Headspace Solid-phase Microextraction-gas Chromatography-mass Spectrometry Research Articles

An integrative pharmacology-based study on the efficacy and mechanism of essential oil of Chaihu Guizhi Decoction on influenza A virus induced pneumonia in mice

Ethnopharmacological relevanceChaihu Guizhi Decoction (CGD) has a long history of use in China for the treatment of influenza, which involves the use of a variety of aromatic herbs. Our previous studies have found that the contents of aromatic constituents in CGD affected the efficacy of treatment of influenza-infected mice, suggesting a clue that essential oil from CGD may play a relatively important role in ameliorating influenza induced pneumonia. Aim of the studyTo evaluate the anti-influenza potential of essential oil derived from Chaihu Guizhi Decoction (CGD-EO), to characterize and predict the key active components in CGD-EO, and to explore the mechanism of action of CGD-EO. Materials and methodsCGD-EO was obtained by steam distillation, and the components of the essential oil were characterized by gas chromatography-mass spectrometry (GC-MS) in conjunction with the retention index. The constituents absorbed into the blood of mice treated with CGD-EO were analyzed by headspace solid phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS). The potential anti-influenza active constituents and their possible action pathway were predicted by simulation using a network pharmacology approach. The protective effect of CGD-EO and its major components on H1N1/PR8-infected cells was determined using the CCK8 assay kit. Mice infected with influenza A virus H1N1/PR8 were administered different doses of CGD-EO orally and the body weights and lung weights were recorded. Mice with varying degrees of H1N1/PR8 infection were administered CGD-EO orally, and their daily weight, water consumption, and clinical indicators were recorded. Necropsies were conducted on days 3 and 5, during which lung weights were measured and lung tissues were preserved. Furthermore, the mRNA expression of the H1N1/PR8 virus and inflammatory factors in lung tissue was analyzed using RT-qPCR. Results(E)-cinnamaldehyde was the most abundant compound in the CGD-EO. The results of serum medicinal chemistry combined with network pharmacological analysis indicated that (E)-cinnamaldehyde and 3-phenyl-2-propenal may be potential active components of the CGD-EO anti-influenza, and may be involved in the NF-κB signalling pathway. In vitro studies have demonstrated that both CGD-EO and cinnamaldehyde exert a protective effect on MDCK cells infected with H1N1/PR8. In a 0.5 TCID50 H1N1/PR8-induced influenza model, mice treated with CGD-EO at a dose of 63.50 μg/kg exhibited a reduction in lung index, pathological lung lesions, and H1N1/PR8 viral gene levels. In addition, CGD-EO treatment was found to regulate the levels of inflammatory cytokines, including IL-6, TNF-α, and IFN-γ. Moreover, following three days of administration, an upregulation of NF-κB mRNA levels in mouse lung tissue was observed in response to CGD-EO treatment. ConclusionsThe findings of our study indicate CGD-EO exerts a protective effect against H1N1-induced cytopathic lesions in vitro and is capable of alleviating H1N1-induced pneumonitis in mice. Moreover, it appears to be more efficacious in the treatment of mild symptoms of H1N1 infection. Studies have demonstrated that CGD-EO has antiviral potential to attenuate influenza-induced lung injury by modulating inflammatory cytokines and NF-κB signalling pathways during the early stages of influenza infection. It is possible that (E)-cinnamaldehyde is a potential active ingredient in the anti-influenza efficacy of CGD-EO.

Characteristic of phenotype, amino acids and volatile compounds for fresh tea leaves of Korean tea cultivars (Camellia sinensis (L.) O. Kuntze)

Tea (Camellia sinensis (L.) O. Kuntze) is a popular beverage consumed worldwide. To establish fundamental scientific data, we analyzed the amino acids and volatile compounds in seven tea cultivars grown in Korea investigated phenotype also. Phenotypically, the leaf area and greenness index of young shoots and leaf blades were particularly different among the four Korean cultivars. Nine amino acids were detected from each cultivar, with the total amino acid and theanine contents being 9.08–41.42 and 2.81–24.60 mg/g, respectively. Moreover, 107 volatile compounds were identified as common components among tea cultivars using headspace solid-phase microextraction / gas chromatography–mass spectrometry (HS-SPME/GC-MS), and 38 key compounds were identified using partial least squares-discriminant analysis (PLS-DA) and hierarchical cluster analysis (HCA). The (Z)-linalool oxide (furanoid) concentrations were significantly high in Korean tea plant cultivars, and linalool concentrations were also high or low, but had high relative contents. Linalool and its various oxides are the major compounds responsible for the tea aroma. In conclusion, Korean tea cultivars have distinct characteristics, and the results of this study will form the basis for identifying Korean tea plant cultivars that can produce high-value tea products.

Impact of Thyme Essential Oil on the Aroma Profile and Shelf Life of Vacuum-Packed Minced Turkey Meat.

There is considerable interest in the use of essential oils for food preservation, but their effect on the aroma profile of a product is poorly understood. This study investigated the effect of thyme essential oil (EO) addition at increasing concentrations (0.005, 0.01, 0.02, and 0.03% v/w) on the volatile compound composition of vacuum-packed minced turkey meat after storage for 8 days at 1-2 °C. The aroma profile of the meat was determined using the HS-SPME/GCMS (headspace solid-phase microextraction/gas chromatography-mass spectrometry) method. The results were also analysed by PCA (principal component analysis). The addition of thyme EO had a modifying effect on the aroma profile of meat-derived components, e.g., the formation of benzeneacetaldehyde, benzyl alcohol, 4,7-dimethylbenzofuran, hexathiane, hexanal, and 1-hexanol was reduced and the appearance of 9-hexadecenoic acid was observed in the stored samples. The increase in EO concentration affected the levels of its individual components in the meat headspace in different ways. In terms of fat rancidity indices, even a 0.005% addition of this essential oil significantly reduced the peroxide value. Quantitative descriptive analysis (QDA) showed that the addition of thyme EO reduced or masked the intensity of unpleasant odours associated with meat spoilage. In the aroma analysis, the turkey with 0.02% v/w EO scored highest, and pleasant citrus notes were found.

Establishment of intermittent ultrasound-complex enzyme deodorization technology for tilapia based on GC-IMS and HS-SPME-GC/MS analysis

The presence of a fishy odor has emerged as a significant obstacle in the processing and commercialization of tilapia. In light of this, the present study employed ultrasonic-assisted enzyme deodorization to address this issue. The deodorization effects were evaluated from multiple perspectives, including chemical indexes (amino acid nitrogen content, trimethylamine content, and thiobarbituric acid value), physical indexes (texture), and sensory scores. Through the application of response surface methodology, an ultrasound-complex enzyme deodorization (UED) technology was ultimately optimized. The UED process resulted in a 56% reduction in trimethylamine content while also enhancing the taste, odor, and texture of the fish, thereby demonstrating its ability to significantly improve overall quality. Additionally, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) and gas chromatography-ion mobility spectrometry (GC-IMS) were utilized to comprehensively analyze the impact of UED on flavor and elucidate its deodorization mechanism. Notably, UED samples exhibited reduced levels of components associated with undesirable fishy flavors such as hexanal, nonanal, 1-octen-3-ol, and ethyl propanoate while experiencing an increase in components such as benzaldehyde, cis-Jasmone, and butyl lactate that contribute pleasant fruity and floral aromas. Overall, this study has developed an efficient convenient method for both deodorizing tilapia enhancing its aroma, making valuable contributions towards improving overall flavor profile tilapia products.

Comparison of head space solid phase micro extraction with conventional and comprehensive gas chromatography mass spectrometry for volatile profiling of Irish whiskey

Whiskey is a traditional distilled product produced on the island of Ireland that is currently experiencing a major expansion in export volume. Different styles of Irish whiskey exist, however only some very limited published information exists on the volatile congener profile of the different styles of Irish whiskey. Such information is potentially indispensable from a quality, flavour and authenticity perspective. As gas chromatography is the established analytical method of choice to identify volatile congeners, this study compared headspace-solid phase microextraction (HS-SPME) using conventional gas chromatography single quadrupole mass spectrometry, to HS-SPME and HS-SPME-Arrow using comprehensive two-dimensional gas chromatography (GC×GC) modulated using reverse flow in tandem with time-of-flight mass spectrometry (TOFMS) detection. Six representative Irish whiskey samples were evaluated consisting of new make spirit and mature whiskies representing Single Malts, Pot Stills and Blends. The number of volatile congeners identified in these samples by HS-SPME/HS-SPME Arrow GC×GC-TOFMS was approximately twice that detected by conventional HS-SPME GCMS. In total 145 unique individual volatile congeners, excluding ethanol were identified, with the majority consisting of esters, but also benzenes, alcohols, aldehydes, terpenoids, furans, ketones, alkanes, alkenes, norisoprenoids, acetals, acids, lactones and phenols. The use of HS-SPME Arrow GC×GC-TOFMS significantly enhances the number of volatile congeners that can be identified and therefore provides much more information that can convey insights into product quality, consistency, flavour and also for authentication purposes.

Relationship between flavor characteristics and lipid oxidation in air-dried beef at different roasting stages

Lipid oxidation plays a key role in the formation of flavor during hot processing. The purpose of this study was to investigate the lipid oxidation, lipid molecular changes and their effects on flavor of air-dried beef at different roasting stages. The results revealed that the degree of lipid oxidation increased and the unsaturation of fatty acids decreased from 47.30% to 30.77%. A total of 48 volatile compounds were identified by headspace-solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Notably, the types and contents of volatile compounds in S3 group exceeded those in S1 and S2, showing significant differences in the degree of separation among all groups. The aroma differences among the groups were associated with aromatic compounds formed by the oxidation of lipids. Moreover, a total of 59 lipids with significant differences were identified through liquid chromatography-tandem mass spectrometry (LC-MS/MS). These lipids may have major roles in the formation of aromatic compounds, particularly triglyceride, phosphatidylcholine, and lysophosphatidylcholine. This investigation elucidated the mechanisms for the flavor developments of air-dried beef during roasting stages.

Comparison of chemical compositions and aroma characteristics of walnut oil prepared by different roasting processes.

Walnut oil is an edible oil with high nutritional value, and the roasting process influences its quality and flavor. This study aimed to investigate the effects of roasting on the fatty acid composition, bioactive compounds (tocopherols, polyphenols, and phytosterols), and antioxidant capacity of walnut oil. Additionally, the aroma compounds and sensory characteristics were evaluated to comprehensively assess the variations in walnut oil after roasting. Roasting resulted in no notable impact on the fatty acid composition of walnut oil but increased the content of tocopherols and polyphenols in walnut oil, increasing its antioxidant capacity. Heavy roasting (160°C/20min) reduced the phytosterol content in walnut oil by 2.3%. In total, 146 volatile compounds were detected in both cold-pressed and roasted walnut oil using headspace solid-phase microextraction-gas chromatography-mass spectrometry, and 32 key aroma compounds were identified. Aromatic aldehydes, aliphatic aldehydes, and heterocyclic compounds significantly contributed to fragrant walnut oil. Furthermore, the principal component analysis based on quality characteristics and sensory evaluation indicated that moderate roasting (130°C/20min, 130°C/30min, and 160°C/10min) provided walnut oil with a sweet, nutty, and roasted aroma, as well as high levels of linoleic acid, phytosterols, and γ-tocopherol. Although heavy roasting (160°C/15min and 160°C/20min) enhanced the antioxidant capacities of walnut oils due to high levels of polyphenols, the oils exhibited an unpleasant burnt aroma. This study showed that roasting promoted the quality and flavor of walnut oil, and moderate conditions endowed walnut oil with a characteristic-rich flavor while maintaining excellent quality.

Comprehensive origin authentication of wolfberry pulp (Lycium barbarum L.) using multimodal sensory analysis and chemometrics

Wolfberry, a valuable commodity straddling the realms of medicine and nutrition, faces increasing scrutiny regarding its provenance authenticity. In this investigation, electronic nose, electronic tongue, headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), and solid phase microextraction-gas chromatography-ion mobility spectrometry (SPME-GC-IMS) were employed for a thorough analysis of wolfberry pulp samples sourced from Ningxia (NX), Qinghai (QH), Gansu (GS), and Xinjiang (XJ). The results of the study showed that wolfberry samples from four regions could be effectively distinguished by combining intelligent sensory techniques with principal component analysis (PCA). In addition, smart sensory technology, combined with support vector machines (SVM) and random forest (RF) classifiers, can accurately distinguish samples from different regions (accuracy = 100 %). HS-SPME-GC-MS and SPME-GC-IMS identified 180 and 73 volatile organic compounds (VOCs), respectively. Through a combination of multivariate analysis (VIP > 1.2) and univariate analysis (P < 0.05), eight VOCs, including Nonadecane and alpha-Terpinolene, emerged as pivotal variables for distinguishing wolfberry pulp based on geographical origin. Overall, this study furnishes robust theoretical underpinnings for addressing concerns regarding the provenance authenticity of wolfberry pulp.

Integrated Transcriptomic and Metabolomic Analysis Revealed Abscisic Acid-Induced Regulation of Monoterpene Biosynthesis in Grape Berries.

Monoterpenes are a class of volatile organic compounds that play crucial roles in imparting floral and fruity aromas to Muscat-type grapes. However, our understanding of the regulatory mechanisms underpinning monoterpene biosynthesis in grapes, particularly following abscisic acid (ABA) treatment, remains elusive. This study aimed to explore the impact of exogenous ABA on monoterpene biosynthesis in Ruiduhongyu grape berries by employing Headspace Solid-Phase Micro-Extraction Gas Chromatography-Mass Spectrometry (HS-SPME/GC-MS) analysis and transcriptome sequencing. The results suggested significant differences in total soluble solids (TSS), pH, and total acid content. ABA treatment resulted in a remarkable increase in endogenous ABA levels, with concentrations declining from veraison to ripening stages. ABA treatment notably enhanced monoterpene concentrations, particularly at the E_L37 and E_L38 stages, elevating the overall floral aroma of grape berries. According to the variable gene expression patterns across four developmental stages in response to ABA treatment, the E_L37 stage had the largest number of differential expressed genes (DEGs), which was correlated with a considerable change in free monoterpenes. Furthermore, functional annotation indicated that the DEGs were significantly enriched in primary and secondary metabolic pathways, underlining the relationship between ABA, sugar accumulation, and monoterpene biosynthesis. ABA treatment upregulated key genes involved in the methylerythritol phosphate (MEP) pathway, enhancing carbon allocation and subsequently impacting terpene synthesis. This study also identified transcription factors, including MYB and AP2/ERF families, potentially modulating monoterpene and aroma-related genes. Weighted gene co-expression network analysis (WGCNA) linked ABA-induced gene expression to monoterpene accumulation, highlighting specific modules enriched with genes associated with monoterpene biosynthesis; one of these modules (darkgreen) contained genes highly correlated with most monoterpenes, emphasizing the role of ABA in enhancing grape quality during berry maturation. Together, these findings provide valuable insights into the multifaceted effects of exogenous ABA on monoterpene compounds and grape berry flavor development, offering potential applications in viticulture and enology.

Flavor Variations in Precious Tricholoma matsutake under Different Drying Processes as Detected with HS-SPME-GC-MS.

By employing headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), this study displayed the compositional changes in volatile organic compounds (VOCs) in Tricholoma matsutake samples subjected to hot-air drying (HAD) and vacuum freeze-drying (VFD) processes from their fresh samples. A total of 99 VOCs were detected, including 2 acids, 10 aldehydes, 10 alcohols, 13 esters, 12 ketones, 24 alkanes, 14 olefins, 7 aromatic hydrocarbons, and 7 heterocyclic compounds. Notably, the drying process led to a decrease in most alcohols and aldehydes, but an increase in esters, ketones, acids, alkanes, olefins, aromatic, and heterocyclic compounds. Venn diagram (Venn), principal component analysis (PCA), and partial least squares-discriminant analysis (PLS-DA) analyses enabled an easy and rapid distinction between the VOC profiles of T. matsutake subjected to different drying methods. Among the identified VOCs, 30 were designated as marker VOCs indicative of the employed drying process. And the VFD method was more capable of preserving the VOCs of fresh T. matsutake samples than the HAD method. Benzaldehyde, 1-Octen-3-ol, 3-Octanol, and (E)-2-Octen-1-ol were identified as markers for FRESH T. matsutake. Conversely, (E)-3-Hexene, lavender lactone, and α-Pinene were associated with VFD T. matsutake. For HAD T. matsutake, olefins, pyrazine, and esters, particularly ocimene, 2,5-Dimethyl-pyrazine, and methyl cinnamate, significantly contributed to its particularities. The results from this present study can provide a practical guidance for the quality and flavor control of volatile organic compounds in preciously fungal fruiting bodies by using drying processes.

Effect of gamma irradiation on sensory and aroma compounds of soaked bayberry jiu

Soaked bayberry jiu is a homely fruit alcoholic beverage that produced by soaking bayberry in Baijiu, a traditional Chinese distilled spirit. To investigate the changes in the sensory and aroma compounds of soaked bayberry jiu following gamma irradiation, the sensory evaluation, electron nose, electron tongue, and headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) were conducted. The results showed that the different irradiation doses of samples could be well separated. The taste and smell of 6 kGy irradiated soaked bayberry jiu were significantly improved, but the color of irradiated samples was deteriorated. Moreover, a total of 53 differential products (21 decreased and 32 increased products) were detected compared 6 kGy irradiated soaked bayberry jiu to unirradiated sample, including some important aroma compounds of Baijiu, indicating that the active free radicals produced by gamma irradiation promote the oxidation-reduction reaction in soaked bayberry jiu and lead to the mutual transformation and equilibrium among the compounds. These findings suggest that gamma irradiation can improve the quality of soaked bayberry jiu.

Characterization of the volatile flavor profiles of black garlic using nanomaterial-based colorimetric sensor array, HS-SPME-GC/MS coupled with chemometrics strategies

This work investigated the feasibility of applying headspace solid phase microextraction-gas chromatography–mass spectrometry (HS-SPME-GC/MS) combining olfactory visualization for flavor characterization of black garlic. Volatile organic compounds (VOCs) analysis was performed to select important differential VOCs during black garlic processing. A multi-channels nanocomposite CSA assembled with two porous metal-organic frameworks was then developed to characterize flavor profiles changes during black garlic processing, and garlic samples during processing could be divided into five clusters, consistent with VOCs analysis. Artificial neural network (ANN) model outperformed other pattern recognition methods in discriminating processing stages. Furthermore, SVR model for odor sensory scores with the correlation coefficient for prediction set of 0.8919 exhibited a better performance than PLS model, indicating a preferable prediction ability for odor quality. This work demonstrated that the nanocomposite CSA combining appropriate chemometrics can offer an effective tool for objectively and rapidly characterizing flavor quality of black garlic or other food matrixes.

Targeted microbial collaboration to enhance key flavor metabolites by inoculating Clostridium tyrobutyricum and Saccharomyces cerevisiae in the strong-flavor Baijiu simulated fermentation system

Ethyl hexanoate and ethyl butyrate are indispensable flavor metabolites in strong-flavor Baijiu (SFB), but batch production instability in fermenting grains can reduce the quality of distilled Baijiu. Biofortification of the fermentation process by designing a targeted microbial collaboration pattern is an effective method to stabilize the quality of Baijiu. In this study, we explored the metabolism under co-culture liquid fermentation with Clostridium tyrobutyricum DB041 and Saccharomyces cerevisiae YS219 and investigated the effects of inoculation with two functional microorganisms on physicochemical factors, flavor metabolites, and microbial communities in solid-state simulated fermentation of SFB for the first time. The headspace solid-phase microextraction-gas chromatography-mass spectrometry results showed that ethyl butyrate and ethyl hexanoate significantly increased in fermented grain. High-throughput sequencing analysis showed that Pediococcus, Lactobacillus, Weissella, Clostridium_sensu_stricto_12, and Saccharomyces emerged as the dominant microorganisms at the end of fermentation. Co-occurrence analysis showed that ethyl hexanoate and ethyl butyrate were significantly correlated (|r| > 0.5, P < 0.05) with a cluster of interactions dominated by lactic acid bacteria (Pediococcus, Lactobacillus, Weissella, and Lactococcus), which was driven by the functional C. tyrobutyricum and S. cerevisiae. Mantel test showed that moisture and reducing sugars were the main physicochemical factor affecting microbial collaboration (|r| > 0.7, P < 0.05). Taken together, the collaborative microbial pattern of inoculation with C. tyrobutyricum and S. cerevisiae showed positive results in enhancing typical flavor metabolites and the synergistic effects of microorganisms in SFB.

Impact of pre- and post-fermentation fining with polyvinylpolypyrrolidone on the chemical stability and aromatic profile of Viognier wine.

Polyvinylpolypyrrolidone (PVPP) is a synthetic, insoluble polymer that can be added to white wines to improve the chemical stability of the final product by precipitating unstable low molecular weight phenolic compounds responsible for visual defects and undesirable flavor characteristics (e.g., excessive bitterness and/or astringency). The objective of this study was to characterize the effects of PVPP on the quality characteristics of Viognier wine when added pre- or post-fermentation as compared to an untreated control wine. Both PVPP-treated wines contained significantly lower concentrations of monomeric phenolics and browning pigments than the control wine (p≤0.05). The addition of PVPP prior to fermentation conferred protection against oxidation of the wine as measured by acetaldehyde concentration (p≤0.05). Analysis of the volatile aroma profile of each wine by headspace solid phase microextraction gas chromatographymass spectrometry (HS-SPME-GC-MS)revealed that the overarching aroma profiles of the PVPP-treated wines were significantly different from the control wine, but there was no difference between wines treated with PVPP pre-fermentation versus those treated post-fermentation. Specifically, statistically significant differences were observed in 9 of the 22 quantified aroma compounds, including those notably associated with the "stone fruit" aroma of Viognier. A negative correlation was identified between aroma compound concentration removal and the hydrophobicity of each compound, suggesting that the observed differences in aroma may be due to adsorption of aroma compounds by PVPP. The findings from this study present risks and benefits to wine quality upon treatment with PVPP at commercially recommended levels, and provide potentially valuable information for industrial wine producers.

Flavor release from walnut kernels in an in-vitro mastication model with decoupled oral parameters

Consumer preferences for walnut products are largely determined by the flavors released during mastication. In this study, a peeled walnut kernel (PWK) model was established with oral parameters decoupled using a Hutchings 3D model. The model explored in vitro variations using head-space solid-phase microextraction-gas chromatography-mass spectrometry and intelligent sensory techniques. The fracture strength, hardness, particle size, adhesiveness, springiness, gumminess, and chewiness were significantly reduced during mastication. We identified 61 volatile compounds and found that 2,5-dimethyl-3-ethylpyrazine is a key component, releasing predominantly baking and milky notes. Glutamic acid, alanine, arginine, and sucrose were identified as the key compounds in taste perception. The method can help establish a mastication model for nuts and facilitate breakthroughs in the development of walnut products and processing methods.

Evaluation of Aromatic Characteristics and Potential Applications of Hemerocallis L. Based on the Analytic Hierarchy Process.

Hemerocallis L. possesses abundant germplasm resources and holds significant value in terms of ornamental, edible, and medicinal aspects. However, the quality characteristics vary significantly depending on different varieties. Selection of a high-quality variety with a characteristic aroma can increase the economic value of Hemerocallis flowers. The analytic hierarchy process (AHP) is an effective decision-making method for comparing and evaluating multiple characteristic dimensions. By applying AHP, the aromatic character of 60 varieties of Hemerocallis flowers were analyzed and evaluated in the present study. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to identify volatile components in Hemerocallis flowers. Thirteen volatile components were found to contribute to the aroma of Hemerocallis flowers, which helps in assessing their potential applications in essential oil, aromatherapy, and medical treatment. These components include 2-phenylethanol, geraniol, linalool, nonanal, decanal, (E)-β-ocimene, α-farnesene, indole, nerolidol, 3-furanmethanol, 3-carene, benzaldehyde and benzenemethanol. The varieties with better aromatic potential can be selected from a large amount of data using an AHP model. This study provides a comprehensive understanding of the characteristics of the aroma components in Hemerocallis flowers, offers guidance for breeding, and enhances the economic value of Hemerocallis flowers.

Revealing the microbial diversity and volatile flavor formation in finger citron kombucha by metagenomic and GC-MS analysis

Kombucha is a kind of health drink formed by the metabolism of Symbiotic Culture of Bacteria and Yeast (SCOBY) composed of yeast, acetic acid bacteria and lactic acid bacteria, which is popular among researchers and fond of consumers because of its antioxidant and hypoglycemic effects. In this study, the finger citron kombucha with different fermentation time (2, 4, 6, 8 day) were analyzed by headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and metagenomic sequencing. The results showed that a total of 76 volatiles were identified, including 15 key volatiles, such as linalool, geraniol, α-terpinene, and limonene, which had a great influence on the flavor of kombucha. Metagenomic analysis showed that unclassified-g-Gluconobacter, Komagataeibacter saccharivorans, Gluconobacter-sp.-R71656 and other microorganisms were the dominant species in finger citron kombucha. Through the correlation heat map analysis of volatiles and microbial composition, it was found that Gluconobacter had a positive effect on the formation of most volatiles of kombucha. In addition, Novacetimonas hansenii, Brettanomyces bruxellensis and Wickerhamiella sorbophila were also closely related to the flavor formation of kombucha. This study provided a theoretical basis for finding the key aroma-producing microorganisms in the fermentation process of finger citron kombucha and the subsequent construction of SCOBY.

Effect of incubation temperature on identification of key odorants of sewage sludge using headspace GC analysis

Currently, headspace gas chromatography-mass spectrometry is a widely used method to identify the key odorants of sludge. However, the effect of incubation temperature on the generation and emission of key odorants from sludge was still uncertain. Thus, in this paper, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS) were carried out to analyze the volatiles emitted from the sludge incubated at different temperatures (30 °C, 50 °C, 60 °C, and 80 °C). The results indicated that the total volatile concentration of the sludge increased with temperatures, which affected the identified proportion of sludge key odorants to a certain extent. Differently from the aqueous solutions, the variation of volatile emission from the sludge was inconsistent with temperature changes, suggesting a multifactorial influence of incubation temperature on the identification of sludge odorants. The microbial community structure and adenosine triphosphate (ATP) metabolic activity of the sludge samples were analyzed at the initial state, 30 °C, and 80 °C. Although no significant effect of incubation temperature on the microbial community structure of the sludge, the incubation at 80 °C led to a noticeable decrease in microbial ATP metabolic activity, accompanied by a significant change in the proportion of odor-related microorganisms with low relative abundances. Changes in the composition and activity of these communities jointly contributed to the differences in odor emission from sludge at different temperatures. In summary, the incubation temperature affects the production and emission of volatiles from sludge through physicochemical and biochemical mechanisms, by which the microbial metabolism playing a crucial role. Therefore, when analyzing the key odorants of sludge, these factors should be considered.

Lacto-fermented garlic handcrafted in the Lower Silesia Region (Poland): Microbial diversity, morpho-textural traits, and volatile compounds

The aim of the present study was to provide a first characterization of lacto-fermented garlic manufactured by local small-scale artisanal producers in the Lower Silesia Region (Poland). The lacto-fermented garlic samples showed high nutritional features in terms of antioxidant activity. A total of 86 compounds, belonging to various chemical classes, were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS). Most of these compounds belonged to six main classes, being sulfur compounds, esters and acetates, oxygenated monoterpenes, monoterpene hydrocarbons, and alcohols. Aldehydes, acids, ketones, furans, and phenols were also identified. In the analyzed samples, counts up to 8 log cfu g−1 were observed for lactic acid bacteria. Metataxonomic analysis revealed the presence of Levilactobacillus, Lactiplantibacillus, Latilactobacillus, Secundilactobacillus, Weissella, Leuconostoc, Lactococcus, Pediococcus, and Lacticaseibacillus among the major taxa. These results were confirmed by the isolation and characterization of viable lactic acid bacteria. Indeed, the presence of the closest relatives to Lacticaseibacillus casei group, Pediococcus parvulus, Levilactobacillus brevis, Levilactobacillus parabrevis, and Lactiplantibacillus plantarum group was observed. A good acidification performance in salty garlic-based medium was observed for all the isolates that, between 8 and 15 days of fermentation, reached pH values comprised between 4 and 3.5, depending on the tested species. Of note, 15 out of the 37 lactic acid bacteria isolates (Levilactobacillus parabrevis, Pediococcus parvulus, Lactiplantibacillus plantarum group, and Lacticaseibacillus casei group) showed the presence of the hdcA gene of Gram-positive bacteria encoding for histidine decarboxylase. Furthermore, for 8 out of the 37 isolates the in-vitro exopolysaccharides production was observed. No isolate showed inhibitory activity against the three Listeria innocua strains used as surrogate for Listeria monocytogenes.

Investigations on the Diffusion Behavior of Smoke-Associated Aroma Compounds into the Sausage Matrix as Affected by Casing, Caliber, and Packaging.

The aim of the study was to investigate how smoke-associated flavoring substances behave during storage in Frankfurter-type sausages. The diffusion behavior of seven selected aroma substances in the sausage matrix and the influence of the packaging and the casing were examined over a storage period of 28 days. The sausages were cut into uniformly thick layers at defined time intervals and examined by headspace-solid phase microextraction-gas chromatography-mass spectrometry. In general, three different groups could be distinguished: (1) even distribution over the entire product on the first day after smoking; (2) clear concentration gradient from outside to inside on the first day of storage, which leveled out until day 28 of storage; and (3) a clear concentration gradient that remained present throughout the storage period. In addition, only small effects were found in the distribution of flavorings between two types of packaging, selected casing, or different calibers.