Longjing tea (Camellia sinensis), an iconic agricultural product distinguished by its geographical indication status, has gained much acceptance and consumption in China. The aroma types and steeping ...conditions of green tea are important factors influencing consumer acceptance. However, the effects of steeping conditions on tea samples with different aroma types are still unknown. Explanation of the above unknowns can provide new insights into the flavor variations of tea when consumed for optimal sensory enjoyment. Here, the aroma profiles of Longjing green teas with bean-like (DX) and fresh aroma (QX) types were analyzed using gas chromatography‒mass spectrometry (GC‒MS), gas chromatography–ion mobility spectrometry (GC‒IMS), and quantitative descriptive analysis (QDA). Geraniol, (E, E)-2,4-heptadienal and other 11 compounds contributed to the bean-like aroma, while heptanal-d, hexanal-d and other 4 compounds contributed to the fresh aroma. Further, the release patterns of volatiles at different steeping temperatures were also revealed. 12 volatiles led to the differences between the two aroma types of Longjing teas at different steeping temperatures. Most volatiles exhibited their aroma characteristics when the steeping temperature exceeded 80 °C. These results enhance the comprehension of green tea's aroma profile, thereby enabling consumers to approach tea drinking from a more scientific perspective.
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•Contributing volatiles in different Longjing tea were revealed by GC-MS and GC-IMS.•18 key volatiles among tea samples were confirmed by multivariate analysis.•Steeping above 80 °C was conducive to the formation of aroma in Longjing tea.•The effect of steeping temperature on 12 key aroma-active compounds was revealed.
•Pyrolysis of a whole tyre in molten metal (zinc) without the need for shredding.•Analysis of the liquid product by gas chromatography and comprehensive gas chromatography mass ...spectrometry.•Utilization of a reversed column set for improved separation of the complex mixture of mainly linear or cyclic hydrocarbon compounds with different degree of unsaturation.•Quantification of selected compounds.
Pyrolysis of scrap tyres is a promising technology to recover valuable materials such as pyrolysis liquids, carbon black and steel. Pyrolysis liquids are complex mixtures of organic compounds and may represent a valuable source for chemicals. And because pyrolysis liquids are complex mixtures, high resolution analytical methods are required to accurately characterize these liquids. In this study comprehensive gas chromatography mass spectrometry (GC×GC–MS) using a reversed column setup (polar×apolar) was used for the analysis of a pyrolysis liquid. The tyre pyrolysis liquid analyzed was obtained from a process which places whole tyres onto molten zinc (460–480°C) providing direct heat transfer and hence rapid pyrolysis. The results show, that the pyrolysis liquid is a complex mixture of acyclic and cyclic, aliphatic, unsaturated and aromatic hydrocarbons and several heteroatomic compounds. Compared to a normal column setup (apolar×polar), the reversed column setup separates structurally similar acyclic and cyclic hydrocarbon compounds with different degree of unsaturation better. A quantification was performed for a set of 40 compounds. A qualitative and quantitative evaluation of the compounds found, that the composition of the pyrolysis liquid is typical for tyre pyrolysis liquids. Nevertheless, comparably high amounts of limonene of 6.6% (w/w) and low amounts of monocyclic aromatic compounds were found. This is attributed to the very high heating rate of this process due to the direct heat contact of the tyres with molten zinc.
The aroma profiles in non-smoked bacon were investigated via GC-O-MS, GC × GC-TOFMS, and GC-IMS. GC-O-MS is advantageous for detecting aldehydes. GC × GC-TOFMS is more sensitive to hydrocarbons and ...alcohols, while GC-IMS detects a balanced range of categories. Only 9 of the 239 detected volatiles were identifiable by all three methods. Therefore, the combination of all three methods proved to be the most effective way to comprehensively analyze the aroma profiles of bacon. Recombination and omission tests were performed using aroma compounds with a flavor dilution (FD) factor greater than 27; five volatiles were identified as key aroma compounds in non-smoked bacon, including hexanal, (E,E)-2,4-decadienal, 1-octen-3-ol, dihydro-5-pentyl-2(3H)-furanone, and 3-methyl-butanoic acid. Among these, hexanal and 1-octen-3-ol exhibited relatively high FD factors and odor activity values (OAVs), so they were confirmed as the primary contributors. Meanwhile, seven volatiles contributed to the unique aroma of non-smoked bacon in different regions. The difference in the aroma of bacon in different regions is mainly due to the content of various volatiles rather than the type. A comprehensive analysis of the aroma in non-smoked bacon can reveal theoretical information for improving the process and quality control of the product.
Extracts of the roots of Panax (ginseng) species are analysed using comprehensive two‐dimensional gas chromatography. Comparison of comprehensive two‐dimensional chromatograms reveals the presence of ...numerous common components, and possible species‐specific components are also observed. Two‐dimensional bubble plot presentations of GC×GC(FID) data allow ready qualitative and semi‐quantitative comparison of the extracts. The use of GC×GC‐quadrupole MS (GC×GC‐qMS), operated at a scanning rate of 20 Hz, in conjunction with retention data, permits identification of separated (major) components. Whilst this scan speed will be insufficient for reliable quantitative analysis, considerably improved quality of uncorrected spectra, arising from the enhanced separation over single column GC‐MS analysis is apparent. Spectral match qualities of up to 99% are found for a number of components. Comparison of GC×GC‐qMS with GC×GC(FID) indicates that good correspondence of peak position patterns is achieved, which aids component identification. It is shown that (quadrupole) mass spectrometric detection is a useful tool for provision of identification of separated compounds in high‐resolution comprehensive two‐dimensional gas chromatography.
•GC×GC allowed the identification of phenols in complex sample of bio-oil from sawdust.•The alkaline extraction of bio-oil was a good up-grade process, providing a fraction rich in phenols.•One ...hundred and thirty compounds (mainly phenols and ketones) were identified in the alkaline extract.
In this paper it is studied the most polar fractions of bio-oil produced by fast pyrolysis of Lignocel BK40-90 (sawdust from forest timber). The biomass was submitted to the pyrolysis in an existing FCC pilot plant that was adapted for this procedure. The equipment consists of a fluidized bed reactor with nitrogen injection. The unit operates with continuous biomass feeding and continuous solids circulation. The produced bio-oil was submitted to an aqueous alkaline extraction, isolating the acidic compounds that were analyzed by one-dimensional gas chromatography and comprehensive two-dimensional gas chromatography with quadrupole mass spectrometry detection (qMS). One hundred and thirty compounds (mainly phenols and ketones) were tentatively identified in the extract, some of them by the use of retention indexes. The main differences between chromatographic techniques were the substantial increasing in the peak capacity of GC×GC and the resolution of some co-elutions that occurred in GC/qMS. It is also possible to conclude that this extract is rich in important raw materials for the chemical industry and can be used for this end.
•We developed a GC×GC-TOFMS method for fire debris analysis.•We examined the halogenated dioxin and furan content of simulated fire debris.•A series of Br and mixed Br/Cl furans were identified in a ...variety of samples.•Residential fire debris simulations contained brominated dibenzofurans.•Commercial fire debris simulations contained Br and mixed Br/Cl furans.
A comprehensive approach was taken to characterize the polyhalogenated dibenzo-p-dioxin and dibenzofuran contents of fire debris. Household and electronics fire simulations were performed to create samples representative of those firefighters most typically come in contact with. Sample analysis was performed using GC×GC-TOFMS to provide a comprehensive profile of the halogenated dioxins and furans present among the two types of fire debris. Both the household fire and electronics fire simulations produced a significant amount of polybrominated dibenzofurans. Only the electronics rich fire simulation produced mixed halogenated (Br/Cl) dibenzofurans in amounts above the limit of detection of the analytical method. Of the mixed halogenated dibenzofurans identified, a majority were those having no commercially available standard to allow for specific congener identification. GC×GC-TOFMS was extremely beneficial for the identification of compound classes due to the manner in which compounds classify in the two-dimensional chromatographic plane, thus aiding data reduction for these materials.
•Hydrothermal liquefaction of cuticular materials led to a 38–41wt.% bio-oil yield.•Bio-oils HHVs were ∼40.5MJkg−1 and contained low amounts of heteroatoms.•Comprehensive chemical analysis of ...feedstock cuticular materials and bio-oils.•2D GC–MS and ESI-FTICR-MS were utilized to chemically characterize the bio-oils.•Bio-oils produced contained desirable fuel related compounds.
Hydrothermal liquefaction (HTL) of cuticular materials from Agave americana and Capsicum annuum was performed for extended periods of time (72h) at 360°C meant to simulate long-term maturation of the organic matter. Both cuticular materials displayed evidence for possible oil production from the amounts of polymethylenic carbons in 13C solid-state nuclear magnetic resonance spectra. The bio-oil yields were approximately 35wt.% and exhibited heating values of 40.5MJkg−1, comparable to those of typical crude petroleum. Analysis by two dimensional gas chromatography indicated that the A. americana bio-oil was dominated by a homologous series of n-alkanes, whereas cyclic and aromatic compounds were the major compounds identified in the C. annumm bio-oil. Further analysis using electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry revealed the bio-oil samples were predominantly lipid-like in character. The result of this study demonstrate that one can utilize highly aliphatic biopolymeric components of certain plant materials to produce bio-oils that have the potential to be utilized as alternative fuels.
•PLE–GC–MS/MS was implemented for the first time for fungicide analysis in bagasse.•PLE has demonstrated much higher extraction efficiency than UAE.•PLE extracts were directly analyzed without ...further cleanup or concentration.•Target fungicides were found in all the samples at high levels although below MRLs.
Ultrasound-assisted extraction (UAE) and pressurized liquid extraction (PLE) followed by gas chromatography–triple quadrupole-mass spectrometry (GC TQ-MS) were used for the rapid determination of 11 fungicides (metalaxyl, cyprodinil, procymidone, iprovalicarb, myclobutanyl, kresoxim-methyl, benalaxyl, fenhexamide, tebuconazole, iprodione and dimethomorph) in white grape bagasse. The extractions were optimized on real non-spiked samples by means of experimental design and the optimal conditions were selected to achieve the method validation. The PLE procedure showed much higher efficiency than UAE for the target fungicides. Under the selected extraction conditions, PLE showed satisfactory linearity, repeatability and reproducibility. Recoveries for the majority of studied fungicides were higher than 80% with relative standard deviations (RSD) lower than 12%. Limits of detection (LODs) for GC TQ-MS were very low, at the sub ngg−1 for the majority of the target fungicides, well below the European maximum residue limits (MRLs) for wine and table grapes, and vine leaves. Eighteen white grape bagasse samples were analyzed and nine out of eleven targets were detected in the samples. Seven of them were detected in more than 50% of the samples and most samples contained at least four of the target analytes. The most frequently found compounds were tebuconazole and dimethomorph with concentrations between 1.6–130 and 2.0–1788ngg−1, respectively. Some samples showed high levels of many of the studied fungicides (high ngg−1, even μgg−1 for cyprodinil, fenhexamide, iprodione and dimethomorph), but all of them below the European maximum residue limits (MRLs) for wine grapes.
•E-tongue and E-nose coupled with SPME/GC–MS were used to analyze flavour difference.•Correlation analysis on flavour and quality indicators of apples were evaluated.•Hierarchical cluster analysis ...based on flavour and quality indicators was employed.
The flavour difference and other quality indicators among five popular apple varieties (‘Ralls’, ‘Jonagold’, ‘Orin’, ‘Indo’, and ‘Hanfu’) were evaluated mainly using electronic nose and electronic tongue coupled with gas chromatography-mass spectrometry (SPME/GC–MS). By linear discriminant analysis (LDA) of E-nose output data, the aroma of ‘Orin’ was found to be quite different from other varieties. There were obvious differences on sourness, saltiness, and umami among the five apple varieties in E-tongue analysis. For five apple varieties, 45 volatile compounds were identified, and their respective concentrations quantified using SPME/GC–MS, and which showed that, the most abundant volatile compounds in apples were esters. By principal component analysis (PCA), hexyl butanoate, (E)-2-hexenal and α-farnesene were the important volatile compounds in apples. The hierarchical cluster analysis (HCA) according electronic nose and electronic tongue analysis and other quality indicators showed that the flavour of ‘Hanfu’ was closely related to ‘Jonagold’, while ‘Indo’ and ‘Ralls’ flavour were closely related to ‘Orin’. The collaborative analysis method of combining electronic nose and electronic tongue had potential significance on flavor difference evaluation.
