• Journal of Applied Biological Chemistry
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• v.58 no.1
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• pp.55-60
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• 2015

To secure the microbial safety of frozen strawberries, they were treated with the combined solution of aqueous chlorine dioxide and acetic acid prior to freezing and the effects of different freezing methods (at $-20^{\circ}C$ in a freezer, at $-70^{\circ}C$ in a gas nitrogen convection chamber, and at $-196^{\circ}C$ in liquid nitrogen) on the quality changes of strawberries were examined. Regarding the color of frozen strawberries, there were negligible changes among freezing treatments. In contrast, vitamin C content and sensory evaluation scores of strawberries frozen at $-70^{\circ}C$ were the highest among the samples. Drip loss of strawberries frozen at $-70^{\circ}C$ was the lowest as 14.39%, compared with strawberries frozen at -20 and $-196^{\circ}C$. In addition, the effects of combined treatment of 50 ppm chlorine dioxide and 1% acetic acid on the microbial growth in frozen strawberries were investigated, and the populations of preexisting microorganisms in the frozen strawberries were not detected by the combined pre-treatment. These results suggest that rapid freezing at $-70^{\circ}C$ using a gas nitrogen convection chamber is an appropriate freezing method for preserving quality of strawberries, and as a pre-freezing treatment, the combined treatment of aqueous chlorine dioxide and acetic acid can be effective for improving microbiological safety of frozen strawberries.

• Food Science and Preservation
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• v.22 no.1
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• pp.44-50
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• 2015

This study was performed to optimize the preparation of frozen lotus roots. Prior to freezing, an optimal blanching condition at $100^{\circ}C$ for 5 min was established, based on the microbial growth, texture, total phenolic content (TPC), and sensory evaluation results. The blanched samples were then frozen under various freezing conditions ($-20^{\circ}C$ in a freezer for 2 hr, $-70^{\circ}C$ in a gas nitrogen convection chamber for 7 min, and $-196^{\circ}C$ in liquid nitrogen for 20 sec), and their qualities after thawing were determined. The scanning electron microscopic analysis indicated that the microstructure of the sample frozen at $-70^{\circ}C$ was similar to that of the control sample, compared with the other freezing conditions (-20 and $-196^{\circ}C$). The antioxidant activities of the frozen samples decreased compared to those of the control, but there was no significant (p<0.05) difference among the treatments. In terms of TPC, the samples frozen at -70 and $-196^{\circ}C$ had significantly (p<0.05) higher values than the sample frozen at $-20^{\circ}C$. In addition, the drip loss of the sample frozen at $-20^{\circ}C$ was higher than those of the other frozen samples. These results suggest that freezing at $-70^{\circ}C$ in a gas nitrogen convection chamber can be an optimal freezing method of producing high-quality frozen lotus roots.

• Journal of Biosystems Engineering
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• v.41 no.2
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• pp.108-115
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• 2016

Purpose: Radio frequency (RF) heating is a promising thawing method, but it frequently causes undesirable problems such as non-uniform heating. This can occur because of the food shape, component distribution, and initial temperature differences between food parts. In this study, RF heating was applied to the thawing of cylindrically shaped pork sirloin by changing the shape of electrodes and the surrounding temperature. Methods: Curved electrodes were utilized to increase the thawing uniformity of cylindrically shaped frozen meat. Pork sirloin in the shape of a half-circle column was frozen in a deep freezer at $-70^{\circ}C$ and then thawed by RF heating with flat and curved electrodes. In order to prevent fast defrosting of the food surface by heat transfer from air to the food, the temperature of the thawing chamber was varied by -5, -10, and $-20^{\circ}C$. The temperature values of the frozen pork sirloin during RF thawing were measured using fiber-optic thermo sensors. Results: After multiple applications of curved electrodes resembling the food shape, and a cooled chamber at $-20^{\circ}C$ the half-cylindrically shaped meat was thawed without surface burning, and the temperature values of each point were similarly increased. However, with the parallel electrode, the frozen meat was partially burned by RF heating and the temperature values of center were overheated. The uniform heating rate and heat transfer prevention from air to the food were crucial factors for RF thawing. In this study, these crucial factors were accomplished by using a curved electrode and lowering the chamber temperature. Conclusions: The curved shape of the electrode and the equipotential surface calculated from the modeling of the parallel capacitor showed the effect of uniform heating of cylindrically shaped frozen food. Moreover, the low chamber temperature was effective on the prevention of the surface burning during RF thawing.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.219-228
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• 2003

Numerical and experimental studies were conducted on the temperature distribution of a buried steel pipe and surrounding granite frozen soils in the closed system. The relationship between unfrozen water content and temperatures was analysed by laboratory test. The thermal conductivity measurements were made to compare the results with a formula presented by Lachenbruch. A steel container model that consists of a freezing chamber and a buried circular steel pipe was built for the laboratory temperature measurements. The time temperature records were measured experimentally, and those records were compared with numerical results obtained from FEM analysis in order to verify the feasibility. The latent heat effect on the granite frozen soils in the numerical study was considered.

• Journal of Embryo Transfer
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• v.4 no.1
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• pp.21-27
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• 1989

Hydrogel chambers made from polymerized 2-hydroxyethyl methacrylate were used for in chamber fertilization. To determine whether sperm motility was preserved in the Hydrogel chamber, chambers which have rabbit sperm or frozen-thawed bovine sperm were transplanted inside of mouse peritoneal cavity and sperm were observed after recovering the chambers in the due time. As a result, it was determined that preservation of sperm motility was good. To determine whether in chamber fertilization was possible, chambers which have rabbit oocytes and sperm were transplanted inside of mouse peritoneal cavity and eggs were observed after recovering the chambers at 84 hr of preservation. As a result, the fact that fertilization and culture was occurred inside of the chamber was determined.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.51-60
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• 2012

In order to characterize the shear strength of the frozen sand for foundation design in cold region and prediction of adfreeze bond strength, many researchers developed test techniques and carried out many tests to analyze shear strength properties of the frozen sand for half a century. However, many studies for shear strength properties of the frozen sand have been carried out with limited circumstances, even though shear strength of the froze sand can be affected by various influence factors such as soil type, temperature conditions, and magnitude of normal stress. In this study, direct shear test equipment was used to analyze the shear strength characteristics of the frozen sand. Direct shear test equipment was designed for cold weather, and the direct shear tests were carried out inside of large-scaled low temperature chamber. Three soil types-two uniform sands and one well graded soil were used to analyze the shear strength of the frozen sand with three different temperature conditions and three different vertical confining pressures. In this research, a series of direct shear tests for shear strength of the frozen sand have been conducted to demonstrate the efficiency of effectiveness of the test equipment and low temperature chamber. This research also showed that shear strength of the froze sand increased with decreasing temperature condition, but the influence of vertical confining pressure was insignificant to the shear strength of the frozen sand.

• Journal of Embryo Transfer
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• v.11 no.1
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• pp.27-33
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• 1996

The efficient cryopreservation of embryos requires optimal times of dehydration and rehydration This study was carried out to investigate the effect of various times of dehydration and rehydration The effects were evaluated through testing morphological normality and developmental ability of 1 cell mouse embryos which were ultrarapidly frozen and thawed. The 1 cell embryos were dehydrated for 1.5, 3, 5, and 10 minutes using mPBS-BSA containing 3.SM DMSO and 0.25M sucrose on cooling chamber or on ice. After ultrarapidly frozen and thawed, they were rehydrated for 0, 0.5 and 5 minutes with mPBS-BSA containing 0.25M sucrose at room temperature. The results obtained were as follows: The embryos that were rehydrated for 0.5 minutes showed higher normality than the embryos for 0 and 5 minutes did. The embryos that were dehydrated for 10 minutes showed higher normality than the embryos for 1.5, 3, and 5 minutes did. The developmental ability of normal thawed-embryos was high in 10 minute dehydration treatment compared to other treatments. However, it was not affected by cooling methods (on ice and on cooling chamber) for embryo dehydration.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.8 s.145
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• pp.1176-1187
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• 2005

The purpose of this study was to evaluate the efficiency of cooling vests developed for farm workers harvesting red pepper in summer. The study was performed using the following two steps: 1) Climatic chamber test, 2) Field test. For the chamber test, a work environment was simulated as $33^{\circ}C$ and $65\%$RH, and the thermo-physiological and subjective responses were measured with and without cooling vests. Twelve young males participated as subjects. For the field test, three farmers participated while harvesting red pepper on the form, in summer. The measurements used were same as in the chamber test. Subjects were tested without any cooling vests, as a control. They were tested wearing vests with 2 frozen gel packs (CV2: Cooling area, $308cm^2$), and vests with 4 frozen gel packs (CV4: Sooting area, $616cm^2$). As a result of the chamber test, rectal temperature($T_{re}$) and mean skin temperature( $T_{sk}$) were lower in both CVs than in Control, and this tendency was statistically significant in CV4 (p<.05). Clothing microclimate temperature ($T_{clo}$) and total sweat rate (TSR) were significantly lower when wearing cooling vests (p<.05) Heart rate (HR) was also lower in wearing cooling vests than in Control, and the speed of recovery to the comfort level was faster when the subjects wore cooling vests. In addition, subjects felt 'less hot, less humid, and less uncomfortable' in both CVs than in Control. Field tests showed a similar tendency with the chamber tests. In particular, wearing the cooling vest was effective in restraining the raise of $T_{clo}$ on the back. It can be concluded that the cooling vest was effective in alleviating heat strain and discomfort in both the chamber test and the field test, despite the cooling area of the cooling vest being just $3.4\%$ of the body surface area ($616cm^2$).

• Korean Journal of Veterinary Research
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• v.38 no.4
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• pp.898-908
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• 1998

The aim of this experiments were to assess the time-interval change of motional characteristics in frozen-thawed semen of Korean native cattle (KNC) by using computer aided semen analysis (CASA) technology. Twenty-six KNC frozen semen straws were obtained from Korean KNC improvement department, livestock improvement main division, national livestock cooperatives federation in Korea. Specimens were allowed to thaw at $37^{\circ}C$ for 30 sec in water bath. Semen analysis was performed on semen image analysis system (SIAS, Medical supply, Korea) adjusted to the gate settings and used the semen droplet ($5{\mu}l$) placed on Makler counting chamber (Sefi medical instrument, Israel) prewarmed at $37^{\circ}C$. The same person used the same micropipette to fill the Makler counting chamber. A total of 150 or more of sperms were analysed in each specimen by a single trained person by scanning at least 5 to 10 fields. The measurement parameters in SIAS were as follows ; frame rate = 30 frames per sec, image capture = 1 sec, minimum motile speed = $10{\mu}m/s$, maximum countable sperm number = 400. Statistical analysis was done by Student t-test with use of the Sigma plot program on a IBM personal computer. The dancemean(DNM) and hyperactivated sperm(HYP) of frozen-thawed KNC semen kinematics were significantly decreased(p < 0.05) after 10 min of incubation at $37^{\circ}C$ water bath. But, wobble(WOB) of same sample semen was significantly increased(p < 0.05) after 10 min of incubation and significantly decrease(p < 0.05) after 60 min of same incubation. And, after 30 mim of incubation, significantly differences were found most of motion kinematics, motifity(MOT), curvilinear velocity(VCL), straight line velocity(VSL), average path velocity(VAP), amplitude of lateral head displacement(ALH), beat cross frequency(BCF), mean angular displacement(MAD), dance(DNC), on same sample semen. The DNM of KNC semen sample was variable kinematics after 30 min of incubation. Also, the linearity(LIN) and straightness(STR) was significantly decreased(p < 0.05) from 60 min of incubation. In conclusion, the AI within 30 min after thawing of frozen semen can be an effective method for obtaining high fertility rate in KNC reproductive program.

• Journal of the Korean Geosynthetics Society
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• v.12 no.3
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• pp.23-29
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• 2013

The mechanical behavior of frozen soils is different from that of unfrozen soils due to the phase change between water and ice. The strength characteristics of frozen soils are governed by the intrinsic material properties such as grain size, ice and water content, air bubbles, and by externally imposed testing conditions such as temperature, freezing time, and strain rate. Especially, the strength of the frozen soils is generally higher than that of unfrozen soils due to ice binding capacity with soil particles, and is strongly affected by a highly complex interaction between the solid soil skeleton and the pore matrix, composed of ice and unfrozen water. In this study, the direct shear test and unconfined compression test are carried out inside of a large-scaled freezing chamber, and the relationships between cohesion and unconfined compression strength under various freezing temperature conditions are discussed.