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Rapid fingerprinting of grape volatile composition using secondary electrospray ionization orbitrap mass spectrometry: A preliminary study of grape ripening
... Over the past two decades, the mass spectrometry-based methodologies such as proton-transfer-reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS), in addition to the gold-standard gas chromatography-mass spectrometry (GC-MS), have been used for the detection and analysis of gas-phase volatile organic compounds (VOCs) [1][2][3][4]. In recent years, secondary electrospray ionization mass spectrometry (SESI-MS) has also emerged for the studies of gas-phase VOCs from yeast, plant, bacteria, and breath [5][6][7][8]. SESI-MS is a real-time, non-invasive, and sensitive technique with a reported limit of detection at as low as 0.2 parts per trillion by volume (ppt) [9]. In addition, SESI coupling to high-resolution mass spectrometry (HRMS) has been shown to enhance the capability to capture as many VOC metabolites as possible in real-time mass spectrometric analysis [10]. ...
... Despite the fact that such limitation of unseparated isomers has been observed in the use of SESI-MS, cumulative numbers of studies across various fields demonstrated the promising bioanalytical potentials of SESI-MS for studying headspace volatilome present in relatively low concentrations, in comparison to standard analytical tools [2,[5][6][7]. Typically, a headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME/GC-MS) technique requires up to one hour for extraction and analysis [50]. ...
Gut microbiota plays essential roles in maintaining gut homeostasis. The composition of gut microbes and their metabolites are altered in response to diet and remedial agents such as antibiotics. However, little is known about the effect of antibiotics on the gut microbiota and their volatile metabolites. In this study, we evaluated the impact of a moderate level of ampicillin treatment on volatile fatty acids (VFAs) of gut microbial cultures using an optimized real-time secondary electrospray ionization coupled with high-resolution mass spectrometry (SESI-HRMS). To evaluate the ionization efficiency, different types of electrospray solvents and concentrations of formic acid as an additive (0.01, 0.05, and 0.1%, v/v) were tested using VFAs standard mixture (C2–C7). As a result, the maximum SESI-HRMS signals of all studied m/z values were observed from water with 0.01% formic acid than those from the aqueous methanolic solutions. Optimal temperatures of sample inlet and ion chamber were set at 130 °C and 85 °C, respectively. SESI spray pressure at 0.5 bar generated the maximum intensity than other tested values. The optimized SESI-HRMS was then used for the analysis of VFAs in gut microbial cultures. We detected that the significantly elevated C4 and C7 VFAs in the headspace of gut microbial cultures six hours after ampicillin treatment (1 mg/L). In conclusion, our results suggested that the optimized SESI-HRMS method can be suitable for the analysis of VFAs from gut microbes in a rapid, sensitive, and non-invasive manner.
... Fragmentation pathway studies support the identification and confirmation of suspect and new related unknown compounds, which can be later selected as future targeted compounds for specific applications. Nevertheless, even single HRMS analyzers do not provide fragmentation data of the detected ions; metabolomics is able to sort out authenticity problems with tentative identification of the most abundant compounds using fingerprinting strategies (Farrell et al., 2017). Most of these studies acquire mass spectral data using both positive and negative ion modes in order to obtain as much as possible information from food samples (Bean et al., 2015;Pereira et al., 2016;Vaclavik et al., 2015). ...
Modern food laboratories are demanding fast screening methods to display a wide range of compounds present at low concentration levels in a large number of complex food samples. For these laboratories, sample treatment and chromatographic separations are often their bottlenecks. The development of ambient ionization mass spectrometry (AIMS) techniques may overcome some of these difficulties, as they allow a rapid, real-time, high-throughput, and in situ analysis of solids, liquids, and gases without the need of rigorous sample treatments. Since the development of the two first AIMS techniques (desorption electrospray ionization and direct analysis in real time), a large number of new ambient ionization strategies have emerged, and nowadays, there are a wide of AIMS techniques available that relay on combining in situ sample processing with different ionization mechanisms. This chapter highlights and assesses the application of AIMS techniques for the analysis of food samples. The fundamentals of AIMS techniques most commonly used for the direct analysis of food are included, and the critical aspects of each technique are commented on. Capabilities and the applicability of these techniques for the rapid screening of both target and nontarget compounds in the food field, as well as new approaches for the on-site analysis, are also discussed.
... A subset of these higher alcohols are comprised of six carbons. C 6 -alcohols such as 1-hexanol, (Z)-3-hexenol and (E)-3-hexenol can reach very high concentrations in Pinot noir grapes and are often associated with "cut-grass" aromas (Farrell et al. 2017;Yuan and Qian 2016b). However, in wine they do not seem to reach concentrations high enough to be perceived (Song et al. 2015;Tomasino et al. 2015). ...
Vitis vinifera L. Pinot noir still wines are some of the most popular and expensive red wines in the world. Several research articles are reported in literature concerning the impacts of viticultural and enological practices, and vineyard location, on Pinot noir still wine aroma. This review summarizes the previous and latest literature pertaining to volatile compounds including esters, higher alcohols and C13-norisoprenoids, and their effect on Pinot noir wine perceived aroma. Their origin and behavior are discussed, as well as their role in regional differentiation. The first part of this review paper presents an overview of volatile compounds that are usually found in Pinot noir still wines at concentrations higher than their odor detection threshold. The second part deals with studies pertaining to human inputs that impact on Pinot noir wine aroma profile such as viticulture and winemaking interventions. The role of the vineyard site is also revised. This review concludes by considering what further opportunities are available to researchers in this field for greater control over Pinot noir wine quality outcomes.
... A subset of these higher alcohols are comprised of six carbons. C 6 -alcohols such as 1-hexanol, (Z)-3-hexenol and (E)-3-hexenol can reach very high concentrations in Pinot noir grapes and are often associated with "cut-grass" aromas (Farrell et al. 2017;Yuan and Qian 2016b). However, in wine they do not seem to reach concentrations high enough to be perceived (Song et al. 2015;Tomasino et al. 2015). ...
Vitis vinifera L. Pinot noir still wines are some of the most popular and expensive red wines in the world. Several research articles are reported in literature concerning the impacts of viticultural and enological practices, and vineyard location, on Pinot noir still wine aroma. This review summarizes the previous and latest literature pertaining to volatile compounds including esters, higher alcohols and C 13-norisoprenoids, and their effect on Pinot noir wine perceived aroma. Their origin and behavior are discussed, as well as their role in regional differentiation. The first part of this review paper presents an overview of volatile compounds that are usually found in Pinot noir still wines at concentrations higher than their odor detection threshold. The second part deals with studies pertaining to human inputs that impact on Pinot noir wine aroma profile such as viticulture and winemaking interventions. The role of the vineyard site is also revised. This review concludes by considering what further opportunities are available to researchers in this field for greater control over Pinot noir wine quality outcomes.
... Besides these two representatives, other ambient ionization techniques, such as secondary electrospray ionization (SESI), 12-15 extractive electrospray ionization (EESI), 16 paper spray (PS) 17,18 and dielectric barrier discharge ionization (DBDI), 19 are also driving mass spectrometry to conquer more and more application territories. [4][5][6][7][8][9]20 Among these ionization methods, SESI has been proposed for more than two decades, and its recent use in some refreshing applications like breath analysis [21][22][23] and plant metabolism study 24,25 is regaining increasing attention to this technique. ...
In this study, a new approach to perform self-aspirating sampling in mass spectrometry (MS) analysis was developed by using the native inspiratory ability of a mass spectrometer. Specifically, the inspiratory channel and sampling inlet of the MS instrument were integrated into a single pathway through a sealed ionization chamber to facilitate analyte delivery and improve sample utilization. Based on this approach, combined with structural simplification and optimization, a versatile electrospray ionization (ESI) source has been constructed and characterized using different mass spectrometers. In addition to the self-aspirating ability, this source configuration can provide sub-ambient pressure (SAP) conditions for ionization, which were conducive to suppressing the background ions generated from some air-involved reactions. Moreover, it can also be used directly for electrospray-driven extraction ionization. With the SAP-ESI source, a conventional mass spectrometer enables rapid analysis of both volatiles and solutions via secondary electrospray ionization and coaxial electrospray ionization, respectively. As the compact gas pathway of the source will promote the efficient transfer and ionization of the sampled substances, the total consumption of the analyte for each analysis can be reduced to subnanogram level and a subppbv limit detection is achieved. Other demonstrated features such as the versatility, easy operation as well as simple assembly will likely contribute to the prevalence of the proposed sampling and ionization strategy.
... A whole range of applications of direct infusion mass spectrometry have been described in the last years, from disease phenotyping to food metabolomics. While highthroughput approaches for wine metabolomics gained constant interest among researchers in the past 5 years [104][105][106][107], the analysis of stilbenes by direct infusion mass spectrometry was not a particular area of interest. ...
Stilbenes represent a class of compounds with a common 1,2-diphenylethylene backbone that have shown extraordinary potential in the biomedical field. As the most well-known example, resveratrol proved to have anti-aging effects and significant potential in the fight against cardiovascular diseases and some types of cancer. Mass spectrometry is an analytical method of critical importance in all studies related to stilbenes that are important in the biomedical field. From the discovery of new natural compounds and mapping the grape metabolome up to advanced investigations of stilbenes’ potential for the protection of human health in clinical studies, mass spectrometry has provided critical analytical information. In this review we focus on various approaches related to mass spectrometry for the detection of stilbenes—such as coupling with chromatographic separation methods and direct infusion—with presentation of some illustrative applications. Clearly, the potential of mass spectrometry for assisting in the discovery of new stilbenes of biomedical importance, elucidating their mechanisms of action and quantifying minute quantities in complex matrices is far from being exhausted.
... Although much work has been done on volatile fingerprinting in apple fruits [23], and grape fruits [24], there has been no systematic study on volatile fingerprinting of fresh pineapple fruits grown in Malaysia. The purpose of this study were: (1) to identify and quantify the volatile compounds in six different varieties of pineapples grown in Malaysia (Moris, Maspine, MD2, N36, Josapine and Sarawak) and (2) apply fingerprinting technique to determine which volatile compounds may be potential markers for pineapple varieties grown in Malaysia. ...
Background:
Pineapple is highly relished for its attractive sweet flavour and it is widely consumed in both fresh and canned forms. Pineapple flavour is a blend of a number of volatile and non-volatile compounds that are present in small amounts and in complex mixtures. The aroma compounds composition may be used for purposes of quality control as well as for authentication and classification of pineapple varieties.
Results:
The key volatile compounds and aroma profile of six pineapple varieties grown in Malaysia were investigated by gas chromatography-olfactometry (GC-O), gas-chromatography-mass spectrometry and qualitative descriptive sensory analysis. A total of 59 compounds were determined by GC-O and aroma extract dilution analysis. Among these compounds, methyl-2-methylbutanoate, methyl hexanoate, methyl-3-(methylthiol)-propanoate, methyl octanoate, 2,5-dimethyl-4-methoxy-3(2H)-furanone, δ-octalactone, 2-methoxy-4-vinyl phenol, and δ-undecalactone contributed greatly to the aroma quality of the pineapple varieties, due to their high flavour dilution factor. The aroma of the pineapples was described by seven sensory terms as sweet, floral, fruity, fresh, green, woody and apple-like.
Conclusion:
Inter-relationship between the aroma-active compounds and the pineapples revealed that 'Moris' and 'MD2' covaried majorly with the fruity esters, and the other varieties correlated with lesser numbers of the fruity esters. Hierarchical cluster analysis (HCA) was used to establish similarities among the pineapples and the results revealed three main groups of pineapples.
... Electrospray plumes not only ionize solvated analytes, but also are capable of ionizing gas-phase species (Whitehouse et al., 1986;Chen et al., 1994), the latter termed secondary electrospray ionization (SESI; Wu et al., 2000;Tam and Hill, 2004). SESI-MS has been used for the real-time analysis of a variety of gas-phase analytes, including pharma- ceuticals (Wu et al., 2000;Meier et al., 2012), explosives (Tam and Hill et al., 2004;Aernecke et al., 2015), human metabolites (Martinez-Lozano et al., 2011;Garcia-Gomez et al., 2015), electronic cigarette vapors , volatile emissions from bacteria cultures (Zhu et al., 2010), food (Bean et al., 2015;Farrell et al., 2017), and plants ( . In SESI, the electrospray plume and incoming sample flow intersect in the ionization region, and analyte ionization proceeds likely via interactions with both small charged droplets and electrosprayproduced gas-phase reagent ions (Wu et al., 2000). ...
We present an electrospray ion source coupled to an orthogonal continuous-flow atmospheric pressure chemical ionization region. The source can generate intense and stable currents of several specific reagent ions using a range of salt solutions prepared in methanol, thereby providing both an alternative to more common radioactive ion sources and allowing for the generation of reagent ions that are not available in current chemical ionization mass spectrometry (CIMS) techniques, such as alkaline cations. We couple the orthogonal electrospray chemical ionization (ESCI) source to a high-resolution time-of-flight mass spectrometer (HR-ToF-MS), and assess instrument performance through calibrations using nitric acid (HNO3), formic acid (HCOOH), and isoprene epoxydiol (trans-β-IEPOX) gas standards, and through measurements of oxidized organic compounds formed from ozonolysis of α-pinene in a continuous-flow reaction chamber. When using iodide as the reagent ion, the HR-ToF-ESCIMS prototype has a sensitivity of 11, 2.4, and 10 cps pptv⁻¹ per million counts per second (cps) of reagent ions and a detection limit (3σ, 5 s averaging) of 4.9, 12.5, and 1.4 pptv to HNO3, HCOOH, and IEPOX, respectively. These values are comparable to those obtained using an iodide-adduct HR-ToF-CIMS with a radioactive ion source and low-pressure ion–molecule reaction region. Applications to the α-pinene ozonolysis system demonstrates that HR-ToF-ESCIMS can generate multiple reagent ions (e.g., I⁻, NO3⁻, acetate, Li⁺, Na⁺, K⁺, and NH4⁺) having different selectivity to provide a comprehensive molecular description of a complex organic system.
The sensory and chemical profiles of commercial bog bilberry (BB) wines were investigated using a multi-analytical approach. Sensory test included scaling and check-all-that-apply (CATA) method with questions on liking of BB wine. The sensory data was correlated with their volatile compound profiles determined using gas chromatography coupled with quadrupole and orbitrap mass spectrometry (GC-Quadrupole/Orbitrap-MS). In general, all BB wines were characterized with “fruity”, “blueberry” and “floral” odors and “sour”, “mouth puckering” and “sweet” flavors. Samples more frequently characterized as “fruity” and “floral” in CATA were preferred by the panelists (n=93). High relative proportions of o-cymene, p-cymenene, 1-octen-3-one and 3-ethylphenol in a sample (described as “ginger” and “chili”) resulted in a lower liking rating. Similarly, generally disliked sample described with “Chinese herbs” and “licorice” was characterized by compounds 3-methylpentan-1-ol, 1,1,6-trimethyl-1,2-dihydronaphthalene, and 4-vinylphenol. The data will give novel information for berry wine and beverage industry on the quality factors of BB wines linked to higher acceptance.
This study aimed to develop and incorporate a secondary electrospray ionization (SESI) setup in combination with both targeted tandem mass spectrometry (MS/MS) and a hybrid metabolomics technique, globally optimized targeted mass spectrometry (GOT-MS), to sensitively detect volatile metabolites from the headspace of in vitro gut microbial culture in a human colonic model (HCM). Two SESI- tandem mass spectrometry panels with a comparable number of targeted metabolites/features (77 compounds in the targeted SESI-MS/MS panel, and 75 features in the SESI-GOT-MS/MS panel) were established. The analytical performance of SESI-GOT-MS/MS method, as well as its biological capability, were examined and compared with the targeted SESI-MS/MS method. As a result, SESI-GOT-MS/MS method detected a similar number of metabolic features with good reproducibility (coefficient of variation < 10%) comparing to the targeted SESI-MS/MS method. Both methods showed a comparable ability to differentiate the gut microbial culture with or without the addition of green tea extract (GTE) to a human colonic model (HCM). The results from analysis of variance (ANOVA) showed that similar numbers of compounds from targeted SESI-MS/MS and metabolic features from SESI-GOT-MS/MS have significant differences when comparing samples collected from different HCM treatment stages. Partial least squares discriminant analysis (PLS-DA) indicated that both methods could clearly differentiate the stages of GTE treatment. In summary, we demonstrated that SESI-MS/MS in combination with either targeted or GOT approaches can be a useful tool for monitoring gut microbial metabolism and their response to perturbations.
Secondary electrospray ionization mass spectrometry (SESI-MS) is an innovative metabolomics approach that primarily focuses on the gas-phase analyte detection. In this study, we developed a secondary electrospray ionization tandem mass spectrometry (SESI-MS/MS) method with a homemade SESI-MS front end, for sensitive, reproducible and selective detection of headspace volatile organic compounds (VOCs) emitted from bacterial culture. The optimized SESI-MS/MS was applied to examine the VOC metabolome of a pair of isogenic methicillin-susceptible and resistant Staphylococcus aureus (MSSA and MRSA) strains. From the headspace of bacterial culture, twelve organic acids and eight amino acids with the mass range of 40-300 Da were specifically targeted with two selected reaction monitoring (SRM) transitions. Our results indicated that MSSA and MRSA strains can be clearly differentiated via partial least squares discriminant analysis (PLS-DA) based on their headspace metabolic profiles. Furthermore, we studied the stress response of MSSA and MRSA to antibiotics treatment. Our result showed that MSSA and MRSA generated dramatically changed VOC metabolic profiles in response to ampicillin, which indicated that SESI-MS/MS could also be used for antibiotic treatment response monitoring in future studies. This study showed that SESI-MS/MS VOC analysis provides an additional approach to the bacterial metabolome detection complementary to traditional aqueous phase metabolite analysis. To the best of our knowledge, this was the first time that SESI-MS/MS was applied to investigate the bacterial metabolic perturbations caused by antibiotic treatment.
Nowadays it is recognized that vineyard yield estimation can bring several benefits to all the vine and wine industry and, consequently, there is a strong demand for fast and reliable yield estimation methods. Recently a strong effort has been made on developing machine vision tools to automatically estimate vineyard yields evolving several research teams worldwide. In this paper we aim to present preliminary results obtained in the frame of an European research project (VINBOT: " Autonomous cloud-computing vineyard robot to optimise yield management and wine quality ") focus on yield estimation. A ground truth evaluation trial was set up in an experimental vineyard with the white variety Viosinho, trained on a vertical shoot positioning system and spur pruned. A sample of contiguous vines was labeled and submitted to a detailed assessment of vegetative and reproductive data to feed a viticulture data library. The vines were scanned during the ripening period of the 2015 season by the VINBOT sensor head composed with a set of sensors capable of capturing vineyard images and 3D data. Ground truth data was used to relate with images taken by the sensors and to test algorithms of image analysis. In this paper we present and discuss the relationships between actual and estimated yield computed using the surface occupied by the grape clusters in the images. Our preliminary results showed that, despite of a slight underestimation of the ground truth, caused mainly by cluster occlusion, when the canopy density allows visualization of most part of the clusters, the yield can be estimated by machine vision with a high fidelity. Further research is ongoing to test those devices and methodologies in other varieties and to improve the estimation accuracy.
The evolution of pre-fermentative volatiles and of the global aroma potential in three Italian neutral varieties (‘Nebbiolo,’ ‘Barbera’ and ‘Dolcetto’) was assessed from véraison to harvest by SBSE–GC/MS. C6 and C9 compounds, benzene derivatives, bound monoterpenes and sesquiterpenes showed differences among varieties in quantity and profiles during berry ripening. Quantitatively, the most of total monoterpenes, C-13 norisoprenoids and sesquiterpenes were detected after acid hydrolysis. Among pre-fermentative norisoprenoids, exclusively β-ionone was detected with different kinetics among varieties. Monoterpene accumulation started around véraison with the exception of (E)-geranylacetone, whose content was already high at véraison. (E)-Geranylacetone, deriving from the degradation of carotenoids, could become a target molecule to study indirectly the accumulation of carotenoids. Data allowed to measure the global aroma potential and the pre-fermentative volatiles of grapes: result interpretation suggested a number of implications on biosynthetic processes that have been addressed.
The process by which ambient vapors are ionized upon interaction with electrosprays is not fully understood , compromising its optimization and widespread use. In this work we evaluated the different scales associated with the processes involved in secondary electrospray ionization (SESI), and developed a new numerical method that merges the analytical solution that describes the angle of aperture and the current of an ideal electrospray, with a finite element method that enables the evaluation of complex geometries. The numerical method showed that, despite the low ionization efficiency (i.e. ion concen-tration/neutral vapor concentration ∼10 −4), depletion of neutral vapors plays an important role. We used this method to optimize and design a low flow SESI source, which was coupled with a commercial high resolution/high mass accuracy mass spectrometer. The system was designed to be interfaced with virtually any pre-existing atmospheric pressure ionization mass spectrometer. The experimental validation for the detection of ambient vapors confirmed qualitatively the numerical predictions in terms of ionization efficiency as a function of sample flow rate. As a result of the optimization, this prototype showed a 5-fold sensitivity increase against standard SESI. This novel add-on is meant to upgrade mass spectrometers to analyze trace gases in real time by SESI technique.
Two novel applications using a portable and wireless sensor system (e-nose) for the wine producing industry—The recognition and classification of musts coming from different grape ripening times and from different grape varieties—Are reported in this paper. These applications are very interesting because a lot of varieties of grapes produce musts with low and similar aromatic intensities so they are very difficult to distinguish using a sensory panel. Therefore the system could be used to monitor the ripening evolution of the different types of grapes and to assess some useful characteristics, such as the identification of the grape variety origin and to prediction of the wine quality. Ripening grade of collected samples have been also evaluated by classical analytical techniques, measuring physicochemical parameters, such as, pH, Brix, Total Acidity (TA) and Probable Grade Alcoholic (PGA). The measurements were carried out for two different harvests, using different red (Barbera, Petit Verdot, Tempranillo, and Touriga) and white (Malvar, Malvasía, Chenin Blanc, and Sauvignon Blanc) grape musts coming from the experimental cellar of the IMIDRA at Madrid. Principal Component Analysis (PCA) and Probabilistic Neural Networks (PNN) have been used to analyse the obtained data by e-nose. In addition, and the Canonical Correlation Analysis (CCA) method has been carried out to correlate the results obtained by both technologies.
Abstract Volatile organic compounds are vital to wine quality, determining their aroma and varietal characteristics. Which are present, and in what quantity, depends on the cultivar, the situation and soil of the vineyard, weather, cultivation methods, and winemaking practices. Here we review the literature on the development of wine aroma compounds in grapes, and how it is affected by the above-named factors. Increasing understanding of these processes at the molecular level will aid vine growers in the optimal selection of harvest dates and other decisions favouring the consistent production of balanced, flavourful berries.
pymzML is an extension to Python that offers (i) an easy access to mass spectrometry (MS) data that allows the rapid development of tools, (ii) a very fast parser for mzML data, the standard data format in MS and (iii) a set of functions to compare or handle spectra.
pymzML requires Python2.6.5+ and is fully compatible with Python3. The module is freely available on http://pymzml.github.com or pypi, is published under LGPL license and requires no additional modules to be installed.
christian@fufezan.net.
The ProteoWizard software project provides a modular and extensible set of open-source, cross-platform tools and libraries. The tools perform proteomics data analyses; the libraries enable rapid tool creation by providing a robust, pluggable development framework that simplifies and unifies data file access, and performs standard proteomics and LCMS dataset computations. The library contains readers and writers of the mzML data format, which has been written using modern C++ techniques and design principles and supports a variety of platforms with native compilers. The software has been specifically released under the Apache v2 license to ensure it can be used in both academic and commercial projects. In addition to the library, we also introduce a rapidly growing set of companion tools whose implementation helps to illustrate the simplicity of developing applications on top of the ProteoWizard library.
Availability: Cross-platform software that compiles using native compilers (i.e. GCC on Linux, MSVC on Windows and XCode on OSX) is available for download free of charge, at http://proteowizard.sourceforge.net. This website also provides code examples, and documentation. It is our hope the ProteoWizard project will become a standard platform for proteomics development; consequently, code use, contribution and further development are strongly encouraged.
Contact: darren@proteowizard.org; parag@ucla.edu
Supplementary information: Supplementary data are available at Bioinformatics online.
We have deployed an efficient secondary electrospray ionization source coupled to an Orbitrap mass analyzer (SESI-MS) to investigate the emissions of a Begonia Semperflorens. We document how hundreds of species can be tracked with an unparalleled time resolution of 2 min during day-night cycles. To further illustrate the capabilities of this system for volatile organic compounds (VOCs) analysis, we subjected the plant to mechanical damage and monitored its response. As a result, ~ 1,200 of VOCs were monitored displaying different kinetics. To validate the soundness of our in vivo measurements, we fully characterized some key compounds via MS/MS and confirmed their expected behavior based on prior gas chromatography-mass spectrometry (GC-MS) studies. For example, β-caryophyllene, which is directly related to photosynthesis, was found to show a periodic day-night pattern with highest concentrations during the day. We conclude that the capability of SESI-MS to capture highly dynamic VOC emissions and wide analyte coverage makes it an attractive tool to complement GC-MS in plant studies.
Abstract The aim of this work was to test a simplified optical prototype for a rapid estimation of the ripening parameters of white grape for Franciacorta wine directly in field. Spectral acquisition based on reflectance at four wavelengths (630, 690, 750 and 850 nm) was proposed. The integration of a simple processing algorithm in the microcontroller software would allow to visualize real time values of spectral reflectance. Non-destructive analyses were carried out on 95 grape bunches for a total of 475 berries. Samplings were performed weekly during the last ripening stages. Optical measurements were carried out both using the simplified system and a portable commercial vis/NIR spectrophotometer, as reference instrument for performance comparison. Chemometric analyses were performed in order to extract the maximum useful information from optical data. Principal component analysis (PCA) was performed for a preliminary evaluation of the data. Correlations between the optical data matrix and ripening parameters (total soluble solids content, SSC; titratable acidity, TA) were carried out using partial least square (PLS) regression for spectra and using multiple linear regression (MLR) for data from the simplified device. Classification analysis were also performed with the aim of discriminate ripe and unripe samples. PCA, MLR and classification analyses show the effectiveness of the simplified system in separating samples among different sampling dates and in discriminating ripe from unripe samples. Finally, simple equations for SSC and TA prediction were calculated.
The development of volatile compounds in Pinot noir grapes during three growing seasons was investigated. Volatile compounds in grapes were analyzed using stir bar sorptive extraction-gas chromatography-mass spectrometry (SBSE-GC-MS) technique. The results showed that different compounds underwent different progressions during grape development. The C6 alcohols continuously decreased during the berry development except at very early stage. The C6 aldehyde, however, continued to accumulate until reaching to harvest maturity when they began to decrease. Most of the free monoterpene alcohols (geraniol, nerol and citronellol) only accumulated at the early grape development stage, and their concentration did not increase much at late stage of ripening, and some monoterpenes even decreased at later stage of ripening. Both β-ionone and vanillin increased only at very early stage of berry development, while benzyl alcohol and 2-phenylethyl alcohol dramatically increased over the whole growing season. There was little change observed for β-damascenone and γ-nonalactone during the ripening process.
Background and AimsRotundone, a potent aroma compound responsible for peppery aroma and flavour in Shiraz, was detected recently in Vitis vinifera L. cv. Duras wines. In 2011 and 2012, two separate experiments were carried out to determine the effect of ripeness and viticultural techniques on rotundone concentration in Duras wine.Methods and ResultsRotundone was measured in wines prepared by microvinification techniques (1 L Erlenmeyer). Accumulation of this compound in wines depended on vintage conditions and the degree of ripening, such that a higher concentration of rotundone was reached 44 days after mid-veraison. Application of exogenous jasmonic acid and grape thinning did not significantly affect rotundone concentration, whereas leaf removal strongly reduced rotundone concentration. Wine from the irrigated treatment had a higher concentration of rotundone, and in most cases, vine water status over the veraison–harvest period was identified as a key variable that was well correlated with observed intraplot variability.Conclusions
These findings confirm that some common viticultural practices can be used to manipulate the peppery character in red wine.Significance of the StudyOur results may assist grape growers to produce Duras, Shiraz and other cultivars where rotundone makes an important contribution to wine aroma.
Changes in volatile compounds in musts and skins of grapes of Airén, Macabeo and Chardonnay white varieties were determined during ripening. The musts of the Airén variety contained higher concentrations of c-3-hexenol; musts of the Macabeo variety were the richest in t-3-hexenol and 2,4-hexadienal, while the Chardonnay musts stood out for having higher concentrations of benzaldehyde, phenylacetaldehyde and benzyl alcohol. The skins of the three varieties were both qualitatively and quantitatively richer in volatiles than were the musts. The skins of the Airén grapes had the highest levels of nerol. Airén grapes were the only variety in which citronellol was present in the skins. Low concentrations of eugenol were detected in the skins of the Chardonnay grape variety but were not present in the other two varieties. Changes in the concentration of the volatile compounds during ripening were not uniform; this made difficult the determination of the optimum level of ripening for each variety on the basis of the volatile compound content. Nevertheless, results indicated that C6 compounds and terpene concentrations reached a maximum at 6-8 ° Baumé in the Airén grapes and at around 11 ° Baumé in the Chardonnay and Macabeo grapes.
A new analytical strategy based on mass spectrometry fingerprinting combined with the NIST-MS search program for pattern recognition is evaluated and validated. A case study dealing with the tracing of the geographical origin of virgin olive oils (VOOs) proves the capabilities of mass spectrometry fingerprinting coupled with NIST-MS search program for classification. The volatile profiles of 220 VOOs from Liguria and other Mediterranean regions were analysed by secondary electrospray ionization-mass spectrometry (SESI-MS). MS spectra of VOOs were classified according to their origin by the freeware NIST-MS search v 2.0. The NIST classification results were compared to well-known pattern recognition techniques, such as linear discriminant analysis (LDA), partial least-squares discriminant analysis (PLS-DA), k-nearest neighbours (kNN), and counter-propagation artificial neural networks (CP-ANN). The NIST-MS search program predicted correctly 96% of the Ligurian VOOs and 92% of the non-Ligurian ones of an external independent data set; outperforming the traditional chemometric techniques (prediction abilities in the external validation achieved by kNN were 88% and 84% for the Ligurian and non-Ligurian categories respectively). This proves that the NIST-MS search software is a useful classification tool.
A field deployable quadrupole ion trap mass spectrometer with atmospheric pressure interface is designed, built, and characterized. The instrument enclosure (48x43x42 cm) includes a roughing pump and a helium lecture bottle, resulting in the 68 kg total weight of the instrument. Peak power consumption during the instrument operation is about 500 W. The instrument has m/z 30-2500 mass range, across which it provides better than unit mass resolution. Typical peak width at half height is 0.3 Th for 4000 Th/s scan speed. Operation of the instrument with two atmospheric pressure ion sources (electrospray and atmospheric pressure matrix assisted laser desorption ionization (AP-MALDI)) is demonstrated. AP-MALDI analysis of low femtomole amounts of peptides reveals that sensitivity of the instrument is on a par with modern commercially available quadrupole ion trap mass spectrometers. Tandem mass spectrometry capabilities of the instrument include the ability to perform simultaneous isolation and fragmentation of several different compounds. Two ways to reduce the size, weight, and power consumption of the portable instrument were explored and results of these initial studies are presented. One of the ways includes utilization of hydrogen as a buffer gas for operation of the ion trap mass analyzer in combination with a metal hydride method for storage of hydrogen in a compact rechargeable cartridge. Furthermore, careful selection of the inlet capillary parameters allowed to eliminate the first "1 Torr" stage of the differential pumping without significant loss of the instrument sensitivity. The elimination of this first pumping stage removed two turbo drag pumps, which substantially decreased the instrument's maximum power consumption (to about 300 W in peak, and about 150 W during standby) as well as its size (to 30x43x50 cm) and weight (to 35 kg).
Background and Aims: Research on concentration changes of volatile compounds during grape physiological development has focused on the period from veraison to harvest. This study compared the developmental changes in the major volatile compounds released after the crushing of Riesling and Cabernet Sauvignon grapes sampled from fruitset to harvest during the 2007–2008 season.
Methods and Results: Volatile compounds were extracted from the headspace of crushed Riesling and Cabernet Sauvignon grapes sampled throughout berry development using solid-phase microextraction and analysed by gas chromatography–mass spectrometry. A multivariate statistical approach coupled with analysis of variance was applied to compare the developmental changes in volatile compounds for the two cultivars. In both cultivars, E-2-hexenal was the most abundant volatile compound, and it showed a significant increase in concentration after veraison. Benzene derivatives discriminated ripe Cabernet Sauvignon grapes, whereas monoterpenes and sesquiterpenes discriminated both cultivars pre-veraison with a broader range of terpenes observed in the Cabernet Sauvignon samples compared with the Riesling samples. At veraison, terpene production in both varieties was low, but Riesling grapes produced some terpenes (geraniol and α-muurolene) post-veraison. Generally, esters and aldehydes were the major class of compounds from Riesling grapes, while Cabernet Sauvignon showed a greater tendency to form alcohols.
Conclusions: Both Riesling and Cabernet Sauvignon grapes had a more complex volatile compound composition pre-veraison than post-veraison. This study suggests that some compounds that contribute to grape aroma may be produced pre-veraison, and not simply accumulate after veraison.
Significance of the Study: Understanding the timing of volatile compound production and cultivar differences will guide viticulture researchers and growers in the optimisation of vineyard strategies to enhance grape aroma attributes that may, in turn, contribute to wine aroma.
The volatile composition of white Agudelo, Blancolexitimo, Godello and red Serradelo cultivars (NW Spain) harvested at two different stages of ripening have been evaluated. C(6)-compounds, alcohols, volatile fatty acids, monoterpenes, C(13)-norisoprenoids, volatile phenols and carbonyl compounds were identified and quantified in free and glycosidically bound forms by gas chromatography-mass spectrometry (GC-MS). The total volatile concentration showed a significant increase between the two ripening stages studied for all cultivars. The free volatile composition increased during maturity for Godello and Serradelo cultivars; however the glycosidically bound concentration increases for all cultivars with exception of B. lexitimo. Free C(6)-compounds ((E)-2-hexanal, 1-hexanol and (E)-2-hexen-1-ol) and bound alcohols (benzyl alcohol and 2-phenylethanol) showed the highest concentrations of volatile compounds for all grape cultivars in the two dates studied. Godello cultivar showed the highest change of volatile concentration between two ripening dates because of the high value of free C(6)-compounds. B. lexitimo was the most terpene-rich cultivar at the last ripening stage due to linalool; however C(13)-norisoprenoids in free form were detected in low concentrations for all cultivars but not in Godello and B. lexitimo cultivars at the last ripening stage. Free hexanoic acid increased during ripening in all cultivars. The evolution of volatiles during ripening of grape juice from the cultivars studied was not proportional to the changes in sugar content, which shows that the technological and aromatic maturities did not occur at the same time in these cultivars. The results also showed the cultivar * ripening date interaction for all, free and bound, groups of compounds.
Plants produce many volatile metabolites. A small subset of these compounds is sensed by animals and humans, and the volatile
profiles are defining elements of the distinct flavors of individual foods. Flavor volatiles are derived from an array of
nutrients, including amino acids, fatty acids, and carotenoids. In tomato, almost all of the important flavor-related volatiles
are derived from essential nutrients. The predominance of volatiles derived from essential nutrients and health-promoting
compounds suggests that these volatiles provide important information about the nutritional makeup of foods. Evidence supporting
a relation between volatile perception and nutrient or health value will be reviewed.
Real time analysis of human breath is achieved in an atmospheric pressure ionization mass spectrometer (API-MS) by negatively charging exhaled vapors via contact with an electrospray cloud. The spectrum observed is dominated by a wide range of deprotonated fatty acids, including saturated chains up to C14. Above C14, the background from cutaneous sources becomes dominant. We also tentatively identify a series of unsaturated fatty acids (C7-C10), ketomonocarboxylic acids (C6-C10), and a family of aldehydes. The ionization probability of large fatty acids increases drastically when the humidity changes from 20% to 95%. Accordingly, distinguishing lung vapors (humid) from those in the background (dry) requires special precautions. Estimated fatty acid vapor concentrations in breath based on our measurements ( approximately 100 ppt) are in fair agreement with values expected from blood concentrations in the range for which data are available (C3-C6).
With the invention of electrospray ionization and matrix-assisted laser desorption/ionization, scientists employing modern mass spectrometry naturally face new challenges with respect to background interferences and contaminants that might not play a significant role in traditional or other analytical techniques. Efforts to continuously minimize sample volumes and measurable concentrations increase the need to understand where these interferences come from, how they can be identified, and if they can be eliminated. Knowledge of identity enables their use as internal calibrants for accurate mass measurements. This review/tutorial summarizes current literature on reported contaminants and introduces a number of novel interferences that have been observed and identified in our laboratories over the past decade. These include both compounds of proteinaceous and non-proteinaceous nature. In the supplemental data a spreadsheet is provided that contains a searchable ion list of all compounds identified to date.
A secondary electrospray ionization (SESI) method was developed as a nonradioactive ionization source for ion mobility spectrometry (IMS). This SESI method relied on the gas-phase interaction between charged particles created by electrospray ionization (ESI) and neutral gaseous sample molecules. Mass spectrometry (MS) was used as the detection method after ion mobility separation for ion identification. Preliminary investigations focussed on understanding the ionization process of SESI. The performance of ESI-IMS and SESI-IMS for illicit drug detection was evaluated by determining the analytical figures of merit. In general, SESI had a higher ionization efficiency for small volatile molecules compared with the electrospray method. The potential of developing a universal interface for both GC- and LC-MS with an addition stage of mobility separation was demonstrated.
Positive- and negative-ion electrospray ionization Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry has been used for direct analysis of five wines (California Red, Corbiere, Zinfandel, Beaujolais, and Sauvignon Blanc), without any prior separation or purification steps. The high mass resolving power (typically m/Delta m(50%) > or = 80,000, in which Delta m(50%) is mass spectral peak full width at half-maximum peak height) and mass accuracy (< or =1 ppm) of FT-ICR mass spectrometry make it ideal for the study of complex mixtures such as wine, because the components are simultaneously resolved and identified as to elemental composition. Moreover, the high dynamic range of the instrument is advantageous for identifying trace components. The positive-ion mass spectra obtained from the wines were somewhat similar and were dominated by sucrose and (for red wines) anthocyanins. More than 30 compounds (phenolics and carbohydrates) were identified. The negative-ion mass spectra exhibited much greater variation among different wines, with several compounds peculiar to each wine. Elemental compositions could be assigned with high confidence to 76-94% of negative ions of >10% relative abundance. The present results suggest that it may be possible to fingerprint a wine on the basis of its negative-ion ESI FT-ICR mass spectrum.
The stir bar sorptive extraction (SBSE) technique is used to determine volatile constituents in Monastrell grapes. The method proposed involves a maceration step lasting 2 h and a sorption time of 6 h. The coefficients of variation obtained were <4% in the case of the volatile compounds and <2% for the internal standard. The behavior of the volatiles during grape ripening was studied, and 34 compounds were determined, among which geranyl acetone, geranyl butyrate, farnesol, and a bicycloterpene, tentatively identified as 6-methylene[3.1.0]byciclohexane, were recorded for the first time in this variety. The highest terpene and norisoprenoid contents together with the lowest values of C6 compounds were observed during the fifth week of ripening, meaning that this would be the optimal time for harvesting in terms of volatile compounds.
Samples of must derived from six different varieties of grapes taken during the fermentation process, as well as the respective wine samples directly after the end of the malolactic fermentation, were analyzed by direct infusion negative ion mode electrospray ionization mass spectrometry (ESI-MS). Diagnostic ions for must were different from those of wine samples, although small variations for each of the grape varieties were also detected. The addition of unfermented must or sugar to wine could also be clearly detected. The spectra were acquired in a few minutes per sample, indicating that ESI-MS can be used for high-throughput analysis of samples and should prove useful for quality control during and after the fermentation process.
Maturity is an essential factor that determines storage-life and final quality of most fruits and vegetables. Maturity monitoring is thus of paramount importance for postharvest handling and fruit quality regulation. Ideal analytical procedures for maturity investigation require high sensitivity, specificity, and high throughput and should be noninvasive. For the purpose of maturity differentiation, extractive electrospray ionization quadrupole time-of-flight mass spectrometry (EESI-QTOF-MS) is developed for rapid fingerprinting of compounds released from various fruits. Ripening stages of bananas, grapes, and strawberries are successfully differentiated by performing principal component analysis (PCA) of the mass spectral fingerprints of the fruits. Methodological reproducibility was also evaluated experimentally and in terms of PCA clusters. The data indicate that EESI-QTOF-MS is a useful noninvasive tool for rapid investigation and differentiation of maturity and quality of fruits without sample preparation.
The variety- and pre-fermentation-related volatile compounds of 'Fernão-Pires' (FP) white grape berries were analyzed during ripening by headspace-solid phase microextraction (HS-SPME) coupled to gas chromatography-quadrupole mass spectrometry (GC-qMS). A preliminary step, in which the grapes were crushed and macerated before HS-SPME analyses, was used. The sampling started at véraison (beginning of berry ripening) and was carried on during 5 weeks in two different vineyards. Sixteen terpenoids, two C13 norisoprenoids, two aromatic alcohols, two C6 aldehydes, and three C6 alcohols were identified. The amount of all volatiles increased since véraison towards day 20. A sharp decrease was observed after this day. The maximum amount of varietal volatile compounds was coincident with the harvesting day for white table wine production defined by the ratio sugar/acid content. The varietal volatile evolution observed for FP grapes shows that the maximum amount of volatiles occurs only in a very short period. As a consequence, the establishment of the optimum moment for harvesting of FP white variety, based on its volatile content, deserves higher accuracy than that necessary for all other already studied grapes. This work also evidences that the analysis of the evolution of the terpenoids with higher GC peak area can represent the evolution of all varietal compounds. For FP grapes, this work shows that the screening of linalool, alpha-terpineol, and geraniol during ripening can be used to define the evolution profile of the varietal volatile compounds.
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