• Journal of Animal Science and Technology
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• v.60 no.11
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• pp.27.1-27.8
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• 2018

Background: Enteric methane ($CH_4$) accounts for about 70% of total $CH_4$ emissions from the ruminant animals. Researchers are exploring ways to mitigate enteric $CH_4$ emissions from ruminants. Recently, nano zinc oxide (nZnO) has shown potential in reducing $CH_4$ and hydrogen sulfide ($H_2S$) production from the liquid manure under anaerobic storage conditions. Four different levels of nZnO and two types of feed were mixed with rumen fluid to investigate the efficacy of nZnO in mitigating gaseous production. Methods: All experiments with four replicates were conducted in batches in 250 mL glass bottles paired with the ANKOM$^{RF}$ wireless gas production monitoring system. Gas production was monitored continuously for 72 h at a constant temperature of $39{\pm}1^{\circ}C$ in a water bath. Headspace gas samples were collected using gas-tight syringes from the Tedlar bags connected to the glass bottles and analyzed for greenhouse gases ($CH_4$ and carbon dioxide-$CO_2$) and $H_2S$ concentrations. $CH_4$ and $CO_2$ gas concentrations were analyzed using an SRI-8610 Gas Chromatograph and $H_2S$ concentrations were measured using a Jerome 631X meter. At the same time, substrate (i.e. mixed rumen fluid+ NP treatment+ feed composite) samples were collected from the glass bottles at the beginning and at the end of an experiment for bacterial counts, and volatile fatty acids (VFAs) analysis. Results: Compared to the control treatment the $H_2S$ and GHGs concentration reduction after 72 h of the tested nZnO levels varied between 4.89 to 53.65%. Additionally, 0.47 to 22.21% microbial population reduction was observed from the applied nZnO treatments. Application of nZnO at a rate of $1000{\mu}g\;g^{-1}$ have exhibited the highest amount of concentration reductions for all three gases and microbial population. Conclusion: Results suggest that both 500 and $1000{\mu}g\;g^{-1}$ nZnO application levels have the potential to reduce GHG and $H_2S$ concentrations.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.6
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• pp.944-950
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• 2015

The purpose of this study was to provide a basis for the management of traditional Doenjang by analyzing characteristics of volatile compounds in local Doenjang certified as a traditional food. The main compounds in Doenjang were acids, esters, aldehydes, and pyrazines, whereas relatively high intensities of acetic acid, ethyl alcohol, benzaldehyde, ethyl acetate, ethyl 2-methyl butanoate, 2,5-dimethyl pyrazine, and tetramethylpyrazine were detected among identified compounds. The analysis revealed that the composition of basic volatile compounds in Doenjang was similar, but isovaleric acid, 2-methylbenzaldehyde, tetramethylpyrazine, benzaldehyde, ethyl alcohol, ethyl caprylate, furfural and butanoic acid can serve as marker compounds for quality evaluation since they were specifically abundant in only some kinds of Doenjang. As a result, the quality status of Doenjang certified as a traditional food was determined by constructing a database of the volatile compounds, which can be suggested as a quality control method.

• Food Engineering Progress
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• v.14 no.1
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• pp.14-20
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• 2010

The objective of the current study was to determine the cryoprotective effects of trehaolse on lactic acid bacteria in the frozen yoghurt during long-term frozen storage conditions. The frozen yoghurts were prepared using starter culture containing Lactobacillus bulgaricus and Streptococcus thermophilus, as well as trehalose and sorbitol as a cryoprotectant. The viable cell numbers of lactic acid bacteria in frozen yoghurt did not significantly decreased during six weeks frozen storage conditions. The MRS broth, which contains either trehalose or sorbitol, cultured with L. bulgaricus and/or S. thermophilus, and then the cultured medium was kept in the frozen condition for six weeks. The results indicated that lactic acid bacteria viability significantly increased with trehalose addition (2 and 5%) in the media compared to those of control and sorbitol supplement groups. The lactic acid bacteria viability in the yoghurts was examined on the effects of repeated freeze and thaw events. The freeze-thaw resistance of lactic acid bacteria significantly increased with trehalose supplement in the yoghurt. The major volatile aroma compounds (acetaldehyde, acetone, ethanol, diacetyl, and acetoin) in yoghurt were separated and indentified by headspace GC-FID analysis. Distinct flavor components and their ratios are known as important quality factors for yoghurt notes. Trehalose addition to the yoghurt was not influenced these factors during lactic acid fermentation. The results in this study demonstrated that trehalose potentially can be applicable as an effective cryoprotectant for lactic acid bacteria in the frozen yoghurt products.

• Journal of Soil and Groundwater Environment
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• v.24 no.3
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• pp.24-35
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• 2019

It is known that ${\delta}^{13}C_{DIC}$ (carbon-13 isotope of dissolved inorganic carbonate (DIC) ions) of water increases when dissolved $CO_2$ degases. However, ${\delta}^{13}C_{DIC}$ could decrease when the pH of water is lower than 5.5 at the early stage of degassing. Laboratory experiments were performed to observe the changes of ${\delta}^{13}C_{DIC}$ as $CO_2$ degassed from three different artificial $CO_2$-rich waters (ACWs) in which the initial pH was 4.9, 5.4, and 6.4, respectively. The pH, alkalinity and ${\delta}^{13}C_{DIC}$ were measured until 240 hours after degassing began and those data were compared with kinetic isotope fractionation calculations. Furthermore, same experiment was conducted with the natural $CO_2$-rich water (pH 4.9) from Daepyeong, Sejong City. As a result of experiments, we could observe the decrease of DIC and increase of pH as the degassing progressed. ACW with an initial pH of 6.4, ${\delta}^{13}C_{DIC}$ kept increasing but, in cases where the initial pH was lower than 5.5, ${\delta}^{13}C_{DIC}$ decreased until 6 hours. After 6 hours ${\delta}^{13}C_{DIC}$ increased within all cases because the $CO_2$ degassing caused pH increase and subsequently the ratio of $HCO_3{^-}$ in solution. In the early stage of $CO_2$ degassing, the laboratory measurements were well matched with the calculations, but after about 48 hours, the experiment results were deviated from the calculations, probably due to the equilibrium interaction with the atmosphere and precipitation of carbonates. The result of this study may be not applicable to all natural environments because the pressure and $CO_2$ concentration in headspace of reaction vessels was not maintained constant as well as the temperature. Nevertheless, this study provides fundamental knowledge on the ${\delta}^{13}C_{DIC}$ evolution during $CO_2$ degassing, and therefore it can be utilized in the studies about carbonated water with low pH and the monitoring of geologic carbon sequestration.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.95-101
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• 2019

In tidal flats that lack plants, methane ($CH_4$) fluxes are both positive (gas emission) and negative (gas "sinking") in nature. The levels of methanotroph populations significantly affect the extent of $CH_4$ sinking. This preliminary study examined $CH_4$ flux in tidal flats using a circular closed-chamber method to understand the effects of macroinvertebrate burrowing activity. The chamber was deployed over decapods (mud shrimp, Laomedia astacina and crab, Macrophthalmus japonicus) burrows for ~ 2 h, and the $CH_4$ and $CO_2$ concentrations were continuously monitored using a closed, diffuse $CH_4/CO_2$ flux meter. We found that Laomedia astacina burrow (which is relatively long) site afforded higher-level $CH_4$ production, likely due to diffusive emission of $CH_4$ in deep-layer sediments. In addition, the large methanotrophic bacteria population found in the burrow wall sediments has $CH_4$ oxidation (consumption) potential. Especially, nitrite-driven anaerobic oxidation of methane (AOM) may occur within burrows. The proposed $CH_4$-oxidation process was supported by the decrease in the ${\delta}^{13}C$ of headspace $CO_2$ during the chamber experiment. Therefore, macroinvertebrate burrows appear to be an important ecosystem environment for controlling atmospheric $CH_4$ over tidal flats.

• 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.

• Food Science and Preservation
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• v.30 no.2
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• pp.334-346
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• 2023

The antioxidant ability of 80% ethanolic extract of nutmeg seed (NM80) was evaluated using in vitro assays and bulk oil and oil-in-water (O/W) emulsion matrices. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) cation radical scavenging, and oxygen radical antioxidant capacity (ORAC) in vitro assays were used to evaluate the antioxidant ability of the extract. The DPPH radical scavenging activities of 25, 50, 100, and 200 ㎍/mL NM80 were 12.5, 20.9, 35.1, and 62.8%, respectively, while the ABTS cation radical scavenging activities were 2.7, 6.5, 30.5, and 29.8%, respectively, demonstrating a dose-dependent effect. The ORAC value was significantly higher at an NM80 concentration of 25 ㎍/mL than the positive control (p<0.05). The conjugated dienoic acid (CDA), ρ-anisidine, and tertiary butyl alcohol values in 90-min-heated corn oil containing 200 ppm of NM80 were significantly reduced by 3.26, 16.94, and 17.34%, respectively, compared to those for the sample without NM80 (p<0.05). However, the headspace oxygen content and CDA value in the O/W emulsion containing 200 ppm of NM80 at 60℃ had 6.29 and 82.85% lower values, respectively, than those for the sample without NM80 (p<0.05). The major volatile compounds of NM80 were allyl phenoxyacetate, eugenol acetate, and eugenol. NM80 could be an effective natural antioxidant in lipid-rich foods in bulk oil or O/W emulsion matrix.

• 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 PACKAGING SCIENCE & TECHNOLOGY
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• v.30 no.2
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• pp.91-100
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• 2024

Packaging method and storage time play a significant role in maintaining the quality, safety, and shelf-life of food. In this study, the quality such as acid value, peroxide value, total bacterial count, color difference, and flavor of Marsupenaeus japonicus Oranda was evaluated depending on the five packaging methods (T-N, P-N, P-O₂R, P-V, and P-N₂) and storage periods. Changes of acid value and peroxide value strongly depend on the existing oxygen of headspace in the Marsupenaeus japonicus Oranda packages. Regardless of packaging methods, the change in acid value, peroxide value, microbial growth and flavor of the Marsupenaeus japonicus Oranda occurred depending on the storage time. Especially, it is identified the quality changes of Marsupenaeus japonicus Oranda stored with P-N₂ package with less oxygen contents were retarded, compared to the them with T-N packaged with high oxygen contents.

• Food Science and Preservation
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• v.14 no.1
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• pp.1-7
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• 2007

This study was conducted to determine if chlorine dioxide ($ClO_{2}$) gas might minimize microbial contamination of fresh produce. After exposing grapes to 20 ppm or 40 ppm of chlorine dioxide gas in a closed container, grapes treated with 20 ppm $ClO_{2}$ were packaged in Ny/PE/L-LDPE pouches, stapes treated with 40 ppm $ClO_{2}$ were placed in an empty corrugated box, and untreated control grapes were placed in a box with a sachet containing $ClO_{2}$ gas adsorbed to silica gel (a silica gel pad). The free volume of the sachet material allowed the release of $ClO_{2}$ gas into the headspace of packages containing fresh grapes. Control fruit not exposed to $ClO_{2}$, was placed in a box and stored at either $25^{\circ}C$ or $0^{\circ}C$. Fruit in Ny/PE/L-LDPE film treated with 20 ppm $ClO_{2}$ lost almost no weight during storage at either $25^{\circ}C$ or $0^{\circ}C$. Such fruit had a lower soluble solid content than did other fruit samples. Titratable acidity tended to fall rapidly during storage at either $25^{\circ}C$ or $0^{\circ}C$. Anthocyanin content of grapes decreased over 21 days at $25^{\circ}C$ but increased over 10 weeks at $0^{\circ}C$. The total microbial count of grapes treated with $ClO_{2}$ gas and silica gel pads were lower than controls at $25^{\circ}C$. Fruit treated with 20 ppm $ClO_{2}$ and packaged in Ny/PE/L-LDPE pouches had lower microbial counts than other fruit samples when stored at $0^{\circ}C$. The silica gel pad did not significantly improve total microbial count (compared to untreated control samples) at $0^{\circ}C$. This result may be attributed to a higher rate of diffusion of $ClO_{2}$ gas at room temperature.