Sample records for 2-methylbutane

  1. Volatile profiles of members of the USDA Geneva Malus Core Collection: utility in evaluation of a hypothesized biosynthetic pathway for esters derived from 2-methylbutanoate and 2-methylbutan-1-ol. (United States)

    Sugimoto, Nobuko; Forsline, Philip; Beaudry, Randolph


    The volatile ester and alcohol profiles of ripening apple fruit from 184 germplasm lines in the USDA Malus Germplasm Repository at the New York Agricultural Experiment Station in Geneva, NY, USA, were evaluated. Cluster analysis suggested biochemical relationships exist between several ester classes. A strong linkage was revealed between 2-methylbutanoate, propanoate, and butanoate esters, suggesting the influence of the recently proposed "citramalic acid pathway" in apple fruit. Those lines with a high content of esters formed from 2-methylbutan-1-ol and 2-methylbutanoate (2MB) relative to straight-chain (SC) esters (high 2MB/SC ratio) exhibited a marked increase in isoleucine and citramalic acid during ripening, but those lines with a low content did not. Thus, the data were consistent with the existence of the hypothesized citramalic acid pathway and suggest that the Geneva Malus Germplasm Repository, appropriately used, could be helpful in expanding our understanding of mechanisms for fruit volatile synthesis and other aspects of secondary metabolism.

  2. New acylated flavone and cyanogenic glycosides from Linum grandiflorum

    DEFF Research Database (Denmark)

    Mohammed, Magdy M. D.; Christensen, Lars Porskjær; Ibrahim, Nabaweya A.


    The first investigation of Linum grandiflorum resulted in the isolation of one new acylated flavone O-diglycoside known as luteolin 7-O-a-D-(6000-E-feruloyl)glucopyranosyl (1!2)--D-glucopyranoside, and one new cyanogenic glycoside known as 2-[(30-isopropoxy-O--D-glucopyranosyl)oxy]-2-methylbutane...

  3. Adsorption and diffusion of alkanes in CuBTC crystals investigated using infra-red microscopy and molecular simulations

    NARCIS (Netherlands)

    Chmelik, C.; Kärger, J.; Wiebcke, M.; Caro, J.; van Baten, J.M.; Krishna, R.


    The adsorption and intra-crystalline diffusion of n-butane (nC4), iso-butane (iC4), 2-methylbutane (2MB), and 2,2-dimethylpropane (neoP) in CuBTC (Cu-3(BTC)(2) where BTC = benzene-1,3,5-tricarboxylate) has been investigated using infrared microscopy (IRM), combined with molecular simulations. Both e

  4. Quantitation and Enantiomeric Ratios of Aroma Compounds Formed by an Ehrlich Degradation of l-Isoleucine in Fermented Foods. (United States)

    Matheis, Katrin; Granvogl, Michael; Schieberle, Peter


    The conversion of parent free amino acids into alcohols by an enzymatic deamination, decarboxylation, and reduction caused by microbial enzymes was first reported more than 100 years ago and is today known as the Ehrlich pathway. Because the chiral center at the carbon bearing the methyl group in l-isoleucine should not be prone to racemization during the reaction steps, the analysis of the enantiomeric distribution in 2-methylbutanal, 2-methylbutanol, and 2-methylbutanoic acid as well as in the compounds formed by secondary reactions, such as ethyl 2-methylbutanoate and 2-methylbutyl acetate, are an appropriate measure to follow the proposed degradation mechanism in the Ehrlich reaction. On the basis of a newly developed method for quantitation and chiral analysis, the enantiomers of the five metabolites were determined in a great number of fermented foods. Whereas 2-methylbutanol occurred as pure (S)-enantiomer in nearly all samples, a ratio of almost 1:1 of (S)- and (R)-2-methylbutanal was found. These data are not in agreement with the literature suggesting the formation of 2-methylbutanol by an enzymatic reduction of 2-methylbutanal. Also, the enantiomeric distribution in 2-methylbutanoic acid was closer to that in 2-methylbutanol than to that found in 2-methylbutanal, suggesting that also the acid is probably not formed by oxidation of the aldehyde as previously proposed. Additional model studies with (S)-2-methylbutanal did not show a racemization under the conditions of food production or during workup of the sample for volatile analysis. Therefore, the results establish that different mechanisms might be responsible for the formation of aldehydes and acids from the parent amino acids in the Ehrlich pathway.

  5. Losartan Administration Reduces Fibrosis but Hinders Functional Recovery after Volumetric Muscle Loss Injury (United States)


    manifest irrecoverable deficits in force production . Losartan admin- istration at 10 mg·kg1·day1 was able to modulate the gene expres- sion of...embedded in a talcum-based gel and frozen in 2-methylbutane (Fisher Scientific) super-cooled in liquid nitrogen using standard methodology reported...containing peroxidase -conjugated goat anti-rabbit secondary antibody diluted 1:2,000. Membranes were rinsed six times in TBST before exposure to ECL

  6. Muscle Stem Cell Therapy for the Treatment of DMD Associated Cardiomyopathy (United States)


    stabilization by endothelial cell TIMP-2 and pericyte TIMP-3. The Journal of Cell Biology. October 9, 2006 2006;175(1):179-191. 33. Au P, Tam J, Fukumura D...intraventricular injection of 1M potassium chloride (KCl) and processed as formerly described.4-6 Harvested hearts were flash frozen in 2-methylbutane (Sigma...supplemented with propidium iodide (1:500, Sigma, St Louis, MO) to stain dead cells and either hydrogen peroxide (300 µmol/l; Sigma) or tumor necrosis

  7. Quantification of aroma compounds in Parmigiano Reggiano cheese by a dynamic headspace gas chromatography-mass spectrometry technique and calculation of odor activity value. (United States)

    Qian, Michael; Reineccius, G A


    Potentially important aroma compounds in Parmigiano Reggiano cheese were quantified. Free fatty acids were isolated with ion-exchange chromatography and quantified by gas chromatography. Neutral aroma compounds were quantified with a purge-trap/gas chromatography-mass spectrometry with selective mass ion technique. Odor activity values were calculated based on sensory thresholds reported in literature. The calculated odor activity values suggest that 3-methylbutanal, 2-methylpropanal, 2-methylbutanal, dimethyl trisulfide, diacetyl, methional, phenylacetaldehyde, ethyl butanoate, ethyl hexanoate, ethyl octanoate, acetic, butanoic, hexanoic, and octanoic acids are the most important aroma contributors to Parmigiano Reggiano cheese.

  8. Kinetic studies on the etherification of C5-alkenes to fuel ether tame


    Pääkkönen, Päivi


    Tertiary ethers are formed in reactions between alcohols and alkenes and are used in reformulated gasoline as octane-enhancing agents. By blending ethers into the gasoline pool, less ground-level ozone is formed and combustion of the gasoline is more efficient as a result of the oxygen boost. The main goal of this research was to study the synthesis of TAME (tert-amyl methyl ether, 2-methoxy-2-methylbutane) and to formulate a kinetic model as precise as possible for process design purpose...

  9. Identification of Halohydrins as Potential Disinfection By-Products in Treated Drinking Water

    Directory of Open Access Journals (Sweden)

    Karl J. Jobst


    It appears that DBP-A is 3-chloro-2-methylbutan-2-ol and that DBP-B is its bromo analogue. DBP-B has been detected in ozonated waters containing bromide. Our study also shows that these DBPs can be laboratory artefacts, generated by the reaction of residual chlorine in the sample with 2-methyl-2-butene, the stabilizer in the CH2Cl2 used for extraction. This was shown by experiments using CH2Cl2 stabilized with deuterium labelled 2-methyl-2-butene. Quenching any residual chlorine in the drinking water sample with sodium thiosulfate minimizes the formation of these artefacts.

  10. Surrogate fuel formulation for light naphtha combustion in advanced combustion engines

    KAUST Repository

    Ahmed, Ahfaz


    Crude oil once recovered is further separated in to several distinct fractions to produce a range of energy and chemical products. One of the less processed fractions is light naphtha (LN), hence they are more economical to produce than their gasoline and diesel counterparts. Recent efforts have demonstrated usage of LN as transportation fuel for internal combustion engines with slight modifications. In this study, a multicomponent surrogate fuel has been developed for light naphtha fuel using a multi-variable nonlinear constrained optimization scheme. The surrogate, consisting of palette species n-pentane, 2-methylhexane, 2-methylbutane, n-heptane and toluene, was validated against the LN using ignition quality tester following ASTM D6890 methodology. Comparison of LN and the surrogate fuel demonstrated satisfactory agreement.

  11. EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF); Scientific Opinion on Flavouring Group Evaluation 8, Revision 3 (FGE.08Rev3): Aliphatic and alicyclic mono-, di-, tri-, and polysulphides with or without additional oxygenated functional groups from chemical

    DEFF Research Database (Denmark)

    Larsen, John Christian; Nørby, Karin Kristiane; Beltoft, Vibe Meister

    The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to evaluate 70 flavouring substances in the Flavouring Group Evaluation 08, Revision 3, using the Procedure in Commission Regulation (EC) No 1565/2000. For the substan......The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to evaluate 70 flavouring substances in the Flavouring Group Evaluation 08, Revision 3, using the Procedure in Commission Regulation (EC) No 1565....../2000. For the substances 2-methylpropane-2-thiol [FL-no: 12.174], methyl methanethiosulphonate [FL-no: 12.159], 2-methylbutane-2-thiol [FL-no: 12.172] and 2,4,4-trimethyl-1,3-oxathiane [FL-no: 16.057] there is an indication of a genotoxic potential in vitro. Therefore, in the absence of further genotoxicity data...

  12. Metabolite production and kinetics of branched-chain aldehyde oxidation in Staphylococcus xylosus

    DEFF Research Database (Denmark)

    Beck, Hans Christian; Hansen, A.M.; Lauritsen, F.R.


    The metabolite production of the gram positive bacterium Staphylococcus xylosus when cultivated in a defined medium containing 18 amino acids, 6 vitamins and 2 purines was characterised. Several compounds not previously reported as metabolites of this organism were identified including 2......,5-methylpyrazine, 2-phenylethylacetate, 2-methyltetrahydrothiophen-3-one, 3-(methylthio)-propanoic acid and 3-(methylthio)-propanal. The organoleptic metabolites derived from branched-chain amino acid catabolism; 2-methylpropanal from valine, 2-methylbutanal from isoleucine and 3-methylbutanal from leucine were...... detected at levels ranging from 0.4 to 2.0μM. The concentrations of the corresponding carboxy acids were 963, 858 and 1486μM respectively. We demonstrated that α-ketoisocaproic acid was biotransformed to 3-methylbutanal which immediately was oxidised into 3-methylbutanoic acid. Kinetic studies...

  13. Wet scrubber analysis of volatile organic compound removal in the rendering industry. (United States)

    Kastner, James R; Das, K C


    The promulgation of odor control rules, increasing public concerns, and U.S. Environmental Protection Agency (EPA) air regulations in nonattainment zones necessitates the remediation of a wide range of volatile organic compounds (VOCs) generated by the rendering industry. Currently, wet scrubbers with oxidizing chemicals are used to treat VOCs; however, little information is available on scrubber efficiency for many of the VOCs generated within the rendering process. Portable gas chromatography/mass spectrometry (GC/MS) units were used to rapidly identify key VOCs on-site in process streams at two poultry byproduct rendering plants. On-site analysis was found to be important, given the significant reduction in peak areas if samples were held for 24 hr before analysis. Major compounds consistently identified in the emissions from the plant included dimethyl disulfide, methanethiol, octane, hexanal, 2-methylbutanal, and 3-methylbutanal. The two branched aldehydes, 2-methylbutanal and 3-methylbutanal, were by far the most consistent, appearing in every sample and typically the largest fraction of the VOC mixture. A chlorinated hydrocarbon, methanesulfonyl chloride, was identified in the outlet of a high-intensity wet scrubber, and several VOCs and chlorinated compounds were identified in the scrubbing solution, but not on a consistent basis. Total VOC concentrations in noncondensable gas streams ranged from 4 to 91 ppmv. At the two plants, the odor-causing compound methanethiol ranged from 25 to 33% and 9.6% of the total VOCs (v/v). In one plant, wet scrubber analysis using chlorine dioxide (ClO2) as the oxidizing agent indicated that close to 100% of the methanethiol was removed from the gas phase, but removal efficiencies ranged from 20 to 80% for the aldehydes and hydrocarbons and from 23 to 64% for total VOCs. In the second plant, conversion efficiencies were much lower in a packed-bed wet scrubber, with a measurable removal of only dimethyl sulfide (20-100%).

  14. Effects of dicarbonyl trapping agents, antioxidants, and reducing agents on the formation of furan and other volatile components in canned-coffee model systems. (United States)

    Zheng, Li Wei; Chung, Hyun; Kim, Young-Suk


    The formation of furan and certain volatiles related to furan formation mechanisms was studied using gas chromatography-mass spectrometry combined with solid-phase micro extraction after adding dicarbonyl trapping agents [epicatechin (EC), epigallocatechin gallate (EGCG), and catechin], water-soluble antioxidants (Trolox, caffeic acid, ferulic acid, and chlorogenic acid), fat-soluble antioxidants (α-tocopherol, BHT, and β-carotene), and reducing agents (glutathione and sodium sulfite) to canned-coffee model systems (CMS). The level of furan formation decreased significantly following the addition of EC (by 65.3%), EGCG (by 60.0%), and catechin (by 44.7%). In addition, the formation of Maillard reaction products, including furan derivatives (furfural and 5-methylfurfural), Strecker aldehyde (2-methylbutanal), pyrazines (2,6-dimethylpyrazine), and lipid oxidation products (including hexanal and 2-pentylfuran) was suppressed when any of the dicarbonyl trapping agents was added. Among the water-soluble antioxidants studied, chlorogenic acid most significantly decreased the furan level, by 67.0%, followed by ferulic acid (57.6%), Trolox (50.1%), and caffeic acid (48.2%) in the CMS. Chlorogenic acid also reduced the formation of furfural and lipid oxidation products. However, the addition of caffeic acid, ferulic acid, and chlorogenic acid decreased the generation of key coffee aroma components, such as Strecker aldehydes (2-methylpropanal and 2-methylbutanal), 5-methylfurfural, and pyrazines (2,6-dimethylpyrazine and 2-ethyl-5-methylpyrazine). Among the fat-soluble antioxidants, BHT and α-tocopherol decreased the furan level by 49.3% and 39.3%, respectively, while β-carotene increased the furan level by 34.8%. The addition of sodium sulfite and glutathione to CMS also led to considerable reductions in furan, of 64.1% and 44.9%, respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Biosynthesis of the cyanogenic glucosides linamarin and lotaustralin in cassava: isolation, biochemical characterization, and expression pattern of CYP71E7, the oxime-metabolizing cytochrome P450 enzyme. (United States)

    Jørgensen, Kirsten; Morant, Anne Vinther; Morant, Marc; Jensen, Niels Bjerg; Olsen, Carl Erik; Kannangara, Rubini; Motawia, Mohammed Saddik; Møller, Birger Lindberg; Bak, Søren


    Cassava (Manihot esculenta) is a eudicotyledonous plant that produces the valine- and isoleucine-derived cyanogenic glucosides linamarin and lotaustralin with the corresponding oximes and cyanohydrins as key intermediates. CYP79 enzymes catalyzing amino acid-to-oxime conversion in cyanogenic glucoside biosynthesis are known from several plants including cassava. The enzyme system converting oxime into cyanohydrin has previously only been identified in the monocotyledonous plant great millet (Sorghum bicolor). Using this great millet CYP71E1 sequence as a query in a Basic Local Alignment Search Tool-p search, a putative functional homolog that exhibited an approximately 50% amino acid sequence identity was found in cassava. The corresponding full-length cDNA clone was obtained from a plasmid library prepared from cassava shoot tips and was assigned CYP71E7. Heterologous expression of CYP71E7 in yeast afforded microsomes converting 2-methylpropanal oxime (valine-derived oxime) and 2-methylbutanal oxime (isoleucine-derived oxime) to the corresponding cyanohydrins, which dissociate into acetone and 2-butanone, respectively, and hydrogen cyanide. The volatile ketones were detected as 2.4-dinitrophenylhydrazone derivatives by liquid chromatography-mass spectrometry. A K(S) of approximately 0.9 μm was determined for 2-methylbutanal oxime based on substrate-binding spectra. CYP71E7 exhibits low specificity for the side chain of the substrate and catalyzes the conversion of aliphatic and aromatic oximes with turnovers of approximately 21, 17, 8, and 1 min(-1) for the oximes derived from valine, isoleucine, tyrosine, and phenylalanine, respectively. A second paralog of CYP71E7 was identified by database searches and showed approximately 90% amino acid sequence identity. In tube in situ polymerase chain reaction showed that in nearly unfolded leaves, the CYP71E7 paralogs are preferentially expressed in specific cells in the endodermis and in most cells in the first cortex

  16. Using generic pheromone lures to expedite identification of aggregation pheromones for the cerambycid beetles Xylotrechus nauticus, Phymatodes lecontei, and Neoclytus modestus modestus. (United States)

    Hanks, Lawrence M; Millar, Jocelyn G; Moreira, Jardel A; Barbour, James D; Lacey, Emerson S; McElfresh, J Steven; Reuter, F Ray; Ray, Ann M


    Males of several species of longhorned beetles in the subfamily Cerambycinae produce sex or aggregation pheromones consisting of 2,3-hexanediols and/or hydroxyhexanones. We tested the hypothesis that this diol/hydroxyketone pheromone motif is highly conserved within the subfamily, and the resulting prediction that multiple cerambycine species will be attracted to compounds of this type. We also tested the concept that live traps baited with generic blends of these compounds could be used as a source of live insects from which pheromones could be collected and identified. Traps placed in a mature oak woodland and baited with generic blends of racemic 2-hydroxyhexan-3-one and 3-hydroxyhexan-2-one captured adults of both sexes of three cerambycine species: Xylotrechus nauticus (Mannerheim), Phymatodes lecontei Linsley, and Phymatodes decussatus decussatus (LeConte). Odors collected from male X. nauticus contained a 9:1 ratio of two male-specific compounds, (R)- and (S)-3-hydroxyhexan-2-one. Field trials with synthetic compounds determined that traps baited with (R)-3-hydroxyhexan-2-one (94% ee), alone or in blends with other isomers, attracted similar numbers of X. nauticus of both sexes, whereas (S)-3-hydroxyhexan-2-one (94% ee) attracted significantly fewer beetles. Phymatodes lecontei and P. d. decussatus also were caught in traps baited with hydroxyhexanones, as well as a few specimens of two other cerambycine species, Neoclytus modestus modestus Fall (both sexes) and Brothylus gemmulatus LeConte (only females). Male N. m. modestus produced (R)-3-hydroxyhexan-2-one, which was not present in extracts from females. Neoclytus m. modestus of both sexes also responded to lures that included (R)-3-hydroxyhexan-2-one as one of the components. The only male-specific compound found in extracts from P. lecontei was (R)-2-methylbutan-1-ol, and adults of both sexes were attracted to racemic 2-methylbutan-1-ol in field bioassays. Surprisingly, P. lecontei of both sexes also

  17. 卢旺达产迷迭香化学成分研究 I%Chemical Constituents from Rwandan PlantRosmarinus officinalisL. (I)

    Institute of Scientific and Technical Information of China (English)

    TIWALADE Adegoke Adelakun; 李晓霞; 瞿璐; 陈玥; 王涛; 张祎


    为了解迷迭香(Rosmarinus officinaisL.)中的化学成分,从其95%乙醇提取物中分离得到了13种化合物,经波谱分析,分别鉴定为(Z)-3-hexenyl glucoside (1),(Z)-3-hexenylO-β-D-glucopyranosyl-(1′→6′)-β-D-glucopyranoside (2),erythritol-1-O-(6-O-trans-caffeoyl)-β-D-glucopyranoside (3),2,3,4,5-tetrahydroxyhexyl-6-O-trans-caffeoyl-β-glucopyranoside (4),1,2,3,4-tetrahydroxy-2-methylbutane-4-O-(6-O-trans-caffeoyl)-β-D-glucopyranoside (5),咖啡酸(6),迷迭香酸(7),methyl rosmarinate (8),methyl benzoate-4-β-glucoside (9),benzyl-β-D-glucopyranoside (10),benzyl-O-β-D-apiofuranosyl-(1→2)-β-D-glucopyranoside (11),1,2-di-O-β-D-glucopranosyl-4-allylbenzene (12)及(+)-syringaresinol-4′-O-β-D-glucopyranoside (13)。其中,化合物1~5和8~13为首次从迷迭香属分离得到,并修正了化合物13的波谱数据。%In order to understand the chemical constituents ofRosmarinus officinalis, 13 compounds were isolated from its 95% EtOH extract. On the basis of spectral data, their structures were identified as (Z)-3-hexenyl glucoside (1), (Z)-3-hexenylO-β-D-glucopyranosyl-(1′′→6′)-β-D-glucopyranoside (2), erythritol-1-O-(6-O-trans-caffeoyl)-β-D-glucopyranoside (3), 2,3,4,5-tetrahydroxyhexyl-6-O-trans-caffeoyl-β-glucopyranoside (4), 1,2,3,4-tetrahydroxy-2-methylbutane-4-O-(6-O-trans-caffeoyl)-β-D-glucopyranoside (5), caffeic acid (6), rosmarinic acid (7), methyl rosmarinate (8), methyl benzoate-4-β-glucoside (9), benzyl-β-D-glucopyranoside (10), benzyl-O-β-D-apiofuranosyl-(1→2)-β-D-glucopyranoside (11), 1,2-di-O-β-D-glucopranosyl-4-allylbenzene (12) and (+)-syringaresinol-4′-O-β-D-glucopyranoside (13). Among them, compounds1–5 and8–13 were isolated from theRosmarinusgenus for the ifrst time. For the known ones, the NMR data of compound13 was corrected.

  18. Exploratory and discriminative studies of commercial processed Brazilian coffees with different degrees of roasting and decaffeinated

    Directory of Open Access Journals (Sweden)

    Juliano Souza Ribeiro


    Full Text Available The fingerprints of the volatile compounds of 21 commercial Brazilian coffee samples submitted to different industrial processing i.e. decaffeinated or different roasting degrees (traditional and dark were studied. The volatiles were collected by headspace solid phase microextraction (HS-SPME and analyzed by GC-FID and GC-MS. The chromatographic data matrices (fingerprints obtained were explored by the principal component analysis (PCA and partial least squares - discriminative analysis (PLS-DA. Initially the chromatographic profiles were aligned by the algorithm correlation optimized warping (COW. The PCA showed the discrimination of the decaffeinated coffees from the others with both the SPME fibres used. This separation probably occurred due to the loss of some volatile precursors during the decaffeination process, such as sucrose. For both the fibres tested, PDMS/DVB and CX / PDMS SPME, the PLS-DA models correctly classified 100% of the samples according to their roasting degree: (medium and dark, the main differences being the concentrations of some of the volatile compounds such as 2-methyl furan, 2-methylbutanal, 2,3-pentanedione, pyrazine, 2-carboxyaldehyde pyrrole, furfural and 2-furanmethanol.

  19. Characterization of volatile aroma compounds in different brewing barley cultivars. (United States)

    Dong, Liang; Hou, Yingmin; Li, Feng; Piao, Yongzhe; Zhang, Xiao; Zhang, Xiaoyu; Li, Cheng; Zhao, Changxin


    Beer is a popular alcoholic malt beverage resulting from fermentation of the aqueous extract of malted barley with hops. The aroma of brewing barley impacts the flavor of beer indirectly, because some flavor compounds or their precursors in beer come from the barley. The objectives of this research were to study volatile profiles and to characterize odor-active compounds of brewing barley in order to determine the variability of the aroma composition among different brewing barley cultivars. Forty-one volatiles comprising aldehydes, ketones, alcohols, organic acids, aromatic compounds and furans were identified using solid phase microextraction combined with gas chromatography/mass spectrometry, among which aldehydes, alcohols and ketones were quantitatively in greatest abundance. Quantitative measurements performed by means of solvent extraction and calculation of odor activity values revealed that acetaldehyde, 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, hexanal, heptanal, octanal, nonanal, 3-methyl-1-butanol, cyclopentanol, 2,3-butanedione, 2,3-pentanedione, 2-heptanone, acetic acid, ethyl acetate, 2-pentylfuran and benzeneacetaldehyde, whose concentrations exceeded their odor thresholds, could be considered as odor-active compounds of brewing barley. Principal component analysis was employed to evaluate the differences among cultivars. The results demonstrated that the volatile profile based on the concentrations of aroma compounds enabled good differentiation of most barley cultivars. © 2014 Society of Chemical Industry.

  20. Lactose-hydrolyzed milk is more prone to chemical changes during storage than conventional ultra-high-temperature (UHT) milk. (United States)

    Jansson, Therese; Clausen, Morten R; Sundekilde, Ulrik K; Eggers, Nina; Nyegaard, Steffen; Larsen, Lotte B; Ray, Colin; Sundgren, Anja; Andersen, Henrik J; Bertram, Hanne C


    The enzymatic hydrolysis of lactose to glucose and galactose gives rise to reactions that change the chemistry and quality of ambient-stored lactose-hydrolyzed ultra-high-temperature (UHT) milk. The aim of the present study was to investigate and compare chemical changes in lactose-hydrolyzed and conventional UHT milk during a 9 month ambient storage period. Several complementary analyses of volatiles, free amino acids, acetate, furosine, and level of free amino terminals were concluded. The analyses revealed an increased level of free amino acids and an increased formation rate of specific compounds such as furosine and 2-methylbutanal in lactose-hydrolyzed UHT milk compared to conventional UHT milk during storage. These observations indicate more favorable conditions for Maillard and subsequent reactions in lactose-hydrolyzed milk compared to conventional UHT milk stored at ambient temperature. Furthermore, it is postulated that proteolytic activity from the lactase-enzyme preparation may be responsible for the observed higher levels of free amino acids in lactose-hydrolyzed UHT milk.

  1. Odor-Active (E -4-Methyl-3-hexenoic Acid in Roasted Coffee Generated in the Maillard Reactions of L-Isoleucine with Sugars

    Directory of Open Access Journals (Sweden)

    Hironari Miyazato


    Full Text Available This study describes a novel odor-active unsaturated aliphatic acid in roasted Brazilian Arabica coffee. (E-4-Methyl-3-hexenoic acid -4M3H, which is responsible for a sweaty odor, was identified for the first time using Gas Chromatography-Mass Spectrometry/Olfactometry (GC-MS/O, Aroma Extract Dilution Analysis (AEDA and Multidimensional Gas Chromatography-Mass Spectrometry (MDGC-MS; its (Z -isomer was also determined. Additionally, we conducted a model formation experiment to detect the presence of 4M3H in coffee and found that it may be produced nonstereoselectively in the Maillard reactions of L-isoleucine with sugars (xylose, fructose, glucose, rhamnose and sucrose. We also found that 2-methylbutanal derived from L-isoleucine and sugar degradation compounds such as α-dicarbonyl compounds (glyoxal, 2-oxopropanal, 2, 3-butanedione and 2, 3-pentanedione and α-hydroxy ketones (1-hydroxy-2-propanone and 3-hydroxy-2-butanone are key factors in the formation of 4M3H. Based on these results, we propose a series of potential nonstereoselective formation pathways for 4M3H.

  2. Characterization of the most odor-active compounds in an American Bourbon whisky by application of the aroma extract dilution analysis. (United States)

    Poisson, Luigi; Schieberle, Peter


    Application of the aroma extract dilution analysis (AEDA) on the volatile fraction carefully isolated from an American Bourbon whisky revealed 45 odor-active areas in the flavor dilution (FD) factor range of 32-4096 among which (E)-beta-damascenone and delta-nonalactone showed the highest FD factors of 4096 and 2048, respectively. With FD factors of 1024, (3S,4S)-cis-whiskylactone, gamma-decalactone, 4-allyl-2-methoxyphenol (eugenol), and 4-hydroxy-3-methoxy-benzaldehyde (vanillin) additionally contributed to the overall vanilla-like, fruity, and smoky aroma note of the spirit. Application of GC-Olfactometry on the headspace above the whisky revealed 23 aroma-active odorants among which 3-methylbutanal, ethanol, and 2-methylbutanal were identified as additional important aroma compounds. Compared to published data on volatile constituents in whisky, besides ranking the whisky odorants on the basis of their odor potency, 13 aroma compounds were newly identified in this study: ethyl (S)-2-methylbutanoate, (E)-2-heptenal, (E,E)-2,4-nonadienal, (E)-2-decenal, (E,E)-2,4-decadienal, 2-isopropyl-3-methoxypyrazine, ethyl phenylacetate, 4-methyl acetophenone, alpha-damascone, 2-phenylethyl propanoate, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, trans-ethyl cinnamate, and (Z)-6-dodeceno-gamma-lactone.

  3. Identification by gas chromatography-mass spectrometry of the volatile organic compounds emitted from the wood-rotting fungi Serpula lacrymans and Coniophora puteana, and from Pinus sylvestris timber. (United States)

    Ewen, Richard J; Jones, Peter R H; Ratcliffe, Norman M; Spencer-Phillips, Peter T N


    Volatile organic compounds (VOCs) emitted by two wood-rotting basidiomycete fungi, Serpula lacrymans (dry rot fungus) and Coniophora puteana (cellar fungus), and the timber of Pinus sylvestris (Scots pine), were identified. Several volatile collection techniques were employed including dichloromethane solvent extraction, solid-phase microextraction (SPME) and thermal desorption of VOCs entrained on Tenax GR. In addition, a new method of solid sample injection (SSI) is described which utilises a low injector temperature and an all-glass deactivated injector liner designed to minimise both the formation of pyrolysis products and analyte degradation. All the volatile compounds collected were analysed using electron impact capillary gas chromatography-mass spectrometry (GC-MS) on HP-5, HP-Innowax and beta-cyclodextrin columns. SSI and Tenax thermal desorption were found to be the most effective extraction methods. A total of 19 VOCs were observed from S. lacrymans grown on glass slides and pine, 15 from C. puteana grown on glass slides and 12 from P. sylvestris timber. S. lacrymans was found to emit, in low abundance, six unique VOCs, of which 2-methylbutanal was the greatest. The major volatile compound emitted by S. lacrymans was 1-octen-3-ol, which was also found in lower abundance from C. puteana. Six VOCs, including diethylene glycol and 4-methyl methylbenzoate, were found to be unique to C. puteana, all in medium abundance: From P. sylvestris, the major volatiles identified were S-alpha-pinene and 3-carene.

  4. Comparison of Aroma-Active Volatiles in Oolong Tea Infusions Using GC-Olfactometry, GC-FPD, and GC-MS. (United States)

    Zhu, JianCai; Chen, Feng; Wang, LingYing; Niu, YunWei; Yu, Dan; Shu, Chang; Chen, HeXing; Wang, HongLin; Xiao, ZuoBing


    The aroma profile of oolong tea infusions (Dongdingwulong, DDWL; Tieguanyin, TGY; Dahongpao, DHP) were investigated in this study. Gas chromatography-olfactometry (GC-O) with the method of aroma intensity (AI) was employed to investigate the aroma-active compounds in tea infusions. The results presented forty-three, forty-five, and forty-eight aroma-active compounds in the TGY, DHP, and DDWL infusions, including six, seven, and five sulfur compounds, respectively. In addition, the concentration of volatile compounds in the tea infusions was further quantitated by solid phase microextraction-gas chromatography (SPME)-GC-MS and SPME-GC-flame photometric detection (FPD). Totally, seventy-six and thirteen volatile and sulfur compounds were detected in three types of tea infusions, respectively. Quantitative results showed that forty-seven aroma compounds were at concentrations higher than their corresponding odor thresholds. On the basis of the odor activity values (OAVs), 2-methylpropanal (OAV: 230-455), 3-methylbutanal (1-353), 2-methylbutanal (34-68), nerolidol (108-184), (E)-2-heptenal (148-294), hexanal (134-230), octanal (28-131), β-damascenone (29-59), indole (96-138), 6-methyl-5-hepten-2-one (34-67), (R)-(-)-linalool (63-87), and dimethyl sulfide (7-1320) presented relatively higher OAVs than those of other compounds, indicating the importance of these compounds in the overall aroma of tea infusions.

  5. Characterization of the aroma signature of styrian pumpkin seed oil ( Cucurbita pepo subsp. pepo var. Styriaca) by molecular sensory science. (United States)

    Poehlmann, Susan; Schieberle, Peter


    Application of the aroma extract dilution analysis on a distillate prepared from an authentic Styrian pumpkin seed oil followed by identification experiments led to the characterization of 47 odor-active compounds in the flavor dilution (FD) factor range of 8-8192 among which 2-acetyl-1-pyrroline (roasty, popcorn-like), 2-propionyl-1-pyrroline (roasty, popcorn-like), 2-methoxy-4-vinylphenol (clove-like), and phenylacetaldehyde (honey-like) showed the highest FD factors. Among the set of key odorants, 2-propionyl-1-pyrroline and another 20 odorants were identified for the first time as constituents of pumpkin seed oil. To evaluate the aroma contribution in more detail, 31 aroma compounds showing the highest FD factors were quantitated by means of stable isotope dilution assays. On the basis of the quantitative data and odor thresholds determined in sunflower oil, odor activity values (OAV; ratio of concentration to odor threshold) were calculated, and 26 aroma compounds were found to have an OAV above 1. Among them, methanethiol (sulfury), 2-methylbutanal (malty), 3-methylbutanal (malty), and 2,3-diethyl-5-methylpyrazine (roasted potato) reached the highest OAVs. Sensory evaluation of an aroma recombinate prepared by mixing the 31 key odorants in the concentrations as determined in the oil revealed that the aroma of Styrian pumpkin seed oil could be closely mimicked. Quantitation of 11 key odorants in three commercial pumpkin seed oil revealed clear differences in the concentrations of distinct odorants, which were correlated with the overall aroma profile of the oils.

  6. Quality and flavour stability of coffee substitute prepared by extrusion of wheat germ and chicory roots. (United States)

    Fadel, H H M; Abdel Mageed, M A; Lotfy, S N


    A mixture of roasted chicory roots and wheat germ (1:1 w/w) was subjected to extrusion processing for preparation of coffee substitute. Comparative studies concerning sensory characteristics and headspace volatiles were carried out between genuine coffee and a freshly prepared coffee substitute. The sensory evaluation revealed similarities between the two samples. The comparative odour profile analysis showed that the sweetish/caramel-like note scored higher in our coffee substitute sample than in real coffee, whereas the other odour quality attributes showed an opposite trend. The high quality of the fresh coffee substitute was correlated to the presence of volatiles that are responsible for the fresh coffee aroma, such as: 2-methylbutanal, 3-methylbutanal, 2-methylfuran and 2,3-butanedione in high concentration. Storage of coffee substitute samples revealed a noticeable decrease in concentration of the Strecker aldehydes and diketones and a remarkable increase in phenolic compounds, whereas pyrazine and furan derivatives showed no linear changes during storage. The ratio of 2,3-butanedione/2-methylfuran (B/M) was used as an indicator for aging of coffee substitute samples. The variation in this ratio (B/M) during storage for 6 months was consistent with that of the odour profile analysis.

  7. Release and Formation of Oxidation-Related Aldehydes during Wine Oxidation. (United States)

    Bueno, Mónica; Carrascón, Vanesa; Ferreira, Vicente


    Twenty-four Spanish wines were subjected to five consecutive cycles of air saturation at 25 °C. Free and bound forms of carbonyls were measured in the initial samples and after each saturation. Nonoxidized commercial wines contain important and sensory relevant amounts of oxidation-related carbonyls under the form of odorless bound forms. Models relating the contents in total aldehydes to the wine chemical composition suggest that fermentation can be a major origin for Strecker aldehydes: methional, phenylacetaldehyde, isobutyraldehyde, 2-methylbutanal, and isovaleraldehyde. Bound forms are further cleaved, releasing free aldehydes during the first steps of wine oxidation, as a consequence of equilibrium shifts caused by the depletion of SO2. At low levels of free SO2, de novo formation and aldehyde degradation are both observed. The relative importance of these phenomena depends on both the aldehyde and the wine. Models relating aldehyde formation rates to wine chemical composition suggest that amino acids are in most cases the most important precursors for de novo formation.

  8. Severe drought stress is affecting selected primary metabolites, polyphenols, and volatile metabolites in grapevine leaves (Vitis vinifera cv. Pinot noir). (United States)

    Griesser, Michaela; Weingart, Georg; Schoedl-Hummel, Katharina; Neumann, Nora; Becker, Manuel; Varmuza, Kurt; Liebner, Falk; Schuhmacher, Rainer; Forneck, Astrid


    Extreme weather conditions with prolonged dry periods and high temperatures as well as heavy rain events can severely influence grapevine physiology and grape quality. The present study evaluates the effects of severe drought stress on selected primary metabolites, polyphenols and volatile metabolites in grapevine leaves. Among the 11 primary metabolites, 13 polyphenols and 95 volatiles which were analyzed, a significant discrimination between control and stressed plants of 7 primary metabolites, 11 polyphenols and 46 volatile metabolites was observed. As single parameters are usually not specific enough for the discrimination of control and stressed plants, an unsupervised (PCA) and a supervised (PLS-DA) multivariate approach were applied to combine results from different metabolic groups. In a first step a selection of five metabolites, namely citric acid, glyceric acid, ribose, phenylacetaldehyde and 2-methylbutanal were used to establish a calibration model using PLS regression to predict the leaf water potential. The model was strong enough to assign a high number of plants correctly with a correlation of 0.83. The PLS-DA provides an interesting approach to combine data sets and to provide tools for the specific evaluation of physiological plant stresses.

  9. An assessment of the role played by some oxidation-related aldehydes in wine aroma. (United States)

    Culleré, Laura; Cacho, Juan; Ferreira, Vicente


    The levels of important oxidation-related aldehydes, such as methional, phenylacetaldehyde, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, methylpropanal, 2-methylbutanal, and 3-methylbutanal, were determined in 41 different wines belonging to different types (young whites and reds, natural sparkling wines, oxidized young whites and reds, Sherry, aged red wines, Port wines). Except (E)-2-hexenal and (E)-2-heptenal, all of them could be found at levels above threshold. Different compositional patterns were identified: Sherry wines have large amounts of branched aldehydes but not of (E)-2-alkenals, wines exposed to oxygen can have large amounts of (E)-2-alkenals but not of branched aldehydes, while aged wine and Port have relatively large amounts of both classes of compounds. Different sensory tests confirmed the active sensory role of these compounds and revealed the existence of interactions (additive or synergic) between them and with other wine volatiles. (E)-2-Alkenals are related to flavor deterioration, while branched aldehydes enhance dried fruit notes and mask the negative role of (E)-2-alkenals.

  10. Methanogenic biodegradation of paraffinic solvent hydrocarbons in two different oil sands tailings. (United States)

    Mohamad Shahimin, Mohd Faidz; Siddique, Tariq


    Microbial communities drive many biogeochemical processes in oil sands tailings and cause greenhouse gas emissions from tailings ponds. Paraffinic solvent (primarily C5-C6; n- and iso-alkanes) is used by some oil sands companies to aid bitumen extraction from oil sands ores. Residues of unrecovered solvent escape to tailings ponds during tailings deposition and sustain microbial metabolism. To investigate biodegradation of hydrocarbons in paraffinic solvent, mature fine tailings (MFT) collected from Albian and CNRL ponds were amended with paraffinic solvent at ~0.1wt% (final concentration: ~1000mgL(-1)) and incubated under methanogenic conditions for ~1600d. Albian and CNRL MFTs exhibited ~400 and ~800d lag phases, respectively after which n-alkanes (n-pentane and n-hexane) in the solvent were preferentially metabolized to methane over iso-alkanes in both MFTs. Among iso-alkanes, only 2-methylpentane was completely biodegraded whereas 2-methylbutane and 3-methylpentane were partially biodegraded probably through cometabolism. 16S rRNA gene pyrosequencing showed dominance of Anaerolineaceae and Methanosaetaceae in Albian MFT and Peptococcaceae and co-domination of "Candidatus Methanoregula" and Methanosaetaceae in CNRL MFT bacterial and archaeal communities, respectively, during active biodegradation of paraffinic solvent. The results are important for developing future strategies for tailings reclamation and management of greenhouse gas emissions.

  11. Low-temperature catalytic oxidation of aldehyde mixtures using wood fly ash: kinetics, mechanism, and effect of ozone. (United States)

    Kolar, Praveen; Kastner, James R


    Poultry rendering emissions contain volatile organic compounds (VOCs) that are nuisance, odorous, and smog and particulate matter precursors. Present treatment options, such as wet scrubbers, do not eliminate a significant fraction of the VOCs emitted including, 2-methylbutanal (2-MB), 3-methylbutanal, and hexanal. This research investigated the low-temperature (25-160 degrees C) catalytic oxidation of 2-MB and hexanal vapors in a differential, plug flow reactor using wood fly ash (WFA) as a catalyst and oxygen and ozone as oxidants. The oxidation rates of 2-MB and hexanal ranged between 3.0 and 3.5 x 10(-9)mol g(-1)s(-1) at 25 degrees C and the activation energies were 2.2 and 1.9 kcal mol(-1), respectively. The catalytic activity of WFA was comparable to other commercially available metal and metal oxide catalysts. We theorize that WFA catalyzed a free radical reaction in which 2-butanone and CO(2) were formed as end products of 2-MB oxidation, while CO(2), pentanal, and butanal were formed as end products of hexanal oxidation. When tested as a binary mixture at 25 and 160 degrees C, no inhibition was observed. Additionally, when ozone was tested as an oxidant at 160 degrees C, 100% removal was achieved within a 2-s reaction time. These results may be used to design catalytic oxidation processes for VOC removal at poultry rendering facilities and potentially replace energy and water intensive air pollution treatment technologies currently in use.

  12. The gamma-ray spectra of 5-carbon alkane isomers in the positron annihilation process

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xiaoguang, E-mail:; Zhu, Yinghao; Liu, Yang


    The gamma-ray spectra of pentane (C{sub 5}H{sub 12}) and its two isomers, i.e., 2-Methylbutane (CH{sub 3}C(CH{sub 3})HC{sub 2}H{sub 5}) and 2,2-Dimethylpropane (C(CH{sub 3}){sub 4}) have been studied theoretically in the present work. The recent experimental gamma-ray spectra of these three molecules show that they have the same Doppler shifts, although their molecular structures are dramatically different. In order to reveal why the gamma-ray spectra of these molecules are less sensitive to the molecular structures, the one-dimensional gamma-ray spectra and spherically averaged momentum (SAM) distributions, the two-dimensional angular correlation of annihilation radiation (ACAR), and the three-dimensional momentum distributions of the positron–electron pair are studied. The one-centered momentum distributions of the electrons are found to play more important role than the multi-centered coordinate distributions. The present theoretical predictions have confirmed the experimental findings for the first time. The dominance of the inner valence electrons in the positron–electron annihilation process has also been suggested in the present work. - Highlights: • The structure effects only play a minor role in the one-dimension gamma-ray spectra. • The present study further confirms the dominance of the inner valence electrons in the positron–electron annihilation process. • The momentum distributions of the electrons play more important role than the coordinate distributions.

  13. New contributions to the photophysical model for all-trans-polyenes from ttbP4, a nonphotolabile octatetraene (United States)

    Catalán, Javier; Hopf, Henning; Martus, Mainrad


    All-trans-octatetraene 3,10-di(tert-butyl)-2,2,11,11-tetramethyl-3,5,7,9-dodecatetraene emits fluorescence in three different regions of the visible spectrum. Thus, it produces an extremely weak emission in the gas phase that can hardly be detected in the condensed phase; such an emission exhibits a negligible Stokes shift with respect to the 1Ag→1Bu absorption transition and can, in principle, be assigned to the 1Bu→1Ag emission for the compound. A second, structureless fluorescence emission, centered in the region of 525nm, is observed in the gas phase and at somewhat higher wavelengths in the condensed phase [viz., 570nm in 2-methylbutane (2MB) and 550nm in squalane (SQ)]. While detectable, this emission increases significantly, with no change in spectral position, as the solution temperature is lowered; also, it is abruptly replaced by a new, strongly blueshifted emission at ˜490nm in 2MB and 455mm in SQ when the viscosity of the medium exceeds a given level. The fact that the two fluorescence emissions considerably depart from the expected behavior for a 1Bu→1Ag emission in an all-trans-polyene, and that one disappears while the other simultaneously appears as the medium becomes more rigid, suggests that the two emissions are produced by two different molecular structures and that the rigidity of the medium switches their production from the originally excited all-trans 1Bu form. The observed spectral behavior is consistent with a recently proposed model [J. Catalan, Chem. Phys. 335, 69 (2007)] in which the 1Bu excited state of octatetraene can give two distinct molecular conformers as a result of twisting about different C-C single bonds.

  14. Kinetic modeling of mechanisms of industrially important organic reactions in gas and liquid phase

    Energy Technology Data Exchange (ETDEWEB)

    Vahteristo, K.


    This dissertation is based on 5 articles which deal with reaction mechanisms of the following selected industrially important organic reactions: 1. dehydrocyclization of n-butylbenzene to produce naphthalene, 2. dehydrocyclization of 1-(p-tolyl)-2-methylbutane (MB) to produce 2,6-dimethylnaphthalene, 3. esterification of neopentyl glycol (NPG) with different carboxylic acids to produce monoesters, 4. skeletal isomerization of 1-pentene to produce 2-methyl-1-butene and 2-methyl-2-butene. The results of initial- and integral-rate experiments of n-butylbenzene dehydrocyclization over selfmade chromia/alumina catalyst were applied when investigating reaction 2. Reaction 2 was performed using commercial chromia/alumina of different acidity, platina on silica and vanadium/calcium/alumina as catalysts. On all catalysts used for the dehydrocyclization, major reactions were fragmentation of MB and 1-(p-tolyl)-2-methylbutenes (MBes), dehydrogenation of MB, double bond transfer, hydrogenation and 1,6-cyclization of MBes. Minor reactions were 1,5-cyclization of MBes and methyl group fragmentation of 1,6- cyclization products. Esterification reactions of NPG were performed using three different carboxylic acids: propionic, isobutyric and 2-ethylhexanoic acid. Commercial heterogeneous gellular (Dowex 50WX2), macroreticular (Amberlyst 15) type resins and homogeneous para-toluene sulfonic acid were used as catalysts. At first NPG reacted with carboxylic acids to form corresponding monoester and water. Then monoester esterified with carboxylic acid to form corresponding diester. In disproportionation reaction two monoester molecules formed NPG and corresponding diester. All these three reactions can attain equilibrium. Concerning esterification, water was removed from the reactor in order to prevent backward reaction. Skeletal isomerization experiments of 1-pentene were performed over HZSM-22 catalyst. Isomerization reactions of three different kind were detected: double bond, cis

  15. Kinetic studies on the etherification of C5-alkenes to fuel ether tame

    Energy Technology Data Exchange (ETDEWEB)

    Paeaekkoenen, P.


    Tertiary ethers are formed in reactions between alcohols and alkenes and are used in reformulated gasoline as octane-enhancing agents. By blending ethers into the gasoline pool, less ground-level ozone is formed and combustion of the gasoline is more efficient as a result of the oxygen boost. The main goal of this research was to study the synthesis of TAME (tert-amyl methyl ether, 2-methoxy-2-methylbutane) and to formulate a kinetic model as precise as possible for process design purposes. The reaction rate was studied as a function of temperature and the reagents feed molar ratio with conventional ion-exchange resin beads and a novel fibrous ion-exchange catalyst. Kinetic modelling favoured the Langmuir-Hinshelwood type model, derived from a dual-site mechanism for the etherification. The influence of the acid capacity of the catalysts on the reaction rate was found to be second order. These results suggest that the etherification reactions occur via a dual-site mechanism. Comparison of the values of the kinetic parameters obtained with a fibre catalyst and with a bead catalyst indicated that diffusion limitations are associated with the latter. Therefore, mass transfer of the reacting components inside the pores of the cationic ion- exchange resin bead was estimated in terms of the effectiveness factors calculated from experiments with different resin bead sizes. It was concluded that mass transfer has to be taken into account when applying the kinetic model, which was derived for resin beads as the catalyst. High temperatures and high alcohol concentrations favoured the formation of the dialkyl ethers (dehydration) as a side reaction. When the reaction was maintained in a kinetic regime, it was highly selective for tert-etherification, since the rate of tert-etherification was 140 to 270 times that of dehydration. The experimental results were best described with a model in which one alcohol molecule is adsorbed and the other reacts from the liquid phase. The

  16. Hydrogen Abstraction from Hydrocarbons by NH2. (United States)

    Siddique, Kamal; Altarawneh, Mohammednoor; Gore, Jeff; Westmoreland, Phillip R; Dlugogorski, Bogdan Z


    This contribution investigates thermokinetic parameters of bimolecular gas-phase reactions involving the amine (NH2) radical and a large number of saturated and unsaturated hydrocarbons. These reactions play an important role in combustion and pyrolysis of nitrogen-rich fuels, most notably biomass. Computations performed at the CBS-QB3 level and based on the conventional transition-state theory yield potential-energy surfaces and reaction rate constants, accounting for tunnelling effects and the presence of hindered rotors. In an analogy to other H abstraction systems, we demonstrate only a small influence of variational effects on the rate constants for selected reaction. The studied reactions cover the abstraction of hydrogen atoms by the NH2 radical from the C-H bonds in C1-C4 species, and four C5 hydrocarbons of 2-methylbutane, 2-methyl-1-butene, 3-methyl-1-butene, 3-methyl-2-butene, and 3-methyl-1-butyne. For the abstraction of H from methane, in the temperature windows 300-500 and 1600-2000 K, the calculated reaction rate constants concur with the available experimental measurements, i.e., kcalculated/kexperimetal = 0.3-2.5 and 1.1-1.4, and the previous theoretical estimates. Abstraction of H atom from ethane attains the ratio of kcalculated/kexperimetal equal to 0.10-1.2 and 1.3-1.5 over the temperature windows of available experimental measurements, i.e., 300-900 K and 1500-2000 K, respectively. For the remaining alkanes (propane and n-butane), the average kexperimental/kcalculated ratio remains 2.6 and 1.3 over the temperature range of experimental data. Also, comparing the calculated standard enthalpy of reaction (ΔrH°298) with the available experimental measurements for alkanes, we found the mean unsigned error of computations as 3.7 kJ mol(-1). This agreement provides an accuracy benchmark of our methodology, affording the estimation of the unreported kinetic parameters for H abstractions from alkenes and alkynes. On the basis of the Evans

  17. Aqueous phase processing of secondary organic aerosol from isoprene photooxidation

    Directory of Open Access Journals (Sweden)

    Y. Liu


    Full Text Available Transport of reactive air masses into humid and wet areas is highly frequent in the atmosphere, making the study of aqueous phase processing of secondary organic aerosol (SOA very relevant. We have investigated the aqueous phase processing of SOA generated from gas-phase photooxidation of isoprene using a smog chamber. The SOA collected on filters was extracted by water and subsequently oxidized in the aqueous phase either by H2O2 under dark conditions or by OH radicals in the presence of light, using a photochemical reactor. Online and offline analytical techniques including SMPS, HR-AMS, H-TDMA, TD-API-AMS, were employed for physical and chemical characterization of the chamber SOA and nebulized filter extracts. After aqueous phase processing, the particles were significantly more hygroscopic, and HR-AMS data showed higher signal intensity at m/z 44 and a lower signal intensity at m/z 43, thus showing the impact of aqueous phase processing on SOA aging, in good agreement with a few previous studies. Additional offline measurement techniques (IC-MS, APCI-MS2 and HPLC-APCI-MS permitted the identification and quantification of sixteen individual chemical compounds before and after aqueous phase processing. Among these compounds, small organic acids (including formic, glyoxylic, glycolic, butyric, oxalic and 2,3-dihydroxymethacrylic acid (i.e. 2-methylglyceric acid were detected, and their concentrations significantly increased after aqueous phase processing. In particular, the aqueous phase formation of 2-methylglyceric acid and trihydroxy-3-methylbutanal was correlated with the consumption of 2,3-dihydroxy-2-methyl-propanal, and 2-methylbutane-1,2,3,4-tetrol, respectively, and an aqueous phase mechanism was proposed accordingly. Overall, the aging effect observed here was rather small compared to previous studies, and this limited effect could possibly be explained by the lower liquid phase OH

  18. Sensory and physicochemical evolution of tropical cooked peeled shrimp inoculated by Brochothrix thermosphacta and Lactococcus piscium CNCM I-4031 during storage at 8°C. (United States)

    Fall, Papa Abdoulaye; Pilet, Marie France; Leduc, François; Cardinal, Mireille; Duflos, Guillaume; Guérin, Camille; Joffraud, Jean-Jacques; Leroi, Françoise


    This study investigated the sensory quality and physicochemical evolution (pH, glucose, l-lactic acid, biogenic amine, free amino-acids and volatile compounds) during storage at 8°C of cooked peeled shrimp inoculated with the specific spoilage bacteria Brochothrix thermosphacta alone or mixed with the protective strain Lactococcus piscium CNCM I-4031. Growth of both bacteria was monitored at regular intervals during storage by microbial counts and the thermal temperature gradient gel electrophoresis (TTGE) technique. Bacterial counts showed that L. piscium and B. thermosphacta inoculated at 7 log CFU/g and 3 log CFU/g were well adapted to shrimp, reaching a maximum level of 9 log CFU/g after 4days and 10days respectively. In mixed culture, the growth of B. thermosphacta was reduced by 3.2±0.1 log CFU/g. The TTGE technique allowed monitoring the colonisation of the strains on the shrimp matrix and confirming the dominance of L. piscium in mixed culture throughout the experiment. Sensory analysis confirmed that B. thermosphacta spoiled the product after 11days, when its cell number attained 8 log CFU/g with the emission of strong butter/caramel off-odours. This sensory profile could be linked to the production of 2,3 butanedione, cyclopentanol, 3-methylbutanol, 3-methylbutanal, 2-methylbutanal, 4-methyl-3-chloro-3-pentanol and ethanol, which were produced in more significant quantities in the B. thermosphacta batch than in the batches in which the protective strain was present. On the contrary, TVBN and TMA were not suitable as quality indicators for B. thermosphacta spoilage activity. In the products where the protective L. piscium strain was present, no adverse effect on sensory quality was noted by the sensory panels. Moreover, biogenic amine assessment did not show any histamine or tyramine production by this strain, underlining its safety profile. Both strains produced lactic acid (1850mg/kg in L. piscium and B. thermosphacta batch on days 3 and 10

  19. 棕榈花、叶、茎挥发油成分及抑菌活性研究%Study on chemical components of the essential oils in flower, leaf and stem of Trachycarpus fortunei (Hook) H.Wendl.and their antimicrobial activities

    Institute of Scientific and Technical Information of China (English)

    卫强; 王燕红


    采用超临界二氧化碳萃取,应用气相色谱-质谱联用( GC-MS)法鉴定棕榈花、叶、茎挥发油化学成分,并考查其体外抗菌活性。结果显示,共鉴定得到224种化合物。棕榈花挥发油中主要有二十三烷(23.86%)、二十八烷(8.48%)等;棕榈叶挥发油中主要有(Z)-3-己烯-1-醇(15.87%)、正己醇(12.60%)、2,3-丁二醇(10.19%)、3-(1-乙氧乙氧基)-2-甲基丁烷-1,4-二醇(9.63%)、甲苯(9.60%)、2-乙氧基-3-氯丁烷(8.10%)等;棕榈茎挥发油中主要有甲苯(13.80%)、1,1-二乙氧基乙烷(25.77%)、2,3-丁二醇(10.65%)等。棕榈花、叶、茎的环己烷、乙醚萃取挥发油对特定病原菌有特殊抑菌效果,可作为抑菌剂使用。%In order to analyze the chemical components of essential oils in flower , leaf and stem of Trachycarpus for-tunei (Hook.) H.Wendl.and their biological activities , the volatile oils were extracted by supercritical CO 2 extrac-tion and were identified by GC-MS.The antimicrobial activities of the identified volatile oils were inspected in vitro. It was shown that 224 components were identified altogether .In flowers, main constituents of the identified volatile oils were tricosane (23.86%) and octacosane(8.48%).(Z)-3-hexen-1-ol (15.87%), 1-hexanol (12.60%), 2, 3-butanediol (10.19%), 3-(1-ethoxyethoxy)-2-methylbutane-1,4-diol (9.63%), toluene(9.60%) and 2-ethoxy-3-chlorobutane (8.10%) were the main volatile oils in the leaf, and toluene (13.80%), 1,1-diethoxy-ethane (25.77%) and 2,3-butanediol (10.65%) were the majority in stem.The extracted volatile oils from flower , leaf and stem by cyclonexane and aether exhibited special inhibiting activities against some pathogenic bacteria , which in-dicated their potential as bacteriostatic agent .