Quantification Of Volatile Compounds Research Articles

Validation of a LLME/GC-MS Methodology for Quantification of Volatile Compounds in Fermented Beverages.

Knowledge of composition of beverages volatile fraction is essential for understanding their sensory attributes. Analysis of volatile compounds predominantly resorts to gas chromatography coupled with mass spectrometry (GC-MS). Often a previous concentration step is required to quantify compounds found at low concentrations. This work presents a liquid-liquid microextraction method combined with GC-MS (LLME/GC-MS) for the analysis of compounds in fermented beverages and spirits. The method was validated for a set of compounds typically found in fermented beverages comprising alcohols, esters, volatile phenols, and monoterpenic alcohols. The key requirements for validity were observed, namely linearity, sensitivity in the studied range, accuracy, and precision within the required parameters. Robustness of the method was also evaluated with satisfactory results. Thus, the proposed LLME/GC-MS method may be a useful tool for the analysis of several fermented beverages, which is easily implementable in a laboratory equipped with a GC-MS.

GC/MS chemical analysis of lavandin (Lavandula x intermedia) hydrolat: Successive extraction fractions

Hydrolats are valuable co-products of the essential oil distillation process, whose volatile compounds can be quantified by various methods. In this paper, we have tried to estimate the liquid-liquid extraction cycle number threshold for volatile compounds quantification of lavandin (Lavandula x intermedia) hydrolat. For this purpose, ten consecutive hydrolat extractions with n-hexane were analyzed GC/MS with hexadecane (C16) as an internal standard and compared with the lavandin essential oil. The chemical composition of the lavandin hydrolat showed similarity with its essential oil to the great extent, while volatile compounds dissolved in hydrolat exclusively belonged to the class of oxygenated monoterpenes. The total amount of extracted compounds has been estimated to 2174.2 mg/L, where the most dominant compounds in lavandin hydrolat were cisand trans-furanoid linalool oxide (676.3 and 634.1 mg/L, respectively), followed by much smaller amounts of linalool, camphor, and 1,8-cineole (167.6, 157.0, and 148.2 mg/L, respectively). Cumulative recoveries of total compounds yield after the third, fifth, and eighth extractions were 88 %, 96 %, and 99 %, respectively. Combined fraction analysis confirmed that in the first 5 cycles more than 95 % of the total yield (from 10 cycles) of extracted volatile compounds can be collected. Based on the results of this study, for volatile compounds quantification in lavandin hydrolat, 5 cycles of n-hexane liquid-liquid extraction can be recommended.

Stability of microencapsulated strawberry flavour by spray drying, freeze drying and fluid bed

The protection and stability of flavours is the great importance in the food industry in order to produce high-quality products. For this reason, the main goal of this paper was.to study the stability of a microencapsulated strawberry flavour using different encapsulating agents and drying techniques: spray drying, freeze drying and fluid bed. According to the quantification of volatile compounds, the blend MDs/Hi-Cap (9/1) at a fixed concentration of CDs (1.7%) was the most appropriate for microencapsulating the strawberry flavour. The best drying yield was observed in the case of freeze drying. In the case of the moisture content, spray drying samples presented the lowest values, followed by freeze drying and fluid bed. The study of stability at different temperatures and times revealed that the presence of CDs in the blend enabled a higher presence of volatile compounds in the powder than in its absence. Microphotographs showed smooth spherical particles in the case of spray drying, whereas the structure of the powder was amorphous, like glass, with freeze drying and irregular in the case of fluid bed.

Measurement of Off-Flavoring Volatile Compounds and Microbial Load as a Probable Marker for Keeping Quality of Pasteurized Milk

(1) Background: Multiple attempts have been conducted to correlate milk keeping quality with chemical, physical or bacteriological parameters. These methods only measure the chemical changes in milk produced by bacteria. Headspace solid-phase micro-extraction (HS-SPME) is an economic and recent method used to measure both volatile compounds and microbial load in milk, also allowing to keep the quality of the milk product. (2) Methods: The present study was conducted to identify and measure the off-flavoring volatile compounds through gas chromatography coupled with flame ionization detector (GC-FID) and the microbial load of pasteurized fluid milk stored at different temperatures, as a possible indicator of its keeping quality. (3) Results: The highest results were obtained to acetone, followed by butanone, pentanal and ethanol. These mean values were significantly enhanced from the 0 to 19th day of storage, at 10 °C. At day 19th, the minimum score for aroma, flavor and overall acceptability were also recorded as 4.33 ± 0.17, 4.02 ± 0.06, 4.00 ± 0.04, respectively. Likewise, maximum values for standard plate count (Log10 CFU 15.54 ± 0.40 mL−1) and total psychotroph count (Log10 CFU 11.67 ± 0.30mL−1) were reported at 10 °C and 4 °C. (4) Conclusion: HS-SPME/GC-FID methodology revealed to be very sensitive and capable to be applied in volatile compounds quantification in pasteurized milk produced during the storage period at different temperatures.

Variability in volatile compounds from lipoxygenase pathway in extra virgin olive oils from Tuscan olive germoplasm by quantitative SPME/GC-MS.

A quantitative method, based on SPME GC-MS, for the quantification of volatile compounds derived from lipoxygenase pathway, considered the most important for the aroma of high-quality olive oil, was developed. The method was used to study the variation within the extra virgin olive oils from 67 cultivars of the Tuscan olive germplasm conserved at "Santa Paolina" experimental farm (Follonica, Italy). A great variability was observed among the 67 cultivars both for the total amount of volatile compounds and for the different ratios between the groups of volatile compounds from common precursors. The aim was to obtain basic information on the characteristics and the quality of the oils obtainable from nonwidely cultivated olive varieties. These data can support the reintroduction in the production chain of old autochthonous varieties and for exploitation in breeding programs as a source of positive characters to transmit to the progeny.

Quantification of volatile compounds released by roasted coffee by selected ion flow tube mass spectrometry.

The major objective of this exploratory study was to implement selected ion flow tube mass spectrometry, SIFT-MS, as a method for the on-line quantification of the volatile organic compounds, VOCs, in the headspace of the ground roasted coffee. The optimal precursor ions and characteristic analyte ions were selected for real-time SIFT-MS quantification of those VOCs that are the most abundant in the headspace or known to contribute to aroma. NO+ reagent ion reactions were exploited for most of the VOC analyses. VOC identifications were confirmed using gas chromatography/mass spectrometry, GC/MS, coupled with solid-phase microextraction, SPME. Thirty-one VOCs were quantified, including several alcohols, aldehydes, ketones, carboxylic acids, esters and some heterocyclic compounds. Variations in the concentrations of each VOC in the seven regional coffees were typically less than a factor of 2, yet concentrations patterns characteristic of the different regional coffees were revealed by heat map and principal component analyses. The coefficient of variation in the concentrations across the seven coffees was typically below 24% except for furfural, furan, methylfuran and guaiacol. The SIFT-MS analytical method can be used to quantify in real time the most important odoriferous VOCs in ground coffee headspace to sufficient precision to reveal some differences in concentration patterns for coffee produced in different countries.

Identification and Quantification of Volatile Compounds Found in Vinasses from Two Different Processes of Tequila Production

Vinasses are the main byproducts of ethanol distillation and distilled beverages worldwide and are generated in substantial volumes. Tequila vinasses (TVs) could be used as a feedstock for biohydrogen production through a dark fermentative (DF) process due to their high content of organic matter. However, TV components have not been previously assayed in order to evaluate if they may dark ferment. This work aimed to identify and quantify volatile compounds (VC) in TV and determine if the VC profile depends upon the type of production process (whether the stems were initially cooked or not). TVs were sampled from 3 agave stems with a not-cooking (NC) process, and 3 agave stems with a cooking (C) process, and volatile compounds were determined by gas chromatography coupled with mass spectrometry (GC–MS). A total of 111 volatile compounds were identified, the TV from the cooking process (C) showed the higher presence of furanic compounds (furfural and 5-(hydroxymethyl) furfural) and organic acids (acetic acid and butyric acid), which have been reported as potential inhibitors for DF. To our knowledge, this is the first description of the VC composition from TVs. This study could serve as a base for further investigations related to vinasses from diverse sources.

Optimization of Headspace Solid-Phase Microextraction and Gas Chromatography Coupled with Mass Spectrometry Technique for the Quantification of Volatile Compounds in a Fresh Cheese (Oaxaca)

The Head Space Solid Phase Microextraction Method (HS-SPME), coupled with Gas Chromatography and Mass Spectrometry (GC-MS) was optimized to quantify Volatile Organic Compounds (VOC’s) in a fresh Oaxaca cheese during its shelf life of 22 days. Optimal extraction conditions were ascertained by means of a multiple linear regression analysis and the generation of a response surface. Conditions to reach the equilibrium of VOC’s at the headspace were established to be 30 minutes of ultrasonic agitation at 50°C. The conditions for extraction were exposure of the fiber at room temperature for 30 minutes. Optimal extraction of volatile compounds released by the Oaxaca cheese allowed identification of 21 volatile compounds: 8 acids, 1 alcohol, 4 aldehydes, 4 ketones, 1 ester, and 3 lactones. Quantification of VOC’s was carried out using the technique of standard addition. The limits of quantification ranged from 0.0033 to 0.0311 ng/μg. Ten compounds were identified with the heaviest concentration and are listed as follows, from heaviest to lightest: propionic acid, acetoin, acetic acid, diacetyl, capric acid, caprylic acid, δ-decalactone, δ-dodecalactone, γ-dodecalactone, butyraldehyde. During storage of the cheese, the most significant changes in the concentration of VOC’s took place between day 1 and day 15. Based on the results obtained, it can be concluded that the optimization of the SPME makes it possible to isolate and quantify VOC’s of fresh cheeses in an efficient and reproducible manner.

Experimental design-based isotope-dilution SPME-GC/MS method development for the analysis of smoke flavouring products

ABSTRACTFor the implementation of Regulation (EC) No 2065/2003 related to smoke flavourings used or intended for use in or on foods a method based on solid-phase micro extraction (SPME) GC/MS was developed for the characterisation of liquid smoke products. A statistically based experimental design (DoE) was used for method optimisation. The best general conditions to quantitatively analyse the liquid smoke compounds were obtained with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, 60°C extraction temperature, 30 min extraction time, 250°C desorption temperature, 180 s desorption time, 15 s agitation time, and 250 rpm agitation speed. Under the optimised conditions, 119 wood pyrolysis products including furan/pyran derivatives, phenols, guaiacol, syringol, benzenediol, and their derivatives, cyclic ketones, and several other heterocyclic compounds were identified. The proposed method was repeatable (RSD% <5) and the calibration functions were linear for all compounds under study. Nine isotopically labelled internal standards were used for improving quantification of analytes by compensating matrix effects that might affect headspace equilibrium and extractability of compounds. The optimised isotope dilution SPME-GC/MS based analytical method proved to be fit for purpose, allowing the rapid identification and quantification of volatile compounds in liquid smoke flavourings.

Determination of flavor constituents in particular types of flour and derived pasta by heart-cutting multidimensional gas chromatography coupled with mass spectrometry and multiple headspace solid-phase microextraction

A Multiple Headspace Solid-Phase Microextraction (MHS-SPME) method was optimized for the isolation and quantification of volatile compounds from samples of flour and pasta, obtained from buckwheat and Khorasan wheat. In a second step, SPME extracts were analyzed by means of a Multidimensional Gas Chromatographic (MDGC) system, operated in both “stand-by” and “heart-cutting” modes. The first dimension was equipped with a non polar column and an FID detector; the second dimension was provided with a modified β-cyclodextrin stationary phase and mass spectrometric detector. Such instrumental apparatus, under accurately optimized conditions, allowed to obtain detailed fingerprints with the definition of markers of quality and traceability among the various samples investigated. Some volatiles (i.e. 3,4-hexanedione, hexanal, 1-octen-3-ol, 2-pentylfuran, germacrene D) were commonly present in all the samples, some others (i.e. undecanal, γ-nonalactone, neryl acetone) only in one cereal species. In addition, the determination of enantiomeric ratios of optically active volatiles was successfully carried out, with the separation of 14 enantiomer pairs. Fifty % of chiral components showed an almost racemic composition, while the remaining pairs evidenced a predominance of the levorotatory enantiomer. Quantification of key volatiles was performed through MHS-SPME, a calibration methodology specifically developed for headspace analysis, which allowed to determine 3,4-hexanedione (2.2 · 10−3 g/kg), 2-pentylfuran (3.4 · 10−3 g/kg) and germacrene D (4.2 · 10−3 g/kg), as major compounds.

IOFI recommended practice for the use of predicted relative‐response factors for the rapid quantification of volatile flavouring compounds by GC‐FID

AbstractThis recommended practice enables the quantification of volatile compounds in flavourings to be made by gas chromatography with flame‐ionization detection, without having authentic compounds available, and also in many cases it can avoid time‐consuming calibration procedures. The relative‐response factors (RRF) can be predicted from the molecular formula of the compound, and this approach can be applied to compounds containing the atoms C, H, O, N, S, F, Cl, Br, I, and Si, providing that the molecular formula and number of benzene rings in the analytes are known. The purity of chemically‐defined flavouring substances or chromatographic standards can also be estimated using these predicted RRF, and this procedure can also be used to quantify (poly)hydroxylated compounds, after their derivatization into trimethylsilyl ethers or esters. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Selected Ion Flow-Drift Tube Mass Spectrometry: Quantification of Volatile Compounds in Air and Breath

A selected ion flow-drift tube mass spectrometric analytical technique, SIFDT-MS, is described that extends the established selected ion flow tube mass spectrometry, SIFT-MS, by the inclusion of a static but variable E-field along the axis of the flow tube reactor in which the analytical ion-molecule chemistry occurs. The ion axial speed is increased in proportion to the reduced field strength E/N (N is the carrier gas number density), and the residence/reaction time, t, which is measured by Hadamard transform multiplexing, is correspondingly reduced. To ensure a proper understanding of the physics and ion chemistry underlying SIFDT-MS, ion diffusive loss to the walls of the flow-drift tube and the mobility of injected H3O(+) ions have been studied as a function of E/N. It is seen that the derived diffusion coefficient and mobility of H3O(+) ions are consistent with those previously reported. The rate coefficient has been determined at elevated E/N for the association reaction of the H3O(+) reagent ions with H2O molecules, which is the first step in the production of H3O(+)(H2O)1,2,3 reagent hydrate ions. The production of hydrated analyte ion was also experimentally investigated. The analytical performance of SIFDT-MS is demonstrated by the quantification of acetone and isoprene in exhaled breath. Finally, the essential features of SIFDT-MS and SIFT-MS are compared, notably pointing out that a much lower speed of the flow-drive pump is required for SIFDT-MS, which facilitates the development of smaller cost-effective analytical instruments for real time breath and fluid headspace analyses.

Prediction of response factors for gas chromatography with flame ionization detection: Algorithm improvement, extension to silylated compounds, and application to the quantification of metabolites.

We previously showed that the relative response factors of volatile compounds were predictable from either combustion enthalpies or their molecular formulae only 1. We now extend this prediction to silylated derivatives by adding an increment in the ab initio calculation of combustion enthalpies. The accuracy of the experimental relative response factors database was also improved and its population increased to 490 values. In particular, more brominated compounds were measured, and their prediction accuracy was improved by adding a correction factor in the algorithm. The correlation coefficient between predicted and measured values increased from 0.936 to 0.972, leading to a mean prediction accuracy of ± 6%. Thus, 93% of the relative response factors values were predicted with an accuracy of better than ± 10%. The capabilities of the extended algorithm are exemplified by (i) the quick and accurate quantification of hydroxylated metabolites resulting from a biodegradation test after silylation and prediction of their relative response factors, without having the reference substances available; and (ii) the rapid purity determinations of volatile compounds. This study confirms that Gas chromatography with a flame ionization detector and using predicted relative response factors is one of the few techniques that enables quantification of volatile compounds without calibrating the instrument with the pure reference substance.

Volatile Composition, Antimicrobial and Antioxidant Properties of Different Parts from Elaeagnus angustifolia L.

:This study deals with the chemical composition, antimicrobial and antioxidant activities of fruit, flower, leaf and fruit peel from Elaeagnus angustifolia L. growing in Malatya province (Turkey). Identification and quantification of volatile compounds were performed on HS/SPME GC/MS. A total of 53 compounds were identified in all parts of the plant. Metabolic extracts from flower and leaf extracts exhibited the highest antimicrobial activity against Gram positive bacteria with minimum inhibitory concentrations (MIC) ranged from 62.5 to 500 µg/mL. Fruit and flower extracts have the highest antioxidant activity with values ranged from 0.03 to 4.64 for 2.22-azinobis-[3-ethylbenzthiazoline-6-sulphonic acid] (ABTS) assay and from 0.54 to 4.45 µg trolox equivalent antioxidant capacity/g dry weights (DWs) for 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. Among the plant parts, the lowest and the highest total phenolic contents were found in fruit extracts with the values ranged from 0.12 to 6.39 µg gallic acid equivalents/g DW, respectively.

Online clean‐up of volatile compounds in complex matrices for GC‐MS quantification: testing with fragranced consumer products

ABSTRACTThe quantification of volatile compounds in cosmetic products or raw materials remains problematic because of the complexity of the matrices. Two approaches were investigated on the basis of a full vaporization of analytes from a sample deposited on a cylinder of polydimethylsiloxane (PDMS) foam: (1) an internal standardization using the same calibration curve for all samples, which gives rise to unexplained peak magnifications that biases the determinations, and (2) a standard addition protocol. The latter was tested for the analysis of suspected allergens and allowed the quantification of all compounds except farnesol and Lyral®. A decision tree was proposed to ascertain peak identity and the validity of the regression curve. Using this strategy in the range of 50–100 mg/l, 91% of all individual results (except farnesol and Lyral®) in all matrices fell within a tolerance interval of ±25%. In addition, the use of disposable PDMS cylinders allowed 400 injections without polluting the injector or the column. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Characterization of aroma compounds in Portuguese extra virgin olive oils from Galega Vulgar and Cobrançosa cultivars using GC–O and GC × GC–ToFMS

Aroma compounds of virgin olive oils extracted from two olive cultivars – Galega Vulgar and Cobrançosa – grown in Beira Baixa region in central Portugal were investigated. Gas chromatography–olfactometry (GC–O) was carried out to select the important odorants for subsequent comprehensive gas chromatography/time of flight mass spectrometry (GC×GC–ToFMS) analysis. By GC–O fifteen odorants were identified. For the quantification of volatile compounds, headspace solid phase microextraction (SPME) technique was optimized. Under optimized conditions, 22 volatile compounds were quantified in all samples. Trans-2-hexenal was the most abundant compound. A discriminant analysis (DA) was used to discriminate among olive oil samples obtained from olives of the two cultivars with different harvest time/ripening stages. Concerning the harvesting time and cultivar, nine volatiles showed to have discriminant power among samples, namely heptanal, trans-2-hexenal, 1-octen-1-ol, nonanal, 2,3-butanedione, ethyl-2-methylbutyrate, hexanal, cis-3-hexenylacetate and 3-methylbuthylacetate.

Real time monitoring of population dynamics in concurrent bacterial growth using SIFT-MS quantification of volatile metabolites

Population dynamics of three different bacterial species, Serratia rubidaea (R), Serratia marcescens (F) and Escherichia coli (Ec), growing in single or mixed populations in liquid media, was monitored by real time headspace quantification of volatile compounds using selected ion flow tube mass spectrometry, SIFT-MS. The three bacterial species interact with each other in a competitive fashion in a way similar to the game "rock-paper-scissors" (R-Ec-F). The concentrations of volatile metabolites (ammonia, ethanol, acetaldehyde, propanol, acetoin, acetone and acetic acid) were measured in the headspace of the individual species and of their mixtures continuously for 24 hour periods. The results demonstrate that dynamics in bacterial cultures can be monitored using SIFT-MS in real time.

Chemical composition and volatile compounds in the artisanal fermentation of mezcal in Oaxaca, Mexico

The differences among the several varieties of mezcal produced in Mexico, besides the Agave species, consist essentially in the individuality of the traditional methods used in the elaboration or fermentation process. Therefore, it is necessary to understand the artisanal fermentation processes and to make clear the factors and management practices that have an influence on the chemical composition. Two mezcal artisanal factories of Agave angustifolia Haw. under two fermentation seasons were investigated in Oaxaca, Mexico. Volatile compounds were analyzed using a gas chromatograph and a capillary column HP-FFAP. Reference standards were used for the identification and quantification of volatile compounds. Samples were successfully separated, and the main volatile compounds identified corresponded to ethyl acetate, ethanol, methanol, 3-methyl-1-butanol, propanol, 2-methyl-1-propanol, and acetic acid. The chemical composition of the artisanal fermentation process differs significantly from factory to factory, season to season, and the interaction between the factories in which the fermentation process takes place and the seasons. Addition of ammonium sulfate reduces the fermentation time and affects significantly the production of ethanol, propanol and butanol, but decreases the methanol, ethyl acetate, and acetic acid production, and this practice is more convenient in fall than in spring. Key words : Fermentation, ammonium sulfate, volatile compounds, higher alcohol, gas chromatography, mezcal.

Modeling Volatile Organic Compounds Released by Bovine Fresh Meat Using an Integration of Solid Phase Microextraction and Databases

The influence of volatile organic compounds is often regarded as a critical factor of food flavor quality. Nevertheless, information about the biochemical origin of odorants is not totally available. Quantification of volatile compounds in meat is not easy, but a new approach that helps is the use of GC/MS–SPME. This technique can generate large-scale data sets that allow for the development of computational technologies for better integration and biochemical interpretation. Volatile organic compounds of bovine fresh meat samples were measured by GC/MS–SPME, using four SPME fibers. The compounds were analyzed using an integration of chemical and biological database systems (NIST and KEGG, respectively). Twelve metabolic pathways were identified. A metabolic network model was constructed using graph elements, linking pathways through a central branch mediated by glycolysis. Experimental data indicated that post-mortem glycolysis is associated with the release of volatile compounds in fresh meat. The proposed technique could be used to study possible sources of biochemical compounds in meat to be applied in food analysis.

Quantification of volatile compounds in Chinese soy sauce aroma type liquor by stir bar sorptive extraction and gas chromatography–mass spectrometry

Considering the important of aroma compounds on the quality of baijiu, stir bar sorptive extraction (SBSE) coupled with gas chromatography-mass spectrometry was applied to the aromas analysis of baijiu (Chinese liquor). Based on the results of optimization, a total of 76 volatile compounds were identified from 14 Chinese liquors, including 25 esters, 10 alcohols, 9 aldehydes and ketones, 8 aromatic compounds, 5 furans, 3 nitrogen-containing compounds, 6 acids, 4 phenols, 3 terpenes, 1 sulfide-containing compound, 1 lactone, and 1 acetal. By principal component analysis based on quantification results, 14 Chinese liquor samples could be classified into three groups. SBSE is a fast, simple, effective, and reliable method for extracting volatile compounds from Chinese liquor. The chemometrics approach revealed that LJ liquor with soy sauce aroma could exhibit more prominent sauce flavor through extending the time of storage, and its peculiar manufacturing practice was responsible for the soy sauce flavor.