• Korean Journal of Food Science and Technology
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• v.34 no.1
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• pp.24-29
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• 2002

The study was performed to investigate the degrees of gelatinization at various processing steps during the preparation of Dangmyuns using sweet potato, potato, corn and tapioca starches, and also determined the rehydration of the freeze dried sweet potato Dangmyun. The degrees of gelatinization after extrusion cooking showed higher value than other processing steps. The degrees of gelatinization after extrusion cooking were 63.5% in sweet potato, 80.0% in potato, 82.3% in corn, and 86.5% in tapioca Dangmyuns. The degree of gelatinization in Dangmyuns after extrusion cooking step decreased as the processing steps, such as cold storage, freezing, thawing, and sun drying, progressed. L values of color in Dangmyuns decreased in the order of corn>tapioca>potato>sweet potato Dangmyuns. The cooking loss decreased in the order of tapioca>corn>potato>sweet potato Dangmyuns. The percentage of weight gain was the highest in sweet potato Dangmyun followed by corn, potato, and tapioca Dangmyuns. The water absorption rate constant was the highest in sweet potato Dangmyun followed by corn, potato, and tapioca Dangmyuns. In the rehydration of freeze dried Dangmyuns, freeze dried sweet potato Dangmyun showed better than the others. An increase from 60% to 70% of the added amount of water in the mixing step resulted in an increase of the degrees of gelatinization after extrusion cooking from $63.4{\sim}70.7%$ to $73.8{\sim}75.0%$. An increase of the added water in the mixing step and a decrease of diameter in the extrusion cooking step slightly improved the rehydration in the boiled water of freeze dried sweet potato Dangmyun.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.115-125
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• 2023

In this study, we evaluated the behavior of frozen soil using an electrical resistivity survey method-a nondestructive technique-and examined its characteristics through field experiments. Frozen soil was artificially prepared by injecting fluid to accelerate the freezing process, and naturally frozen soil was selected in a nearby area for comparison. A dynamic cone penetration test (DCPT) was performed to compare the reliability of the electrical resistivity survey, and time-domain reflectometry surveys were performed to assess the moisture content of the ground. Field experiments were conducted in February-when the atmosphere temperature was below freezing-and May-when the temperature was above freezing. This temperature-compensated method was used to determine reliability because the behavior of frozen soil depends on the underlying temperature. In the resistivity survey method, a section of high electrical resistivity was observed under freezing conditions due to the frozen water and converted into porosity. The converted porosity was compared with the porosity inferred from the DCPT, and the results showed that the measured electrical resistivity was valid.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.350-356
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• 1988

A pilot plant scale freeze dryer was designed and manufactured and its performance was tested. Freezing capacity of water vapor in the developed freeze dryer was 8㎏/batch and heating and defrosting methods were conduction and hot gas types, respectively. And exhausting time of vacuum pump was 7-8 minutes and temperature of cold trap was kept below $-50^{\circ}C$. In the freeze drying of fruits and vegetables, its optimum and maximum drying capacities were 2 and 4㎏/batch, respectively. Performance of the new freeze dryer was compared quite well with a foreign made freeze dryer.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.43-47
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• 2011

Korea has seasonal weathers which result in the frosting of soil in winter times, and the thawing of soil in spring. These climate characteristics result in the damaging of pavements, due to the repeated freezing and thawing of road pavements during winter and spring. In order to reduce these pavement damages, anti-frost heave layers are being specially installed, however it is being applied based on foreign researches, and therefore result in the waste of national budget. With this study, a database system was constructed for effective management and monitoring of measured temperatures and function data of 2 meters below the embankment, cut slope, and the cutting-embankment boundary, which are 15 regions picked by the frost index diagram. As the study result, an effective storage and management-purpose database was established for easy data searching and downloading for the pavement design engineers.

• Journal of the Korean Geotechnical Society
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• v.39 no.9
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• pp.5-11
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• 2023

In analyzing geotechnical structures, the analysis fields are becoming increasingly diversified. In particular, the need for predicting the thermal behavior of ground materials has become important in fields related to soil freezing. To ensure a reliable assessment of the freezing behavior of the ground, considering the variation in the effective thermal conductivity of soil specimens under various conditions is crucial. In this study, probe experiments were conducted by varying the porosity, initial degree of saturation, and read time settings of the meter. Next, the factors influencing the effective thermal conductivity of the frozen sandy soil were evaluated. The experimental results conducted under different porosity conditions showed a tendency for the effective thermal conductivity of frozen soil to increase as the specimen's porosity decreased. However, as the degree of saturation of the specimen increased, the effective thermal conductivity also increased. The sensitivity of the meter's read time setting to the measurement of effective thermal conductivity was observed. When the read time was set to 1 min, the measured values were in a range similar to that obtained in previous studies conducted in Korea with the same soil specimen.

• Journal of Life Science
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• v.28 no.2
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• pp.153-161
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• 2018

Hot-air and freeze dried powder from aged black ginger were mixed under the ratio conditions of sample "A" (8:2), "B" (5:5), "C"(2:8), "D" (10:0) and "E" (0:10), respectively. The physicochemical properties and antioxidant activities in the 5 kinds of powder were compared. The water absorption index was significantly higher in freeze dried powder, and it tended to be significantly increased depend on the ratio of freeze dried sample. The browning intensity was significantly higher in the hot-air dried samples, but the color intensity was not significant. Total and reducing sugar contents were significantly higher in freeze dried sample. Total sugar content in mixed sample tended to significantly increased as the amount of freeze dried sample. Total phenol content was significantly higher in the sample "A". The contents of gingerol and shogaol were significantly higher in mixed sample "A", 6-gingerol content showed no significant difference according to the drying method. Cholesterol absorption activity was significantly higher in the freeze dried sample "E". The DPPH radical scavenging activity showed a little difference according to the drying method, but the ABTS radical scavenging activity and reducing power in the hot-air dried sample were significantly higher than those of freeze dried. And the activity of mixed powder "A" was significantly higher than others. These results suggest that aged black ginger was superior in terms of quality and functionality of the hot-air drying compared to freeze-drying, and it would be economically effective to the mixed sample "A".

• Journal of the Korean GEO-environmental Society
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• v.18 no.3
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• pp.5-14
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• 2017

Experimental study on strength characteristics of frozen soils is necessary for the safety evaluation of design and construction in cold region. The objective of this study is to evaluate the direct shear strength of frozen soils obtained from traditional system (Type-1), system with roller on the upper shear box (Type-2), and system with fixed upper shear box separated from bottom shear box (Type-3). Specimens mixed with sand, silt, and water are frozen to $-5^{\circ}C$, and then direct shear tests are conducted under the normal stress of 5, 10, 25, and 50 kPa. Experimental results show that the upper shear box of Type-1 touches the bottom shear box due to the rotation of the upper shear box. The shear strength obtained from Type-2 is overestimated because the preventing rotation force is added to shear force. Type-3 may acquire the only strength of the specimen, and shear strain at peak shear strength is similar to that at the beginning of vertical displacement occurrence. In addition, internal friction angle and cohesion at both peak and residual stresses in Type-3 are smaller than those of Type-2. This study shows that high strength specimens including frozen soils can be effectively evaluated using improved shear box system such as Type-3.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.2
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• pp.230-235
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• 2005

Volatile organic components from fresh and freeze-dried onions were extracted by SDE apparatus and analyzed by GC/MS. Components of 40 and 31 were identified in fresh and freeze-dried onions respectively. These components included esters, aldehydes, ketones, alcohols and S-containing compounds. Major compounds of S-containing compounds such as 1-propanethiol, dipropyl trisulfide, and methyl propyl trisulfide in fresh onions were clearly decreased in freeze-dried onions. Then, S-containing compounds such as methyl allyl sulfide, propyl ally sulfide, dially disulfide and 3,5-diethyl-l,2,4-trithiolane and alcohols such as pentanol, hexanol and propanol were disappeared by freeze-drying. Exceptionally, ethyl acetate, dimethyl disulfide and 2-methyl-2-pentenal were increased as different trend with major S-containing compounds. (Z)-Propenyl methyl disulfide and (E)-propenyl methyl disulfide were also changed by freeze-drying in the similar pattern as mentioned above compounds.

• International Journal of Highway Engineering
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• v.4 no.2 s.12
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• pp.1-8
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• 2002

Latex modified concrete(LMC) became to be applied as a new material for newly constructed bridge deck overlays in Korea due to its excellent bond strength, flexural strength and impermeability against water and chloride. However, it could not be adopted at repair job site because of its long curing time required. Thus, a research on latex modified concrete with rapid-setting cement(RSLMC) is necessary if it could develope the sufficient strength for early opening to traffic. This study focused on the durability of latex modified concrete with rapid-setting cement mainly on water permeable resistance and freeze-thaw resistance. The main experimental variables were latex contents(0, 5, 10, 15 and 20%) and antifoamer contents (0, 1.6, 3.2, 4.8 and 6.4%). Test results show that the permeability of RSLMC is very low indicating below 100 coulombs at 15% of latex contents at all antifoamer contents. The freeze-thaw resistance of RSLMC maintains above 90% of relative dynamic modulus at 3.2% of antifoamer content until 300 freezing-thawing cycles.

• Korean Journal of Food Science and Technology
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• v.43 no.6
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• pp.696-701
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• 2011

To evaluate the processing adaptability of taro flours, the physicochemical properties of taro flour with different drying, roasting and steaming conditions were investigated. The moisture content and total dietary fiber were decreased as temperature increased with hot-air drying. Freeze-dried taro flours showed the highest vitamin C contents. Taro flours made by freeze-drying and hot-air drying showed significantly higher total dietary fiber content than those with roasting and steaming process. Steamed taro flours had the highest water absorption index, while hot-air dried and freeze dried taro flours had the highest water solubility index. No differences were displayed in the differential scanning calorimetry (DSC) thermal characteristics among hot-air dried and freeze dried taro flours. Roasted taro displayed decreased onset temperature and peak temperature as roasting temperature increased. Using a rapid visco-analyzer, the peak viscosity, through viscosity, and final viscosity of dried and steamed taro flours were higher than roasted taro flours, whereas the set back value, which is a prediction of retrogradation, decreased with steaming processing. From those results, it could be concluded that hotair dried taro flours, which have high gelatinization viscosity, are beneficial in imparting viscosity to dough products and hot-air drying after steaming taro flours, which retard retrogradation, is good for porridge and flake base products.