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The combination of volatile compounds endows wines with unique aromatic characteristics and is closely related to their geographical origins. In the pursuit of origin identification and the subdivision of homogeneous production areas, clarifying the characteristics of production areas is of great significance for improving wine quality and commercial value. In this study, GC×GC-TOFMS technology was used to analyze the aroma characteristics of "Cabernet Sauvignon" wines from 26 wineries in the Helan (HL), Yinchuan (YC), Yongning (YN), Qingtongxia (QTX), and Hongsibu (HSP) sub-producing areas in the eastern foothills of Helan Mountain in Ningxia, China. The results indicate a gradual increase in relative humidity from the southern part of Ningxia, with the YN sub-region showing optimal fruit development and the QTX region having the highest maturity. A total of 184 volatile compounds were identified, with 36 compounds with an OAV > 1, crucial for the aroma profiles of primarily fermentation-derived alcohols and esters. An aromatic vector analysis revealed that "floral" and "fruity" notes are the primary characteristics of Cabernet Sauvignon wines from the Helan Mountain East region, with lower maturity aiding in the retention of these aromas. By constructing a reliable OPLS-DA model, it was determined that 15 substances (VIP > 1) played a crucial role in identifying production areas, among which phenylethyl alcohol and isoamyl alcohol were the main contributors. In addition, a Pearson correlation analysis showed a negative correlation between sunlight duration during the growing season and benzyl alcohol accumulation, while a significant positive correlation was observed during the ripening period. Due to the critical role of phenyl ethanol in identifying producing areas, this further demonstrates that sunshine conditions may be a key factor contributing to the differences in wine flavor across regions. This study offers a theoretical foundation for understanding the relationship between climatic factors and flavor characteristics, addressing the issue of wine homogenization in small production areas, clarifying typical style characteristics, and establishing a traceability technology system based on characteristic aroma. [ABSTRACT FROM AUTHOR]

Douchi is a kind of soybean-fermented food in China. To explore the common and differential compounds in different Douchi, Douchi was fermented by Aspergillus niger, Rhizopus arrhizus, and Bacillus circulans, respectively, and co-fermented by the three strains in this study. The common and characteristic flavor compounds and common and characteristic non-volatile components of different strains of fermented Douchi were explored through GC×GC-TOFMS and UPLC–Q-TOFMS omics analysis. The result suggested that Pyrazines, ketones, and alkenes such as tetramethyl-pyrazine, 2,5-dimethyl pyrazine, furaneol, 2,3-butanedione, gamma-terpinene might contribute to the basic flavor of the Douchi fermented by A. niger, R. arrhizus, and B. circulans. Peptides, amines, and flavonoids, such as N–acetylhistamine, 7,3′,4′–trihydroxyflavone, (3S,8As)-3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione might contribute to the basic function of the above three Douchi. The common metabolic pathways involved in the fermentation were isoflavonoid biosynthesis, flavonoid biosynthesis, etc. Ketones and esters such as 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 3-octanone, 5-methylfurfural and nonanal contributed to the unique flavor, while betaine, oleanolic acid, saikosaponin D and leucine might contribute to the unique function of A. niger fermented Douchi. Alkenes, pyrazine, and ketones such as α-terpinene, ethyl-pyrazine, dihydro-3-methyl-2(3H)-furanone, and linalool might contribute to unique flavor, while cordycepin, 2-Phenylacetamide might contributed to the unique function of R. arrhizus fermented Douchi. The unique flavor of B. circulans fermented Douchi might derived from ketones and esters such as 3-acetyl-2-butanone, 2-tridecanone, propionic acid-2-phenylethyl ester, while vitexin, astragalin, and phenethylamine might contribute to the unique function. Compared with single-strain fermented Douchi, the flavor substances and non-volatile components in multi-strain fermented Douchi were more abundant, such as hexadecanoic acid methyl ester, benzeneacetic acid ethyl ester, 9,12-octadecadienoic acid ethyl ester, nuciferine, and erucamide. It was speculated that there were common and differential substances in Douchi fermented by Aspergillus niger, Rhizopus arrhizus, and Bacillus circulans, which might contribute to the basic and unique flavor and function. Compared with single-strain fermented Douchi, the flavor substances and metabolites in multi-strain fermented Douchi were more abundant. This study provided a reference for the research of flavor and functional substances of Douchi. [ABSTRACT FROM AUTHOR]

Disinfection during tertiary municipal wastewater treatment is a necessary step to control the spread of pathogens; unfortunately, it also gives rise to numerous disinfection byproducts (DBPs), only a few of which are regulated because of the analytical challenges associated with the vast number of potential DBPs. This study utilized polydimethylsiloxane (PDMS) passive samplers, comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS), and non-negative matrix factorization (NMF) spectral deconvolution for suspect screening of DBPs in treated wastewater. PDMS samplers were deployed upstream and downstream of the chlorination unit in a municipal wastewater treatment plant located in Abu Dhabi, and their extracts were analyzed using GC×GC-TOFMS. A workflow incorporating a multi-tiered, eight-filter screening process was developed, which successfully enabled the reliable isolation of 22 candidate DBPs from thousands of peaks. The NMF spectral deconvolution improved the match factor score of unknown mass spectra to the reference mass spectra available in the NIST library by 17% and facilitated the identification of seven additional DBPs. The close match of the first-dimension retention index data and the GC×GC elution patterns of DBPs, both predicted using the Abraham solvation model, with their respective experimental counterparts—with the measured data available in the NIST WebBook and the GC×GC elution patterns being those observed for the candidate peaks—significantly enhanced the accuracy of peak assignment. Isotopic pattern analysis revealed a close correspondence for 11 DBPs with clearly visible isotopologues in reference spectra, thereby further strengthening the confidence in the peak assignment of these DBPs. Brominated analogues were prevalent among the detected DBPs, possibly due to seawater intrusion. The fate, behavior, persistence, and toxicity of tentatively identified DBPs were assessed using EPI Suite™ and the CompTox Chemicals Dashboard. This revealed their significant toxicity to aquatic organisms, including developmental, mutagenic, and endocrine-disrupting effects in certain DBPs. Some DBPs also showed activity in various CompTox bioassays, implicating them in adverse molecular pathways. Additionally, 11 DBPs demonstrated high environmental persistence and resistance to biodegradation. This combined approach offers a powerful tool for future research and environmental monitoring, enabling accurate identification and assessment of DBPs and their potential risks.

Piper longum L. (long pepper) is an economically and industrially important medicinal plant. However, the characterization of its volatiles has only been analyzed by gas chromatography–mass spectrometry (GC–MS). In the present study, precise characterization of P. longum fruit volatiles has been performed for the first time through advanced two‐dimensional gas chromatography–time‐of‐flight spectrometry (GC×GC–TOFMS). A total of 146 constituents accounting for 93.79% were identified, of which 30 were reported for the first time. All these constituents were classified into alcohols (4.5%), alkanes (8.9%), alkenes (6.71%), esters (6.15%), ketones (0.58%), monoterpene hydrocarbons (1.64%), oxygenated monoterpenes (2.24%), sesquiterpene hydrocarbons (49.61%), oxygenated sesquiterpenes (13.03%), phenylpropanoid (0.23%), and diterpenes (0.2%). Among all the classes, sesquiterpene hydrocarbons were abundant, with germacrene‐D (2.87% ± 0.01%) as the major one, followed by 8‐heptadecene (2.69% ± 0.03%), β‐caryophyllene (2.43% ± 0.03%), n‐heptadecane (2.4% ± 0.04%), n‐pentadecane (2.11% ± 0.05%), and so forth. Further, 20 constituents were observed to be coeluted and separated precisely in the two‐dimensional column. The investigation provides an extensive metabolite profiling of P. longum fruit volatiles, which could be helpful to improve its therapeutic potential. [ABSTRACT FROM AUTHOR]

Disinfection during tertiary municipal wastewater treatment is a necessary step to control the spread of pathogens; unfortunately, it also gives rise to numerous disinfection byproducts (DBPs), only a few of which are regulated because of the analytical challenges associated with the vast number of potential DBPs. This study utilized polydimethylsiloxane (PDMS) passive samplers, comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS), and non-negative matrix factorization (NMF) spectral deconvolution for suspect screening of DBPs in treated wastewater. PDMS samplers were deployed upstream and downstream of the chlorination unit in a municipal wastewater treatment plant located in Abu Dhabi, and their extracts were analyzed using GC×GC-TOFMS. A workflow incorporating a multi-tiered, eight-filter screening process was developed, which successfully enabled the reliable isolation of 22 candidate DBPs from thousands of peaks. The NMF spectral deconvolution improved the match factor score of unknown mass spectra to the reference mass spectra available in the NIST library by 17% and facilitated the identification of seven additional DBPs. The close match of the first-dimension retention index data and the GC×GC elution patterns of DBPs, both predicted using the Abraham solvation model, with their respective experimental counterparts—with the measured data available in the NIST WebBook and the GC×GC elution patterns being those observed for the candidate peaks—significantly enhanced the accuracy of peak assignment. Isotopic pattern analysis revealed a close correspondence for 11 DBPs with clearly visible isotopologues in reference spectra, thereby further strengthening the confidence in the peak assignment of these DBPs. Brominated analogues were prevalent among the detected DBPs, possibly due to seawater intrusion. The fate, behavior, persistence, and toxicity of tentatively identified DBPs were assessed using EPI Suite™ and the CompTox Chemicals Dashboard. This revealed their significant toxicity to aquatic organisms, including developmental, mutagenic, and endocrine-disrupting effects in certain DBPs. Some DBPs also showed activity in various CompTox bioassays, implicating them in adverse molecular pathways. Additionally, 11 DBPs demonstrated high environmental persistence and resistance to biodegradation. This combined approach offers a powerful tool for future research and environmental monitoring, enabling accurate identification and assessment of DBPs and their potential risks. [ABSTRACT FROM AUTHOR]

Sensory descriptive analysis of aged feng-flavored Baijiu liquor indicated notable differences in samples of different ages. The samples of freshly distilled Baijiu and those with shorter storage times exhibit bran and fresh green flavors, whereas, with increasing storage time, honey, sweet, and floral fragrances are gradually enhanced. Samples of feng-flavored Baijiu were prepared using headspace solid-phase microextraction, followed by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. A total of 496 compounds were identified in all samples, mainly categorized as 14 groups of substances, including esters and aldehydes. Interestingly, 42 of these substances were found in Feng-flavored Baijiu for the first time. Chemometrics was used to analyze the key differential compounds. First, 143 differential compounds closely related to aging were preliminarily screened, and principal component analysis revealed that these compounds were separated by baijiu age. Then, 65 differential compounds were selected by partial least squares discriminant analysis. Furthermore, 43 key differential compounds were selected by combined analysis with variable importance in projection and Pearson correlation coefficients. Partial least squares regression was used to study the correlation between the sensory properties and key differential compounds, and the results indicated that most compounds were closely related to the aging period of the Baijiu. The results of this study provide a theoretical basis and reference for flavor research on feng-flavored Baijiu. [ABSTRACT FROM AUTHOR]

The combination of volatile compounds endows wines with unique aromatic characteristics and is closely related to their geographical origins. In the pursuit of origin identification and the subdivision of homogeneous production areas, clarifying the characteristics of production areas is of great significance for improving wine quality and commercial value. In this study, GC×GC-TOFMS technology was used to analyze the aroma characteristics of “Cabernet Sauvignon” wines from 26 wineries in the Helan (HL), Yinchuan (YC), Yongning (YN), Qingtongxia (QTX), and Hongsibu (HSP) sub-producing areas in the eastern foothills of Helan Mountain in Ningxia, China. The results indicate a gradual increase in relative humidity from the southern part of Ningxia, with the YN sub-region showing optimal fruit development and the QTX region having the highest maturity. A total of 184 volatile compounds were identified, with 36 compounds with an OAV > 1, crucial for the aroma profiles of primarily fermentation-derived alcohols and esters. An aromatic vector analysis revealed that “floral” and “fruity” notes are the primary characteristics of Cabernet Sauvignon wines from the Helan Mountain East region, with lower maturity aiding in the retention of these aromas. By constructing a reliable OPLS-DA model, it was determined that 15 substances (VIP > 1) played a crucial role in identifying production areas, among which phenylethyl alcohol and isoamyl alcohol were the main contributors. In addition, a Pearson correlation analysis showed a negative correlation between sunlight duration during the growing season and benzyl alcohol accumulation, while a significant positive correlation was observed during the ripening period. Due to the critical role of phenyl ethanol in identifying producing areas, this further demonstrates that sunshine conditions may be a key factor contributing to the differences in wine flavor across regions. This study offers a theoretical foundation for understanding the relationship between climatic factors and flavor characteristics, addressing the issue of wine homogenization in small production areas, clarifying typical style characteristics, and establishing a traceability technology system based on characteristic aroma.

Douchi is a kind of soybean-fermented food in China. To explore the common and differential compounds in different Douchi, Douchi was fermented by Aspergillus niger, Rhizopus arrhizus, and Bacillus circulans, respectively, and co-fermented by the three strains in this study. The common and characteristic flavor compounds and common and characteristic non-volatile components of different strains of fermented Douchi were explored through GC×GC-TOFMS and UPLC–Q-TOFMS omics analysis. The result suggested that Pyrazines, ketones, and alkenes such as tetramethyl-pyrazine, 2,5-dimethyl pyrazine, furaneol, 2,3-butanedione, gamma-terpinene might contribute to the basic flavor of the Douchi fermented by A. niger, R. arrhizus, and B. circulans. Peptides, amines, and flavonoids, such as N–acetylhistamine, 7,3′,4′–trihydroxyflavone, (3S,8As)-3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione might contribute to the basic function of the above three Douchi. The common metabolic pathways involved in the fermentation were isoflavonoid biosynthesis, flavonoid biosynthesis, etc. Ketones and esters such as 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 3-octanone, 5-methylfurfural and nonanal contributed to the unique flavor, while betaine, oleanolic acid, saikosaponin D and leucine might contribute to the unique function of A. niger fermented Douchi. Alkenes, pyrazine, and ketones such as α-terpinene, ethyl-pyrazine, dihydro-3-methyl-2(3H)-furanone, and linalool might contribute to unique flavor, while cordycepin, 2-Phenylacetamide might contributed to the unique function of R. arrhizus fermented Douchi. The unique flavor of B. circulans fermented Douchi might derived from ketones and esters such as 3-acetyl-2-butanone, 2-tridecanone, propionic acid-2-phenylethyl ester, while vitexin, astragalin, and phenethylamine might contribute to the unique function. Compared with single-strain fermented Douchi, the flavor substances and non-volatile components in multi-strain fermented Douchi were more abundant, such as hexadecanoic acid methyl ester, benzeneacetic acid ethyl ester, 9,12-octadecadienoic acid ethyl ester, nuciferine, and erucamide. It was speculated that there were common and differential substances in Douchi fermented by Aspergillus niger, Rhizopus arrhizus, and Bacillus circulans, which might contribute to the basic and unique flavor and function. Compared with single-strain fermented Douchi, the flavor substances and metabolites in multi-strain fermented Douchi were more abundant. This study provided a reference for the research of flavor and functional substances of Douchi.

Sensory descriptive analysis of aged feng-flavored Baijiu liquor indicated notable differences in samples of different ages. The samples of freshly distilled Baijiu and those with shorter storage times exhibit bran and fresh green flavors, whereas, with increasing storage time, honey, sweet, and floral fragrances are gradually enhanced. Samples of feng-flavored Baijiu were prepared using headspace solid-phase microextraction, followed by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. A total of 496 compounds were identified in all samples, mainly categorized as 14 groups of substances, including esters and aldehydes. Interestingly, 42 of these substances were found in Feng-flavored Baijiu for the first time. Chemometrics was used to analyze the key differential compounds. First, 143 differential compounds closely related to aging were preliminarily screened, and principal component analysis revealed that these compounds were separated by baijiu age. Then, 65 differential compounds were selected by partial least squares discriminant analysis. Furthermore, 43 key differential compounds were selected by combined analysis with variable importance in projection and Pearson correlation coefficients. Partial least squares regression was used to study the correlation between the sensory properties and key differential compounds, and the results indicated that most compounds were closely related to the aging period of the Baijiu. The results of this study provide a theoretical basis and reference for flavor research on feng-flavored Baijiu.

By 2D gas chromatography and time-of-flight mass spectrometry (GC×GC-TOFMS), 81 ethanodiamondoids with 1-3 cages were detected quantitatively in Ordovician crude oil from well SN1, Shuntuoguole area, Tarim Basin, including 47 ethanoadamantanes with total content of 27 594.0 μg/g, 32 ethanodiamantanes with total content of 4 415.1 μg/g, and 2 ethanotriamantanes with total content of 16.8 μg/g. The template of 2D chromatogram retention index of diamondoids-ethanodiamondoids was constructed. The results demonstrated that the position of retention time of diamondoids and ethanodiamondoids has the following relationship, namely, adamantanes < ethanoadamantanes < diamantanes < ethanodiamantanes < triadamantanes < ethanotriamantanes < tetradamantanes. Quantitative analytical result of ethanoadamantanes as saturated hydrocarbons with the highest thermal stability in crude oil, is expected to provide new indexes for secondary reservoir reconstruction, i.e. crude oil cracking and thermochemical sulfate reduction (TSR).

Whisky, brandy, rum, and Chinese baijiu are popular distilled spirits globally, and the volatile components play an essential role in the aroma of these distilled liquors. Volatile compounds in whisky, brandy, rum, and three main aroma types of Chinese baijiu (strong, light, and sauce) were investigated using comprehensive two‐dimensional gas chromatography‐time‐of‐flight mass spectrometry (GC×GC–TOFMS). Two significant variable detection approaches, the variable importance in the projection (VIP) and nonparametric test (Mann–Whitney U test), were compared to determine the volatile markers among these samples. It was found that the VIP model was more efficient in screening significant variants than the U test. A total of 117 common markers were selected by both the VIP and U test methods with potential aroma contributions. Esters and acids were the main aroma markers for baijiu, diethyl esters were the main aroma markers for brandy, whereras pyrazines, lactones, and furans were the main aroma markers for whisky. Based on the chosen markers, different unknown distilled liquors were successfully classified in the model validation. This study provided a feasible methodology for spirit sample speculation based on volatile composition obtained by GC×GC‐TOFMS. [ABSTRACT FROM AUTHOR]

The metabolic profiles of human feces are influenced by various genetic and environmental factors, which makes feces an attractive biosample for numerous applications, including the early detection of gut diseases. However, feces is complex, heterogeneous, and dynamic with a significant live bacterial biomass. With such challenges, stool metabolomics has been understudied compared to other biospecimens, and there is a current lack of consensus on methods to collect, prepare, and analyze feces. One of the critical steps required to accelerate the field is having a metabolomics stool reference material available. Fecal samples are generally presented in two major forms: fecal water and lyophilized feces. In this study, two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) was used as an analytical platform to characterize pooled human feces, provided by the National Institute of Standards and Technology (NIST) as Research-Grade Test Materials. The collected fecal samples were derived from eight healthy individuals with two different diets: vegans and omnivores, matched by age, sex, and body mass index (BMI), and stored as fecal water and lyophilized feces. Various data analysis strategies were presented to determine the differences in the fecal metabolomic profiles. The results indicate that the sample storage condition has a major influence on the metabolic profiles of feces such that the impact from storage surpasses the metabolic differences from the diet types. The findings of the current study would contribute towards the development of a stool reference material. [ABSTRACT FROM AUTHOR]

To comprehensively understand the volatile compounds and assess the aroma profiles of different types of Pyrus ussuriensis Maxim. Anli, Dongmili, Huagai, Jianbali, Jingbaili, Jinxiangshui, and Nanguoli were detected via headspace solid phase microextraction (HS-SPME) coupled with two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS). The aroma composition, total aroma content, proportion and number of different aroma types, and the relative quantities of each compound were analyzed and evaluated. The results showed that 174 volatile aroma compounds were detected in various cultivars, mainly including esters, alcohols, aldehydes, and alkenes: Jinxiangshui had the highest total aroma content at 2825.59 ng/g; and Nanguoli had the highest number of aroma species detected at 108. The aroma composition and content varied among pear varieties, and the pears could be divided into three groups based on principal component analysis. Twenty-four kinds of aroma scents were detected; among them, fruit and aliphatic were the main fragrance types. The proportions of aroma types also varied among different varieties, visually and quantitatively displaying changes of the whole aroma of the different varieties of pears brought by the changes in aroma composition. This study contributes to further research on volatile compound analysis, and provides useful data for the improvement of fruit sensory quality and breeding work. [ABSTRACT FROM AUTHOR]

Colorectal cancer (CRC) ranks as the third most frequently diagnosed cancer and the second leading cause of cancer-related deaths. The current endoscopic-based or stool-based diagnostic techniques are either highly invasive or lack sufficient sensitivity. Thus, there is a need for less invasive and more sensitive screening approaches. We, therefore, conducted a study on 64 human serum samples representing three different groups (adenocarcinoma, adenoma, and control) using cutting-edge GC×GC–LR/HR-TOFMS (comprehensive two-dimensional gas chromatography coupled with low/high-resolution time-of-flight mass spectrometry). We analyzed samples with two different specifically tailored sample preparation approaches for lipidomics (fatty acids) (25 μL serum) and metabolomics (50 μL serum). In-depth chemometric screening with supervised and unsupervised approaches and metabolic pathway analysis were applied to both datasets. A lipidomics study revealed that specific PUFA (ω-3) molecules are inversely associated with increased odds of CRC, while some PUFA (ω-6) analytes show a positive correlation. The metabolomics approach revealed downregulation of amino acids (alanine, glutamate, methionine, threonine, tyrosine, and valine) and myo-inositol in CRC, while 3-hydroxybutyrate levels were increased. This unique study provides comprehensive insight into molecular-level changes associated with CRC and allows for a comparison of the efficiency of two different analytical approaches for CRC screening using same serum samples and single instrumentation. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS)-based techniques, including liquid chromatography coupling, shotgun lipidomics, MS imaging, and ion mobility, are widely used to analyze lipids. However, with enhanced separation capacity and an optimized chemical derivatization approach, comprehensive two-dimensional gas chromatography (GC×GC) can be a powerful tool to investigate some groups of small lipids in the framework of lipidomics. This study describes the optimization of a dedicated two-stage derivatization and extraction process to analyze different saturated and unsaturated fatty acids in plasma by two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC–TOFMS) using a full factorial design. The optimized condition has a composite desirability of 0.9159. This optimized sample preparation and chromatographic condition were implemented to differentiate between positive (BT) and negative (UT) boar-tainted pigs based on fatty acid profiling in pig serum using GC×GC–TOFMS. A chemometric screening, including unsupervised (PCA, HCA) and supervised analysis (PLS–DA), as well as univariate analysis (volcano plot), was performed. The results suggested that the concentration of PUFA ω-6 and cholesterol derivatives were significantly increased in BT pigs, whereas SFA and PUFA ω-3 concentrations were increased in UT pigs. The metabolic pathway and quantitative enrichment analysis suggest the significant involvement of linolenic acid metabolism. [ABSTRACT FROM AUTHOR]

Two prominent plant genera, Plectranthus, and Coleus, many species of which are indigenous to southern Africa, have been previously classified as a single genus of the name Plectranthus. However, phylogenetic analysis of markers of the plastid genome of subtribe Plectranthinae (family: Lamiaceae) has led to the recognition of Coleus as a sister taxon to Plectranthus. The purpose of this study is to analyse the profiles of foliar volatile organic compounds (VOCs), from the leaves of southern African species of Plectranthus and Coleus, as predictive chemotaxonomic markers of genus, using two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) and machine learning. Foliar VOCs from fresh crushed leaves of representative species of each genera (nine Plectranthus, six Coleus) were extracted in triplicate using static headspace solid-phase microextraction (HS-SPME), and analysed using GC×GC-TOFMS. Profiles of the foliar VOCs for each sample were constructed from their total ion chromatograms, and machine learning algorithms were used to model the data, to make predictions on the genus of new samples, and to tentatively identify putative markers of genus for Plectranthus and Coleus. A high predictive accuracy (up to 90%) was obtained, with a sensitivity (for genus Coleus) of up to 100%. Top ranking variables included C6C15 compounds of various chemical classes, but most notably of the sesquiterpene isomers, which were found to occur more prevalently in genus Coleus.

Scientists around the world are interested in edible insects as a source of valuable nutrients. Among the most often described are crickets, which represent a source of significant amounts of protein, lipids, vitamins, and minerals. This article reports results of a study into the effect of starch-to--cricket powder (CP) addition on the free amino acid profile as well as potential odorants in gluten-free (GF) bread. A significant 2.6-fold increase was observed in the content of essential amino acids in the CP-enriched GF bread. Moreover, the CP addition resulted in the formation of many volatile compounds, such as pyrazines, furans, and sulfur-containing compounds, which exhibit strong aroma-enhancing properties. The attractiveness of the CP-enriched bread was confirmed by the results of the sensory analysis, showing a significant improvement in its flavor when compared to the traditional GF bread without CP. GF bread enriched with CP was characterized by caramel, roasty, and cooked potatoes notes. On the basis of the obtained results, it was concluded that the use of CP not only improves the nutritional value but also aroma of GF bread. [ABSTRACT FROM AUTHOR]

In order to quantify organic impurities in gas produced from renewable sources, thermal desorption coupled with GC-MS or GC×GC-MS is very useful. However, the preparation of the standard tubes appears not to be trivial. For that, different strategies, based on commercial setups, have been developed. The goal of this study was to compare the classical manual deposit of a liquid standard solution with other commercial methods such as gas stream assisted deposit and vaporization followed by adsorption assisted by gas stream. A standard mixture of 48 compounds from different families was used for the comparison of the performances of the three strategies using the accuracy profile methodology. A global validation score was attributed to each strategy as well as a score according to family of compounds and boiling point range, in order to provide a detailed comparison of the techniques. On the set of studied molecules, commercial setups were found to be more efficient than the manual deposit. [ABSTRACT FROM AUTHOR]

The metabolic profiles of human feces are influenced by various genetic and environmental factors, which makes feces an attractive biosample for numerous applications, including the early detection of gut diseases. However, feces is complex, heterogeneous, and dynamic with a significant live bacterial biomass. With such challenges, stool metabolomics has been understudied compared to other biospecimens, and there is a current lack of consensus on methods to collect, prepare, and analyze feces. One of the critical steps required to accelerate the field is having a metabolomics stool reference material available. Fecal samples are generally presented in two major forms: fecal water and lyophilized feces. In this study, two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) was used as an analytical platform to characterize pooled human feces, provided by the National Institute of Standards and Technology (NIST) as Research-Grade Test Materials. The collected fecal samples were derived from eight healthy individuals with two different diets: vegans and omnivores, matched by age, sex, and body mass index (BMI), and stored as fecal water and lyophilized feces. Various data analysis strategies were presented to determine the differences in the fecal metabolomic profiles. The results indicate that the sample storage condition has a major influence on the metabolic profiles of feces such that the impact from storage surpasses the metabolic differences from the diet types. The findings of the current study would contribute towards the development of a stool reference material.

Introduction: Feces is a highly complex matrix containing thousands of metabolites. It also contains live bacteria and enzymes, and does not have a static chemistry. Consequently, proper control of pre-analytical parameters is critical to minimize unwanted variations in the samples. However, no consensus currently exists on how fecal samples should be stored/processed prior to analysis. Objective: The effects of sample handling conditions on fecal metabolite profiles and abundances were examined using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Methods: Solid-phase microextraction (SPME) and derivatization via trimethylsilylation (TMS) were employed as complementary techniques to evaluate fresh, frozen, and lyophilized fecal samples with expanded coverage of the fecal metabolome. The total number of detected peaks and the signal intensities were compared among the different handling conditions. Results: Our analysis revealed that the metabolic profiles of fecal samples depend greatly on sample handling and processing conditions, which had a more pronounced effect on results obtained by SPME than by TMS derivatization. Overall, lyophilization resulted in a greater amount of total and class-specific metabolites, which may be attributed to cell lysis and/or membrane disintegration. Conclusions: A comprehensive comparison of the sample handling conditions provides a deeper understanding of the physicochemical changes that occur within the samples during freezing and lyophilization. Based on our results, snap-freezing at -80 °C would be preferred over lyophilization for handling samples in the field of fecal metabolomics as this imparts the least change from the fresh condition. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS)-based techniques, including liquid chromatography coupling, shotgun lipidomics, MS imaging, and ion mobility, are widely used to analyze lipids. However, with enhanced separation capacity and an optimized chemical derivatization approach, comprehensive two-dimensional gas chromatography (GC×GC) can be a powerful tool to investigate some groups of small lipids in the framework of lipidomics. This study describes the optimization of a dedicated two-stage derivatization and extraction process to analyze different saturated and unsaturated fatty acids in plasma by two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC–TOFMS) using a full factorial design. The optimized condition has a composite desirability of 0.9159. This optimized sample preparation and chromatographic condition were implemented to differentiate between positive (BT) and negative (UT) boar-tainted pigs based on fatty acid profiling in pig serum using GC×GC–TOFMS. A chemometric screening, including unsupervised (PCA, HCA) and supervised analysis (PLS–DA), as well as univariate analysis (volcano plot), was performed. The results suggested that the concentration of PUFA ω-6 and cholesterol derivatives were significantly increased in BT pigs, whereas SFA and PUFA ω-3 concentrations were increased in UT pigs. The metabolic pathway and quantitative enrichment analysis suggest the significant involvement of linolenic acid metabolism.

• The proficiency of GC×GC-TOFMS for biomarker investigation has been explored. • A lot more sterane peaks were observable using GC×GC-TOFMS as compared to 1D GC. • Oldest occurrence of lanostanes in crude oils is reported. • Distinct assemblage of A-ring methylated steranes is found to be present. • The steranes are likely produced by taphonomic alterations during diagenesis. The late Neoproterozoic marine succession (Marwar Supergroup) deposited in the Bikaner-Nagaur Basin in western India is an excellent provenance to study steroid biomarkers. Traditional one-dimensional gas chromatography mass spectrometry (GC–MS) and metastable reaction monitoring (MRM) transitions have been previously employed for routine biomarker analyses of crude oils and sediments. The present study with GC×GC-TOFMS (time-of-flight mass spectrometer) demonstrates an improved distribution of the sterane compounds segregated from the co-eluting n -alkanes, cycloalkanes and triterpanes in terminal Proterozoic crude oils. The steranes identified here offer novel insights into the molecular taphonomic alteration of eukaryotic lipids during the late Neoproterozoic. The presence of lanostane and 3β alkyl steranes is probably indicative of a depositional environment stressed by high salinity. To the best of our knowledge, this is the oldest known record of lanostane steroids found in the geosphere. Secosteranes with an open C-ring form as a result of diagenetic cleaving of carbon–carbon bonds. The concomitant presence of 2α-, 3β - and 4α-methyl steranes (A-ring methylated steranes) reflects specific biological input and a distinct palaeo-depositonal environment. The 3β - and 2α-methyl steranes probably form by migration of methyl substituents within the steroid structure. The recognition of a diverse range of steroid compounds by GC×GC-TOFMS advocates its excellent analytical potential in the study of natural products in geological samples. Hence, this state-of-the-art technology will be worth using for re-evaluating and investigating hydrocarbon biomarkers in order to minimize the gaps that exist in the understanding of biotic evolution over geological time scales. [ABSTRACT FROM AUTHOR]

[Display omitted] • Volatiles in fresh scent green tea during processing were studied by volatolomics. • Significant changes in volatiles occurred during spreading and fixation stages. • A total of 10 key odorants were screened out in fresh scent green tea. • Lipid degradation and glycoside hydrolysis dominated aroma generation. Processing technology plays a crucial role in the formation of tea aroma. The dynamic variations in volatile metabolites across different processing stages of fresh scent green tea (FSGT) were meticulously tracked utilizing advanced analytical techniques such as GC-E-Nose, GC–MS, and GC × GC-TOFMS. A total of 244 volatile metabolites were identified by GC–MS and GC × GC-TOFMS, among which 37 volatile compounds were concurrently detected by both methods. Spreading and fixation stages were deemed as pivotal processes for shaping the volatile profiles in FSGT. Notably, linalool, heptanal, 2-pentylfuran, nonanal, β -myrcene, hexanal, 2-heptanone, pentanal, 1-octen-3-ol, and 1-octanol were highlighted as primary contributors to the aroma profiles of FSGT by combining odor activity value assessment. Furthermore, lipid degradation and glycoside hydrolysis were the main pathways for aroma formation of FSGT. The results not only elucidate the intricate variations in volatile metabolites but also offer valuable insights into enhancing the processing techniques for improved aroma quality of green tea. [ABSTRACT FROM AUTHOR]

[Display omitted] • Untargeted volatolomics to determine VOC profiles from boar tainted meat. • GC×GC-TOFMS is a powerful tool for untargeted volatolomics. • Characterization of fat volatolome specific to boar tainted whole males. • Statistical model elaboration for boar taint discrimination. • Statistical classification model available for phenotyping and genomic studies. This study aims to characterize a complete volatile organic compound profile of pork neck fat for boar taint prediction. The objectives are to identify specific compounds related to boar taint and to develop a classification model. In addition to the well-known androstenone, skatole and indole, 10 other features were found to be discriminant according to untargeted volatolomic analyses were conducted on 129 samples using HS-SPME-GC×GC-TOFMS. To select the odor-positive samples among the 129 analyzed, the selection was made by combining human nose evaluations with the skatole and androstenone concentrations determined using UHPLC-MS/MS. A comparison of the data of the two populations was performed and a statistical model analysis was built on 70 samples out of the total of 129 samples fully positive or fully negative through these two orthogonal methods for tainted prediction. Then, the model was applied to the 59 remaining samples. Finally, 7 samples were classified as tainted. [ABSTRACT FROM AUTHOR]

Soymilks were fermented by two starter cultures and with different levels of added glucose or lactose respectively. GC-MS, HS-GC-IMS and GC × GC-TOFMS were compared and the latter reported much more volatile organic compounds (VOCs). The VOCs profiles of the fermented soymilks were divided into four groups using principal component analysis and hierarchical clustering analysis. Based on the variable importance in the projection value greater than 1.0 and one way ANOVA (P < 0.05), 22 VOCs were respectively identified as the critical differential VOCs in starter culture A and B fermented soymilk, and the concentrations of the critical differential VOCs changed in different patterns in response to the addition of carbohydrates. Four significant metabolic pathways were involved via the metabolite set enrichment analysis, including the glycolysis/gluconeogenesis, pyruvate metabolism. Among critical differential VOCs, there were 11 and 13 aroma-active compounds with odor activity values greater than 1.0, for starter culture A and B fermented soymilks respectively. The deductive sensory properties of the fermented soymilks as affected by carbohydrate addition were evaluated. This study provides experimental and theoretical bases for improving flavor quality of fermented soymilks. [Display omitted] • GC-MS, GC-IMS and GC × GC-TOFMS were compared. • Starter cultures generated different VOCs profiles. • Differential VOCs included both soybean derived and fermentation generated VOCs. • The significant metabolic pathways involved were glycolysis, pyruvate routes. [ABSTRACT FROM AUTHOR]

Freshwater fish are usually unpopular with people, mainly because of their unappealing earthy and fishy smell. Comprehensive two-dimensional gas chromatography is a relatively new analytical technique. Finally, different parts (the dorsal meat, belly meat, dark meat, skin, intestines, and gills) were investigated by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) to explore their characteristic volatile components. In this study, a total of 49, 48, 61, 70, 73, and 65 volatile components were isolated in these six groups of samples, respectively, by GC×GC-TOFMS. Of these, 6, 7, 10, 13, 11, and 11 characteristic (ROAV ≥ 1) volatile compounds were identified in this study, including: Hexanal, Octanal, Nonanal, Heptanal, Decanal, 1-Heptanol, 1-Octen-3-ol, 2,4-Decadienal and (E,E)-2,4-Nonadienal, the majority of which were aldehydes and alcohols. The intensity range of fishy smells were identified, from strongest to weakest, as follows: gills, intestines, skin, dark meat, and belly/dorsal meat.

Wuliangye baijiu is one of the most famous Chinese liquors with a protected geographical indication. This study used LiChrolut® EN-based solid-phase extraction (SPE) and fractionation combined with comprehensive two-dimensional chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) to unveil its volatile composition. The volatiles were isolated with LiChrolut® EN-based SPE and traditional liquid-liquid extraction (LLE). The neutral/basic fractions from LLE and the SPE were fractionated on a LiChrolut® EN SPE column and analyzed by comprehensive GC×GC-TOFMS. Compared with LLE, more esters and alcohols were detected in the SPE-based extraction. The SPE fractionation and GC×GC-TOFMS analysis resulted in the identification of about 500 volatile compounds in more than 3000 peaks of the Wuliangye baijiu. The approach simplifies the complex baijiu composition into functional group-based fractions for reliable identification and analysis. This study provided a confidence volatile identification approach for Chinese baijiu based on the SPE fractionation GC×GC-TOFMS.

In this study, compositions of bio-oil and bio-oil with composite additives before and after accelerated aging treatment were analyzed by two-dimensional gas chromatography with time flight mass spectrometry detector (GC × GC-TOFMS) in order to evaluate the effect of the composite additives on the characteristics of bio-oil. The effects of composite additives on bio-oil components and the changes of the components of the bio-oil with or without accelerated aging treatment were compared. A structured distribution of compounds of classification groups was observed in the two-dimensional space. At a signal-to-noise ratio of 1000, more than 3000 peaks were detected by GC × GC-TOFMS, and more than 340 peaks (relative content > 0.02%) were identified after further analysis. After accelerated aging, the content of various compounds in bio-oil decreased. The content of the classification group and the total content of compounds in the bio-oil with composite additives changed less than that of the crude bio-oil. Before aging, the most abundant substance in bio-oil was 2(5H)-furanone. After aging, the largest content in crude bio-oil is 2(5H)-furanone, and the most abundant substance in the bio-oil with composite additives is Hydroxyacetone. Regardless of whether composite additives are added or not, the component with the highest content before and after aging of bio-oil is ketones. In crude bio-oil, the substance with the most reduced content was phenols, whose content was reduced by 0.51 wt%. The contents of alcohols, esters, furanones, furans and sugars in the bio-oil with composite additives were increased after aging. The maximum increase in content was furanones, whose content was increased by 0.15 wt%. Analysis of bio-oil components showed that high added value compounds existed in bio-oil such as 2(5H)-furanone, Hydroxyacetone and (S)-(+)-2′,3′-Dideoxyribonolactone. The research can provide detailed information on bio-oil composition. • More than 3000 peaks were detected by GC × GC-TOFMS in bio-oil. • Composite additives could affect progress of components reactions that could improve the stability of bio-oils gradually. • Many components detected in bio-oil by GC × GC-TOFMS have high added value. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) and semi-VOCs detected on the human skin surface are of great interest to researchers in the fields of metabolomics, diagnostics, and skin microbiota and in the study of anthropophilic vector mosquitoes. Mosquitoes use chemical cues to find their host, and humans can be ranked for attractiveness to mosquitoes based on their skin chemical profile. Additionally, mosquitoes show a preference to bite certain regions on the human host. In this study, the chemical differences in the skin surface profiles of 20 human volunteers were compared based on inter-human attractiveness to mosquitoes, as well as inter- and intra-human mosquito biting site preference. A passive, non-invasive approach was followed to sample the wrist and ankle skin surface region. An in-house developed polydimethylsiloxane (PDMS) passive sampler was used to concentrate skin VOCs and semi-VOCs prior to thermal desorption directly in the GC inlet with comprehensive gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Compounds from a broad range of chemical classes were detected and identified as contributing to the differences in the surface skin chemical profiles. 5-Ethyl-1,2,3,4-tetrahydronaphthalene, 1,1′-oxybisoctane, 2-(dodecyloxy)ethanol, α,α-dimethylbenzene methanol, methyl salicylate, 2,6,10,14-tetramethylhexadecane, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester, 4-methylbenzaldehyde, 2,6-diisopropylnaphthalene, n-hexadecanoic acid, and γ-oxobenzenebutanoic acid ethyl ester were closely associated with individuals who perceived themselves as attractive for mosquitoes. Additionally, biological lead compounds as potential attractants or repellants in vector control strategies were tentatively identified. Results augment current knowledge on human skin chemical profiles and show the potential of using a non-invasive sampling approach to investigate anthropophilic mosquito-host interactions. [ABSTRACT FROM AUTHOR]

A suite of untargeted methods has been applied for the characterization of aerosol from the Tobacco Heating System 2.2 (THS2.2), a heated tobacco product developed by Philip Morris Products S.A. and commercialized under the brand name IQOS®. A total of 529 chemical constituents, excluding water, glycerin, and nicotine, were present in the mainstream aerosol of THS2.2, generated by following the Health Canada intense smoking regimen, at concentrations ≥ 100 ng/item. The majority were present in the particulate phase (n = 402), representing more than 80%of the total mass determined by untargeted screening; a proportion were present in both particulate and gas-vapor phases (39 compounds). The identities for 80% of all chemical constituents (representing > 96% of the total determined mass) were confirmed by the use of authentic analytical reference materials. Despite the uncertainties that are recognized to be associated with aerosol-based untargeted approaches, the reported data remain indicative that the uncharacterized fraction of TPM generated by THS2.2 has been evaluated to the fullest practicable extent. To the best of our knowledge, this work represents the most comprehensive chemical characterization of a heated tobacco aerosol to date. [ABSTRACT FROM AUTHOR]

Cinnamomum stenophyllum (Meisn.) Vattimo-Gil (Lauraceae) is a native and vulnerable Brazilian species restricted to the Atlantic Forest. The leaf essential oil obtained by hydrodistillation was characterized for the first time by two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC-TOFMS). This analysis resulted in the tentatively identification of 80 compounds, showing the superior performance of this method in comparison to the seven compounds identified by GC–MS. The identified compounds included 8 ketones, 7 monoterpene hydrocarbons, 30 oxygenated monoterpenes, 4 sesquiterpene hydrocarbons and 23 oxygenated sesquiterpenes, showing that the C. stenophyllum oil contained mostly oxygenated mono and sesquiterpenes. The oil cytotoxicity was tested against two human cancer cell lines, colon adenocarcinoma (HCT-116) and breast cancer carcinoma (MCF-7), and the non-tumor retinal pigment epithelial cells (RPE) using the colorimetric MTT assay. Both cancer cell lines were sensible to leaf essential oil, with IC 50 < 20 μg/mL (HCT, IC 50 = 9.95 μg/mL and MCF-7, IC 50 = 16.65 μg/mL), while there was no cytotoxicity against the non-tumor cells at tested concentrations (IC 50 > 50 μg/mL), suggesting selectivity to cancer cells. The results showed that the C. stenophyllum leaf essential oil has a cytotoxic potential, presenting several compounds already known as biologically active against tumor cells. [ABSTRACT FROM AUTHOR]

Gracilaria vermiculophylla has the potential to be used as a food ingredient due to its nutritional and bioactive values, however, the aroma is considered a restrictive factor for its large acceptance by consumers. In-depth knowledge about its volatile profile is crucial for the definition of mitigation strategies to overcome this drawback and to improve its acceptability. This work aims to characterize the volatile profile of G. vermiculophylla using an advanced multidimensional chromatographic technique. For the first time, G. vermiculophylla volatile profile was unveiled and a total of 136 volatile compounds were determined and grouped by 10 chemical families, including aldehydes, ketones, alcohols, mono and sesquiterpenic compounds, norisoprenoids, esters, lactones, carboxylic acids, and halogenated compounds. From these, monoterpenic compounds were present in higher number (31 out 136) and aldehydes exhibited the largest GC areas (17–27 % of the total). A G. vermiculophylla aroma wheel was developed by combining data from the list of the detected volatile components with the respective aroma descriptors available in the literature. This strategy allowed to identify the volatile compounds whose aroma descriptors may potentially explain ca. 70 % of the aroma notes present in the algal aroma wheel. This included undesired fishy and sulfuric notes from dimethyltrisulfide and herbaceous notes from fatty acid derivatives, as aldehydes, and positive citric notes linked to monoterpenic compounds. However, G. vermiculophylla volatile compounds related to sweet, almond, beany, fresh, and minty notes, not yet considered in the algal aroma wheel, were also determined. This information may be further used to define mitigation strategies of non-valued algae aromas through volatiles' insights, contributing to the future acceptance of algae food products. [Display omitted] • Unveiling G. vermiculophylla volatile profile by HS-SPME/GC × GC–ToFMS • 136 volatiles were determined across 10 chemical families. • Aroma descriptors of 38 volatiles are related to 22 out 32 algal wheel aroma notes. • Volatiles with undesired fishy, sulfuric, and herbaceous notes were determined. [ABSTRACT FROM AUTHOR]

Daqu quality is determined by its aroma characteristics. In this study, molecular sensory techniques were used to investigate the sensory attributes of Jiangxiangxing high temperature Daqu, resulting in the development of a sensory wheel. A physicochemical and enzymatic analysis of different grades of Daqu revealed notable differences, especially in acidity. Furthermore, the volatile components of various grades of Daqu were investigated with HS-SPME-GC × GC-TOFMS, resulting in the identification of 524 volatile compounds belonging to 11 distinct classes within Daqu. Univariate analysis demonstrated significant differences in flavor components among Daqu samples of diverse quality grades. By employing GC-O-MS techniques and ROAV≥ 0.1, a comprehensive analysis identified a total of 29 key aroma active compounds that contribute to the overall flavor profile of Daqu. Notably, butyl acrylate and (2E)-2-octenal were found to make substantial contributions to the floral and fruity odor, as well as linalool and benzeneacetaldehyde, which were found to make substantial contributions to sweet odor. These compounds significantly enriched the aroma of Daqu and played a crucial role in enhancing the overall flavor quality of Daqu. In conclusion, these results provide a theoretical base for further investigation of different grades of Daqu, as well as the control and improvement of Daqu quality. • The sensory wheel of jiangxiangxing high-temperature Daqu was established for the first time by molecular sensory science. • Comprehensive analysis of the aroma composition of high-temperature Daqu using HS-SPME combined with GC × GC-TOFMS. • 29 key aroma active compounds were identified to contribute to the overall flavor of Daqu. [ABSTRACT FROM AUTHOR]

Homochiral proteins orchestrate biological functions throughout all domains of life, but the origin of the uniform l-stereochemistry of amino acids remains unknown. Here, we describe enantioselective adsorption experiments of racemic alanine and leucine onto homochiral d- and l-quartz as a possible mechanism for the abiotic emergence of biological homochirality. Substantial racemate resolution with enantiomeric excesses of up to 55% are demonstrated to potentially occur in interstitial pores, along grain boundaries or small fractures in local quartz-bearing environments. Our previous hypothesis on the enhanced enantioselectivity due to uranium-induced fission tracks could not be validated. Such capillary tubes in the near-surface structure of quartz have been proposed to increase the overall chromatographic separation of enantiomers, but no systematic positive correlation of accumulated radiation damage and enantioselective adsorption was observed in this study. In general, the natural l-quartz showed stronger enantioselective adsorption affinities than synthetic d-quartz without any significant trend in amino acid selectivity. Moreover, the l-enantiomer of both investigated amino acids alanine and leucine was preferably adsorbed regardless of the handedness of the enantiomorphic quartz sand. This lack of mirror symmetry breaking is probably due to the different crystal habitus of the synthetic z-bar of d-quartz and the natural mountain crystals of l-quartz used in our experiments.

The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79–117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R2 > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME–GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices.

Sorghum is the major raw material for the production of Chinese Baijiu (Chinese liquor) and has a great effect on the flavor of Baijiu. Volatiles in cooked glutinous and non-glutinous sorghum samples were extracted using solid-phase microextraction (SPME) and analyzed via comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) and gas chromatography-olfactometry/mass spectrometry (GC-O/MS). A total of 145 volatile compounds and 52 potent odorant compounds were identified from both sorghum types according to the retention index, MS, aroma, and standards. Based on their aroma features, the compounds were grouped into eight general categories, and the intensities of each aroma group were summed. Moreover, most of the compounds detected in the cooked sorghums were also detected in commercial Chinese Baijiu, indicating that the aroma compounds produced during the sorghum cooking process have a direct and significant influence on the final flavor quality of Baijiu.

The objective of the current study was to formulate RP-3 kerosene surrogate by emulating fuel properties affecting the physical and chemical processes of the target fuel under the engine relevant conditions. This study utilized two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC-TOFMS) and 13C and 1H nuclear magnetic resonance (NMR) spectroscopy to characterize the compositional characteristics of RP-3 fuel, and various standard test methods were applied to measure the physical and chemical properties of the target fuel. Two surrogate fuels (K1, a mixture of five components and K2, a mixture of seven components) were optimally determined through a multi-property regression algorithm by matching carbon types (CTs), distillation curve, cetane number (CN), density, and threshold sooting index (TSI) of the target fuel. The measured and estimated values of both target properties and non-target properties of surrogates were validated against the experimental data of RP-3 kerosene. Ignition delay times (IDTs) of both surrogates were investigated in a heated shock tube and a heated rapid compression machine under engine relevant conditions and validated against the measured results of RP-3. Overall, K1 and K2 both exhibited good matching on the compositional characteristics, physical-chemical properties, and gas phase ignition behaviors with the target fuel. In contrast, the seven-component K2 was more competitive and more comprehensive. [ABSTRACT FROM AUTHOR]

Cadaver-detection dogs are trained to locate victim remains; however, their training is challenging owing to limited access to human remains. Animal analogues, such as pigs, are typically used as alternative training aids. This project aimed to compare the visual decomposition and volatile organic compound (VOC) profile of human and pig remains in an Australian environment, to determine the suitability of pig remains as human odour analogues for cadaver-detection dog training. Four human cadavers and four pig carcasses were placed in an outdoor environment at the Australian Facility for Taphonomic Experimental Research (AFTER) across two seasons. Decomposition was monitored progressively in summer and winter. VOCs were collected onto sorbent tubes and analysed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry. Visual observations highlighted the differences in decomposition rates, with pig remains progressing through all stages of decomposition, and human remains undergoing differential decomposition and mummification. Chemical and statistical analysis highlighted variations in the composition and abundance of VOCs over time between the odour profiles. This study concluded that the visual decomposition and VOC profile of pig and human remains was dissimilar. However, in cooler conditions the results from each species became more comparable, especially during the early stages of decomposition. [ABSTRACT FROM AUTHOR]

Highlights • GC × GC-TOFMS was applied to analyze five lignite pyrolysis tars (LPTs). • The analysis identified as many as 469 oxygenates in a LPT. • A wide variety of oxygenates were found as significant biomarkers. • Biogenic oxygenates radically decomposed by thermal cracking above 600 °C. Abstract GC×GC-TOFMS was applied to characterize oxygenates in five lignite tars, which were produced from the pyrolysis of a low-maturity lignite in a two-stage reactor with thermal cracking of volatile matter at a different temperature (500–800 °C) and without thermal cracking. The analysis of the two tars obtained by no cracking and cracking at 500 °C identified 349 and 469 oxygenates with a higher reliability, respectively. Those oxygenates embraced a considerable variety of biomarker species. Many biomarker compounds were the constituents of essential oils or extracts of plants, including long-chain fatty oxygenates (e.g., linolenic acid, erucic acid and 2-hexyldecanol), terpenoids (e.g., cedrenol, caryophyllene oxide and artemisinin) and aromatic compounds (e.g. vanillin, cinnamic acids and flavoniods). Besides, cellulose-degraded primary compounds (e. g., levoglucosenone and furfural) and lignin-derived guaiacols were detected. The results strongly indicated the preservation of various biogenic compositions in the lignite due to the low microbial activity and immature diagenesis. The study also reported the changes of oxygenate classes with cracking temperature by classifying them into chain fatty oxygenates, alicyclic oxygenates and aromatic oxygenates. [ABSTRACT FROM AUTHOR]

Abstract The present work addresses the detailed structural elucidation by high resolution techniques of both liquid pyrolysis products from slow pyrolysis of crambe seeds. Bio-oil and aqueous phase were obtained at 400 °C with 32% and 15.8% (w/w) yield and were separated by density difference. Lyophilization was applied to concentrate the organic compounds present in aqueous phase (OCAP). Bio-oil and the OCAP were analyzed by comprehensive bidimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) and positive and negative-ion electrospray (ESI) high resolution Orbitrap mass spectrometry (HRMS). For the bio-oil, 1,400 analytes were identified by GC×GC-TOFMS and the most abundant classes were hydrocarbons (448.6 mg g−1) and N-containing compounds (172.2 mg g−1). In the bio-oil ESI-(+) Orbitrap HRMS data, the N2 class was the most abundant (79.9%). In the negative mode, ca. 87.6% of assigned peaks corresponded to O2 class for bio-oil. The major compounds identified by GC×GC-TOFMS in the OCAP were oxygenated (49.8%) and NO containing compounds (45.9%). ESI (−) Orbitrap HRMS analysis for OCAP presented high percentage of O2 (57.2%) and NO (28.3%) classes, while ESI (+) Orbitrap MS of N2 (51.8%) and NO (28.8%) classes. The aqueous fraction composition profile indicates a potential biological activity due to the presence of N-heterocyclic compounds and the bio-oil (38.9 MJ kg−1; 5.4% H 2 O) has the potential to be used as a second generation (ASTM D7544) or hydrotreated to improve fuel quality. Graphical abstract Image 1 Highlights • Crambe is an interesting non-food biomass with a low production cost. • The liquid products of slow pyrolysis from crambe seeds were analyzed. • The bio-oil consists mainly of compounds with apolar characteristics. • The organic compounds present in the aqueous phase (OCAP) have a more polar profile. • Bio-oil is rich in hydrocarbons while OCAP is rich in N- and O-containing compounds. [ABSTRACT FROM AUTHOR]

In this study, biomarkers, together with stable carbon (δ13C) and hydrogen (δD) isotopic compositions of n-alkanes have been examined in a suite of condensates collected from the East China Sea Shelf Basin (ECSSB) in order to delineate their source organic matter input, depositional conditions and evaluate their thermal maturity. Previously, GC-MS analyses have shown that all the condensates are formed in oxidizing environment with terrestrial plants as their main source input. No significant differences were apparent for biomarker parameters, likely due to the low biomarker content and high maturity of these condensates. Conventional GC-MS analysis however, may provides limited information on the sources and thermal maturity of complex mixtures due to insufficient component resolution. In the current study, we used comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) to increase the chromatographic resolution. Compounds such as alkyl cyclohexanes, alkyl cyclopentanes and diamondoids, which can be difficult to identify using conventional GC-MS analysis, were successfully identified using GC×GC-TOFMS. From our analyses we propose two possibly unreported indicators, including one maturity indicator (C5−-cyclohexane/5+-cyclohexane) and one oxidation-reduction environment indicator (alkyl-cyclohexane/alkyl-cyclopentane). Multiple petroleum charging events were proposed as an explanation for the maturity indicators indexes discrepancy between methyl-phenanthrene index (MPI) and methyl-adamantane index (MDI). In addition, the stable isotopic results show that condensates from the Paleogene have significantly higher positive δ13C values of individual n-alkanes than the Neogene samples. Based on δD values, the samples can be divided into two groups, the differences between which are likely to be attributed to different biosynthetic precursors. Variation within each group can likely be attributed to vaporization. [ABSTRACT FROM AUTHOR]

Abstract Dark tea is a special type of tea that requires microbial fermentation during the post-fermentation process, and its volatile composition is quite different from other tea kinds. The present study aimed at charactering the volatile composition of two typical Chinese dark teas (Fu-brick tea and Pu-erh tea). Volatile compounds from both teas were extracted and analyzed using simultaneous distillation extraction (SDE) combined with two-dimensional gas chromatography-time-of-flight-mass spectrometry (GC × GC-TOFMS). A total of 373 and 408 major aromatic components were tentatively identified in Fu-brick tea and Pu-erh tea, respectively. The relative quantification results showed that ketenes (24.87%), ketones (16.86%), aldehydes (14.36%) and olefine aldehydes (9.11%) were more abundant in Fu-brick teas, while in Pu-erh teas, ketenes accounted for 17.95%, followed by aldehydes (14.51%), ally esters and ketones (11.94% and 10.78%). Multivariate analysis indicated that obvious differences existed in the levels of some aromatic compounds between the two dark teas. Benzaldehyde and benzeneacetaldehyde in Fu-brick teas were considerably lower and accounted for approximately 55% of those in Pu-erh teas; whilst, nonanal and 2-hexenal in Fu-brick tea were twice as high as in Pu-erh tea. The application of pre-enrichment extraction with GC × GC-TOFMS analysis gives a thorough view of the aromatic constituents of dark teas. Graphical abstract Image 1 Highlights • Fu-brick and Pu-erh teas were compared using SDE-GC × GC-TOF/MS. • Ketenes were the most abundant aroma components in both dark teas. • Concentrations of nonanal and 2-hexenal in Fu-brick were twice those in Pu-erh tea. • This is the first comprehensive report of volatile compounds in two dark teas. [ABSTRACT FROM AUTHOR]

Foodomics, emergent field of metabolomics, has been applied to study food system processes, and it may be useful to understand sensorial food properties, among others, through foods metabolites profiling. Thus, as beer volatile components represent the major contributors for beer overall and peculiar aroma properties, this work intends to perform an in-depth profiling of lager beer volatile metabolites and to generate new data that may contribute for molecules’ identification, by using multidimensional gas chromatography. A set of lager beers were used as case-study, and 329 volatile metabolites were determined, distributed over 8 chemical families: acids, alcohols, esters, monoterpenic compounds, norisoprenoids, sesquiterpenic compounds, sulfur compounds, and volatile phenols. From these, 96 compounds are reported for the first time in the lager beer volatile composition. Around half of them were common to all beers under study. Clustering analysis allowed a beer typing according to production system: macro- and microbrewer beers. Monoterpenic and sesquiterpenic compounds were the chemical families that showed wide range of chemical structures, which may contribute for the samples’ peculiar aroma characteristics. In summary, as far as we know, this study presents the most in-depth lager beer volatile composition, which may be further used in several approaches, namely, in beer quality control, monitoring brewing steps, raw materials composition, among others.

Citrus blend black teas are popular worldwide, due to its unique flavor and remarkable health benefits. However, the aroma characteristics, aroma profiles and key odorants of it remain to be distinguished and cognized. In this study, the aroma profiles of 12 representative samples with three different cultivars including citrus (Citrus reticulata), bergamot (Citrus bergamia), and lemon (Citrus limon) were determined by a novel approach combined head space-solid phase microextraction (HS-SPME) with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). A total of 348 volatile compounds, among which comprised esters (60), alkenes (55), aldehydes (45), ketones (45), alcohols (37), aromatic hydrocarbons (20), and some others were ultimately identified. The further partial least squares discrimination analysis (PLS-DA) certified obvious differences existed among the three groups with a screening result of 30 significant differential key volatile compounds. A total of 61 aroma-active compounds that mostly presented green, fresh, fruity, and sweet odors were determined in three groups with gas chromatography-olfactometry/mass spectrometry (GC-O/MS) assisted analysis. Heptanal, limonene, linalool, and trans-β-ionone were considered the fundamental odorants associated with the flavors of these teas. Comprehensive analysis showed that limonene, ethyl octanoate, copaene, ethyl butyrate (citrus), benzyl acetate, nerol (bergamot) and furfural (lemon) were determined as the characterized odorants for each type.

Although new storage technologies have been emerging in recent years, preservation of pear (Pyrus communis L.) remains a challenge for suppliers. Maintenance of desired organoleptic properties throughout cold storage using non-chemical strategies has been investigated and the use of edible coatings has shown potential to delay fruit quality deterioration during cold storage. Thus, the objective of this study is to evaluate the impact of pectin coatings including plant extracts, in “Rocha” pear (Pyrus communis L. cv. Rocha) preservation. A four-month pilot scale assay was performed in both dynamic controlled atmosphere (DCA) (−0.5 °C, 0.5% O2, and 0.4% CO2) and normal atmospheric (NA) conditions (2 °C). For each storage condition, the following three coatings were tested: pectin (3% w/v) (PCT), pectin (3% w/v) + strawberry tree leaves extract (9.5 mg/mL) (CT1), and pectin (3% w/v) + apple pomace extract (16 mg/mL) (CT2). Volatile compounds, potentially related to aroma or ripening status of “Rocha” pear, were monitored alongside with conjugated trienols (CTs) and maturity parameters. The combination of DCA conditions and the application of pectin coatings were able to reduce the release of Rocha pear volatiles associated with ripening status, (particularly esters and sesquiterpenes), as well as reduce CTs, which could contribute to the preservation of Rocha pear for longer periods.

Urine is a popular biofluid for metabolomics studies due to its simple, non-invasive collection and its availability in large quantities, permitting frequent sampling, replicate analyses, and sample banking. The biggest disadvantage with using urine is that it exhibits significant variability in concentration and composition within an individual over relatively short periods of time (arising from various external factors and internal processes regulating the body’s water and solute content). In treating the data from urinary metabolomics studies, one must account for the natural variability of urine concentrations to avoid erroneous data interpretation. Amongst various proposed approaches to account for broadly varying urine sample concentrations, normalization to creatinine has been widely accepted and is most commonly used. MS total useful signal (MSTUS) is another normalization method that has been recently reported for mass spectrometry (MS)-based metabolomics studies. Herein, we explored total useful peak area (TUPA), a modification of MSTUS that is applicable to GC×GC-TOFMS (and data from other separations platforms), for sample normalization in urinary metabolomics studies. Performance of TUPA was compared to the two most common normalization approaches, creatinine adjustment and Total Peak Area (TPA) normalization. Each normalized dataset was evaluated using Principal Component Analysis (PCA). The results showed that TUPA outperformed alternative normalization methods to overcome urine concentration variability. Results also conclusively demonstrate the risks in normalizing data to creatinine.

In this study, the detailed volatile compositions of Chinese herbaceous aroma-type Baijiu (HAB) were characterized by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOFMS). A total of 606 compounds were tentatively identified by similarity, mass spectral data, and retention indices, among which 247 compounds were positively verified by authentic standards. Esters were present in higher numbers (179), followed by aldehydes and ketones (111), and alcohols (81). In addition, there were also many terpenes (82), sulfides (37), furans (29), nitrogenous compounds (29), lactones (17), and so on. Meanwhile, the extraction effects of volatile components from different sample pretreatment methods (headspace solid-phase microextraction (HS-SPME), solid phase extraction (SPE), and stir bar sorptive extraction (SBSE)) for HAB were also revealed. The results indicated that HS-SPME has a better extraction effect on easily volatile compounds, such as alcohols and sulfides, especially for terpenes. SPE was particularly beneficial for the analysis of nitrogen-containing compounds; SBSE showed medium extraction ability for most types of compounds and was more suitable for the target analysis of trace content substances.

In vitro cultivation of staphylococci is fundamental to both clinical and research microbiology, but few studies, to-date, have investigated how the differences in rich media can influence the volatilome of cultivated bacteria. The objective of this study was to determine the influence of rich media composition on the chemical characteristics of the volatilomes of Staphylococcus aureus and Staphylococcus epidermidis. S. aureus (ATCC 12600) and S. epidermidis (ATCC 12228) were cultured in triplicate in four rich complex media (brain heart infusion (BHI), lysogeny broth (LB), Mueller Hinton broth (MHB), and tryptic soy broth (TSB)), and the volatile metabolites produced by each culture were analyzed using headspace solid-phase microextraction combined with comprehensive two-dimensional gas chromatography—time-of-flight mass spectrometry (HS-SPME-GC×GC-TOFMS). When comparing the chemical compositions of the staph volatilomes by the presence versus absence of volatiles produced in each medium, we observed few differences. However, when the relative abundances of volatiles were included in the analyses, we observed that culturing staph in media containing free glucose (BHI and TSB) resulted in volatilomes dominated by acids and esters (67%). The low-glucose media (LB and MHB) produced ketones in greatest relative abundances, but the volatilome compositions in these two media were highly dissimilar. We conclude that the staphylococcal volatilome is strongly influenced by the nutritional composition of the growth medium, especially the availability of free glucose, which is much more evident when the relative abundances of the volatiles are analyzed, compared to the presence versus absence.