan); T2 (guar/carrageenan); T3 (carrageenan/xanthan) and T4 (without hydrocolloids). Were evaluated the rheological behavior of the mixture, melting behavior, sensorial analysis, the initial freezing temperature, texture, and chemical composition of the concentrated whey. It was observed that different combinations of hydrocolloids influenced the viscosity of the mixture. On the melting behavior, the presence of hydrocolloids influences this parameter positively delaying the melting initial time of the frozen dessert. T1 and T4 resulted in the highest and lowest values of firmness respectively. The results of the sensory analysis showed that T1 and T2 were those that had the highest scores on the parameters of taste, texture, softness, appearance, purchase intention and overall impression. The correlation between sensory and instrumental data was proved using a multiple factor analysis. It was concluded that the combinations of guar and xanthan hydrocolloids are technologically the most appropriate on the application for formulations of frozen dessert made with concentrated whey considering the quality and acceptance standards.

Evaluation of Transbronchial Lung Cryobiopsy Size and Freezing Time: A Prognostic Animal Study

Background: Transbronchial lung biopsy using a cryoprobe is a novel way of sampling lung parenchyma. Correlation of freezing time with biopsy size and complications has not been evaluated in vivo. Objectives: The primary aim of the study is to evaluate the correlation between transbronchial cryobiopsy freezing time and size. The secondary aims are to evaluate histological quality of the biopsy and evaluate procedure-associated complications. Methods: Transbronchial lung cryobiopsies were obtained from two anaesthetised sheep using a 1.9-mm cryoprobe inserted into a flexible bronchoscope under fluoroscopic guidance. Freezing times ranged from 1 to 6 s (n = 49). The cryobiopsies were evaluated histologically with respect to their size and quality. Complications of bleeding and pneumothorax were recorded. Results: The mean cross-sectional area of the cryobiopsy ranged from 4.7 ± 2.1 to 15.7 ± 15.3 mm². There was a significant positive correlation between increasing freezing time and cryobiopsy cross-sectional area (p = 0.028). All biopsies contained lung tissue with preserved parenchyma. Crush and freeze artefacts were not observed and tissue architecture was intact in all specimens. Small blood vessels and terminal bronchioles were observed in 88% of specimens. All cryobiopsies caused nil or mild haemorrhage with the exception of only 1 episode of severe haemorrhage at 6 s freezing time. Pneumothoraces occurred at 2, 5 and 6 s freezing time and required chest tube insertion. The most significant haemorrhage and pneumothoraces occurred at 5 and 6 s. Our results suggest an initial freezing time of 3 s can provide the maximal biopsy size while minimising major complications. Conclusion: The optimal transbronchial cryobiopsy freezing time is initially 3 s. This time is associated with minimal complications and large artefact-free biopsies.

Sensible Heat Balance Estimates of Transient Soil Ice Contents

Core Ideas Soil ice content is difficult to quantify. A sensible heat balance with heat pulse probes may indicate soil ice contents. A sensible heat balance can determine transient soil ice content from −5 to 0°C. Soil ice contents below −5°C can be determined with heat capacity changes. Heat pulse probes can monitor soil ice contents at and below 0°C. Soil ice content is an important component for winter soil hydrology. The sensible heat balance (SHB) method using measurements from heat pulse probes (HPPs) is a possible way to determine transient soil ice content. In a previous study, in situ soil ice content estimates with the SHB method were inaccurate, due to thermal conductivity errors and the use of relatively long time steps for calculations. The objective of this study is to reexamine the SHB method for soil ice content determination. A soil freezing and thawing laboratory experiment was performed with soil columns and heat exchangers. Transient soil ice contents in the soil columns during soil freezing and thawing were determined with the SHB method. The SHB method was able to determine dynamic changes in soil ice contents during initial freezing and final thawing for soil temperatures between −5 and 0°C when latent heat values associated with ice formation or with thawing were relatively large. During an extended freezing period, when soil temperatures were below −5°C, the small associated latent heat fluxes were below the sensitivity of the SHB method, and the SHB method did not provide accurate estimates of ice contents with time. However, the soil ice contents during the extended freezing period could be estimated well from changes in volumetric heat capacity (C) determined with HPP. Thus, combining the SHB method for initial freezing and final thawing, with a change in C method for extended freezing periods, allowed determination of dynamic soil ice contents for the entire range of freezing and thawing soil temperatures investigated. HPPs were able to measure soil ice contents.

Directional Freezing of Nanocellulose Dispersions Aligns the Rod-Like Particles and Produces Low-Density and Robust Particle Networks.

We show that unidirectional freezing of nanocellulose dispersions produces cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment in the long direction of the tubular pores with X-ray diffraction shows high orientation of cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) at particle concentrations above 0.2 wt % (CNC) and 0.08 wt % (CNF). Aggregation of CNF by pH decrease or addition of salt significantly reduces the particle orientation; in contrast, exceeding the concentration where particles gel by mobility constraints had a relatively small effect on the orientation. The dense nanocellulose network formed by directional freezing was sufficiently strong to resist melting. The formed hydrogels were birefringent and displayed anisotropic laser diffraction patterns, suggesting preserved nanocellulose alignment and cellular structure. Nondirectional freezing of the hydrogels followed by sublimation generates foams with a pore structure and nanocellulose alignment resembling the structure of the initial directional freezing.

Ready and waiting: Freezing as active action preparation under threat

Freezing is a defensive response characterized by rigidity and bradycardia, but it is unclear whether it is a passive versus active preparatory state. We developed a shooting task in which preparation and threat were manipulated independently: Participants were either helpless or able to respond to a possible upcoming attack, and attacks were either associated with an electric shock or not. Essentially, a purely anticipatory preparatory period was used during which no stimuli occurred. Freezing was assessed during this period. In addition to heart rate, body sway was measured, using a stabilometric force platform. The efficacy of the threat manipulation was confirmed via self-report. The ability to prepare led to decreases in heart rate and postural sway, while threat led to decreased heart rate. Further, exploratory analyses suggested that aggressive participants showed reduced initial freezing for threatening opponents, but increased postural freezing when armed. The results suggest that freezing may involve active preparation. Relations to results in passive viewing tasks are discussed.

Effect of freeze–thaw cycles on carbon stocks of saline–alkali paddy soil

ABSTRACTThis study aims to provide basic data to support accurate estimation of carbon stocks and reveal the physicochemical factors that influence the carbon cycle in saline–alkali soils. Soil samples were collected during initial freezing, complete freezing, initial thawing and complete thawing stages. Levels of soil organic carbon (SOC), soil inorganic carbon (SIC), moisture, salinity, pH and available nitrogen were determined, and variations were observed during the freezing and thawing periods. Correlation analysis and regression analysis of carbon contents and physicochemical properties were performed. The results showed that freeze–thaw cycles have significant effects on carbon contents. The SOC content initially decreased in the freezing stage and then increased in the thawing stage. However, the SIC content initially increased in the freezing stage, decreased in the initial thawing stage and finally increased in the complete thawing stage. The migration and transformation of SOC and SIC were observed both temporally and spatially. SOC was positively correlated with available nitrogen, moisture and salinity and negatively correlated with pH; while SIC was negatively correlated with available nitrogen, moisture and salinity and positively correlated with pH. Among the factors evaluated, available nitrogen and salinity exerted the greatest effects on SOC and SIC contents, respectively.

Air-ice carbon pathways inferred from a sea ice tank experiment

Abstract Given rapid sea ice changes in the Arctic Ocean in the context of climate warming, better constraints on the role of sea ice in CO2 cycling are needed to assess the capacity of polar oceans to buffer the rise of atmospheric CO2 concentration. Air-ice CO2 fluxes were measured continuously using automated chambers from the initial freezing of a sea ice cover until its decay during the INTERICE V experiment at the Hamburg Ship Model Basin. Cooling seawater prior to sea ice formation acted as a sink for atmospheric CO2, but as soon as the first ice crystals started to form, sea ice turned to a source of CO2, which lasted throughout the whole ice growth phase. Once ice decay was initiated by warming the atmosphere, the sea ice shifted back again to a sink of CO2. Direct measurements of outward ice-atmosphere CO2 fluxes were consistent with the depletion of dissolved inorganic carbon in the upper half of sea ice. Combining measured air-ice CO2 fluxes with the partial pressure of CO2 in sea ice, we determined strongly different gas transfer coefficients of CO2 at the air-ice interface between the growth and the decay phases (from 2.5 to 0.4 mol m−2 d−1 atm−1). A 1D sea ice carbon cycle model including gas physics and carbon biogeochemistry was used in various configurations in order to interpret the observations. All model simulations correctly predicted the sign of the air-ice flux. By contrast, the amplitude of the flux was much more variable between the different simulations. In none of the simulations was the dissolved gas pathway strong enough to explain the large fluxes during ice growth. This pathway weakness is due to an intrinsic limitation of ice-air fluxes of dissolved CO2 by the slow transport of dissolved inorganic carbon in the ice. The best means we found to explain the high air-ice carbon fluxes during ice growth is an intense yet uncertain gas bubble efflux, requiring sufficient bubble nucleation and upwards rise. We therefore call for further investigation of gas bubble nucleation and transport in sea ice.

Effective thermal conductivity prediction of foods using composition and temperature data

Thermal conductivity data are important for food process modelling and design. Where reliable thermal conductivity data are not available, they need to be predicted. The most accurate ‘first approximation’ methodology for predicting the isotropic thermal conductivity of foods based only on data for composition, initial freezing temperature and temperature dependent thermal conductivity of the major food components was sought. A key feature of the methodology was that no experimental measurements were to be required. A multi-step prediction procedure employing the Parallel, Levy and Effective Medium Theory models sequentially for the components other than ice and air, ice and then air respectively is recommended. It was found to provide the most accurate predictions over the range of foods considered (both frozen and unfrozen, porous and non-porous). The Co-Continuous model applied in a single step also provided prediction accuracy within ±20% (on average), except for the porous frozen foods considered. For greater accuracy more rigorous modelling approaches based on knowledge of the foods structure would be required.

Freeze–thaw durability of high strength concrete under deicer salt exposure

Freeze–thaw resistance of high strength concrete (HSC) and normal strength concrete (NSC) mixes with varying air contents was investigated by moisture uptake, mass loss and internal damage measurements. Sufficiently air-entrained HSC mixes demonstrate significant improvement in salt frost scaling resistance and the characteristics of air-void system is not a major factor. This can be attributed to the reduced capillary porosity and connectivity which curtails ice-growth promoted by capillary suction of surface liquid under freezing. A clear bi-linear pattern is found for the mass loss and moisture uptake curves of HSC mixes, the transition point of which coincides with each other. This demonstrates the importance of initial moisture condition in concrete prior to F–T test. Increased imperviousness of HSC to moisture ingress renders it more prone to long-term frost damage intrinsically, which is evidenced by much higher initial freezing strain in HSC from the length-change measurement on thin specimens at various degrees of saturation levels.

Salt precipitation in sea ice and its effect on albedo, with application to Snowball Earth

AbstractDuring the initial freezing of the tropical ocean on Snowball Earth, the first ice to form would be sea ice, which contains salt within inclusions of liquid brine. At temperatures below −23°C, significant amounts of the salt begin to crystallize, with the most abundant salt being hydrohalite (NaCl·2H2O). These crystals scatter light, increasing the ice albedo. In this paper, we present field measurements of the albedo of cold sea ice and laboratory measurements of hydrohalite precipitation. Precipitation of salt within brine inclusions was observed on windswept bare ice of McMurdo Sound at the coast of Antarctica (78°S) in early austral spring. Salinity and temperature were measured in ice cores. Spectral albedo was measured on several occasions during September and October. The albedo showed a gradual increase with decreasing temperature, consistent with salt precipitation. Laboratory examination of thin sections from the ice cores showed that the precipitation process exhibits hysteresis, with hydrohalite precipitating over a range of temperatures between −28°C and −35°C but dissolving at about −23°C. The causes of the hysteresis were investigated in experiments on laboratory‐grown sea ice with different solute mixtures. All mixtures showed hysteresis, suggesting that it may be an inherent property of hydrohalite precipitation within brine inclusions rather than being due to biological macromolecules or interactions between various salts in seawater.

Microphysical Properties of Slow-Falling and Fast-Falling Ice Pellets Formed by Freezing Associated with Evaporative Cooling

Abstract This paper describes a numerical and observational study focused on ice-pellet formation and microphysical properties near 0°C from an ice-pellet-dominated storm associated with an unusually warm and dry atmosphere on 10 April 2005, in Sapporo, Japan. A one-dimensional numerical model simulation indicated that precipitation particle temperatures were sensitive to environmental temperature and relative humidity and close to the wet-bulb temperature. The simulation demonstrated that completely melted snowflakes could refreeze by evaporative cooling. Moreover, initial freezing could be explained by contact ice nucleation at the height of the minimum wet-bulb temperature. Observations using a 2D video distrometer (2DVD) indicated that ice pellets exhibited two modes of fall velocities at surface temperatures near 0°C during the same time period: slow falling and fast falling. The slow-falling ice pellets exhibited a velocity similar to the average terminal velocity of hail, whereas the velocities of the fast-falling ice pellets were closer to those of raindrops. Surface roundness and fracturing characteristics of ice pellets suggest that slow-falling ice pellets froze rapidly and uniformly in a relatively cold dry layer with a wet-bulb temperature near −4°C. In contrast, the fast-falling ice pellets exhibited the properties of ice particles with a wet smooth surface, suggesting that they froze slowly in a relatively warm layer by contacting ice crystals or splinters generated by preceding slow-falling ice pellets.

Dehydrofreezing of Apple Fruits: Freezing Profiles, Freezing Characteristics, and Texture Variation

The present study deals with the dehydrofreezing of apples. Fresh samples (700 % db) and samples dehydrated up to different water contents (200, 100, and 30 % db) were frozen at high practical freezing rate (PFR+) and low practical freezing rate (PFR−). The effects of water content (W) and practical freezing rate (PFR) were investigated in terms of freezing characteristics: initial freezing temperature (IFT), practical freezing time (PFT), specific freezing time (SFT), thaw exudate water (TEW), and texture (maximum puncture force as index of firmness). Only high W samples (700 and 200 % db) had a significant impact of PFR in terms of PFT, SFT, and TEW. IFT decreased sharply with the decrease in the sample W. PFT greatly depended on PFR for fresh apples. PFT varied from 86 to 329 min for fresh apples at PFR+ and PFR−, respectively, whereas it was lower than 32 min for samples with W = 30 % db. SFT decreased, equally, with sample W decrease. The TEW of fresh frozen samples, during thawing, was approximately 12 g/100 g water for low PFR (PFR−), whereas it was lower than 3 g/100 g water for samples with W = 200 % db at the same PFR. Moreover, the impact of PFR on TEW was significant and very important for high W samples. Finally, the firmness increased when W decreased for both PFR+ and PFR−. Nevertheless, an insignificant impact of PFR on apple firmness was found. Thus, partial removal of water constitutes a promising solution to prevent the negative impacts of freezing on apple fruit firmness.

Droplet freezing and ice adhesion strength measurement on super-cooled hydrophobic surfaces

ABSTRACTThis report investigates the freezing of water droplets on hydrophobic surfaces and reports a means to quantitatively measure the ice-adhesion strength at micro-patterned hydrophobic surfaces. Water droplets were placed on a super-cooled surface where they froze following the heterogeneous nucleation phase-transition. The freezing occurred with two distinct transitions: (a) an initial snapping transition freezing of the external shell of the droplet, and (b) a subsequent bulk freezing of the droplet with a characteristic formation of peaked apex protruding upwardly. To measure the ice-adhesion strength, frozen droplets were sheared from the surface using a Universal Materials Tester (UMT) measuring the resulting knock-off forces. Ice formation and adhesion was investigated on three variations of hydrophobic polydimethylsiloxane (PDMS) surfaces: regularly patterned with high and low surface densities of micro-pillar arrays and non-patterned flat surfaces. Patterning the surfaces was found to accelerate freezing transitions but decrease the measured ice-adhesion strength in correlation with a reduction of total interfacial contact area. However, a more concentrated local stress was observed for the less dense surface structures, indicating a potential area of concern for more fragile systems.

Thermal Conductivity of Mango Pulp (Mangifera indica L.) Cultivar “Ubari” in Freezing Temperatures

The aim of this study was the experimental determination of the thermal conductivity of mango pulp of cultivar “ubari” and its subsequent comparison with values estimated using different structural models, such as the serial, parallel, and Maxwell-Eucken models. A linear heating probe calibrated with a solution of 10% sucrose was utilized. Heat was applied to the probe, generating an increase in temperature, which was recorded through a signal conditioning system. The thermal conductivity of the pulp was calculated from the slope obtained by linear regression of the natural logarithm of the temperature versus time. The data was within the range of 0.465 to 1.595 W/m.K for temperatures of 0 and –30°C, respectively, showing an increase of conductivity with freezing. The initial freezing temperature and ice fraction were determined at every temperature of analysis for further use in the models. The best fit to the experimental data were obtained using the Maxwell-Eucken model, yielding minimum and maximum errors of 10.8 and 17.8%, respectively. An exponential model was fitted, which allowed for the direct calculation of the thermal conductivity of mango pulp using only the knowledge of the recorded temperature during thermal processing.

The use of cryoscopy method for determination of freezing temperature of waters having different content of deuterium

Using the method of cryoscopy we determined the freezing temperature of light water with D/H= 4.2 ppm, 18O/16O = 910 ppm. It was found that light water freezes at the above zero temperature (0.3 ± 0.1°C) irrespective of cooling rate. It is shown that light water begins to freeze only at an overcooled metastable state. Under conditions of experiment the nucleation and growth of dendrite crystals of ice depends on the cooling rate and starts at the temperature −5.3; −8.8; −9.8 ± 0.1°C at the average cooling rate respectively 0.2; 0.3; 0.5°C·min−1. It is shown than in usual water the growth of dendrite ice crystals starts at minus temperature (−6.4;−7.5; −8.8 ± 0.1°C) and increases with an increase of the average cooling rate respectively from 0.2 to 0.6°C·min−1. It was found that the initial freezing temperature of heavy water constituted −3.0− −4.0 ± 0.1° at the rate of its cooling 0.2−1.0°C·min−1. However in this case the freezing temperature of normal and heavy waters does not depend on the cooling rate and freezing of normal and heavy waters and according to reference data constitutes respectively 0.1 ± 0.1 and 3.9 ± 0.1°C.

Changes in Ultrastructure and Sensory Characteristics on Electro-magnetic and Air Blast Freezing of Beef during Frozen Storage.

The ultrastructure in the beef muscle of the electro-magnetic resonance and air blast freezing during the frozen storage, and the changes in the quality characteristics after thawing were evaluated. The size of ice crystal was small and evenly formed in the initial freezing period, and it showed that the size was increased as the storage period was elapsed (p<0.05). The beef stored by the electro-magnetic resonance freezing showed the size of ice crystal with a lower rate of increase than the air blast freezing during the frozen storage. The thawing loss of beef stored by the electro-magnetic resonance freezing was significantly lower than the air blast freezing during frozen storage (p<0.05), and it showed that the thawing loss of the round was higher than the loin. Water holding capacity decreased as the storage period became longer while the electro-magnetic resonance freezing was higher than the air blast on 8 month (p<0.05). As a result of sensory evaluation, the beef stored by the electro-magnetic resonance freezing did not show the difference until 4 months, and it showed higher acceptability in comparison with the beef stored by the air blast freezing. Thus, it is considered that the freezing method has an effect on the change in the ultrastructure and quality characteristics of the beef.

Experimental Study on the Freezing Temperatures of Saline Silty Soils

AbstractThe freezing temperature of soil is an important index to judge whether it is in a frozen state or not, and plays a key role in distinguishing salt expansion from frost heave. Freezing experiments on sulfate saline soil and its ion solution indicate that the initial freezing temperature of the soil is mainly determined by the properties of the ion solution. The effects of saline soil types and saline solution concentrations on the freezing temperature are also investigated. An equation to calculate the freezing temperature of the sulfate salt solution is deduced from the Pitzer ion model and its validity is verified by the experimental results. Under the assumption that the soil freezing temperature is determined by the freezing temperature of the corresponding ion solution and the energy of the ice‐liquid interface, a precise relation between the soil freezing temperature and the radius of the ice‐liquid interface is obtained and a general equation to determine the freezing temperature of the silty clay of the Qinghai‐Tibet Plateau is proposed. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Long-term stability of acyclovir in 0.9% NaCl infusion polyolefin bags at 5 ± 3 °C after freeze-thaw treatment: A generic product versus the brand name

The aim of the study was to investigate the long-term stability of acyclovir 5 mg/mL (a generic product versus the brand name) in NaCl 0.9% after storage at 5±3°C and to evaluate the influence of initial freezing and microwave thawing on this stability. Five bags of Acyclovir® Hospira 5 mg/mL (A) and five bags of Zovirax® GSK 5 mg/mL (B) were prepared under aseptic conditions and stored 3 months at -20°C, then thawed and stored 30 days at 4°C. Five bags of Acyclovir® 5 mg/mL (C) and five bags of Zovirax® 5 mg/mL (D) were also prepared under aseptic conditions and stored 30 days at 5±3°C. Optic density measurement at different wavelengths, pH measurement and optic microscope observations were performed periodically during the storage. A forced degradation test with HCl 12 M and NaOH 5 M before and after heating at 100°C was also performed. The concentrations were measured by HPLC-PDA. The only one forced degradation test that yielded chromatograms with degradation products peak was the test with the acid solution heated at 100°C without interference with the native product. No significant change in pH values or optic densities were seen during the study for both products. No crystals were seen with the optic microscope during the study. Acyclovir® and Zovirax® solutions were stable for at least 21 days according to the FDA recommendations. Moreover, there was no statistical difference between regression lines of those two products and two storage conditions. Under the conditions of this study, Acyclovir® 5 mg/mL in 100 mL of NaCl 0.9% infusion remains stable at least for 21 days at 5±3°C with or without freezing at -20°C during the three previous months. There is no statistical difference between the brand name and a generic product. Acyclovir may be prepared in advanced by a centralized intravenous additive service, frozen in polyolefin bags and microwave thawed before storage under refrigeration until 21 days.