Headspace Solid-phase Microextraction Research Articles

Impact of salt content on Douchi metabolites: biogenic amines, non-volatile compounds and volatile compounds.

The excessive salt intake associated with Douchi has become a topic of controversy. Addressing this concern and enhancing its market competitiveness necessitates the application of salt reduction fermentation in Douchi. Therefore, to promote the application of salt reduction fermentation in Douchi, a comprehensive study was undertaken aiming to investigate the differences in biogenic amines, volatile compounds and non-volatile compounds in Douchi with varying salt content. The findings unequivocally demonstrate that salt hampers the formation of metabolites in Douchi. As the salt content increased, there was a significant decrease (P < 0.05) in the levels of total acid, amino-type nitrogen and free amino acids in Douchi. Notably, when the salt content exceeded 80 g kg-1, there was a substantial reduction (P < 0.05) in putrescine, lactic acid and malic acid levels. Similarly, when the salt content surpassed 40 g kg-1, β-phenethylamine and oxalic acid levels exhibited a significant decline (P < 0.05). Furthermore, the results of E-nose and principal component analysis based on headspace solid phase microextraction gas chromatography-mass spectrometry revealed notable discrepancies in the volatile compound content between Douchi samples with relatively low salt content (40 and 80 g kg-1) and those with relatively high salt content (120, 160 and 200 g kg-1) (P < 0.05). By employing partial least squares discriminant analysis, eight distinct volatile compounds, including o-xylene, benzaldehyde and 1-octen-one, were identified. These compounds exhibited higher concentrations in Douchi samples with relatively low salt content (40 and 80 g kg-1). The sensory results showed that Douchi samples with lower salt content exhibited higher scores in the soy sauce-like and Douchi aroma attributes. In conclusion, this study significantly enhances our understanding of the impact of salt on metabolites in Douchi and provides invaluable insights for the development of salt reduction fermentation in this context. © 2024 Society of Chemical Industry.

Oregano and thyme by-products of olive oil aromatization process with microwave assisted extraction as a rich source of bio-active constituents

IntroductionProcessing of Medicinal Aromatic Plants (MAPs) results in the production of a significant amount of by-products, which are not commercially exploitable. Towards this direction, we studied extensively the by-products of oregano and thyme, remaining after the aromatization of olive oils with microwave assisted extraction (MAE). The purpose of the study was the exploitation of the “wastes” of these two economically significant herbs of Greece, for the potential development of innovative bioactive products.MethodsHence, superior and inferior quality plant material from Origanum vulgare subsp. hirtum and Thymus vulgaris, were extracted with extra virgin olive oil using MAE. For the evaluation of raw plant material, beside the characterization of the essential oils (EOs), the hydroalcoholic extracts of superior and inferior plant material were afforded by ultrasound assistant extraction (UAE). In addition, the remaining plant material after the flavoring of olive oil by MAE, was extracted with c-Hex, MeOH, H2O:MeOH using UAE. All the extracts were evaluated for their DPPH free radical scavenging activity and total phenolic content (TPC) as well as their chemical profile was investigated by HPTLC. In parallel, the EOs, the olive oils and the c-Hex extracts were analyzed by GC–MS and Headspace Solid Phase Microextraction (HS-SPME)-GC–MS.Results and DiscussionThe results showed that the composition of the EOs and the volatile fraction of the olive oil extracts were similar for the superior quality material whereas for the inferior the composition of the volatile fraction of olive oil extracts was not analogous to the respective EOs. GC–MS analyses of oregano and thyme by-products revealed the presence of carvacrol, thymol, γ-terpinene and p-cymene among the major constituents. Moreover, the hydroalcoholic extracts obtained from the plant material remaining after olive oil flavoring with MAE showed similar phenolic content and scavenging activity with the hydroalcoholic extracts of the corresponding raw plant materials underlying their potent use in the preparation of high-added value products such as nutraceuticals and cosmeceuticals as well as enriched animal nutrition products.

Comparable analysis of flavor compounds and quality assessment of fermented bean curd using HS-SPME-GC/MS and colorimetric sensor array

This study aims to develop an effective tool by integrating traditional analysis methods with advanced sensor array technology and multiple algorithms, to achieve rapid characterization, qualitative identification, and flavor quality evaluation of fermented bean products. Firstly, the flavor compounds and flavor profiles of fermented bean curd from different manufacturers were identified using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) and quantitative descriptive analysis (QDA). A total of 63 volatile compounds were identified, of which 13 volatile compounds were identified as the key differential compounds in selected samples. Eight descriptors were selected to represent the aroma characteristics of fermented bean curd. Based on the key differential compounds, a low-cost colorimetric sensor array (CSA) was designed and constructed. Furthermore, the feasibility of CSA combined with multiple algorithms was investigated for brand discrimination and flavor quality assessment. Linear discriminant analysis (LDA) exhibited a better performance in distinguishing different flavor quality samples, and the recognition accuracy of its prediction set was 97.22%. The study suggests that CSA combined with multiple algorithms can be an effective tool for flavor characterization and qualitative discrimination of fermented bean curd, and can provide a new multi-dimensional analysis method for food analysis.

Analysis of Seven Terpenoids by HS-SPME Coupled with GC-MS for the Identification and Classification of Different Teas

Background: Terpenoids are essential aroma substances in teas, and their concentration brings various characteristics to different teas. Therefore, developing a simple and stable method is necessary for distinguishing tea categories. Objective: In previous studies, more attention was paid to non-chiral isomers of terpenes due to the challenges of separating chiral isomers. So, this paper aims to present a method for effectively separating seven terpenoid substances, including chiral isomers and non-chiral isomers, to facilitate the classification and identification of teas. objective: In previous studies, more attention was paid to non-chiral isomers of terpeniods due to the challenges with separating chiral isomers. So, this paper aims to present a method for effectively separating seven terpenoid substances, including chiral isomers and non-chiral isomers, to facilitate the classification and identification of teas. Methods: A method utilizing headspace solid-phase microextraction coupled with gas chromatography- mass spectrometry was used to isolate and analyze 7 terpenoid compounds. After optimized conditions, the BGB-176 chiral column and the PDMS/DVB fiber were selected for subsequent analysis. Results: This method has a good linear range of 0.1-200 mg/L, and its linear correlation coefficients are between 0.9974 and 0.9994, and the limit of detection and the limit of quantification is 0.02–0.03 and 0.06–0.09 mg/L, respectively. Only five terpenoid substances were detected in a total of 15 tea samples. Furthermore, In the detection of carvon and α-ionone optical isomers, the S isomer was mainly detected. Conclusions: An effective approach was developed to separate and analyze 7 terpenoid compounds in natural and synthetic teas. Meanwhile, 15 tea samples can be identified and classified using principal component analysis.

MOF-derived porous carbon microspheres Ni@C-acid as solid-phase microextraction coating for extraction of polycyclic aromatic hydrocarbons from tea infusions

The improvement of the stability and adsorption properties of materials on targets in sample pre-treatment has long been an objective. Extensive efforts have been made to achieve this goal. In this work, metal-organic framework Ni-MOF precursors were first synthesized by solvothermal method using polyvinylpyrrolidone (PVP) as an ideal templating agent, stabiliser and nanoparticle dispersant. After carbonization and acid washing, the nanoporous carbon microspheres material (Ni@C-acid) was obtained. Compared with the material without acid treatment (Ni@C), the specific surface area, pore volume, adsorption performance of Ni@C-acid were increased. Thanks to its excellent characteristics (high stability, abundant benzene rings), Ni@C-acid was used as fiber coatings in headspace solid-phase microextraction (HS-SPME) technology for extraction and preconcentration of polycyclic aromatic hydrocarbons (PAHs) prior to gas chromatography-flame ionization detector (GC-FID) analysis. The experimental parameters of extraction temperature, extraction time, agitation speed, desorption temperature, desorption time and sodium chloride (NaCl) concentration were studied. Under optimal experimental conditions, the wide linear range (0.01-30 ng mL−1), the good correlation coefficient (0.9916-0.9984), the low detection limit (0.003-0.011 ng mL−1), and the high enrichment factor (5273-13793) were obtained. The established method was successfully used for the detection of trace PAHs in actual tea infusions samples and satisfied recoveries ranging from 80.94-118.62 % were achieved. The present work provides a simple method for the preparation of highly stable and adsorbable porous carbon microsphere materials with potential applications in the extraction of environmental pollutants.

Direct Extraction and Determination of Free Nicotine in Cigarette Smoke.

The accurate determination of the free nicotine content in cigarette smoke is crucial for assessing cigarette quality, studying harm and addiction, and reducing tar levels. Currently, the determination of free nicotine in tobacco products primarily relies on methods such as pH calculation, nuclear magnetic resonance (NMR) spectroscopy, headspace solid-phase microextraction (HS-SPME), and traditional solvent extraction. However, these methods have limitations that restrict their widespread application. In this study, the free nicotine in cigarette smoke was directly extracted by using cyclohexane according to the traditional solvent extraction method and detected via gas chromatography-mass spectrometry. Compared with the traditional two-phase solvent extraction, our experimental method is easy to execute and eliminates the influence of aqueous solutions on the original distribution of nicotine in cigarette smoke particulate matter. Furthermore, the presence of protonated nicotine in tobacco does not affect the determination. Compared with HS-SPME and NMR spectroscopy, our approach, which involves solvent extraction followed by chromatographic separation and instrumental detection, offers simplicity, improved precision, better detection limits, and reduced interference during the instrumental detection stage. The standard addition recoveries in the conducted experiment ranged from 96.2% to 102.5%. The limit of detection was 2.8 μg/cig, and the correlation coefficient (R2) for the quadratic regression of the standard curve exceeded 0.999. The relative standard deviation for parallel samples was between 1.7% and 3.4% (n = 5), fully meeting the requirements for the determination of free nicotine in cigarette smoke. Analysis of cigarette samples from 38 commercially available brands revealed that the content of free nicotine ranged from 0.376 to 0.716 mg/cig, with an average of 0.540 mg/cig, and free nicotine accounted for 39.1%-88.8% of the total nicotine content.

Cultivar authentication of olive oil from Ionian islands using volatile compounds and chemometric analyses

AbstractTwo hundred and twenty-three olive samples of different olive cultivars (Koroneiki, Asprolia, Lianolia, Ntopia, Thiaki, Mavrolia, and Others) grown in the Ionian islands (Kefalonia, Kerkyra, Leukada, and Zakynthos) were subjected to headspace solid phase microextraction coupled to gas chromatography/mass spectrometry analysis. The aim of the study was to characterize the aroma pattern of these olive oil cultivars, and track whether specific volatile compounds could be used for olive oil cultivar authentication using chemometrics. Multivariate analysis of variance implemented on the semi-quantitative data of volatile compounds (alcohols, aldehydes, benzene derivatives, esters, hydrocarbons, ketones, and terpenoids), showed that olive cultivar had a significant impact on the volatile composition of olive oil samples. Factor analysis and linear discriminant analysis indicated those specific volatile compounds that could be related to olive oil cultivar and established statistical models for the olive oil cultivar authentication from Ionian islands, thus indicating a characteristic aroma fingerprint of these olive oils.

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.

Decoding the Volatile Profile of White Romanian Fetească Wines

The wine’s volatilome, most of the time, defines not only its aroma, but also, its major attributes. In the case of wines, the authentication process has become imperative, in light of increased production of alcoholic beverages; consequently, reliable analytical methods have served for it. Therefore, the goal of this research was to establish the global volatile profile of traditional Romanian white wines from Fetească varieties (Fetească albă, Fetească regală) in order to identify its unique characteristics by means of a headspace solid-phase microextraction coupled with gas chromatography analysis (HS-SPME/GC-MS) and e-Nose devoted techniques. Statistics was also employed aimed at differentiating the analyzed wine by varietal groups. Consequently, 23 volatile compounds were detected and quantified in 39 Fetească white wine samples originating from various production areas (Muntenia, Oltenia, Transylvania, Banat and Dobrogea), then further classified according to their odor thresholds in five aromatic classes (floral, fruity, sweet, lactic (cheesy) and other). In addition, statistics (Principal Component Analysis (PCA), Hieratical Clustering Analysis (HCA)) were used aiming to differentiate the analyzed varietal groups. The outcomes have pointed out the existence of distinct clusters connected with ethyl esters or alcohol composition and production year, depending on each examined variety.

Tracking dry gin volatile organic compounds over distillation: a time course study

Why was the work done: The influence of distillation time on the volatile composition of gin has not been examined in detail at a commercial distillery. How was the work done: Headspace Solid-Phase Micro-Extraction Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) was used to tentatively identify 74 aroma compounds, with their concentration tracked in distillate samples over the course of three gin distillations. What are the main findings: Four unique fractions were identified using Agglomerative Hierarchical Clustering: ‘heads’, ‘early hearts’, ‘late hearts, and ‘tails’. The hearts fraction (n=24 samples) was examined further, fitting statistically appropriate models to 54 aroma volatiles. Three sub-groups of volatiles were identified, (i) highly volatile monoterpenes with rapidly decreasing concentration over the early hearts fraction, (ii) volatiles whose concentration increased gradually over the hearts fraction and (iii) less volatile sesquiterpenes, sesquiterpenoids, and monoterpenoids which increased rapidly in concentration in the later distillate. Complex cubic models fit 34 volatiles with very high significance (p&gt;0.0001) over the hearts fraction (72%). Informal aroma sensory bench testing identified distinct aroma categories with, for example, ‘Spicy’ being commonly detected in the later distillate. Why is the work important: This investigation characterises the kinetics of flavour extraction over the course of a commercial gin distillation process. These findings highlight the potential for the expression of specific flavour characteristics by modifying the cut points of the distillation process

Gas chromatography-stable isotope ratio mass spectrometry prior solid phase microextraction and gas chromatography-tandem mass spectrometry: development and optimization of analytical methods to analyse garlic (Allium sativum L.) volatile fraction

Garlic (Allium sativum L.) is not only appreciated for its flavour and taste, but it is also recognized for various health properties. The European Commission, through the attribution of the Protected Designation of Origin (PDO) certification mark, has officially recognized some specific varieties of garlic. To protect not only the commercial value but also the reputation of this appreciated product, effective tools are therefore required. For the first time, a new compound specific isotope analysis method based on carbon stable isotopic ratio measurement of the three major volatile garlic compounds allyl alcohol (AA), diallyl disulphide (DD) and diallyl trisulphide (DT) through head-space solid phase microextraction (HS-SPME) followed by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) was developed. A within-day standard deviation (Srwithin-day) of 0.3‰, 0.4‰ and 0.2‰ for δ(13C) and a between-day standard deviation (Srbetween-day) of 0.8‰, 1.0‰ and 0.6‰ of AA, DT and DD was estimated. For the first time, the ranges of isotopic variability for the three volatile compounds of red garlic from two neighbouring Italian regions (Abruzzo and Lazio) were defined analysing 30 samples. The same dataset was also considered in analysing the percentage composition of the previously mentioned three volatile compounds through gas chromatography-tandem mass spectrometry (GC-MS/MS). The two analytical approaches were combined in this explorative study, aiming to provide potential parameters to discriminate garlic samples based on their geographical origin.

Investigation of Volatile Organic Compounds in Aromatic Phalaenopsis Cultivars Using Gas Chromatography–Mass Spectrometry

Phalaenopsis is a globally popular potted plant possessing a few aromatic cultivars, but analysis of volatile organic compounds (VOCs) in these cultivars is limited. Here, using nonaromatic cultivar Phal. Big Chili as a control, flower VOCs of four aromatic cultivars were investigated by headspace solid-phase microextraction in conjunction with gas chromatography–mass spectrometry (GC-MS). The results revealed that 43 VOCs classified into seven categories were identified in the nonaromatic Phal. Big Chili and four aromatic cultivars. Hexyl acetate and hexan-1-ol were common VOCs in aromatic cultivars. On the basis of partial least squares discriminant analysis, the five cultivars were classified into three groups, the nonaromatic Phal. Big Chili (group 1) and the strong-aromatic Phal. Cherry Tomato (group 2) were easily distinguished from the other three aromatic cultivars (group 3). Moreover, 17 key VOCs with the different aromatic thresholds and characteristics were identified in the four aromatic cultivars, and the types and relative contents of key VOCs varied among the aromatic cultivars, resulting in different characteristics and intensities of floral fragrance in aromatic cultivars. In aromatic cultivars, the types and relative contents of key VOCs in Phal. Cherry Tomato significantly exceeded those in the other three cultivars. Eight key VOCs belonging to terpenoids, olefins, and alcohols had the highest relative contents in Phal. ‘Cherry Tomato’, which led to a strong and mixed aromatic type containing cedarwood, camphor, and mint fragrances.

A Device for the Simultaneous Cooling of the Fiber and the Evaporated Sample in the Determination of Pesticides from Soil Samples Using Fiber Headspace Solid-Phase Microextraction

A Device for the Simultaneous Cooling of the Fiber and the Evaporated Sample in the Determination of Pesticides from Soil Samples Using Fiber Headspace Solid-Phase Microextraction

Geographical identification of Chinese wine based on chemometrics combined with mineral elements, volatile components and untargeted metabonomics

Identifying the geographic origin of a wine is of great importance, as origin fakery is commonplace in the wine industry. This study analyzed the mineral elements, volatile components, and metabolites in wine using inductively coupled plasma-mass spectrometry, headspace solid phase microextraction gas chromatography–mass spectrometry, and ultra-high-performance liquid chromatography-quadrupole-exactive orbitrap mass spectrometry. The most critical variables (5 mineral elements, 13 volatile components, and 51 metabolites) for wine origin classification were selected via principal component analysis and orthogonal partial least squares discriminant analysis. Subsequently, three algorithms—K-nearest neighbors, support vector machine, and random forest —were used to model single and fused datasets for origin identification. These results indicated that fused datasets, based on feature variables (mineral elements, volatile components, and metabolites), achieved the best performance, with predictive rates of 100% for all three algorithms. This study demonstrates the effectiveness of a multi-source data fusion strategy for authenticity identification of Chinese wine.

Antipathogenic Activities of Volatile Organic Compounds Produced by Bacillus velezensis LT1 against Sclerotium rolfsii LC1, the Pathogen of Southern Blight in Coptis chinensis.

This study explores the antipathogenic properties of volatile organic compounds (VOCs) produced by Bacillus velezensis LT1, isolated from the rhizosphere soil of Coptis chinensis. The impact of these VOCs on the mycelial growth of Sclerotium rolfsii LC1, the causative agent of southern blight in C. chinensis, was evaluated using a double Petri-dish assay. The biocontrol efficacy of these VOCs was further assessed through leaf inoculation and pot experiments. Antifungal VOCs were collected using headspace solid-phase microextraction (SPME), and their components were identified via gas chromatography-mass spectrometry (GC-MS). The results revealed that the VOCs significantly inhibited the mycelial growth and sclerotia germination of S. rolfsii LC1 and disrupted the morphological integrity of fungal mycelia. Under the influence of these VOCs, genes associated with chitin synthesis were upregulated, while those related to cell wall degrading enzymes were downregulated. Notably, 2-dodecanone and 2-undecanone exhibited inhibition rates of 81.67% and 80.08%, respectively. This research provides a novel approach for the prevention and management of southern blight in C. chinensis, highlighting the potential of microbial VOCs in biocontrol strategies.

Characterization of Key Aroma Compounds and Main Contributing Amino Acids in Hot-Pressed Oil Prepared from Various Peanut Varieties.

The production of peanut oil in the industrial sector necessitates the utilization of diverse raw materials to generate consistent batches with stable flavor profiles, thereby leading to an increased focus on understanding the correlation between raw materials and flavor characteristics. In this study, sensory evaluations, headspace solid-phase micro-extraction gas chromatography mass spectrometry (HS-SPME-GC-MS), odor activity value (OAV) calculations, and correlation analysis were employed to investigate the flavors and main contributing amino acids of hot-pressed oils derived from different peanut varieties. The results confirmed that the levels of alcohols, aldehydes, and heterocyclic compounds in peanut oil varied among nine different peanut varieties under identical processing conditions. The OAVs of 25 key aroma compounds, such as methylthiol, 3-ethyl-2,5-dimethylpyrazine, and 2,3-glutarone, exceeded a value of 1. The sensory evaluations and flavor content analysis demonstrated that pyrazines significantly influenced the flavor profile of the peanut oil. The concentrations of 11 amino acids showed a strong correlation with the levels of pyrazines. Notably, phenylalanine, lysine, glutamic acid, arginine, and isoleucine demonstrated significant associations with both pyrazine and nut flavors. These findings will provide valuable insights for enhancing the sensory attributes of peanut oil and selecting optimal raw peanuts for its production.

Evaluation of Dynamic Changes of Volatile Organic Components for Fishmeal during Storage by HS-SPME-GC-MS with PLS-DA.

Headspace solid-phase microextraction, combined with gas chromatography-mass spectrometry and partial least squares discriminant analysis, was adopted to study the rule of change in volatile organic compounds (VOCs) for domestic and imported fishmeal during storage with different freshness grades. The results showed that 318 kinds of VOCs were detected in domestic fishmeal, while 194 VOCs were detected in imported fishmeal. The total relative content of VOCs increased with storage time, among which acids and nitrogen-containing compounds increased significantly, esters and ketones increased slightly, and phenolic and ether compounds were detected only in domestic fishmeal. Regarding the volatile base nitrogen, acid value, pH value, and mold counts as freshness indexes, the freshness indexes were significantly correlated with nine kinds of VOCs (p < 0.05) through the correlation analysis. Among them, volatile base nitrogen had a significant correlation with VOCs containing nitrogen, acid value with VOCs containing carboxyl group and hydrocarbons, pH value with acids which could be used to adjust pH value, and mold counts with part of acids adjusting pH value and VOCs containing nitrogen. Due to the fact that the value of all freshness indexes increased with freshness degradation during storage, based on volatile base nitrogen and acid value, the fishmeal was divided into three freshness grades, superior freshness, corrupting, and completely corrupted. By using partial least squares discriminant analysis, this study revealed the differences in flavor of the domestic and imported fishmeal during storage with different freshness grades, and it identified four common characteristic VOCs, namely ethoxyquinoline, 6,7,8,9-tetrahydro-3H-benzo[e]indole-1,2-dione, hexadecanoic acid, and heptadecane, produced by the fishmeal samples during storage, as well as the characteristic VOCs of fishmeal at each freshness grade.

Key odorants of 'Keemun Aroma' and their changes during the preliminary processing of Keemun BLack Tea (Camellia sinensis)

Chinese Keemun black tea (KBT) is one of the most renowned black teas worldwide due to its alluring floral/fruity/honey-like odor. However, the key odorants of the so-called Keemun aroma have not been systematically characterized. A comparative sensory-guided flavor analysis was conducted on the aroma compounds in two orthonasally distinguishable KBTs with high and low grades (HG-KBT and LG-KBT). This well-established methodology included the following steps: volatile collection through solvent-assisted flavor evaporation and headspace solid-phase microextraction, aroma identification based on gas chromatography–olfactometry/mass spectrometry, odor contribution calculation according to stable isotope dilution assay, odor activity values (OAVs), and aroma recombination. A total of 42 odorants were characterized, 16 and 10 of which were regarded as key odorants in HG- and LG-KBT, respectively. Among them, dimethyl sulfide, geraniol, β-ionone, 2-/3-methylbutanal, linalool, and 2-methylpropanal showed the highest OAVs and played a pivotal role in ‘Keemun aroma’. In general, floral odorants had higher OAVs in HG-KBT. In addition, the quantitative changes during the entire preliminary manufacturing step of the tea leaves indicated the great importance of fresh leaves’ quality and withering for the formation of the final aroma quality of the beverage.

Identification and inhibition of key off-odorants in boiled greenfin horse-faced filefish (Thamnaconus septentrionalis) subjected to perilla polyphenols extract

The generation of off-flavor during boiling significantly hampers the acceptability and popularity of the greenfin horse-faced filefish (BFF). Adding perilla to Chinese fish dishes can enhance the flavor of fish. A total of 72 volatile compounds were quantified in BFF with different addition of Perilla polyphenol extract (PPE) (i.e., 0, 0.1 %, 0.3 %, 0.5 %, w: w) by headspace solid phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS). Based on the gas chromatography-olfactometry (GC-O), odor activity value (OAV) and recombination omission testing, (Z)-4-heptenal, (E,E)-2,4-heptadienal, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, heptanal, nonanal, octanal, decanal, (E)-2-hexenal, (E)-2-octenal, (E)-2-nonenal were identified as volatiles contributing to the off-flavor, while linalool and β-ionone exhibited a mitigating effect. Moreover, the antioxidant capacities of PPE assessed through 2,2-diphenyl-1-picrylhydrazyl (DPPH) and thiobarbituric acid reactive substances (TBARs) assays, exhibited a positive correlation with perilla polyphenols contents. Orthogonal partial least square discriminate analysis (OPLS-DA) and partial least-squares regression (PLSR) results indicated a significant relationship between the off-flavor of BFF and lipid oxidation, adding 0.3% PPE resulted in a marked improvement in flavor profile, with a reduction in off-flavors associated with fishy, oily/fatty and marine, while simultaneously enhancing the freshness, herbal flavors, and overall acceptability of the product.

Characterization of the aroma-active compounds in Xiaokeng green tea by three pretreatment methods combined with gas chromatography−olfactometry (GC-O)

Chinese Xiaokeng green tea (XKGT) possesses elegant and fascinating aroma characteristics, but its key odorants are still unknown. In this study, 124 volatile compounds in the XKGT infusion were identified by headspace-solid phase microextraction (HS-SPME), stir bar sorptive extraction (SBSE), and solvent extraction-solid phase extraction (SE-SPE) combined with gas chromatography-mass spectrometry (GC–MS). Comparing these three pretreatments, we found HS-SPME was more efficient for headspace compounds while SE-SPE was more efficient for volatiles with higher boiling points. Furthermore, SBSE showed more sensitive to capture ketones then was effective to the application of pretreatment of aroma analysis in green tea. The aroma intensities (AIs) were further identified by gas chromatography–olfactometry (GC-O). According to the AI and relative odor activity value (rOAV), 27 compounds were identified as aroma-active compounds. Quantitative descriptive analysis (QDA) showed that the characteristic aroma attributes of XKGT were chestnut-like, corn-like, fresh, and so on. The results of network analysis showed that (E, Z)-2,6-nonadienal, nonanal, octanal and nerolidol were responsible for the fresh aroma. Similarly, dimethyl sulfide, (E, E)-2,4-heptadienal, (E)-2-octenal and β-cyclocitral contributed to the corn-like aroma. Furthermore, indole was responsible for the chestnut-like and soybean-like aroma. This study contributes to a better understanding of the molecular mechanism of the aroma characteristics of XKGT.