• Journal of Mushroom
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• v.21 no.4
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• pp.222-227
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• 2023

Mushrooms have a unique taste and aroma, so in the processing of mushroom products with other ingredients, a separate pre-processing step is often taken to eliminate the mushroom aroma. In this study, we analyzed the changes in the concentration of volatile compounds according to drying conditions to promote the activation of processing using the fruiting bodies of yellow oyster mushrooms(Pleurotus citrinopileatus) and pink oyster mushrooms(P. djamor). The caps and stipes of yellow oyster and pink oyster mushrooms were separated and freeze-dried at -70℃ for 120 hours. Subsequently, they were hot air-dried at temperatures of 40, 50, 60, and 70℃ for 24, 24, 16, and 12 hours, respectively. The dried samples were pulverized and quantitatively analyzed by SPME-GC-MS. In the case of yellow oyster mushrooms, the concentration of t-2-nonenal in caps and stipes during freeze-drying was 164.43 ㎍/g d.w. and 174.80 ㎍/g d.w., respectively, whereas during hot air-drying, it significantly decreased to 0.35~3.41 ㎍/g d.w. and 0.98~59.88 ㎍/g d.w. In a similar manner, for pink oyster mushrooms, the concentration of 1-octen-3-ol during freeze-drying in caps and stipes was 31.05 ㎍/g d.w. and 176.17 ㎍/g d.w., respectively, whereas during hot air-drying, it significantly decreased to 1.59~9.66 ㎍/g d.w. and 1.96~15.77 ㎍/g d.w. Furthermore, most volatile compounds showed a tendency to decrease in concentration as the temperature during hot air-drying increased.

• Tunnel and Underground Space
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• v.15 no.3 s.56
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• pp.169-176
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• 2005

The decreasing pattern of underground temperature measured at 'Gonjiam cold storage cavern' during 7 years which was the first commercial scale underground food storage cavern in Korea was analyzed. The variation of energy consumption was discussed by comparing the consumed energy at the initial operation stage with that at later stage, when the temperature distribution reached a stabilized condition. The point to be considered at the design stage was also discussed by comparing the required refrigerator capacity at the initial operation stage with that at later stage. The extra energy to freeze the groundwater contained in pore space was discussed by analyzing the changing pattern of the rock temperature. The variation of measured rock temperature was compared with the estimated temperature using a numerical code, FLAC. The accuracy of the numerical estimation was discussed by comparing the heat flux measured by the operation time of the refrigerator with that estimated numerically.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.2
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• pp.135-144
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• 1995

Understanding on nutrient solute movement during the course of freezing and thawing was attempted through laboratory and field obsevations. Small sectioned tubes with 5cm inner diameter, 0.2cm thick and 1cm long were connected to 30cm long soil columns for laboratory study. The columns were filled with soil, and treated with 20mmol/kg $KNO_3$ for upper 5cm. The upper end was set in the freezing section, and the lower end was set in the refrigerating section of a refrigerator. Temperature was controlled at $-7({\pm}1)^{\circ}C$ and $1.5({\pm}1)^{\circ}C$, respectively. After top 5cm soil was frozen, the columns were sectioned, and analyzed for $NO_3^-$, $NH_4^+$ and $K^+$. For field study, the 20cm inner diameter and lm long soil columns were installed in Chuncheon and Daegwanryung, where the altitude was 74m and 840m, respectively. The soils used were silt loam and clay loam. The top 20cm soils were treated with 50mmol/kg as $KNO_3$. The soil columns were taken during winter freezing and after thawing. By laboratiry study, upward movement of $NO_3^-$ and $K^+$ during the course of freezing was confirmed. The upward movement of $K^+$ was, however, one fifth to one tenth of $NO_3^-$. The upward movement of inorganic nitrogen as well as laboratory during the course of freezing, but large amount of nitrogen was lost from the profile after thawing in early spring. Leached nitrogen from the upper 20cm to lower part was 17 to 24 percents. The maximum depth of leaching during the experiment was 50cm for all soils. The net loss of inorganic nitrogen from the whole profile ranged 8.7 to 39.5 percents. The net loss was greater in Daegwanryung where temperature was lower and snowfall was larger than Chuncheon, and the loss was greater from the silt loam soil than clay loam soil of which percolation rate was small. The results implied that reasons for nitrogen loss during the winter might include surface washing by snow melt as well as leaching and denitrification.

• The Journal of Engineering Geology
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• v.34 no.3
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• pp.367-379
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• 2024

We analyzed the changes in the properties of the Mudeungsan tuff by conducting an artificial weathering experiment based on the climatic conditions of Mudeungsan National Park, to evaluate the long-term stability of the columnar jointing in the tuff. The climate of Mudeungsan National Park over 20 years suggests the temperature conditions for freeze-thaw are -20 to 30℃. The change in tuff properties due to weathering were estimated by measuring the elastic wave velocity, which was measured after every 40 freeze-thaw cycles. Based on the origin of the Mudeungsan tuff and fracture distribution in the tuff, the elastic wave velocity in samples from 24 locations was measured at regular intervals in the axial and radial directions. The axial elastic wave velocity of the Mudeungsan tuff is 5,187~5,367 m/s, and the radial elastic wave velocity is 4,001~5,290 m/s. As a result of 200 freeze-thaw cycles, the axial elastic wave velocity decreased by 5.53% for sample MT-1, 4.89% for MT-2, and 5.36% for MT-3. The radial elastic wave velocity decreased by 20.00% for MT-1, 17.02% for MT-2, and 19.84% for MT-3. The decrease in elastic wave velocity due to the freeze-thaw cycles is greater for low values of elastic wave velocity. For the axial elastic wave velocity, the weathering is accelerated after 120 cycles and, for the radial elastic wave velocity, weathering actively progresses from the start of the freeze-thaw cycles. In summary, for a low elastic wave velocity, experimental weathering results in a large decrease in elastic wave velocity. In addition, the Mudeungsan tuff and its columnar joints have a distinct anisotropy.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.2
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• pp.79-92
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• 1992

This study was carried out to develop new techniques useful for cryopreservation, thawing and artificial insemination, and ultrastructural changes of cryopreserved spermatozoa in rainbow trout(Oncorhynchus mykiss) . Two extenders, such as Tyrode solution and Whittingham's $T_6$ solution, were used to preserve rainbow trout sperm in refrigerator $(-20,\;-40\;and\;-70^{\circ}C)$ or liquid nitrogen $%(-196^{\circ})$. Hand-stripped semen was diluted to 1:16 with two extenders, an then the semen were frozen after mixing semen and each extender containing 1M or 1.5M DMSO solution to 1:1. After 60 days cryopreserved semen was thawed in a $13^{\circ}$ water bath, and subsequently centrifugated. After centrifugation at 1,000 rpm for 5 min thawed semen was washed with extenders, and then fertilized with fresh eggs. The results obtained in these experiments were summarized as follows: After cryopreservation, over 75% of spermatozoa were appeared motile and the survival rate was high. Following cryopreservation by the addition of cryoprotectant such as DMSO, methanol and glycerol, the fertilization rate of the thawed spermatozoa appeared over $99\%$ compared with the control having $99\%$ of fertilization rate. There was no difference between the control and experimental groups such as $(-20^{\circ}C\;-40^{\circ}C\;and\;-70^{\circ}C)$ and $-196^{\circ}$ in fertilization rate. Following cryopreservation at $-196^{\circ}$ by the addition of 1M DMSO of cryoprotectant, each fertilization rate following 24 hours and hatching rate following 24 days showed $96\%$ and $8\%$ by the addition of BSA, but showed $98\%\;and\;10%$ by no addition of BSA. Following 2 months of cryopreservation by the addition of 1M DMSO of cryoprotectant, there were $10%$ of hatching rate at $-196^{\circ}\;and\;10\%\;and\;35\%,\;respectively,\;at\;-40^{\circ}C\;and\;-70^{\circ}C$. Following 2 months of cryopreservation by the addition of 1M methanol of cryoprotectant, there were $22\%$ of fertilization rate at $-20^{\circ}C,\;and\;28\%,\;at\;-70^{\circ}C$ Following 2 months of cryopreservation by the addition of 1M glycerol of cryoprotectant, there were $22\%$ of fertilization rate at $-20^{\circ}C$, and $33\%,\;at\;-70^{\circ}C$. pollowing 2 months of cryopreservation by the addition of 1.5M DMSO of cryoprotectant, there were $27\%$ of fertilization rate at $-20^{\circ}C,\;an\;36\%\;and \;35\%,\;respectively,\;at\;-40^{\circ}C\;and\;-70^{\circ}C$. Following 2 months of cryopreservation by the addition of 1.5M glycerol of cryoprotectant, there were $34\% \;of\;fertilization\;rate\;at\;-20^{\circ}C, \;and\;31\%\;and\;31\%,\;respectively,\;at \;-40^{\circ}C\;and\;-70^{\circ}$. Following 2 months of cryopreservation by the addition of 1.5M methanol of cryoprotectant, there were $28\%$ of fertilization rate at $-20^{\circ}C,\;and\;29\%\;and\;28\%,\;respectively,\;at\;-40^{\circ}C\;and\;-70^{\circ}C.$ From 10 days and 15 days following fertilization at $13^{\circ}C\;and\;10^{\circ}C$, respectively, the mortality rate of fertilized ova was markedly increased. The middle piece of spermatozoa had two set of central doublets, nine set of outer coarse fibres, and mitochondrial sheath. Spermatozoa went through morphological changes during storage, e.g. winding of flagella, detachment of the nuclear envelope and the plasma membrane from the nucleus of the sperm head. There were $1\%$ abnormal spermatozoa in fresh sperm and about $15\%$ during storage.

• Korean journal of applied entomology
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• v.36 no.3
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• pp.256-263
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• 1997

Supercooling points (SCP) and cold tolerance of the tobacco cutworm, Spodol~rera litura Fabricius. were measured in response to subzero temperatures. SCPs were varied among developmental stages. Eggs showed the lowest SCP (-27$^{\circ}$C). Pupae and adults had the intermediate SCP(- 18$^{\circ}$C). The SCPs (- I0 to - 16$^{\circ}$C) of larvae increased with their ages. Lethal low temperature of each stage was higher than its SCP. Preexposure of eggs and larvae to a sublethal low temperature increased their survival capacities under lethal low temperatures. The sublethal temperature also induced the fifth instar larvae to increase hemolymph osmolality and to produce cold-induced proteins of apparent molecular weights of 20 and 27 kD. These results indicate that this species is classified into a freeze-susceptible insect.

• Tunnel and Underground Space
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• v.25 no.2
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• pp.144-154
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• 2015

Mechanical energy is accumulated in the object when stress is exerted on rock specimens, and the failure is occurred when the stress is larger than critical stress. The accumulated energy is emitted as various forms including physical deformation, light, heat and sound. Uniaxial compression strength test and point load strength test were carried out in low temperature environment, and thermal variation of rock specimens were observed and analyzed quantitatively using thermal infrared camera images. Temperature of failure plane was increased just before the failure because of concentration of stress, and was rapidly increased at the moment of the failure because of the emission of thermal energy. The variations of temperature were larger in diorite and basalt specimens which were strong and fresh than in tuff specimens which were weak and weathered. This study can be applied to prevent disasters in rock slope, tunnel and mine in cold regions and to analyze satellite image for predicting earthquake in cold regions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.3
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• pp.425-433
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• 2015

This study investigated changes in physicochemical characteristics by drying and fermentation in order to utilize Actinidia arguta. Moisture content of A. arguta was 85.81%. Major sugar and organic acids were sucrose, succinic acid, and citric acid. A. arguta contained 19 kinds of amino acids, including 8 kinds of essential amino acids such as valine, methionine, isoleucine, leucine, threonine, phenylalanine, tryptophan, and lysine. For total organic acids, sample fermented for 17 h at $50^{\circ}C$ under a relative humidity of 80% showed 29,026.53 mg/100 g total organic acids. For total free sugars, cold-dried sample showed the highest level at 6,560.86 mg/100 g, which decreased to 2,386.73 mg/100 g after blanching. For the ratio of essential amino acids, freeze-dried sample showed a content of 11.66%, which increased 4-fold up to 40.71~55.50% with fermentation. Both GABA and vitamin U were highest after 17 h of fermentation (110.29 mg and 6.78 mg/100 g fresh weight, respectively). A. arguta contains a variety of free amino acids that increase in amount after fermentation and thus is expected to be developed as a functional food and substitute tea.

• Korean Journal of Medicinal Crop Science
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• v.6 no.4
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• pp.245-250
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• 1998

This research was carried out to investigate the effective methods of browning inhibition on Paeonia lactiflra Pall during hot air dehydratin. After drying for 36 hrs without pretreatment and with briquet fumigation moisture contents of Paeonia lactiflora Pall. was 16.0% and 16.2%, respectively, while with acidic solution, sulfite salt solution and blanching it was lower of 13.5, 12.9 and 14.8%, respectively. Using freeze drying moisture content was highest of 18.8%. The Hunter values of dried Paeonia lactiflora Pall., L, a, band ${\triangle} E$ showed that non-treatment had the most browning with 61.60, 1.89, 10.20 and 39.78, respectively, while briquet fumigation and sulfite salt solution were excellent in reducing browning. During freeze drying browning didn't occur. Paeoniflorin content was 2.41 and 2.51 %, respectively, in briquet fumigation and sulfite salt solution and was the highest (2.70%) in freeze drying. The content of $SO_2$, was 0.63% both in briquet fumigation and sulfite salts. It was 0.15% and 0.17% higher than nontreatment and freeze drying. The most effective pretreatment to inhibit browning of Paeonia lactiflora Pall. was soaking in sulfite salt solution $(0.5% NaHSO_4-0.5% Na_2S_2O_3)$ considering many things such as manpower, economical efficiency, drying time, commodity, etc. but safety should be evaluated to treat sulfite salts solution on peony roots.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.249-255
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• 2006

The optimum culture conditions for the ice nucleating activity and the cell growth of Xanthomonas translucens KCTC 2751 were investigated. The optimum initial pH and temperature for the cell growth and the ice nucleating activity were 6.5 and $25^{\circ}C$, respectively. The optimum culture medium for the ice nucleating activity was composed of 1.0% maltose, 1.4% yeast extract, 0.8% digested of gelatin, and 0.03% KCI in distilled water. Freezing operations carried out on distilled water showed that the degrees of supercooling were $-7.90^{\circ}C$ without ice nucleators, $-1.56^{\circ}C$ with silver iodide as a commercial ice nucleator, and $-1.36^{\circ}C$ when Xanthomonas translucens KCTC 2751 were added. During progressive freeze-concentration assays, the addition of Xanthomonas translucens KCTC 2751 led to lower saccharose concentrations in the crystals, while the cells led to higher saccharose concetrations in the concentrated phase.