Headspace-gas Chromatography-ion Mobility Spectrometry Research Articles

Influence of germination and roasting on the characteristic volatile organic compounds of quinoa using sensory evaluation, E-nose, HS-GC-IMS, and HS-SPME-GC-MS

This study aimed to investigate the effects of germination and roasting on the flavor of quinoa. Firstly, the aroma of quinoa and germinated quinoa roasted under different conditions was analyzed using sensory evaluation and electronic nose (E-nose). Results showed that the best favorable aroma of quinoa and germinated quinoa was obtained when roasted at 160 °C for 15 min. Then, a total of 34 and 80 volatile organic compounds (VOCs) of quinoa and germinated quinoa roasted at 160 °C for 15 min were determined using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS), respectively. Germination and roasting effectively reduced the contents of VOCs that produced undesirable flavor. Moreover, germination improved the floral aromas, while roasting mainly produced caramel, cocoa, and roasted nut aromas of quinoa. This study indicated that germination and roasting treatments might serve as promising processing methods to improve the flavor of quinoa.

Physicochemical properties and volatile compounds of whole lotus root powders prepared by different drying methods

This research aimed to evaluate the effects of freeze-drying (FD), hot air drying (HAD), hot air drying combined with baking (HADB) on the color, antioxidant activity, thermal and pasting properties, as well as volatile compounds of whole lotus root powders (WLRPs). The highest browning degree and antioxidant activity of WLRP was obtained by HAD at 80°C for 6 h. The gelatinization temperatures of the FD sample were higher than those of the HAD and HADB samples. WLRP prepared by HADB at 120°C for 5 min had the highest trough and final viscosities. Furthermore, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) analysis showed that 125 and 97 volatile compounds were detected from WLRPs in dried and hydrated states, respectively. The types of identified compounds were the most in dried HADB, followed by dried HAD and FD, which were also affected by the drying temperature and time. The hydration treatment led to an increase in the detected compounds from the FD sample and a decrease in those from the HAD and HADB samples. These observations indicated that the quality of WLRPs depended on the drying technique and conditions, which could be useful for selecting an appropriate drying method to prepare desirable WLRPs products.

Characterization of flavor and taste profile of different radish (Raphanus Sativus L.) varieties by headspace-gas chromatography-ion mobility spectrometry (GC/IMS) and E-nose/tongue

A comprehensive study of the overall flavor and taste profile of different radishes is lacking. This study systematically compared the volatile profile of six radish varieties using HS-GC-IMS and their correlation with the E-nose analysis. Organic acids and amino acids were quantified, and their association with the E-tongues analysis was explored. A total of 73 volatile compounds were identified, with diallyl sulfide and dimethyl disulfide being the primary sulfides responsible for the unpleasant flavor in radish. Compared to other varieties, cherry radishes boast a significantly higher concentration of allyl isothiocyanate, which likely contributes to their characteristic radish flavor. Moreover, oxalic acid was identified as the most abundant organic acid in radish, accounting for over 97% of its content, followed by malic acid and succinic acid. In conclusion, the distinct flavor and taste characteristics of different radish varieties partially explain their suitability for diverse culinary preferences.

Discrimination and screening of volatile metabolites in atractylodis rhizoma from different varieties using headspace solid-phase microextraction-gas chromatography-mass spectrometry and headspace gas chromatography-ion mobility spectrometry, and ultra-fast gas chromatography electronic nose

Atractylodis rhizoma is a common bulk medicinal material with multiple species. Although different varieties of atractylodis rhizoma exhibit variations in their chemical constituents and pharmacological activities, they have not been adequately distinguished due to their similar morphological features. Hence, the purpose of this research is to analyze and characterize the volatile organic compounds (VOCs) in samples of atractylodis rhizoma using multiple techniques and to identify the key differential VOCs among different varieties of atractylodis rhizoma for effective discrimination. The identification of VOCs was carried out using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), resulting in the identification of 60 and 53 VOCs, respectively. The orthogonal partial least squares discriminant analysis (OPLS-DA) model was employed to screen potential biomarkers and based on the variable importance in projection (VIP ≥ 1.2), 24 VOCs were identified as critical differential compounds. Random forest (RF), K-nearest neighbor (KNN) and back propagation neural network based on genetic algorithm (GA-BPNN) models based on potential volatile markers realized the greater than 90 % discriminant accuracies, which indicates that the obtained key differential VOCs are reliable. At the same time, the aroma characteristics of atractylodis rhizoma were also analyzed by ultra-fast gas chromatography electronic nose (Ultra-fast GC E-nose). This study indicated that the integration of HS-SPME-GC–MS, HS-GC-IMS and ultra-fast GC E-nose with chemometrics can comprehensively reflect the differences of VOCs in atractylodis rhizoma samples from different varieties, which will be a prospective tool for variety discrimination of atractylodis rhizoma.

60Co γ‐radiation at low‐dose level alters volatile compounds of blueberry during storage

Summary60Co γ‐radiation was applied to blueberry fruits in an effort to investigate a safe, eco‐friendly and effective blueberry preservation technique. However, the preservation effects were variable depending on tissue tolerance to irradiation doses. Moreover, irradiation may cause off‐odour. In this study, we examined the effects of three low doses of 60Co γ‐radiation on the physical and flavour attributes of blueberry. The results showed that 60Co γ‐radiation did not significantly improve fruit quality but extend the shelf life up to 15 days at 25 °C and 30 days at 4 °C. Compared with the control group, the preservation effect of 0.5–1.0 kGy irradiation treatment on blueberry fruit was not obvious before 15 days but maintained 65% of fruit firmness and reduced the loss of nutrients afterwards at 4 °C. At 25 °C, irradiation treatment caused up to a 150% increase in polyphenol oxidase activity, which was relevant to colour changes in late storage. Headspace Gas Chromatography Ion Mobility Spectrometry (HS‐GC‐IMS) was applied, and 33 volatile organic compounds (VOCs) in blueberry treated with different radiation doses were identified, including 11 esters, 8 aldehydes, 7 alcohols, 6 ketones and other substances, which increased with increasing radiation dose. Radiation reduced the green taste of blueberry and promoted their ripening. Radiation above the level of 1.02 kGy led to the flavour deterioration of blueberry such as ethyl trans‐2‐butenoate. The side effects of radiation on the aroma of blueberry could be offset by low‐temperature storage. Blueberry stored at 4 °C contained more aldehydes with a heavier fresh/green aroma. Six aromas were proposed to be characteristic odour markers of radiated blueberry.

Characteristic Flavor Substances of Guizhou Black Tea and the Environmental Factors Influencing Their Formation Using Stable Isotopes and Headspace Gas Chromatography-Ion Mobility Spectrometry

Characteristic Flavor Substances of Guizhou Black Tea and the Environmental Factors Influencing Their Formation Using Stable Isotopes and Headspace Gas Chromatography-Ion Mobility Spectrometry

GC-IMS and multivariate analyses of volatile organic components in different Chinese breeds of chickens

This study examined the difference in volatile flavor characteristics among four different local breeds of chicken by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with multivariate analysis. In total, 65 volatile organic compounds (VOCs) were identified (17 aldehydes, 12 alcohols, 7 ketones, 5 esters, 2 acids, and 22 unidentified, i.e., 26.15% aldehydes, 18.46% alcohols, 10.77% ketones, 7.69% esters, 3.08% acids, and 33.84% unidentified), of which 43 were annotated. The chicken meats from the four breeds exhibited good separation in topographic plots, VOC fingerprinting, and multivariate analysis. Meanwhile, 20 different volatile components, with variable importance in projection value > 1, were selected as potential markers to distinguish different breeds of chicken by partial least squares discriminant analysis (PLS-DA). These findings provide insights into the flavor traits of chicken meat. Also, HS-GC-IMS combined with multivariate analysis can be a convenient and powerful method for characterizing different meats.

Detection and Comparison of Volatile Organic Compounds in Four Varieties of Hawthorn Using HS-GC-IMS

Hawthorn is a type of natural food with significant medicinal and nutritional properties; it has been listed in the “Both Food and Drug” list by the Chinese Ministry of Health Item List since 1997. However, hawthorn varieties have complex origins, and there are significant differences in the content, type, and medicinal efficacy of the chemically active ingredients in different varieties of hawthorn. This leads to the phenomenon of mixed varieties and substandard products being passed off as high-quality. In this work, by using headspace gas chromatography–ion mobility spectrometry (HS-GC-IMS), we identified and analyzed volatile organic compounds (VOCs) in four varieties of hawthorn, establishing their characteristic fingerprints. As a result, a total of 153 peaks were detected, and 139 VOCs were also identified. As shown by the fingerprint profiles, the different hawthorn samples contained different VOCs. Meanwhile, by using principal component analysis (PCA), Euclidean distance, and partial least-squares discriminant analysis (PLS-DA), the relationship between the VOCs found in the different varieties of hawthorn was revealed. This study developed a simple, fast, accurate, and sensitive method for identifying, tracking, and evaluating hawthorn varieties.

Effects of Heating Treatment on the Physicochemical and Volatile Flavor Properties of Argentinian Shortfin Squid (Illex argentinus).

In this study, the effect of different heating temperatures (80, 90, 100, and 121 °C) on the physicochemical and volatile flavor properties of fried mantles (Argentinian shortfin) was investigated. The squid mantles were soaked in a maltose syrup solution (20% w/v) for 10 s and fried in soybean oil for 10 s (160 °C), vacuum-packed, and processed at different temperatures for 10 min. Then, the squid mantles were subjected to colorimetric analysis, sensory evaluation, free amino acid analysis, and texture profile analysis. In addition, the volatile organic compounds (VOCs) in the squid mantles were analyzed. The results revealed that lower treating temperatures (80 and 90 °C) improved the chromatic and textural properties, along with organoleptic perception. Additionally, the content of amino acid in the squid mantles treated at 121 °C was significantly lower than that of the samples treated at other temperatures (p < 0.05). Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was used to detect 41 VOCs, including their monomers and dimers. Among these detected VOCs, the contents of alcohols, ketones, and pyrazines were positively correlated with temperature. However, the content of aldehydes in the squid mantles gradually decreased as the heating temperature increased (p < 0.05). The combined HS-GC-IMS and E-nose results revealed that the lower temperatures (80 and 90 °C) were more suitable for flavor development and practical processing. This study provides valuable information for properly controlling the heating process of squid products, as well as flavor and practical applications for the aquatic industry.

Characterization of Flavor Profiles of Cigar Tobacco Leaves Grown in China via Headspace-Gas Chromatography-Ion Mobility Spectrometry Coupled with Multivariate Analysis and Sensory Evaluation.

Although cigar tobacco leaves (CTLs) have a high economic value, research regarding the flavor characteristics of CTLs is currently limited. A comprehensive study of the flavor characteristics of CTLs from different regions of China was conducted by identifying their volatile-flavor-containing compounds (VFCs) and flavors. The samples were analyzed via gas chromatography-ion mobility spectrometry (GC-IMS) and sensory evaluation. Results revealed considerable differences in the VFC contents of CTLs from different regions of China, suggesting that the VFLs of CTLs could be influenced by geographical origin. Mainly, phenols, pyrazines, and aldehydes were present in the CTLs from Sichuan. High contents of esters and pyrazines were present in the CTLs from Hubei, while esters were the major components of the CTLs from Hainan. Multivariate analysis results showed the effective differentiation of samples from different geographical origins based on the GC-IMS results. Sensory evaluation revealed that the flavors of CTLs from different geographical origins were different. 1,8-Pinene, 3-methyl-3-butene-1-ol, 2,3-dimethyl-5-ethylpyrazine, 4-methyl-3-penten-2-one, and (E)-2-pentenal might serve as geographical marker compounds, indicating the geographical origin of CTLs based on the results of GC-IMS and sensory evaluation. This study may be beneficial for the trade of CTLs and the development of cigar products.

Geographical discrimination of Paw San rice cultivated in different regions of Myanmar using near-infrared spectroscopy, headspace-gas chromatography-ion mobility spectrometry and chemometrics

Paw San rice, also known as “Myanmar pearl rice”, is considered the highest quality rice in Myanmar. There are considerable differences in terms of the premium commercial value of Paw San rice, which is an incentive for fraud, e.g. adulteration with cheaper rice varieties or mislabelling its geographical origin. Shwe Bo District is one of the most popular rice growing areas in the Sagaing region of Myanmar which produces the most valued and highly priced Paw San rice (Shwe Bo Paw San). The verification of the geographical origin of Paw San rice is not readily undertaken in the rice supply chain because the existing analytical approaches are time-consuming and expensive. Therefore, there is a need for rapid, robust and cost-effective analytical techniques for monitoring the authenticity and geographical origin of Paw San rice.In this 4-year study, two rapid screening techniques, Fourier-transform near-infrared (FT-NIR) spectroscopy and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), coupled with chemometric modelling, were applied and compared for the regional differentiation of Paw San rice. In addition, low-level fusion of the FT-NIR and HS-GC-IMS data was performed and its effect on the discriminative power of the chemometric models was assessed. Extensive model validation, including the validation using independent samples from a different production year, was performed. Furthermore, the effect of the sample preparation technique (grinding versus no sample preparation) on the performance of the discriminative model, obtained with FT-NIR spectral data, was assessed. The study discusses the suitability of FT-NIR spectroscopy, HS-GC-IMS and the combination of both approaches for rapid determination of the geographical origin of Paw San rice.The results demonstrated the excellent potential of the FT-NIR spectroscopy as well as HS-GC-IMS for the differentiation of Paw San rice cultivated in two distinct geographical regions. The OPLS-DA model, built using FT-NIR data of rice from 3 production years, achieved 96.67% total correct classification rate of an independent dataset from the 4th production year. The DD-SIMCA model, built using FT-NIR data of ground rice, also demonstrated the highest performance: 94% sensitivity and 97% specificity. This study has demonstrated that FT-NIR spectroscopy can be used as an accessible, rapid and cost-effective screening tool to discriminate between Paw San rice cultivated in the Shwe Bo and Ayeyarwady regions of Myanmar.

Strategy on rapid discrimination of different varieties based on the combination of HS-GC-IMS and DNA Mini-barcode, spore powder of Ganoderma as a case study

The demand for the consumption of Ganoderma (LingZhi) is increasing significantly nowadays. While the wild resources of Ganoderma lucidum and Ganoderma sinense have been reduced severely, and artificially cultivated products are gradually occupying the market. However, it is usually difficult to distinguish the different species of Ganoderma spore powder (GSP). In this research, a rapid and accurate identification method which combined headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) with the DNA mini-barcode was successfully developed to discriminate different GSP. The feasibility of the method was evaluated by both GSP and its Chinese patent medicines. HS-GC-IMS was used to characterize GSP volatile organic compounds (VOCs) and a total of seventy-one VOCs were identified. Principal component analysis could be utilized to show the significantly difference between Korean LingZhi (KL) and American LingZhi (AL) or Taishan LingZhi (TL). Then, we clarified the species information of all samples based on the internal transcribed spacer (ITS) regions. The identification results showed that TL and KL were Ganoderma lucidum, and the AL was Ganoderma resinaceum. Furthermore, according to the mutation sites of the above ITS sequences, the specialized DNA mini-barcode was successfully developed and applied. The artificial mixtures of the three types of GSP and Chinese patent medicines containing GSP were used to authenticate the barcode capability. The mixing experiment found that there was a linear relationship between the sequence numbers and the mixed biomass, indicating that the qualitative and quantitative ability of DNA mini-barcode performed well. The investigation of the ingredients of commercially available GSP products found that the commercial products maybe contain Ganoderma resinaceum, Ganoderma applanatum and Daedaleopsis confragosa, except for Ganoderma lucidum. Therefore, the results suggested that the available GSP products might be adulterated according to Chinese Pharmacopoeia. In this paper, we established a novel approach to distinguish the different GSP samples based on HS-GC-IMS and DNA mini-barcode, and the results indicated that our strategy could not only discriminate different GSP samples, but also identify the origins in their related products.

Characteristic flavor compounds in Guizhou green tea and the environmental factors influencing their formation: Investigation using stable isotopes, electronic nose, and headspace-gas chromatography ion migration spectrometry

The Guizhou province is a significant contributor to the production of green tea within China. The present study aims to examine the characteristic flavor compounds found in Guizhou green tea and explore the environmental factors that contribute to the development of these unique flavor compounds. Accordingly, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and electronic nose were employed in conjunction with odor activity value (OAV) analysis to develop an orthogonal projections to latent structures discriminant analysis (OPLS-DA) model that was capable of discerning between the three distinct habitats (QE, QM, QW) of Guizhou green tea based on their flavor constituents. The findings show that the primary constituents contributing to the flavor profile of Guizhou green tea consisted of 3-methyl-2-butenal, butanal, pentanal, linalool, 6-methyl-5-hepten-2-one, dimethyl disulfide, and dimethyl sulfide. Subsequently, the stable isotope technique was employed to examine the growth environmental factors of Guizhou green tea, based on the identification of the flavoring compounds that differentiate green tea from various habitats within the Guizhou province. Accordingly, temperature and sunshine were found to have the greatest impact on the flavor compounds present in Guizhou green tea.

Influence of heating temperatures and storage on the odor of duck meat and identification of characteristic odorous smell compounds

To clarify the characteristic odor of compounds present in duck meat, especially reheating after storage, the effect of duck breast cooked at three temperatures (90 °C, 100 °C, 105 °C) and reheating after 7 days of storage was studied. Electronic nose analysis and sensory evaluation revealed a significant increase (p < 0.05) in reheated duck meat odor after 7 days of storage. The 90 °C treatment group had the heaviest odor, which increased by 12.19 % after seven days of storage. Using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), 60 volatile flavor compounds were identified across various groups. Although the volatile compounds were consistent among different groups, their relative contents varied. By combining the sensory evaluation results with the Relative Odor Activity Value (ROAV) of these flavor compounds, chemometric orthogonal partial least squares discriminant analysis (OPLS-DA) was used to identify the following 9 characteristic volatile compounds: 2-methylbutanal, pentanal, octanal, heptanal, hexanal, (E)-2-octenal, (E)-2-nonenal, and 2-pentyl furan

Screening tools combined with multivariate data analysis to predict or confirm virgin olive oil classification by the Panel test

AbstractA particular aspect of quality control of virgin olive oil (VOO) is the mandatory application, together with chemical and instrumental determinations, of a standardized and official method for sensory assessment. The latter, known as Panel test, is carried out by trained assessors and contributes to the classification of VOOs into three commercial categories (extra virgin, virgin, and lampante). One drawback of this method is related to the large number of samples to be analyzed, compared to the work capacity of a sensory panel, especially during the selection for purchase by companies that blend and market virgin oils and the quality control conducted by the authorities to verify the declared commercial category. For this reason, it is helpful to develop and validate robust and rapid screening methods, based on volatile fingerprints, to preclassify each sample into one of the three commercial categories. Considering the strict relation between volatile compounds and the main sensory attributes (fruity and defects), a gas‐chromatographic volatile fingerprint can be the right choice. In this paper, the comparison of two emerging techniques, namely, headspace‐gas chromatography‐ion mobility spectrometry (HS‐GC‐IMS) and flash‐gas chromatography (FGC), applied on a sample set of 49 VOOs, using calibrations previously built with a larger number of samples, is presented. The number of correctly classified samples, with respect to the commercial category determined by the Panel test, was satisfactory and comparable (92% for HS‐GC‐IMS, and 94% for FGC), confirming the effectiveness of both methods and the robustness of the predictive models.Practical Applications: The demand for rapid screening tools to reduce the number of samples to be assessed by the Panel test has increased in recent years. The validation of robust models and their joint adoption by companies that market VOOs as well as official control bodies could reduce nonconformities and increase the batches of VOO being controlled, thus better protecting the consumer. Therefore, it is desirable to have different tools available to analyze volatile compounds, together with the associated calibration models, along with detailed instructions for their application, to have different alternatives that suit the equipment of individual laboratories.

Endophytic Stenotrophomonas geniculata KJ-6 via producing antifungal volatile organic compounds effectively control Lanzhou lily postharvest diseases

The endophytic bacterial Stenotrophomonas geniculata KJ-6, was isolated from Arisaematis rhizoma. This strain has the ability to control three postharvest pathogenic fungi of Lanzhou lily (Trichoderma lixii F-2, Talaromyces tumuli F-3, and Fusarium annulatum F-6) by releasing volatile organic compounds (VOCs). The experiment utilized the double-layer sealed bottom plate method. The results demonstrate that KJ-6 effectively inhibits the mycelial growth of F-2, F-3, and F-6, with inhibition rates of 81.59%, 79.87%, and 84.7%, respectively. Moreover, scanning electron microscopy (SEM) revealed abnormal mycelium morphology in the test pathogenic fungi treated with KJ-6 VOCs, characterized by multiple wrinkles, cracks, and distortions. Using five common phytopathogenic fungi as controls, our results demonstrated that the VOCs from KJ-6 exhibited broad-spectrum antifungal effects. Analysis using headspace gas chromatography-ion mobility spectrometry identified three components of the VOCs produced by KJ-6, including 1-propanethiol, isoamyl acetate, and 2-methyl-1-butanol. Antifungal tests revealed that 1-propanethiol plays a crucial role in the inhibitory activity of VOCs. It exhibited inhibitory rates of 64.17%, 72.73%, and 26.71% on the mycelium growth of F-2, F-3, and F-6, respectively. In vivo experiments further confirmed that VOCs can significantly reduce the disease index and decay rate of Lanzhou lily bulbs during storage. Moreover, KJ-6 treatment led to a significant reduction in the degree of browning of lily bulbs. Additionally, it enhanced the activity of defense-related enzymes, improved disease resistance, and extended the shelf life of lily bulbs. As a result, this study offers a theoretical foundation for the biological control of postharvest diseases in Lanzhou lily.

Comparative Analysis of Volatile Compounds in the Flower Buds of Three Panax Species Using Fast Gas Chromatography Electronic Nose, Headspace-Gas Chromatography-Ion Mobility Spectrometry, and Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry Coupled with Multivariate Statistical Analysis.

The flower buds of three Panax species (PGF: P. ginseng; PQF: P. quinquefolius; PNF: P. notoginseng) widely consumed as health tea are easily confused in market circulation. We aimed to develop a green, fast, and easy analysis strategy to distinguish PGF, PQF, and PNF. In this work, fast gas chromatography electronic nose (fast GC e-nose), headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were utilized to comprehensively analyze the volatile organic components (VOCs) of three flowers. Meanwhile, a principal component analysis (PCA) and heatmap were applied to distinguish the VOCs identified in PGF, PQF, and PNF. A random forest (RF) analysis was used to screen key factors affecting the discrimination. As a result, 39, 68, and 78 VOCs were identified in three flowers using fast GC e-nose, HS-GC-IMS, and HS-SPME-GC-MS. Nine VOCs were selected as potential chemical markers based on a model of RF for distinguishing these three species. Conclusively, a complete VOC analysis strategy was created to provide a methodological reference for the rapid, simple, and environmentally friendly detection and identification of food products (tea, oil, honey, etc.) and herbs with flavor characteristics and to provide a basis for further specification of their quality and base sources.

Discrimination and characterization of volatile organic compounds in Lonicerae Japonicae flos and Lonicerae flos using multivariate statistics combined with headspace gas chromatography-ion mobility spectrometry and headspace solid-phase microextraction gas chromatography-mass spectrometry techniques.

The volatile organic compounds (VOCs) of Lonicerae Japonicae flos (LJF) and Lonicera flos (LF) play a pivotal role in determining their sensory characteristics, medicinal properties, and subsequent impact on market pricing and consumer preferences. However, the differences and specificity of these VOCs remain obscure. Hence, it is crucial to conduct a comprehensive characterization of the VOCs in LJF and LF and pinpoint their potential differential VOCs. In this study, headspace gas chromatography-ion mobility spectrometry (HS-GC/IMS) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) were employed to comprehensively investigate the compositional characteristics and distinctions in VOCs between LJF and LF. Multivariate statistical analysis was used to identify candidate differential VOCs of LJF and LF samples. A total of 54 and 88 VOCs were identified using HS-GC/IMS and HS-SPME-GC/MS analysis, respectively. Primary VOCs detected in LJF include leaf alcohol, (E)-2-hexen-1-ol dimer, 2-octyn-1-ol, and (E)-3-hexen-1-ol. Key VOCs prevalent in LF encompass farnesol, heptanoic acid, octanoic acid, and valeric acid. Multivariate statistical analysis indicates that compounds such as phenethyl alcohol and leaf alcohol were selected as potential VOCs for distinguishing between LJF and LF. This research conducted a comprehensive analysis of the fundamental volatile components in both LJF and LF. It subsequently elucidated the distinctions and specificities within their respective VOC profiles. And this study enables differentiation between LJF and LF through the analysis of VOCs, offering valuable insights for enhancing the quality control of both LJF and LF.

Authenticity assessment of ground black pepper by combining headspace gas-chromatography ion mobility spectrometry and machine learning

Currently, the authentication of ground black pepper is a major concern, creating a need for a rapid, highly sensitive and specific detection tool to prevent the introduction of adulterated batches into the food chain. To this aim, head space gas-chromatography ion mobility spectrometry (HS-GC-IMS), combined with machine learning, is tested in this initial, proof-of-concept study. A broad variety of authentic samples originating from eight countries and three continents were collected and spiked with a range of adulterants, both endogenous sub-products and an assortment of exogenous materials. The method is characterized by no sample preparation and requires 20 min for chromatographic separation and ion mobility data acquisition. After an explorative analysis of the data, those were submitted to two different machine learning algorithms (partial least squared discriminant analysis-PLS-DA and support vector machine-SVM). While the PLS-DA model did not provide fully satisfactory performances, the combination of HS-GC-IMS and SVM successfully classified the samples as authentic, exogenously-adulterated or endogenously-adulterated with an overall accuracy of 90 % and 96 % on withheld test set 1 and withheld test set 2, respectively (at a 95 % confidence level). Some limitations, expected to be mitigated by further research, were encountered in the correct classification of endogenously adulterated ground black pepper. Correct categorization of the ground black pepper samples was not adversely affected by the operator or the time span of data collection (the method development and model challenge were carried out by two operators over 6 months of the study, using ground black pepper harvested between 2015 and 2019). Therefore, HS-GC-IMS, coupled to an intelligent tool, is proposed to: (i) aid in industrial decision-making before utilization of a new batch of ground black pepper in the production chain; (ii) reduce the use of time-consuming conventional analyses and; (iii) increase the number of ground black pepper samples analyzed within an industrial quality control frame.

Volatile-compound fingerprinting and discrimination of positional isomers in stamp-pad ink tracing using HS-GC-IMS combined with multivariate statistical analysis.

The rising crime rate associated with document forgery has a significant impact on public safety and social stability. In document fraud cases, determining the origin of a particular stamp-pad ink is the most important objective. In this study, a comprehensive analysis of the volatile compounds in quick-drying stamp-pad inks from six commonly used brands were performed for the first time, utilizing a combination of headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and multivariate statistical analysis methods. Visual and comparative analysis of the differential volatile components among different stamp-pad ink samples was conducted using fingerprints and volcano plots. A total of 127 volatile compounds were accurately identified, with ketones, esters, alcohols, and aldehydes being the most abundant compounds in the stamp-pad inks. Hierarchical clustering analysis (HCA), including dendrograms and clustering heatmaps, was utilized to explore the correlations between these compounds and the samples. Additionally, the precise identification of positional isomers and functional group isomers of aliphatic compounds was achieved. To achieve accurate discrimination of various stamp-pad ink samples, a multivariate statistical analysis method was utilized to establish a classification model for them. Based on the results obtained from HS-GC-IMS, effective discrimination among different brands of stamp-pad ink samples was achieved through principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The model exhibited excellent performance, with the fit index of dependent variables (R2Y) and the predictive index of the model (Q2) values of 0.99 and 0.984, respectively. These results provided significant theoretical evidence for the application of HS-GC-IMS as an efficient technique in the analysis of volatile compounds, identification of positional isomers and functional group isomers, as well as tracing the origin of stamp-pad ink and analyzing the formation time of documents.