• Food Science of Animal Resources
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• v.38 no.2
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• pp.291-301
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• 2018

To shorten the production cycle of Zaodan, this study first pickled Zaodan by a novel technology - vacuum decompression technology. Vacuum decompression technology could reduce the pickling time of Zaodan from 20 wk to about 9 wk. The protein content, moisture and pH of the Zaodan egg white gradually decreased with a concomitant increase in salt during the pickling process. The total sulfhydryl group (SH) group content of the egg white proteins was increased to $2.43{\times}10^{-3}mol/L$ after being pickled for 30 d, whereas the content of disulphide bonds (SS) was reduced to $23.35{\times}10^{-3}mol/L$. The surface hydrophobicity was lowest after pickling for 30 d. In addition, great changes occurred in the secondary structure of the egg white proteins after pickling for 20 d. The disappearance of ovomucin was noticeable based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.45-50
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• 2013

Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop $N_2$ decompression system in terms of nitrogen consumption. In this study, two closed-loop pure $N_2$ J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are invstigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled $N_2$ J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

• Analytical Science and Technology
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• v.34 no.1
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• pp.23-35
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• 2021

In order to measure the volatile organic compounds (VOCs) of a sample which is too large to use commercially available chamber, a stainless steel vacuum chamber (VC) (with an internal diameter of 205 mm and a height of 50 mm) was manufactured and the temperature of the chamber was controlled using an oven. After concentrating the volatiles of the sample in the chamber by helium gas, it was made possible to remove residual volatile substances present in the chamber under reduced pressure ((2 ± 1) × 10-2 mmHg). The chamber was connected to a purge & trap (P&T) using a 6 port valve to concentrate the VOCs, which were analyzed by gas chromatography-mass spectrometry (GC-MS) after thermal desorption (VC-P&T-GC-MS). Using toluene, the toluene recovery rate of this device was 85 ± 2 %, reproducibility was 5 ± 2 %, and the detection limit was 0.01 ng L-1. The method of removing VOCs remaining in the chamber with helium and the method of removing those with reduced pressure was compared using Korean drinking water regulation (KDWR) VOC Mix A (5 μL of 100 ㎍ mL-1) and butylated hydroxytoluene (BHT, 2 μL of 500 ㎍ mL-1). In case of using helium, which requires a large amount of gas and time, reduced pressure ((2 ± 1) × 10-2 mmHg) only during the GC-MS running time, could remove VOCs and BHT to less than 0.1 % of the original injection concentration. As a result of analyzing volatile substances using VC-P&T-GC-MS of six types of cell phone case, BHT was detected in four types and quantitatively analyzed. Maintaining the chamber at reduced pressure during the GC-MS analysis time eliminated memory effect and did not affect the next sample analysis. The volatile substances in a cell phone case were also analyzed by dynamic headspace (HT3) and GC-MS, and the results of the analysis were compared with those of VC-P&T-GC-MS. Considering the chamber volume and sample weight, the VC-P&T configuration was able to collect volatile substances more efficiently than the HT3. The VC-P&T-GC-MS system is believed to be useful for VOCs measurement of inhomogeneous large sample or devices used inside clean rooms.

• Journal of Microbiology and Biotechnology
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• v.27 no.6
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• pp.1112-1119
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• 2017

The aim of this study was to develop a potential process for bioethanol production from Hydrodictyon reticulatum (HR), a filamentous freshwater alga, using Saccharomyces cerevisiae (KCTC7017). From the sugar solutions prepared by the four different hydrolysis methods, bioethanol production ranged from 11.0 g/100 g dried material (acid hydrolysis) to 22.3 g/100 g dried material (enzymatic hydrolysis, EH). Bioethanol was fermented from a highly concentrated sugar solution obtained by a decompression-mediated (vacuum) enrichment method (VE). As the results, ethanol was more efficiently produced from HR when sugar solutions were concentrated by VE following EH (EH/VE). Using multiple feeding of the sugar solution prepared by EH/VE from HR, ethanol reached up to a concentration of 54.3 g/l, corresponding to 24.9 g/100 g dried material, which attained the economic level of product concentration (approximately 5%). The results indicate that by using HR, it is feasible to establish a bioethanol production process, which is effective for using microalgae as the raw material for ethanol production.