The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
W.l. Boatright - One of the best experts on this subject based on the ideXlab platform.
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Methionine is the Methyl Group Donor for Sulfite-Associated Methanethiol Formation in Isolated Soy Proteins
Journal of Food Science, 2006Co-Authors: Q. Lei, W.l. BoatrightAbstract:ABSTRACT: Addition of 3.2 mM sodium sulfite resulted in a 5.1-time higher amount of Methanethiol in aqueous slurries of isolated soy proteins (ISP) over the corresponding controls after being stirred for 60 min. Introduction of 4.0 mM methionine to the slurries induced a 2.7-time increase. However, when both sodium sulfite (3.2 mM) and methionine (4.0 mM) were added, a 25.7-time higher amount in Methanethiol concentration was observed. Similar results were obtained when sodium sulfite and methionine were added to a partially purified protein fraction prepared from defatted soy flakes. Mass spectra of the Methanethiol formed with addition of L-methionine-methyl-13C1 and unlabeled sulfite showed that the carbon-13 labeled methyl group was actually integrated into Methanethiol. But no incorporation of isotopic sulfur was observed when 34S-labeled sodium sulfite was applied. The free methionine contents in commercial and lab-prepared ISP and in-process protein extracts ranged from 10.34 μg/g to 52.74 μg/g, which were not proportional to the indigenous Methanethiol contents. Results from the current study showed that methionine is an important methyl group donor for Methanethiol in ISP associated with sulfite as a reducing agent.
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factors influencing the occurrence of Methanethiol in aqueous slurries of soy protein concentrates
Journal of Food Science, 2003Co-Authors: Q. Lei, W.l. BoatrightAbstract:: Aqueous slurries of 6 commercial soy protein concentrate (SPC) contained from 9.8 to 21.7 ppb Methanethiol, which corresponds to odor values (in water) of 49 to 108. Effects of temperature (5.5, 24, and 65°C), pH (4.8,6.6, and 9.0), transition metals (FeCl3, FeCl2, and CuCl2), lipoxygenase, and EDTA on Methanethiol levels in SPC slurries were investigated. Higher temperature (65°C), basic pH (9.0), transition metals, lipoxygenase, and EDTA caused significant increases in Methanethiol compared with the control. CuCl2 caused greater increases in Methanethiol than FeCl3 and FeCl2. In contrast, treatments with lower temperature (5.5°C) or acidic pH (4.8) resulted in lower levels of Methanethiol in all commercial SPC samples examined.
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Compounds Contributing to the Odor of Aqueous Slurries of Soy Protein Concentrate
Journal of Food Science, 2001Co-Authors: Q. Lei, W.l. BoatrightAbstract:Gas chromatography olfactometry/mass spectrometry (GCO/MS) studies on static and concentrated headspace of the aqueous slurries from soy protein concentrate (SPC) revealed acetaldehyde, Methanethiol, hexanal, dimethyl trisulfide (DMTS), and 2-pentyl furan as the most odorous volatiles. Further aroma extract dilution analy- sis (AEDA) of the volatile extracts identified the following as the odorous substances: hexanal, 2-heptanone, octanal, 2-octanone, 1-octen-3-one, DMTS, 3-octen-2-one, 2-decanone, benzaldehyde, 2-pentyl pyridine and trans, trans- 2,4- nonadienal, along with several unidentified odorants. Methanethiol and acetaldehyde, which have low boiling points, were not detected by AEDA, however. This is the first time that acetaldehyde, Methanethiol, and dimethyl
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Development of a new Methanethiol quantification method using ethanethiol as an internal standard.
Journal of agricultural and food chemistry, 2001Co-Authors: Q. Lei, W.l. BoatrightAbstract:Development of a new method to quantify Methanethiol in which ethanethiol was employed as an internal standard is reported. Recovery yields for Methanethiol from an aqueous model system and a soy protein concentrate (SPC) aqueous slurry determined with this method ranged from 97 to 107% and from 103 to 121%, respectively. The Methanethiol content of two commercial SPCs and two commercial soy protein isolate (SPI) samples, on a dry basis, ranged from 835 to 1190 times greater than the odor threshold for Methanethiol. Relative standard deviations for quantifying Methanethiol with the method from these samples were
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Headspace Evaluation of Methanethiol and Dimethyl Trisulfide in Aqueous Solutions of Soy-protein Isolates
Journal of Food Science, 2000Co-Authors: W.l. Boatright, Q. LeiAbstract:Volatile compounds from 2 samples of aqueous soy-protein isolates (SPI) (7%) were analyzed using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were (1) dimethyl trisulfide, (2) Methanethiol, (3) hexanal, (4) an unidentified charred, sweaty feet-like odor, (5) 2-pentyl furan, (6) 2,3-butadione, and (7) an unknown burnt-like odor. The most powerful odorants by static headspace analyses were (1) dimethyl trisulfide, (2) hexanal, (3) Methanethiol, and (4) 2-pentyl furan. Using deuterium labeled DMTS as an internal standard, DMTS was quantified at 60.1 and 45.5 ppb in the SPIs. This corresponds to odor values of 6014 and 4554, respectively. Using a cool, on-column technique, direct injection of concentrated-headspace volatiles and solvent-recovered volatiles with an internal standard of d6-DMTS detected both Methanethiol and DMTS at similar levels as with the traditional injection methods.
Q. Lei - One of the best experts on this subject based on the ideXlab platform.
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Methionine is the Methyl Group Donor for Sulfite-Associated Methanethiol Formation in Isolated Soy Proteins
Journal of Food Science, 2006Co-Authors: Q. Lei, W.l. BoatrightAbstract:ABSTRACT: Addition of 3.2 mM sodium sulfite resulted in a 5.1-time higher amount of Methanethiol in aqueous slurries of isolated soy proteins (ISP) over the corresponding controls after being stirred for 60 min. Introduction of 4.0 mM methionine to the slurries induced a 2.7-time increase. However, when both sodium sulfite (3.2 mM) and methionine (4.0 mM) were added, a 25.7-time higher amount in Methanethiol concentration was observed. Similar results were obtained when sodium sulfite and methionine were added to a partially purified protein fraction prepared from defatted soy flakes. Mass spectra of the Methanethiol formed with addition of L-methionine-methyl-13C1 and unlabeled sulfite showed that the carbon-13 labeled methyl group was actually integrated into Methanethiol. But no incorporation of isotopic sulfur was observed when 34S-labeled sodium sulfite was applied. The free methionine contents in commercial and lab-prepared ISP and in-process protein extracts ranged from 10.34 μg/g to 52.74 μg/g, which were not proportional to the indigenous Methanethiol contents. Results from the current study showed that methionine is an important methyl group donor for Methanethiol in ISP associated with sulfite as a reducing agent.
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factors influencing the occurrence of Methanethiol in aqueous slurries of soy protein concentrates
Journal of Food Science, 2003Co-Authors: Q. Lei, W.l. BoatrightAbstract:: Aqueous slurries of 6 commercial soy protein concentrate (SPC) contained from 9.8 to 21.7 ppb Methanethiol, which corresponds to odor values (in water) of 49 to 108. Effects of temperature (5.5, 24, and 65°C), pH (4.8,6.6, and 9.0), transition metals (FeCl3, FeCl2, and CuCl2), lipoxygenase, and EDTA on Methanethiol levels in SPC slurries were investigated. Higher temperature (65°C), basic pH (9.0), transition metals, lipoxygenase, and EDTA caused significant increases in Methanethiol compared with the control. CuCl2 caused greater increases in Methanethiol than FeCl3 and FeCl2. In contrast, treatments with lower temperature (5.5°C) or acidic pH (4.8) resulted in lower levels of Methanethiol in all commercial SPC samples examined.
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Compounds Contributing to the Odor of Aqueous Slurries of Soy Protein Concentrate
Journal of Food Science, 2001Co-Authors: Q. Lei, W.l. BoatrightAbstract:Gas chromatography olfactometry/mass spectrometry (GCO/MS) studies on static and concentrated headspace of the aqueous slurries from soy protein concentrate (SPC) revealed acetaldehyde, Methanethiol, hexanal, dimethyl trisulfide (DMTS), and 2-pentyl furan as the most odorous volatiles. Further aroma extract dilution analy- sis (AEDA) of the volatile extracts identified the following as the odorous substances: hexanal, 2-heptanone, octanal, 2-octanone, 1-octen-3-one, DMTS, 3-octen-2-one, 2-decanone, benzaldehyde, 2-pentyl pyridine and trans, trans- 2,4- nonadienal, along with several unidentified odorants. Methanethiol and acetaldehyde, which have low boiling points, were not detected by AEDA, however. This is the first time that acetaldehyde, Methanethiol, and dimethyl
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Development of a new Methanethiol quantification method using ethanethiol as an internal standard.
Journal of agricultural and food chemistry, 2001Co-Authors: Q. Lei, W.l. BoatrightAbstract:Development of a new method to quantify Methanethiol in which ethanethiol was employed as an internal standard is reported. Recovery yields for Methanethiol from an aqueous model system and a soy protein concentrate (SPC) aqueous slurry determined with this method ranged from 97 to 107% and from 103 to 121%, respectively. The Methanethiol content of two commercial SPCs and two commercial soy protein isolate (SPI) samples, on a dry basis, ranged from 835 to 1190 times greater than the odor threshold for Methanethiol. Relative standard deviations for quantifying Methanethiol with the method from these samples were
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Headspace Evaluation of Methanethiol and Dimethyl Trisulfide in Aqueous Solutions of Soy-protein Isolates
Journal of Food Science, 2000Co-Authors: W.l. Boatright, Q. LeiAbstract:Volatile compounds from 2 samples of aqueous soy-protein isolates (SPI) (7%) were analyzed using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were (1) dimethyl trisulfide, (2) Methanethiol, (3) hexanal, (4) an unidentified charred, sweaty feet-like odor, (5) 2-pentyl furan, (6) 2,3-butadione, and (7) an unknown burnt-like odor. The most powerful odorants by static headspace analyses were (1) dimethyl trisulfide, (2) hexanal, (3) Methanethiol, and (4) 2-pentyl furan. Using deuterium labeled DMTS as an internal standard, DMTS was quantified at 60.1 and 45.5 ppb in the SPIs. This corresponds to odor values of 6014 and 4554, respectively. Using a cool, on-column technique, direct injection of concentrated-headspace volatiles and solvent-recovered volatiles with an internal standard of d6-DMTS detected both Methanethiol and DMTS at similar levels as with the traditional injection methods.
Georgios M. Kontogeorgis - One of the best experts on this subject based on the ideXlab platform.
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VAPOR–LIQUID–LIQUID EQUILIBRIUM MEASUREMENTS AND MODELING OF Methanethiol OR ETHANETHIOL OR OR 1-BUTANETHIOL IN METHANE + WATER TERNARY SYSTEMS AT 303, 335, AND 365 K AND PRESSURE UP TO 9 MPA
2015Co-Authors: Javeed Awan, Christophe Coquelet, Ioannis Tsivintzelis, Georgios M. KontogeorgisAbstract:Submit your abstract below (400 words): Abstract: New vapor−liquid−liquid equilibrium (VLLE) data for Methanethiol + methane + water, ethanethiol + methane + water, 1-propanethiol + methane+ water, and 1-butanethiol + methane + water ternary systems have been measured at three temperatures (303, 335, and 365 K) and pressures up to 9 MPa. A " static-analytic " method was used for performing all the measurements. The total system pressure was maintained by CH 4. The objective of this work is to provide experimental VLLE data with thermodynamic modeling for mixtures of mercaptans (thiols) with other natural gas contents at its crude form, for which no data are available in the open literature. Such data will help the industrial modeling of processes relevant to reduction of sulfur emissions. The Cubic-Plus-Association (CPA) equation of state was applied to describe the phase behavior of the investigated systems. It is shown that the CPA EoS satisfactorily describes the solubilities of mercaptans (thiols) in all phases. It is observed from the experimental data that the solubility of CH 4 in the aqueous and organic phases increases with an increase of the total system pressure and decreases with an increase of the temperature. However, the solubility of CH 3 SH in the aqueous and organic phases decreases slightly with an increase of the total system pressure and increases significantly with an increase of the temperature. The new VLLE data of ternary system were compared with predictions of the cubic-plus-association equation of state. The model tends to under predict the concentration of CH3SH in all phases, particularly the vapor phase. However, the model underestimates the water content of the vapor phase, especially at low pressures and at the highest investigated temperature, i.e., at 365 K. Only the ethanethiol + methane + water system showed significant cross-association effects. Furthermore, no cross association (solvation) was found to be significant in 1-propanethiol + methane + water and 1-butanethiol + methane +water ternary systems. Highlight 1: New vapor−liquid−liquid equilibrium (VLLE) data for Methanethiol + methane + water, ethanethiol + methane + water, 1-propanethiol + methane+ water, and 1-butanethiol + methane + water ternary systems have been measured at three temperatures (303, 335, and 365 K) and pressures up to 9 MPa.
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vapor liquid liquid equilibrium measurements and modeling of Methanethiol or ethanethiol or or 1 butanethiol in methane water ternary systems at 303 335 and 365 k and pressure up to 9 mpa
European Conference on Cognitive Ergonomics, 2015Co-Authors: Javeed Ashraf Awan, Christophe Coquelet, Ioannis Tsivintzelis, Georgios M. KontogeorgisAbstract:Submit your abstract below (400 words): Abstract: New vapor−liquid−liquid equilibrium (VLLE) data for Methanethiol + methane + water, ethanethiol + methane + water, 1-propanethiol + methane+ water, and 1-butanethiol + methane + water ternary systems have been measured at three temperatures (303, 335, and 365 K) and pressures up to 9 MPa. A " static-analytic " method was used for performing all the measurements. The total system pressure was maintained by CH 4. The objective of this work is to provide experimental VLLE data with thermodynamic modeling for mixtures of mercaptans (thiols) with other natural gas contents at its crude form, for which no data are available in the open literature. Such data will help the industrial modeling of processes relevant to reduction of sulfur emissions. The Cubic-Plus-Association (CPA) equation of state was applied to describe the phase behavior of the investigated systems. It is shown that the CPA EoS satisfactorily describes the solubilities of mercaptans (thiols) in all phases. It is observed from the experimental data that the solubility of CH 4 in the aqueous and organic phases increases with an increase of the total system pressure and decreases with an increase of the temperature. However, the solubility of CH 3 SH in the aqueous and organic phases decreases slightly with an increase of the total system pressure and increases significantly with an increase of the temperature. The new VLLE data of ternary system were compared with predictions of the cubic-plus-association equation of state. The model tends to under predict the concentration of CH3SH in all phases, particularly the vapor phase. However, the model underestimates the water content of the vapor phase, especially at low pressures and at the highest investigated temperature, i.e., at 365 K. Only the ethanethiol + methane + water system showed significant cross-association effects. Furthermore, no cross association (solvation) was found to be significant in 1-propanethiol + methane + water and 1-butanethiol + methane +water ternary systems. Highlight 1: New vapor−liquid−liquid equilibrium (VLLE) data for Methanethiol + methane + water, ethanethiol + methane + water, 1-propanethiol + methane+ water, and 1-butanethiol + methane + water ternary systems have been measured at three temperatures (303, 335, and 365 K) and pressures up to 9 MPa.
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Phase equilibria of three binary mixtures: Methanethiol + methane, Methanethiol + nitrogen, and Methanethiol + carbon dioxide
Journal of Chemical and Engineering Data, 2012Co-Authors: Javeed A. Awan, Christophe Coquelet, Ioannis Tsivintzelis, Georgios M. KontogeorgisAbstract:New vapor-liquid equilibrium (VLE) data for Methanethiol (MM) + methane (CH 4), Methanethiol (MM) + nitrogen (N 2), and Methanethiol (MM) + carbon dioxide (CO 2) is reported for temperatures of (304, 334, and 364) K in the pressure range (1 to 8) MPa. A "static- analytic" method was used for performing the measurements. The objective is to provide experimental VLE data for Methanethiol with other natural gas contents at its crude form, for which no data are available in the open literature. The new VLE data for the aforementioned systems have been modeled successfully with the cubic-plus-association equation of state (CPA EoS).
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phase equilibria of three binary mixtures Methanethiol methane Methanethiol nitrogen and Methanethiol carbon dioxide
Journal of Chemical & Engineering Data, 2012Co-Authors: Javeed A. Awan, Christophe Coquelet, Ioannis Tsivintzelis, Georgios M. KontogeorgisAbstract:New vapor–liquid equilibrium (VLE) data for Methanethiol (MM) + methane (CH4), Methanethiol (MM) + nitrogen (N2), and Methanethiol (MM) + carbon dioxide (CO2) is reported for temperatures of (304, 334, and 364) K in the pressure range (1 to 8) MPa. A “static–analytic” method was used for performing the measurements. The objective is to provide experimental VLE data for Methanethiol with other natural gas contents at its crude form, for which no data are available in the open literature. The new VLE data for the aforementioned systems have been modeled successfully with the cubic-plus-association equation of state (CPA EoS).
Jacek Namieśnik - One of the best experts on this subject based on the ideXlab platform.
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Monitoring of odors emitted from stabilized dewatered sludge subjected to aging using proton transfer reaction–mass spectrometry
Environmental Science and Pollution Research, 2019Co-Authors: Hubert Byliński, Radosław J. Barczak, Jacek Gębicki, Jacek NamieśnikAbstract:One of the potential emission sources of odorous compounds from wastewater treatment plants is sludge processing. The odorous compounds released from dewatered sludge can result in odor nuisance. This study concerns the use of flux hood chamber combined with proton transfer reaction—time of flight—mass spectrometry (PTR-MS) technique for periodical monitoring of odorous compounds emitted from aged, stabilized dewatered sludge samples from 2 different wastewater treatment plants located in Pomeranian Voivodeship, Poland. Based on determined concentration of the chemical compounds and olfactory threshold values, theoretical odor concentrations (known also as “odor activity value” or “odor index”) were calculated for 17 selected odorous compounds. As a result, sulfur compounds such as diethyl sulphide, dimethyl sulphide, Methanethiol, and ethanethiol were estimated as the most significant chemical compounds responsible for malodorous effect (average results, e.g., Methanethiol, 178 ou/m^3; diethyl sulphide, 184 ou/m^3). Based on Pearson correlation coefficient, we revealed a correlation between odorous substances emitted from aged, stabilized dewatered sludge cakes. It was revealed that stabilized dewatered sludge still possessed significant amount of odorous compounds and applied measurement technique could be used for monitoring of odor concentration level of selected malodorous compounds.
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Monitoring of odors emitted from stabilized dewatered sludge subjected to aging using proton transfer reaction-mass spectrometry.
Environmental Science and Pollution Research, 2019Co-Authors: Hubert Byliński, Radosław J. Barczak, Jacek Gębicki, Jacek NamieśnikAbstract:One of the potential emission sources of odorous compounds from wastewater treatment plants is sludge processing. The odorous compounds released from dewatered sludge can result in odor nuisance. This study concerns the use of flux hood chamber combined with proton transfer reaction-time of flight-mass spectrometry (PTR-MS) technique for periodical monitoring of odorous compounds emitted from aged, stabilized dewatered sludge samples from 2 different wastewater treatment plants located in Pomeranian Voivodeship, Poland. Based on determined concentration of the chemical compounds and olfactory threshold values, theoretical odor concentrations (known also as "odor activity value" or "odor index") were calculated for 17 selected odorous compounds. As a result, sulfur compounds such as diethyl sulphide, dimethyl sulphide, Methanethiol, and ethanethiol were estimated as the most significant chemical compounds responsible for malodorous effect (average results, e.g., Methanethiol, 178 ou/m3; diethyl sulphide, 184 ou/m3). Based on Pearson correlation coefficient, we revealed a correlation between odorous substances emitted from aged, stabilized dewatered sludge cakes. It was revealed that stabilized dewatered sludge still possessed significant amount of odorous compounds and applied measurement technique could be used for monitoring of odor concentration level of selected malodorous compounds.
Yiquan Yang - One of the best experts on this subject based on the ideXlab platform.
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The Promoting Effect of Tellurium on K2MoO4/SiO2 Catalyst for Methanethiol Synthesis from High H2S-Containing Syngas
Catalysis Letters, 2007Co-Authors: Aiping Chen, Qi Wang, Yinjuan Hao, Weiping Fang, Yiquan YangAbstract:Tellurium used as promoter was investigated in the preparation of K2MoO4/SiO2 catalyst for Methanethiol synthesis from high H2S-containing syngas. The experimental results showed that the addition of Te to K2MoO4/SiO2 improved the activity of catalysts and the selectivity of Methanethiol. ESR results reveal that the addition of Te decreases the content of “oxo-Mo5+” species and increase that of the “oxysulfo-Mo5+” species, simultaneously increase the low valence states of sulfur species. XPS results reveal that the addition of Te to K2MoO4/SiO2 increase the amount of low valence states of molybdenum and sulfur species, which are related to the formation of Methanethiol.
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On Methanethiol synthesis from H2S-containing syngas over K2MoS4/SiO2 catalysts promoted with transition metal oxides
Catalysis Letters, 1999Co-Authors: Shen‐jun Dai, Yiquan Yang, Youzhu Yuan, Ding-liang Tang, Ren‐cun Lin, Hong-bin ZhangAbstract:The catalysts K2MoS4/SiO2 promoted with transition metal oxides Fe2O3, CoO, NiO and MnO2 were prepared and used to catalyze the synthesis of Methanethiol from H2S‐containing syngas. The results of activity assay show that the catalysts promoted with Fe2O3, CoO and NiO can remarkably increase the hour space yield of Methanethiol. Nevertheless, MnO2 was found to have a disadvantageous effect on the selectivity of Methanethiol. The results of XRD and XPS characterization indicate that the addition of the transition metal oxides promoters is in favor of the formation of a Mo–S–K active phase and also retards the decomposition of K2MoS4 to MoS2, thereby suppressing both the deep reduction of Mo species and the formation of (S–S)2 species, which are reflected by the increment of the concentration ratios of both Mo6+/Mo4+ and S2/(S–S)2.