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PubMed2005

Identification of characteristic aroma-active compounds from water dropwort (Oenanthe javanica DC.).

Characteristic aroma components of water dropwort (Oenanthe javanica DC.) were evaluated by aroma extract dilution analysis and solid-phase microextraction-gas chromatography-olfactometry. Alpha-Terpinolene (plastic/cucumber-like) was the most intense aroma-active compound in water dropwort. Other potent aroma-active compounds included p-cymene (kerosene-like), alpha-terpinene (lemon), (E)-caryophyllene (woody), (Z,E)-alpha-farnesene (woody), hexanal (green), (Z)-3-hexenol (green), phenylacetaldehyde (honey), (E)-2-nonenal (cucumber), bornyl acetate (cooked vegetable), and gamma-terpinene (lemon). Of these, p-cymene was believed to be primarily responsible for the distinct kerosene-like aroma note of water dropwort. The aroma property of p-cymene was dependent on its concentration and was described as kerosene-like at relatively high concentrations but changed to citrus and green aroma notes at low concentrations.

Chromatography, Gas↗
PubMed2006

Characterization of volatile compounds of Mezcal, an ethnic alcoholic beverage obtained from Agave salmiana.

Commercial mezcals (white, white with worm, rested, rested with worm, and aged) produced from Agave salmiana were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). Thirty-seven compounds were identified, and nine of them were classified as major compounds of mezcal (MCM). Saturated alcohols, ethyl acetate, ethyl 2-hydroxypropanoate, and acetic acid form the MCM group. Minor compounds of mezcal group include other alcohols, aldehydes, ketones, large chain ethyl esters, organic acids, furans, terpenes, alkenes, and alkynes. Most of the compounds found in mezcals in this study are similar to those present in tequilas and other alcoholic beverages. However, mezcals contain unique compounds such as limonene and pentyl butanoate, which can be used as markers for the authenticity of mezcal produced from A. salmiana.

Agave↗
PubMed2006

Study of precursors responsible for off-flavor formation during storage of potato flakes.

Off-flavors frequently appear during the storage of potato flakes. Volatile profile analysis performed by solid-phase microextraction-gas chromatography-mass spectrometry revealed that hexanal is the main compound that appears during the storage period. Hexanal may be a degradation product of linoleic acid formed through linoleic acid hydroperoxide cleavage. Profiles of hexanal precursors were determined from potato flakes at different storage time points. Linoleic acid-derived oxylipins are predominant in potato flakes. The free oxylipins identified, in descending order, are as follows: hexanal, hydroxy polyunsaturated fatty (PUFAs), oxo PUFAs, divinyl ether PUFAs, and hydroperoxy PUFAs. However, the main oxylipins detected were esterified: esterified hydroxy, hydroperoxy, and oxo PUFAs. Oxylipins reveal different evolutions during the storage period. Chiral high-performance liquid chromatography analysis of the precursors of hexanal and other oxylipins revealed a racemic composition that supports the nonenzymatic formation of hexanal and most of the other oxylipins identified.

Aldehydes↗
PubMed2006

Changes in the enantiomeric distribution of selected volatile constituents of Mentha pulegium L. powders caused by hot water treatment.

The variation, in general, of the composition of the aromatic fraction and, in particular, of the enantiomeric composition of certain chiral volatile compounds of commercial Mentha pulegium L. powders caused by boiling water was evaluated. A comparison between the volatile profile of the studied herbs demonstrated that most M. pulegium L. samples contained high proportions of Mentha piperita L., even when this information was not specified on the label. Likewise, substantial changes in the volatile fraction of the infusions with respect to the composition of the original plant used in their preparation were found. The enantiomeric composition of some chiral compounds of the dried plant material, particularly limonene, was modified by adding hot water, whereas others were kept invariable. The results shown in this work reflect the need for the control of the composition of commercial powders and brews of M. pulegium L. to ensure their correct application.

Gas Chromatography-Mass Spectrometry↗
PubMed2006

Characterization of the chemical composition of a byproduct from siam benzoin gum.

The mixture of bark and gum obtained after size-grading of Siam benzoin gum was studied to establish its potential application as a valuable new grade of the balsamic resin. An analysis of its volatile constituents by means of static headspace and SPME led to the identification of 26 and 50 compounds, respectively. Significant differences were observed in both the headspace composition and olfactory properties of the byproduct as compared to those of Siam benzoin gum. This prompted the further analysis of its volatile extract and its resinoid by GC techniques, resulting in the identification of 60 (99.5%) and 16 (89.1%) components, respectively. To examine the influence of bark pieces, different extracts obtained from the raw material and from a sorted sample were analyzed by GC and HPLC techniques. The chemical compositions and the yields determined for the two resinoids lead to the conclusion that this harvesting byproduct is a new grade of Siam benzoin gum, providing interesting olfactory notes that differ from those of other grades.

Gas Chromatography-Mass Spectrometry↗
PubMed2002

Continuous monitoring of thermooxidative degradation products of polystyrene by membrane extraction with sorbent interface and gas chromatography.

A novel method for the continuous monitoring of thermooxidative degradation products of polystyrene by membrane extraction with sorbent interface (MESI) and gas chromatography (GC) is developed. The results are compared with solid-phase microextraction-GC, which can extract gases, vapors, and aerosols. The volatile and semivolatile degradation products are identified by mass spectrometry. The membrane used in the MESI-GC analysis shows a high permeation for volatile aromatic hydrocarbons; a low permeation for corresponding volatile aldehydes; and no permeation for less volatile alcohols, acids, and degradation products with a high molecular weight, thus reducing significantly the number of compounds detected from MESI-GC. Sensitivity of the method depends on the time of trapping, which is limited by the breakthrough of the trap. By heating the trap at fixed intervals of time, consecutive gas chromatograms are obtained.

Journal Article↗
PubMed2004

Determination of volatile organic compounds from truffles via SPME-GC-MS.

Volatile organic compounds (VOCs) of nine Tuber species and two corresponding forms are identified via solid-phase microextraction-gas chromatography-mass spectrometry analysis. Seventy-five compounds are identified. The most abundant are dimethylsulphide, 2- and 3-methylbutanal, 2-methylpropanol, and butanone.

Ascomycota↗
PubMed2006

Use of SPME-GC-MS in the study of time evolution of the constituents of saffron aroma: modifications of the composition during storage.

The effect of storage on the composition of saffron aroma is studied. Six samples of saffron from different areas of Italy are analyzed by solid-phase microextraction-gas chromatography-mass spectrometry. Samples 1, 2, and 3 are derived from cultivations of Crocus sativus in the zone of Salerno (Southern Italy) from 2000 to 2002. Samples 4, 5, and 6 are derived from cultivations in Sardinia, Italy (from 1998, 2000, and 2001, respectively). In all samples, 3,5,5-trimethyl-2-cyclohexen-1-one; 3,5,5-trimethyl-2-cyclohexen-1,4-dione; safranal; and 2,4,4-3,5,5-trimethyl-2-cyclohexen-1,4-dione; safranal; and 2,4,4-trimethyl-6-hydroxy-3-carboxaldehyde-2,5-cyclohexadien-1-one are found. 5,5-Dimethyl-2-methylene-1-carboxaldehyde-3-cyclohexene; 3,5,5-trimethyl-1,4-cyclohexandione; and beta-ionone are found with nonanal, dihydro-beta-ionone, and 2,6-di-t-butylphenol. Safranal is the main component in all of the samples. The most important changes are in the presence of alcohols and aldehydes and oxidation products of the major terpenoids components. Furthermore, the presence of safranal--the most important constituent of the flavor--changes during the time, increasing during 3 years, then decreasing after 5 years.

Crocus↗
PubMedDate not supplied

Tetrachloroethylene and trichloroethylene fatality: case report and simple headspace SPME-capillary gas chromatographic determination in tissues.

We describe a simple, precise, and sensitive assay of tetrachloroethylene and trichloroethylene in tissues, suitable both for emergency cases and forensic medicine. The method employs headspace solid phase microextraction-capillary gas chromatography and electron capture detection. The case is relative to a 45-year-old woman discovered unconscious in a laundry area. The concentrations of the solvents in tissues were determined and compared to other previously published fatalities.

Chromatography, Gas↗
PubMed2006

Organic contamination in dialysis water: trichloroethylene as a model compound.

BACKGROUND: Routine water monitoring in a haemodialysis centre revealed high trichloroethylene (TCE) concentrations. The aim of this study is to describe the measures adopted after organic contamination of dialysis water in order to avoid the possibility of patient exposure. We also carried out in vitro experiments to evaluate the accumulation of TCE in various devices normally used in a dialysis water treatment system (DWTS). METHODS: In vivo and in vitro blood and water TCE levels were determined by means of solid phase microextraction-gas chromatography/mass spectrometer. RESULTS: High TCE concentrations were found throughout the DWTS; acceptably low levels were obtained only by replacing the activated charcoal, ionic-exchange resins, microfilters and PVC pipes. The adsorption and realising capacities of these devices were tested in vitro, and the elimination curves made it possible to calculate the total percentage of the previously absorbed TCE mass released into the water. Evidence of exposure was confirmed by the relatively high TCE levels in the patient blood samples taken 30 days after the last exposure even if the subjects were asymptomatic. In vivo experiments showed that the blood gain of TCE through the low flux membrane during the course of dialysis was about 77+/-10.4% of the amount carried by dialysis fluid as calculated on the basis of its partition coefficient value (K(b/w) 3.75). CONCLUSIONS: This study shows that, when present in dialysis water, the lipophilic TCE contaminant can accumulate in various devices, thus transforming them into possible sources of exposure. This highlights the importance of periodically monitoring dialysis water for organic substances that have a great affinity to the blood compartment, in order to prevent occasional or chronic patient exposure.

Aged↗
PubMed2006

Evaluation of freeze-dried kefir coculture as starter in feta-type cheese production.

The use of freeze-dried kefir coculture as a starter in the production of feta-type cheese was investigated. Maturation of the produced cheese at 4 degrees C was monitored for up to 70 days, and the effects of the starter culture, the salting method, and the ripening process on quality characteristics were studied. The use of kefir coculture as a starter led to increased lactic acid concentrations and decreased pH values in the final product associated with significantly higher conversion rates compared to salted rennet cheese. Determination of bacterial diversity at the end of the ripening process in salted kefir and rennet cheeses by denaturing gradient gel electrophoresis technology, based on both DNA and RNA analyses, suggested a potential species-specific inhibition of members of the genera Staphylococcus and Psychrobacter by kefir coculture. The main active microbial associations in salted kefir cheese appeared to be members of the genera Pseudomonas and Lactococcus, while in salted rennet cheese, Oxalobacteraceae, Janthinobacterium, Psychrobacter, and Pseudomonas species were noted. The effect of the starter culture on the production of aroma-related compounds responsible for cheese flavor was also studied by the solid-phase microextraction-gas chromatography-mass spectrometry technique. Kefir coculture also appeared to extend the shelf life of unsalted cheese. Spoilage of kefir cheese was observed on the 9th and 20th days of preservation at 10 and 5 degrees C, respectively, while spoilage in the corresponding rennet cheese was detected on the 7th and 16th days. Microbial counts during preservation of both types of unsalted cheese increased steadily and reached similar levels, with the exception of staphylococci, which were significantly lower in unsalted kefir cheese. All types of cheese produced with kefir as a starter were approved and accepted by the panel during the preliminary sensory evaluation compared to commercial feta-type cheese.

Animals↗
PubMed1998

Characterization of metabolites in the biotransformation of 2,4,6-trinitrotoluene with anaerobic sludge: role of triaminotoluene.

The present study describes the biotransformation of 2,4,6-trinitrotoluene (TNT) (220 microM) by using anaerobic sludge (10%, vol/vol) supplemented with molasses (3.3 g/liter). Despite the disappearance of TNT in less than 15 h, roughly 0.1% of TNT was attributed to mineralization (14CO2). A combination of solid-phase microextraction-gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry identified two distinctive cycles in the degradation of TNT. One cycle was responsible for the stepwise reduction of TNT to eventually produce triaminotoluene (TAT) in relatively high yield (160 microM). The other cycle involved TAT and was responsible for the production of azo derivatives, e.g., 2,2',4,4'-tetraamino-6,6'-azotoluene (2,2',4, 4'-TA-6,6'-azoT) and 2,2',6,6'-tetraamino-4,4'-azotoluene (2,2',6, 6'-TA-4,4'-azoT) at pH 7.2. These azo compounds were also detected when TAT was treated with the anaerobic sludge but not with an autoclaved sludge, suggesting the biotic nature of their formation. When the anaerobic conditions in the TAT-containing culture medium were removed by aeration and/or acidification (pH 3), the corresponding phenolic compounds, e.g., hydroxy-diaminotoluenes and dihydroxy-aminotoluenes, were observed at room temperature. Trihydroxytoluene was detected only after heating TAT in water at 100 degrees C. When 13CH3-labeled TNT was used as the N source in the above microcosms, we were unable to detect 13C-labeled p-cresol or [13CH3]toluene, indicating the absence of denitration or deamination in the biodegradation process. The formation and disappearance of TAT were not accompanied by mineralization, suggesting that TAT acted as a dead-end metabolite.

Anaerobiosis↗
PubMed1998

Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp.

The psychorotrophic Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 degrees C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C10 to C21 alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5 degrees C. Mineralization of hexadecane at 5 degrees C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-dodecanol and 2-dodecanone, respectively) by solid-phase microextraction-gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis the A gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25 degrees C.

Alkanes↗
PubMed2006

Solid-liquid extraction fluorescence line narrowing spectroscopy of fluoroquinolones in aqueous samples.

We present a simple, selective, and sensitive method for the analysis of fluoroquinolones in water samples without previous separation. Octadecyl silica membranes are used with the dual purpose of sample preconcentration and solid substrate for fluorescence line narrowing spectroscopy. Measurements at liquid helium temperature (4.2 K) are easily made with the aid of a cryogenic fiber-optic probe. The entire procedure takes less than 15 minutes per sample and it consumes only 100 microL of organic solvent. Unambiguous fluoroquinolone determination is accomplished via wavelength-time matrices, which provide simultaneous information on spectral peak purity and fluorescence lifetime. We show that 10 mL of water sample are enough to detect analyte concentrations at parts-per-billion levels. The potential of this approach for the analysis of real world samples is demonstrated with the analysis of a synthetic mixture of seven fluoroquinolones spiked in a heavily contaminated water sample.

Algorithms↗
PubMed2004

Volatile free fatty acids as ripening indicators for Serra da Estrela cheese.

Serra da Estrela cheese is an artisanal cheese manufactured from raw ewe's milk coagulated with Cynara cardunculus; it is highly appreciated for its unique flavor and bouquet. This research effort focused on a search for the molecules responsible for those organoleptic characteristics. Eighty cheeses manufactured in 4 dairies located in the Appelation d'Origine Protegee region of Serra da Estrela, Portugal, were thus assayed for volatiles, in an attempt to characterize their odorous profile. Cheeses were analyzed from the time of manufacture up to 180 d of ripening. The volatile fraction was assayed by solid phase microextraction-gas chromatography/mass spectroscopy, and several compounds belonging to different chemical groups (e.g., fatty acids, esters, carbonyl compounds, pyrazines, and sulfur compounds) were detected in that traditional cheese. Among these, free fatty acids (FFA) were quantitatively the dominant family present. Furthermore, sensory descriptors for the typical aroma of this cheese included acidic, sweaty, and sheepy-like. Acetic, isobutyric, and isovaleric acids increased in concentration during the ripening process up to 90 d, and remained constant thereafter. Preliminary sensory analysis was performed by addition of the major FFA to an unripened cheese matrix; results showed that they could successfully be used as ripening indicators for this cheese. Such key molecules may thus be used to monitor ripening, and hence find the optimal consumption time for this gourmet dairy product.

Animals↗
PubMed2003

Enantiomeric distribution of chiral compounds in orange juices according to their geographical origins.

Chiral terpenes in nonprocessed orange juices of different geographical origins were examined by two different approaches: steam distillation-solvent extraction-gas chromatography-mass spectrometry (SDE-GC-MS) and solid-phase microextraction-gas chromatography (SPME-GC). The two sample preparation techniques were compared with regard to their effectiveness in determining the enantiomeric distributions of chiral compounds. Most target compounds exhibited constant enantiomeric ratios in all juices when either of the two approaches was used. Exceptions were found for terpinen-4-ol and beta-citronellol, whose of enantiomeric purity ratios varied significantly according to the geographical origin of the sample. These results may aid in guaranteeing the authenticity and thus the quality and safety of orange juice. A comparison between the two extraction procedures revealed SPME to be more reliable for stereochemical studies, since harsh experimental conditions that can bring about racemization are not required in such studies.

Beverages↗
PubMed2004

Effect of thermal treatment during processing of orange juice on the enantiomeric distribution of chiral terpenes.

Chiral terpenes in orange juices were examined by solid-phase microextraction-gas chromatography-mass spectrometry to study the dependence of their enantiomeric composition on the thermal treatment applied during the industrial manufacture. The experimental conditions used in the isolation and concentration of the compounds of interest produced relative standard deviations ranging from 2.9 to 15.1% when absolute areas were used and from 1.7 to 18.3% when normalized areas were used. Recovery varied between 8.8 and 56.1%, and detection limits ranged from 0.11 to 0.32 microg/ml. The enantiomeric compositions of the majority of the chiral terpenes varied within a reasonably narrow range. Nevertheless, the enantiomeric ratio of two monoterpene alcohols, alpha-terpineol and linalool, exhibited considerable variation according to the thermal treatment used in the manufacture of the juices. Therefore, the knowledge of the enantiomeric composition of alpha-terpineol and linalool might be useful for thermal treatment control purposes.

Beverages↗