Headspace Gas Chromatography-mass Spectrometry Research Articles

Qualitative Assessment of Off-Gassing of Compounds from Field-Contaminated Firefighter Jackets with Varied Air Exposure Time Intervals Using Headspace GC-MS.

Firefighters are exposed to a complex mix of volatile and semi-volatile compounds from burning construction materials, consumer products, and other elements during fire suppression and rescue. These compounds can be absorbed onto the gear worn by firefighters and, depending on their volatility, can be released from the gear under different conditions. Few studies have focused on the off-gassing of toxic compounds from firefighters' gear, particularly in terms of qualitative analysis methods. This study introduces a novel qualitative analysis method using headspace gas chromatography-mass spectrometry (HS-GC-MS) to assess off-gassing from field-contaminated jackets at regular intervals. Our findings show that certain compounds, such as acetic acid and di-ethyl-hexyl-phthalate (DEHP), remained present even after the gear were allowed to air out for 48 h. The persistent off-gassing of chemicals, even under ambient conditions, raises concerns about potential hazards that could pose risks for personnel in the vicinity of contaminated gear, including inside fire stations. The implications of these findings extend beyond fire stations and may have significant public health implications for firefighters who are repeatedly exposed to these compounds over time.

Immunotoxicity induced by occupational inhalation exposure to waste anesthetic gases: a historical cohort study.

This was a historical cohort study in which 30 male participants with at least one year of work experience in the operating room at the time of the study and 30 unexposed referent subjects were investigated. Exposure levels were quantified by measuring the urinary concentrations of nitrous oxide (N2O), isoflurane, and sevoflurane gases by headspace gas chromatography-mass spectrometry. Serum concentrations of interleukin-4 (IL-4), Th2-type cytokines, and interferon-gamma (IFN-γ) were measured by the ELISA method. Additionally, an automated hematology analyzer was used for the white blood cell count and white blood cell differential test. The data were analyzed using SPSS software for Windows version 21. Mean urinary concentrations of N2O, isoflurane, and sevoflurane were found to be 211.57±75.15, 4.06±0.96, and 19.51±12.96 ppb, respectively. In simplistic statistical data analysis, significant differences were noted between exposed and control groups as far as the mean serum cytokines levels (IFN-γ, IL-4) were concerned. Furthermore, after adjusting for important confounders, statistical analysis showed that the IFN-γ, IL-4, and the ratio of IFN-γ/IL-4 were significantly higher in the exposed group than in the referent subjects. These findings provide corroborative evidence to further substantiate the contention that exposure to anesthetics agents (N2O, isoflurane, and sevoflurane) is associated with subtle, subclinical, prepathological changes in the parameters of immune function. The long-term ramification of these changes requires further investigation.

Application of untargeted volatile profiling in inflammatory bowel disease research

Inflammatory bowel disease (IBD) diagnosis depends on criteria based on histological, endoscopic, radiological, and clinical results. These studies show drawbacks as being expensive, invasive, and time-consuming. In this work, an untargeted metabolomic strategy based on the monitoring of volatile compounds in serum by headspace gas chromatography–mass spectrometry is proposed as a complementary, fast, and efficient test for IBD patient diagnosis. To develop the method and build a chemometric model that allows the IBD diagnosis, serum samples including IBD patients and healthy volunteers were collected. Analyses were performed by incubating 400 µL of serum for 10 min at 90 °C. For data processing, an untargeted metabolomic strategy was used. A total of 96 features were detected, of which a total of 10 volatile compounds could be identified and confirmed by means of the analysis of real standards. The chemometric treatment consisted of a discriminant analysis of orthogonal partial least squares (OPLS-DA) obtaining a 100% of classification rate, since all the analyzed samples were correctly classified.Graphical abstract

Headspace GC/MS and LC/MS analysis of bioactive compounds from Gossypium barbadense L. stem and assessment of their antimicrobial and cytotoxic activities

ABSTRACT. In line with the global interest and demand in finding sustainable ways to the emerging antimicrobial and cytotoxic activities, our study highlights the unique chemical composition of G. barbadense stem. Petroleum ether extracts were analyzed via headspace-gas chromatography/mass spectrometry (HS-GC/MS) revealing 48 compounds, thirteen major and accounting for 56.29% of total peak areas. By using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) identify 16 major phenolic compounds from the methanolic extract. Both petroleum ether and methanolic extracts were tested for antibacterial activity against four pathogenic bacterial strains (Escherichia coli ATCC10536, Staphylococcus aureus ATCC6538, Salmonella enterica ATCC 14028, and Pseudomonas aeruginosa ATCC 9027) by using disk diffusion method. The antifungal activity against two fungal strains (Aspergillus niger and Aspergillus fumigatus) was evaluated. The results were compared to the activity of ciprofloxacin as a stander. The in-vitro cytotoxic activity of the methanolic extract showed a potent effect against liver (HEPG2) with IC50 values (18.8±7.4 μg/mL) and moderate activity against colon (HCT116) and breast (MCF7) cancer.
 
 KEY WORDS: Gossypium Barbadense L. Stem, Headspace/GC/MS, LC-ESI-MS, Bioactive compounds, Antimicrobial, Cytotoxic activities
 
 Bull. Chem. Soc. Ethiop. 2023, 37(4), 1021-1032. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i4.17

Static headspace gas chromatography–mass spectrometry for volatile organic compounds in bovine milk samples

AbstractVolatile organic compounds (VOCs) provide insight into the taste and aroma of milk. VOCs in milk are typically analyzed using headspace gas chromatography–mass spectrometry (GC‐MS). While static headspace GC‐MS is a simple and widely applicable analytical technique for the analysis of VOCs in various samples, it has not been frequently applied to milk samples. In this study, static headspace GC‐MS was used to compare the VOCs of three different brands of commercial milk. Three components were identified in the samples, that is, acetone, toluene, and 2‐heptanone, where the concentration ranges of acetone, toluene, and 2‐heptanone in the milk samples were 2.284–3.256, 0.028–0.178, and 0.014–0.020 μg/mL, respectively. A literature review found that all three components were previously reported in milk, while toluene and 2‐heptanone were newly identified using headspace GC‐MS in this study.

Biochemical and Physiological Responses of Cucumis sativus L. to Application of Potential Bioinsecticides—Aqueous Carum carvi L. Seed Distillation By-Product Based Extracts

The extensive application of synthetic insecticides and herbicides over the past 50 years has led to a number of problems, including negative effects on non-target organisms and the evolution of pesticide-resistant pests. As an alternative means of pest control, plant-based biopesticides have emerged. While developing a new bioinsecticide, allelopathy on both target pests and target crops must be evaluated. We evaluated volatile organic compounds (VOCs), total phenolic content (TPC), total sugars and antiradical activity (ARA), as well as 18 photosynthetic apparatus characterizing functional parameters as stress signaling response to aqueous caraway seed distillation by-product-based extracts. VOCs were detected by headspace gas chromatography mass spectrometry (HS-GC-MS). The caraway extract application decreased “green leaf volatile” C4, C5 and C6 alcohol content in the cucumber leaves. Total phenolic content (TPC), total sugars and antiradical activity (ARA) using high-throughput 96-well plate spectrophotometric methods were tested in dried leaves. No significant changes in these parameters were detected in cucumber leaves after the application of extracts. The caraway extract application did not cause changes in the functioning of the photosynthesis apparatus. Aqueous caraway seed distillation by-product-based extracts can be considered non-phytotoxic to cucumber plants; however, they modify the VOC emissions even ten days after treatment.

Phytochemical Diversity Comparison in Leaves and Roots of Wild and Micropropagated Latvian Sea Holly (Eryngium maritimum L.).

The goal of the current study was to compare the chemical composition of the roots, shoots, and leaves of wild-growing Eryngium maritimum L., and of in vitro and in field-cultivated plants in Latvia. The essential oil yield obtained by hydrodistillation ranged from 0.14% to 0.54%, while analysis of the chemical composition using GC-MS revealed a total of 44 different volatiles, with differences in the types and amounts of volatiles between the leaves and roots. Using 96-well plate techniques, the concentration of total phenolic compounds, saponins, and sugars in the aqueous ethanolic extracts of E. maritimum were assessed, along with their capacity to scavenge stable DPPH radicals. Extracts from roots had a lower concentration of total phenolic compounds compared to those from the leaves of wild grown and cultivated plants but did not differ from in vitro shoots. Root, leaf, and shoot samples of the same genotype from different growth conditions had approximately the same concentration of total saponins, while total sugar concentrations were higher in the roots. The growth conditions had a significant effect on the concentration of total phenolic compounds and antiradical activity, with differences that were significant observed between plant aboveground and belowground parts. Analysis using UHPLC-ESI-q-TOF-MS revealed 63 compounds, with amino acids and hydroxycinnamic acid derivatives (such as chlorogenic and rosmarinic acid) being the major compound groups that significantly differed between plant growth conditions. We also demonstrated that rapid screening of volatile compounds in in vitro plants using headspace gas chromatography mass spectrometry analyses can predict the formation of marker compounds in the same mericlones grown in field conditions. These findings provide valuable insights into the chemical composition of E. maritimum and its potential for use in various applications.

Sex Differentiation from Human Scent Chemical Analysis

Human scent traces are often the only pieces of evidence providing information about individuals that were present at a crime scene. In this study, the possibility of sex differentiation using detailed chemical analyses of human scent samples for forensic purposes is discussed. The human scent samples were analyzed through the use of headspace-gas chromatography/mass spectrometry (HS-GC/MS). The results of these chemical analyses were evaluated using several data processing approaches (Linear Support Vector Machine, Quadratic Discriminant Analysis, and Ridge Regression), which were applied to distinguish between sexes from the human scent samples obtained from the palms of six volunteers for twelve weeks. This study indicates that sex differentiation based on the chemical analysis of human scent samples using HS-GC/MS is possible. The best results were obtained using the Ridge Regression with thresholding providing accuracy and a critical sensitivity of the sex differentiation of better than 91%.

Soap application alters mosquito-host interactions

To find nutrients, mosquitoes use volatile organic compounds (VOCs) emitted by plants and animal hosts. These resources overlap in their chemical composition, and an important layer of information resides in VOCs' relative abundance in the headspace of each resource. In addition, a large majority of the human species regularly uses personal care products such as soaps and perfumes, which add plant-related VOCs to their olfactory signature. Using headspace sampling and gas chromatography-mass spectrometry, we quantified how human odor is modified by soap application. We showed that soaps alter mosquito host selection, with some soaps increasing the attractiveness of the host and some soaps reducing it. Analytical methods revealed the main chemicals associated with these changes. These results provide proof-of-concept that data on host-soap valences can be reverse-engineered to produce chemical blends for artificial baits or mosquito repellents, and evince the impact of personal care products on host selection processes.

Influences of Spices on the Flavor of Meat Analogs and Their Potential Pathways.

This study evaluated the correlation between the sensory characteristics and spices of 50 commercial meat analogs and selected 4 spices to improve the flavor characteristics of soy protein concentrate (SPC) extrudates. Volatile compounds in extrudates and commercial meat analogs were investigated using headspace solid-phase microextraction and gas chromatography-mass spectrometry. The total concentrations of off-flavor volatile compounds in commercial products decreased with an increasing degree of processing. Furthermore, after adding spices during extrusion, the concentrations of volatile compounds such as aldehydes, alcohols, and furans related to thermal treatment decreased by approximately 5-39%, 5-15%, and 11-56%, respectively. Among them, compounds such as nonanal, 2-pentlyufuran, and 1-octen-3-ol, typical off-flavors in soy-based food, decreased by 8-42%, 11-55%, 2-52%, respectively. The correlation analysis between the antioxidative abilities of spices and volatile compounds showed that the contents of total phenolics were negatively correlated with the contents of ketones and alcohols in extrudates (p < 0.001). Moreover, the aroma-active compounds in extrudates were changed. More pleasant compounds, including alkanes and olefins, were observed by adding different spices as well. Especially in black pepper treated extrudates, the OAV value of off-flavor volatile compounds such as hexanal, octanal, 2-pentlyfuran decreased. In conclusion, the addition of spices can reduce off-flavor compounds related to thermal reactions, such as oxidation and the Maillard reaction, and impart newly pleasant flavors to extrudates during the extrusion of SPC. It is important to explore new methods that can be used to improve the flavor of extrudates so that consumers' preferences of meat analog products can be improved.

Rapid screening of Chemical Weapons Convention-related chemicals in oil matrix by headspace solid-phase microextraction and gas chromatography-mass spectrometry

The Chemical Weapons Convention (CWC) requires verification of a large number of compounds with different types and properties. The results of the verification are of great political and military sensitivity. However, the sources of verification samples are complex and diverse, and the contents of the target compounds in these samples are usually very low. These issues increase the likelihood of missed or false detection. Thus, establishing rapid and effective screening methods for the accurate identification of CWC-related compounds in complex environmental samples are of great importance. In this study, a fast and simple procedure based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-electron ionization mass spectrometry (GC-EI/MS) in full-scan mode was developed to determine CWC-related chemicals in oil matrix. A total of 24 CWC-related chemicals with different chemical characteristics were selected to simulate the screening procedure. The selected compounds were divided into three groups based on their properties. The first group included volatile and semi-volatile CWC-related compounds with relatively low polarity, which could be extracted by HS-SPME and directly analyzed by GC-MS. The second group included moderately polar compounds with hydroxyl or amino groups; such compounds are related to nerve, blister, and incapacitating agents. The compounds in the third group included non-volatile CWC-related chemicals with relatively strong polarity, such as alkyl methylphosphonic acids and diphenyl hydroxyacetic acid. These compounds must be derivatized into vaporizable derivatives prior to extraction by HS-SPME and analysis by GC-MS. Variables that influence the SPME process, such as fiber type, extraction temperature and time, desorption time, and derivatization protocol, were optimized to improve the sensitivity of the method. The screening procedure for CWC-related compounds in the oil matrix samples included two main steps. First, low-polarity volatile and semi-volatile compounds (i. e. the first group) were extracted by HS-SPME with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibers and analyzed in split-injection mode (split ratio, 10∶1) using GC-MS. The use of a large split ratio can reduce the solvent effect, which is conducive to the detection of low-boiling-point compounds. If necessary, the sample could be extracted once more and analyzed in splitless mode. The derivatization agent bis(trimethylsilyl)trifluoroacetamide (BSTFA) was then added to the sample. Mid- and high-polarity compounds (i. e. the second and third groups) were extracted with polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibers after derivatization and analyzed in splitless mode using GC-MS. The established method exhibited good repeatability and sensitivity. The detection limits for the compounds in the first group ranged from 0.5 ng/mL to 100 ng/mL, whereas the detection limits for the compounds in the second and third groups ranged from 20 ng/mL to 300 ng/mL. Except for compounds with extremely high boiling points and a few compounds that are not suitable for derivatization with BSTFA, the method can be used to analyze most CWC-related compounds in oil matrix samples. In particular, it greatly shortened the preparation time of the oil matrix samples and reduced the loss of low-boiling-point compounds owing to the sample concentration process, thereby avoiding missed detection. The method was successfully applied to the Organization for the Prohibition of Chemical Weapons (OPCW) proficiency tests and proved to be a useful technique for the rapid screening of trace levels of CWC-related chemicals in oil matrix.

Release of Fragrances from Polymer Coatings Triggered by Contact with Sweat

Fragrances are active compounds that suffer from the fact that fragrances are usually quickly volatile and hence display a limited use in daily life applications. To overcome this problem, the fragrances benzaldehyde and heptanal are conjugated to a monomer via a hydrazone linkage. The functional monomers are then reacted with a urethane acrylate by photopolymerization to yield thin polymer coatings. The release of fragrances from the coatings was measured by UV–visible spectroscopy and headspace gas chromatography–mass spectrometry techniques, showing sustained release in artificial sweat due to the slow kinetics of the hydrolysis of the hydrazone linkage. This simple strategy can be applied for the rapid preparation of coatings on contact with wet human skin in labeling applications.

Chemical Characteristics and Comparison of Schizonepetae Herba and Schizonepetae Herba Carbonisata by Combination of GC-MS and UHPLC-MS Strategies.

Schizonepetae Herba (SH, Jingjie) and Schizonepetae Herba Carbonisata (SHC, Jingjie Tan) are two different forms of the same herbal material, with SHC being the processed product of SH. The different clinical efficacies of SH and SHC may be caused by changes in their chemical compositions. Despite this, there have been few studies that have reported on the comparative identification of SH and SHC. Therefore, the aims of this experiment are to investigate the differential changes of non-volatile and volatile components before and after SH processing. To establish combination strategies for identifying the chemical markers in SH and SHC, ultra-high-performance liquid chromatography quadrupole time of flight mass spectrometry (UHPLC-Q-TOF-MS) and headspace gas chromatography mass spectrometry (HS-GC-MS) to use. An untargeted metabolomics approach using UHPLC-Q-TOF-MS and HS-GC-MS was utilized to comprehensively discriminate between SH and SHC. To identify chemical markers, principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed on 14 batches of SH and SHC. A total of 71 non-volatile compounds and 81 volatile compounds were tentatively identified in SH and SHC. Among these, 14 non-volatile compounds and 18 volatile oils were found to be potential characteristic markers that can differentiate between SH and SHC. The present work provides valuable information for understanding the chemical differences between SH and SHC. The results obtained from this research may serve as a scientific foundation for comprehensively revealing the mechanisms involved in the carbonizing processing method of stir-frying SH. The chemical changes that occur before and after carbonizing Schizonepetae Herba were investigated using integrated methods based on LC-MS and GC-MS, and chemical markers in SH and SHC were identified.

Study on Cut Tobacco Drying Process Based on HS-GC/MS: Principal Component Analysis, Similarity Analysis, Drying Conditions, and Drying Mechanism

In order to study the volatile and semivolatile components changes of cut tobacco in the drying process, the cut tobacco were determined by headspace-gas chromatography/mass spectrometry (HS-GC/MS). Principal component analysis (PCA) and similarity analysis were used to analyze the HS-GC/MS results. Based on the similarity, the drying conditions and drying mechanism have been studied. The results showed that the increase in water content would reduce the dying rate, and if the temperature increased, the dying rate increased. The preliminary study on the drying kinetics of the drying process shows that Henderson and Pabis model appeared to be the most suitable for describing the drying process of cut tobacco, and the drying activation energy is 111.9 kJ.

Metabolomics approach to identify key volatile aromas in Thai colored rice cultivars.

In addition to white jasmine rice, Thailand has many native-colored rice varieties with numerous health benefits and the potential to become a global economic crop. However, the chemical characteristics of aromatic substances in native-colored rice are still mostly unknown. This study aimed to identify the key volatile aroma compounds and the biosynthetic pathways possibly involved in their formation in Thai native-colored rice varieties, and thus leading to the search for potential genetic markers for breeding colored rice with better aromatic properties. Twenty-three rice varieties in four categories: aromatic white, aromatic black, non-aromatic black, and non-aromatic red, were investigated (n=10 per variety). Seed husks were removed before the analysis of rice volatile aromas by static headspace gas chromatography-mass spectrometry. Untargeted metabolomics approach was used to discover the key volatile compounds in colored rice. Forty-eight compounds were detected. Thirty-eight of the 48 compounds significantly differed among groups at p<0.05, 28 of which at p<0.0001, with the non-aromatic black and red rice containing much lower content of most volatile constituents than the aromatic black and white rice. Focusing on the aromatic black rice, the samples appeared to contain high level of both compound groups of aldehydes (3-methylbutanal, 2-methylbutanal, 2-methylpropanal, pentanal, hexanal) and alcohols (butane-2,3-diol, pentan-1-ol, hexan-1-ol). Biosynthetically, these distinctive black-rice volatile compounds were proposed to be formed from the metabolic degradation of branched-chain amino acids (L-leucine, L-isoleucine and L-valine) and polyunsaturated fatty acids (linoleic acid and α-linolenic acid), involving the branched-chain aminotransferases and keto-acid decarboxylases and the 9-lipoxygonases and 13-lipoxygeases, respectively. The proposed degradative pathways of amino acids and fatty acids were well agreed with the profiles key volatile compounds detected in the Thai native-colored rice varieties.

Profiling flavourings in strawberry-flavoured e-liquid using headspace-gas chromatography-mass spectrometry.

E-liquids typically contain nicotine and flavourings in a matrix of propylene glycol (PG) and vegetable glycerine (VG). Some nicotine-free e-liquids are flavouring only in the aerosol carrier with the option for users to add their own nicotine. It is only the nicotine that is monitored in terms of level, as specified by the manufacturers. Little is known of the toxicological effect for some of the flavourings in the context of vaping as these are only regulated for ingestion and not inhalation. A method was developed to analyse volatile organic compounds (VOCs) evolved when e-liquids are vaporised based on headspace-gas chromatography-mass spectrometry (HS-GC-MS) for e-liquids. An in-house standard was prepared with sample matrix and purchased strawberry flavouring to simulate a simple e-liquid but with known levels. This standard was then used to optimise the analysis for use with e-liquid samples but not for full quantification purposes. These were purchased from a range of retailers and with different batches but mainly focussed on strawberry flavour. The results identified three key components indicative of strawberry flavour (ethyl-3-methyl butanoate, ethyl 2-methyl butanoate and ethyl butanoate) and showed considerable variation between both manufacturers and batches. Flavouring VOCs areregulated for ingestion but are not regulated for e-liquid inhalation, so these could have toxicological implications. In addition, the inconsistency between samples suggests further issues when users add their own nicotine to the e-liquids as the viscous sample matrix makes homogeneous mixing difficult.

μ-Raman Determination of Essential Oils' Constituents from Distillates and Leaf Glands of Origanum Plants.

A novel, inexpensive and simple experimental setup for collecting μ-Raman spectra of volatile liquids in very small quantities was developed. It takes advantage of capillary forces to detain minute volatile liquid volumes. Spectra of volatile and even scattering or absorbing media can be measured more effectively. The method is used to facilitate the collection of intensity-consistent Raman spectra from a series of reference compounds present in Origanum essential oils, in order to quantify their constituents by multiple linear regression. Wild grown Origanum plants, collected from five different regions in Greece and taxonomically identified as O. onites, O. vulgare subsp. hirtum and O. vulgare subsp. vulgare, were appropriately distilled to acquire their essential oils. Comparison of the Raman results with those from headspace gas chromatography-mass spectrometry (HS GC-MS) confirmed the successful relative quantification of the most abundant essential oil constituents, highlighting the similarities and differences of the three Origanum taxa examined. Finally, it is demonstrated that directly measuring the leaf peltate glandular hairs yields exploitable results to identify the main components of the essential oil they contain, underlining the potential of in situ (field or industry) measurements utilizing microscope-equipped portable Raman spectrometers.

Diversity of volatile organic compounds in 14 rose cultivars

ABSTRACT This study illustrates the importance of multivariate analysis in profiling the levels of 104 volatiles across 14 modern rose cultivars obtained using headspace gas chromatography–mass spectrometry analysis. Despite differences in the abundance of volatiles, the cultivars ‘Lady Emma Hamilton’, ‘Golden Celebration’ and ‘The Poet’s Wife’ share similar profiles of volatile organic compounds (VOCs) and the absence of phenethyl alcohol, which is usually associated with a characteristic ‘rose’ fragrance. R. ‘Hansa’ is the cultivar with the greatest abundance of volatiles, with high levels of acyclic monoterpenes and aromatic compounds. No monoterpenes were detected from the climbing rose R. ‘August Gervais’. The study revealed that highly fragrant cultivars tend to produce VOCs in higher intensity and greater diversity. These findings also demonstrate the potential of using headspace analysis to compare the natural aromas of rose cultivars, which provides information to inspire innovation in the perfumery and food industries. Abbreviations AMT, acyclic monoterpenes; ARM, aromatic compounds; CMT, cyclic monoterpenes; GLV, green leaf volatiles; HEX, C6 lipid derivatives; OTH, other volatiles; PCoA, principal coordinates analysis; PEA, phenethyl alcohol; RI, retention index; SSQ, sesquiterpenes; TD-GC-MS, thermal desorption-gas chromatography-mass spectrometry; VOC, volatile organic compounds.

Variations in volatile flavour compounds in Crataegi fructus roasting revealed by E-nose and HS-GC-MS.

Crataegi fructus (CF) is an edible and medicinal functional food used worldwide that enhances digestion if consumed in the roasted form. The odour of CF, as a measure of processing degree during roasting, significantly changes. However, the changes remain unclear, but are worth exploring. Herein, the variations in volatile flavour compounds due to CF roasting were investigated using an electronic nose (E-nose) and headspace gas chromatography-mass spectrometry (HS-GC-MS). A total of 54 components were identified by GC-MS. Aldehydes, ketones, esters, and furans showed the most significant changes. The Maillard reaction, Strecker degradation, and fatty acid oxidation and degradation are the main reactions that occur during roasting. The results of grey relational analysis (GRA) showed that 25 volatile compounds were closely related to odour (r > 0.9). Finally, 9 volatile components [relative odour activity value, (ROAV) ≥ 1] were confirmed as key substances causing odour changes. This study not only achieves the objectification of odour evaluation during food processing, but also verifies the applicability and similarity of the E-nose and HS-GC-MS.

Optimizing the Distillation of Greek Oregano-Do Process Parameters Affect Bioactive Aroma Constituents and In Vitro Antioxidant Activity?

The aim of the present work was to optimize the conditions of the distillation process at a pilot scale to maximize the yield of specific bioactive compounds of the essential oil of oregano cultivated in Greece, and subsequently to study the in vitro antioxidant activity of these oils. Steam distillation was conducted at an industrial distillery and a Face-Centered Composite (FCC) experimental design was applied by utilizing three distillation factors: time, steam pressure and temperature. Essential oil composition was determined by static headspace gas chromatography-mass spectrometry (HS-GC/MS). To obtain a comprehensive profile of the essential oils, instrumental parameters were optimized, including sample preparation, incubation conditions, sampling process, injection parameters, column thermal gradient and MS conditions. With the applied GC-MS method, more than 20 volatile compounds were identified in the headspace of the oregano essential oils and their relative percentages were recorded. Carvacrol was the most prominent constituent under all distillation conditions applied. Data processing revealed time as the main factor which most affected the yield. The Desired Space (DSc) was determined by conducting a three-dimensional response surface analysis of the independent and dependent variables, choosing yields of thymol and carvacrol as optimization criteria. The in vitro antioxidant activity of the essential oils of all samples was measured in terms of the interaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) after 20 and 60 min. The most prominent essential oils at different distillation conditions were also tested as inhibitors of lipid peroxidation. Higher % values of carvacrol and thymol were correlated to higher antioxidant activity. Evaluating the impact of the distillation conditions on the in vitro results, it seems that lower pressure, less time and higher temperature are crucial for enhanced antioxidant activities.