• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.5
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• pp.917-920
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• 2004

The migration potential of volatile organic solvents widely employed in the printing process of food packaging was investigated by using a closed experimental system, which contained a food sample and a paper sheet spiked with the contaminant solvents. The studied organic compounds included toluene and p,m,o-xylene which are relatively highly volatile. Typical food samples of caramel, beef jerky and butter were selected based on their chemical composition and were assigned to the migration system at 10, 25 and 4$0^{\circ}C$. The equilibrated migration level was very high with almost complete transfer in the butter with high fat, while caramel of high carbohydrate content and beef jerky of high protein showed migration degree of 37∼56% and 37∼77%, respectively. Temperature did significantly influence the migration on beef jerky with higher level at higher temperature. There was no difference in the migration level among the solvents.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.27-35
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• 2014

The headspace solid-phase microextraction (HS-SPME) followed by gas chromatography/mass spectrometry procedure has been developed for the simultaneous determination of petroleum aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylene isomers (BTEX) and polycyclic aromatic hydrocarbons (PAHs) in seawater. The advantages of SPME compared to traditional methods of sample preparation are ease of operation, reuse of fiber, portable system, minimal contamination and loss of the sample during transport and storage. SPME fiber, extraction time, temperature, stirring speed, and GC desorption time were key extraction parameters considered in this study. Among three kinds of SPME fibers, i.e., PDMS ($100{\mu}m$), CAR/PDMS ($75{\mu}m$), and PDMS/DVB ($65{\mu}m$), a $65{\mu}m$ PDMS/DVB fiber showed the most optimal extraction efficiencies covering molecular weight ranging from 78 to 202. Other extraction parameters were set up using $65{\mu}m$ PDMS/DVB. The final optimized extraction conditions were extraction time (60 min), extraction temperature (50), stirring speed (750 rpm) and GC desorption time (3 min). When applied to artificially contaminated seawater like water accommodated fraction, our optimized HS-SPME-GC/MS showed comparable performances with other conventional method. The proposed protocol can be an attractive alternative to analysis of BTEX and PAHs in seawater.

• Journal of Microbiology and Biotechnology
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• v.28 no.2
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• pp.199-209
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• 2018

Volatile organic compounds (VOCs) are increasingly been recognized as the chemical mediators of mold interactions, shaping their community dynamics, growth, and metabolism. Herein, we selectively examined the time-correlated (0 D-11 D, where D = incubation days) effects of intraspecies VOC-mediated interactions (VMI) on Aspergillus oryzae KCCM 60345 (S1), following co-cultivation with partner strain A. oryzae KACC 44967 (S2), in a specially designed twin plate assembly. The comparative evaluation of $S1_{VMI}$ (S1 subjected to VMI with S2) and its control ($S1_{Con}$) showed a notable disparity in their radial growth ($S1_{VMI}$ < $S1_{Con}$) at 5 D, protease activity ($S1_{VMI}$ > $S1_{Con}$) at 3-5 D, amylase activity ($S1_{VMI}$ < $S1_{Con}$) at 3-5 D, and antioxidant levels ($S1_{VMI}$ > $S1_{Con}$) at 3 D. Furthermore, we observed a distinct clustering pattern for gas chromatography-time of flight-mass spectrometry datasets from 5 D extracts of $S1_{VMI}$ and $S1_{Con}$ in principle component analysis (PC1: 30.85%; PC2: 10.31%) and partial least squares discriminant analysis (PLS-DA) (PLS1: 30.77; PLS2: 10.15%). Overall, 43 significantly discriminant metabolites were determined for engendering the metabolic variance based on the PLS-DA model (VIP > 0.7, p < 0.05). In general, a marked disparity in the relative abundance of amino acids ($S1_{VMI}$ > $S1_{Con}$) at 5 D, organic acids ($S1_{VMI}$ > $S1_{Con}$) at 5 D, and kojic acid ($S1_{VMI}$ < $S1_{Con}$) at 5-7 D were observed. Examining the headspace VOCs shared between S1 and S2 in the twin plate for 5 D incubated samples, we observed the relatively higher abundance of C-8 VOCs (1-octen-3-ol, (5Z)-octa-1,5-dien-3-ol, 3-octanone, 1-octen-3-ol acetate) having known semiochemical functions. The present study potentially illuminates the effects of VMI on commercially important A. oryzae's growth and biochemical phenotypes with subtle details of altered metabolomes.

• Korean Journal of Food Science and Technology
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• v.42 no.5
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• pp.533-540
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• 2010

Effects of pH (1.8-10.2) and time (56 sec-15 min 4 sec) at high hydrostatic pressure (500 MPa) on the reduction of volatile compounds in garlic were studied. Volatile components of garlic were obtained from the headspace, analyzed, and identified by gas chromatography (GC)-mass spectrometry and an electronic nose. Nineteen sulfur compounds were identified as major compounds in garlic, and furan, aldehydes, alcohols, and ketones were also detected. Off-flavor compounds were more effectively reduced under strong acidic conditions. As the residence time at 500 MPa increased from 56 sec to 15 min 4 sec, the total amount of volatile compounds decreased significantly. The total amount of sulfur compounds decreased about 70% compared to those of raw garlic when the garlic was soaked in buffer (pH 6.0) and treated at 500 MPa for 15 min 4 sec. A principal component analysis showed that the off-flavors of garlic were reduced by the operating time of high hydrostatic pressure as well as pH treatment. The correlation coefficient of the results between GC and the electronic nose analysis was 0.9620. Therefore, pH and high hydrostatic pressure treatment could be used as an efficient method for reducing of garlic off-flavor.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.166-174
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• 2016

In order to find an efficient bacterial strain that can carry out nitrification and denitrification simultaneously, we isolated many heterotrophic nitrifying bacteria from wastewater treatment plant. One of isolates NS13 showed high removal rate of ammonium and was identified as Alcaligenes faecalis by analysis of its 16S rDNA sequence, carbon source utilization and fatty acids composition. This bacterium could remove over 99% of ammonium in a heterotrophic medium containing 140 mg/L of ammonium at pH 6-9, $25-37^{\circ}C$ and 0-4% of salt concentrations within 2 days. It showed even higher ammonium removal at higher initial ammonium concentration in the medium. A. faecalis NS13 could also reduce nitrate and nitrous oxide by nitrate reductase and nitrous oxide reductase, respectively, which was confirmed by detection of nitrate reductase gene, napA, and nitrous oxide reducase gene, nosZ, by PCR. One of metabolic intermediate of denitrification, $N_2O$ was detected from headspace of bacterial culture. Based on analysis of all nitrogen compounds in the bacterial culture, 42.8% of initial nitrogen seemed to be lost as nitrogen gas, and 46.4% of nitrogen was assimilated into bacterial biomass which can be removed as sludge in treatment processes. This bacterium was speculated to perform heterotrophic nitrification and aerobic denitrification simultaneously, and may be utilized for N removal in wastewater treatment processes.

• Food Science and Preservation
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• v.30 no.3
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• pp.492-501
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• 2023

In this study, we wanted to understand the impact of different decaffeination processes on aroma compounds of coffee. Therefore, we analyzed differences in physical characteristics and volatile aroma compounds profiles of regular coffee (RC), Swiss water process decaffeinated coffee (SWDC), and supercritical CO₂ decaffeinated coffee (SCDC) after roasting the coffee beans. The electronic nose analysis identified RC and SCDC as different groups which indicates that these groups volatile aroma compound compositions were different. The principal component analysis of volatile compound patterns identified using an electronic nose indicated that there was a large difference in volatile compounds between RC, which was not decaffeinated, and both decaffeinated SWDC and SCDC. The major aroma compounds of RC, SWDC and SCDC were propan-2-one and hexan-2-one which are ketone, and hexanal and (E)-2-pentenal which are aldehyde and 3-methyl-1-butanol which is an alcohol. After roasting, the composition of major volatile compounds appearing in the beans was similar, but the relative odor intensity was different. We identified 28 volatile aroma compounds from RC, SWDC, and SCDC using headspace-solid phase microextraction-gas chromatography/mass spectrometry (HS-SPME-GC/MS), and analyzed 10 major compounds that were present in high abundance, including furfural, 2-furanmethanol, 2,5-dimethylpyrazine, and 2-ethyl-3-methylpyrazine.

• Korean Journal of Food Science and Technology
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• v.51 no.6
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• pp.543-550
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• 2019

In this study, volatile compounds in 13 aged and 3 commercial rice-distilled soju samples were isolated by headspace solid phase microextraction (HS-SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 85 volatile components including 35 esters, 15 alcohols, 5 ketones, 3 aldehydes, 15 miscellaneous, and 14 unknowns were identified. Esters and alcohols were the largest groups among the quantified volatiles. Differences in volatile compounds among the distilled soju samples and possible sample groupings were examined by principal component analysis of the GC-MS datasets. The first and second principal components (PC1 and PC2, respectively) explained 51.94% of the total variation across the 16 samples. The samples aged in oak containers had higher concentrations of ketones, aldehydes, and miscellaneous compounds. In the positive direction of PC1, oak-aged samples were observed, while, pot-aged samples were observed on the far negative side. Furthermore, samples aged for longer periods, such as 18 months, were observed in the positive direction of PC2.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.263-273
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• 2019

South Korea's OF cable is reaching its expected design life of 30 years, and as a result, the risk of failure is increasing. Therefore, it is necessary to diagnose the long-term operating OF cables through accurate diagnosis at the right time to prevent the failure. Currently, the KEPCO periodically conducts DGA. However, the gas found in DGA is caused by oil deterioration as well as insulation paper. Therefore, the analysis of the degree of polymerization and furan compounds which is an evaluation of insulation paper considered to be the life of OF cables is required. In addition, the results of the evaluation of deterioration of insulation paper need to be checked for correlation with the results of DGA. In this study, DGA carried out through GC, the degree of polymerization was analyzed using an automatic viscometer, and HPLC was used to detect the furan compounds. In addition, the obtained results were applied to the SVM technique, which was recently introduced to determine abnormalities in OF cable. And the results which were accurate and reliable were obtained.

• Korean Journal of Food Science and Technology
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• v.47 no.2
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• pp.137-144
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• 2015

Although instant coffee is less palatable than freshly brewed coffee, it is widely consumed primarily due to its convenience. Frequently, instant coffee is consumed in the form of a coffee-mix. It contains coffee creamer or dried skim milk, and sugar in addition to soluble coffee. The aim of this study was to investigate the volatile aroma compounds (VACs) of instant black coffee mixed with coffee creamer or dried skim milk by Gas Chromatography-Headspace-Solid Phase Microextraction (GC-HS-SPME) and sensory evaluation. A total of 16 different coffee samples including instant black coffee and coffee mixes with coffee creamer or dried skim milk, were chosen for this study. The coffee samples contained several common VACs such as pyrazine, pyridine, and pyrrole. Sensory evaluation indicated that the flavor intensity of coffee mix was less pronounced than that of instant black coffee alone. Coffee creamer and skim milk had little distinctive aroma per se; however, they significantly contributed to the flavor profile of coffee mixes, suggesting that coffee creamer and skim milk acted as flavor modifiers in coffee mix.

• Korean Journal of Food Science and Technology
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• v.50 no.2
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• pp.152-164
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• 2018

Fermented seasoning pastes were prepared by Aspergillus oryzae and Bacillus subtilis using three edible insects, Tenebrio molitor larvae (TMP), Gryllus bimaculatus (GBP), and Bombyx mori pupa (SPP), with soybean (SBP) as a negative control. Volatile compounds were extracted by the headspace solid-phase microextraction (HS-SPME) method and confirmed by gas chromatograph-mass spectrometry (GC-MS). In total, 121 volatiles from four samples were identified and sub-grouped as 11 esters, 18 alcohols, 23 aldehydes, 5 acids, 10 pyrazines, 2 pyridines, 7 aromatic hydrocarbons, 10 ketones, 19 alkanes, 9 amides, 4 furans and 3 miscellaneous. TMP, GBP, SPP and SBP had 48, 54, 36, and 55 volatile compounds, respectively. Overall, 2,6-dimethylpyrazine and trimethylpyrazine were found by a high proportion in all samples. Tetramethylpyrazine, a main flavor of doenjang, a Korean fermented seasoning soybean paste, was identified as one of the major compounds in TMP, SPP, and SBP. SBP had benzaldehyde, hexanal, n-pentanal, and aldehydes and SPP with pyrazines.