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

Analysis of volatile compounds in rice porridge of different japonica rice varieties in Northeast China

Japonica rice is a widely cultivated and consumed cereal globally. There are many studies on the aroma of japonica rice, but few are on japonica rice porridge. Electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) techniques combined with sensory evaluation were used to analyze the volatile compounds of 21 kinds of japonica rice porridges from Northeast China. The results of electronic nose analysis showed that different varieties of rice porridges had distinct aromas, and principal component analysis effectively distinguished between them. A total of 69 volatile compounds were identified by GC-MS, including 19 hydrocarbons, 17 aldehydes, 9 alcohols, 3 ketones, 3 phenols, 5 esters, 4 ethers, 4 acids, and 5 other compounds. Then the odor activity value (OAV) was calculated to determine the contribution of each aroma compound to the overall aroma of rice porridge. Finally, it is found that the key aroma compounds of japonica rice porridge were hexanal, octanal, nonanal, decanal, (E)-2-nonenal, naphthalene, (E, E)-2,4-decadienal, butylated hydroxytoluene, 1-dodecanol, and 2-pentadecanone. This study preliminarily determined the key aroma substances and aroma attributes in japonica rie porridge, which can provide a valuable theoretical basis for selecting rice raw materials in the japonica rice porridge processing industry.

Analysis of the Volatile Organic Compound Fingerprint of Greek Grape Marc Spirits of Various Origins and Traditional Production Styles

The most well-known traditional Greek grape marc distillate made from winemaking pomace is called “Tsipouro”. Its production involves various grape pomace cultivars, preparation protocols, and anise-flavoring or not, and it should be a colorless liquid with intense organoleptic properties due to the raw materials used in its production and have a minimum alcoholic strength of 37.5% by volume. This study aimed to characterize the volatilome of tsipouro products by covering as many geographical areas and production styles as possible, as there is a lack of characterization of the aromatic composition of this Greek traditional alcoholic beverage. A Headspace Solid Phase Microextraction Gas Chromatography–Mass Spectrometry (HS-SPME-GC-MS) method was applied in 60 samples, resulting in the identification and semi-quantification of over 90 volatile compounds. The statistical analysis pointed out the metabolites that characterized each traditional product group and underlined the influence of the geographical origin and the production protocol. Aniseed spirits from Northern Greece, Macedonia, Limnos Island, and Thessaly, produced from Muscat pomaces, were found to be richer in terpenes, terpenoids, and flavored compounds, attributing to product aroma and quality; different terpenoids were found to be dominant in Muscat distillates from different regions, showing the importance of geographical origin and production process. In conclusion, the results demonstrated the high aroma variability of the Greek Tsipouro, explained that this diversity is caused mainly by the raw material, and could be helpful in the better protection of the origin of this traditional product and the improvement of its quality.

Discrimination and characterization of different coconut water (CW) by their phenolic composition and volatile organic compounds (VOCs) using LC-MS/MS, HS-SPME-GC-MS, and HS-GC-IMS.

Three varieties of coconut (Cocos nucifera L.) water (CW) at two maturity stages were investigated for physicochemical and nutritional properties. The profile of phenolic compounds and volatile organic compounds (VOCs) was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). Most of the properties of CW changed significantly with maturity rather than variety. The five most relevant phenolic compounds in CW were chlorogenic acid, 4-hydroxy-3,5-dimethoxycinnamic acid, L-epicatechin, and procyanidins B2 and B1. Variety played a more important role in phenolic composition than maturity, and Wenye No. 4 can be distinguished from other two varieties. Alcohols and esters were the main VOCs in CW identified by HS-GC-IMS and HS-SPME-GC-MS, respectively. Five and four compounds (VIP scores>1) were characteristic compounds for CW by HS-GC-IMS and HS-SPME-GC-MS, respectively. The VOCs of Wenye Nos. 2 and 3 were more similar than those of Wenye No. 4. These findings could provide useful information for the selection of raw materials of CW used for different industrial purposes.

Distinguishing raw pu-erh tea production regions through a combination of HS-SPME-GC-MS and machine learning algorithms

The authenticity of the geographical origin of agricultural products has received widespread attention. Tea tree varieties, processing processes and origins influence the quality and price of raw pu-erh tea (RPT). This study distinguished RPT from 10 different production areas through headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with orthogonal partial least squares–discriminant analysis (OPLS-DA) model and machine learning algorithms. Among the thirty-five types of common volatiles identified, pentanal, heptanal, naphthalene, cedrol, and 2,6-di-tert-butylbenzoquinone were considered the key differential compounds distinguishing the 10 different production areas of the RPT samples through the screening of variable importance in projection values of the OPLS-DA and coefficient weights of the linear discriminant analysis function. Among them, heptanal and 2,6-di-tert-butylbenzoquinone had the highest content in West of Bingdao and the lowest content in Nannuoshan. The random forest algorithm achieved a discrimination accuracy of 98.4% based on the discrimination of five key compounds in 63 RPT samples. The random forest model was demonstrated to be reliable and valid by using receiver operating characteristic curves (area under the curve = 0.7603). The study results serve as a reference for the differentiation of 10 production areas of RPT.

Effects of cold plasma treatment on maintaining the quality of fresh-cut bamboo shoots during shelf-life storage

Cold plasma (CP) is an emerging preservation technology that involves minimal processing and retains the freshness of fresh-cut products. In this study, we applied CP (50 kV, 30 s) to evaluate the potential use on the freshly cut Ma bamboo (Dendrocalamus latiflorus Munro) shoots using physicochemical, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS), 16S rRNA gene sequencing, and metabolomic analyses. The results showed that the firmness of CP treated bamboo was 57% higher than control groups, and CP treatment could effectively inhibit yellowing for up to 5 day at 25 °C. Six key flavor compounds (odor activity value (OAV) > 1) were detected. 4-Hydroxy-benzaldehyde was the most abundant compound, accounting for 45.53%–78.46% in bamboo shoots. Aldehyde, ketone, and ester contents increased significantly, whereas alcohols and alkenes were reduced by CP treatment. CP induced higher microorganism community diversity within four days. Freshly cut bamboo shoots had a high concentration of metabolites that were closely related to the lignin biosynthesis. Through the accumulating of stress-related hormones, fatty acids, and flavonoids, CP boosted the response to external stress. This method offers a new approach to preserve the quality of freshly cut bamboo shoots.

Analysis of Tieguanyin aged aroma compounds and their correlation with microbial communities

Aged Tieguanyin has a unique, long-lasting aged aroma. However, a lack of research has hindered further improvements in its quality. This study analyzed the compounds contributing to the aroma of Tieguanyin at different aging times and correlated the results with microorganisms to explore the underlying aging mechanism, using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) and MiSeq methods. A total of 85 volatile compounds were identified. The volatiles in tea aged for over 11 years were stable, similar, and significantly different from those of unaged tea. The 13 upregulated discriminatory volatiles in the late aging period were speculated to be the characteristic compounds constituting the aged aroma: 2-heptanone, 2-nonanone, 6,10-Dimethylundecan-2-one, dehydro-β-ionone, β-ionone epoxide, (−)-α-terpineol, 1-octen-3-ol, linalool oxide (II), propanoic acid, butanoic acid, 5-hydroxymethylfurfural, safranal, and caffeine. These compounds are mainly produced through the enzymatic degradation pathway of carotenoids, glycosides hydrolysis, and lipids oxidation. Based on Spearman's correlation analysis, bacteria and fungi had strong interactions with aged aroma compounds. Specifically, Sphingomonas, Acinetobacter, Halomonas, Trichosporon, Aspergillus, and Cyberlindnera were the core functional microorganisms of aged Tieguanyin. These genera had the potential to promote the formation of aged aroma through the accumulation of metabolic precursors.

Physiochemical Quality, Microbial Diversity, and Volatile Components of Monascus-Fermented Hairtail Surimi.

In order to study the effects and mechanism of Monascus on the quality of hairtail surimi, high-throughput sequencing technology, headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS), and electronic nose techniques were used to investigate the changes in the quality, microbial diversity, and volatile flavor compounds of Monascus-fermented hairtail surimi (MFHS) during fermentation. The results showed that the total volatile basic nitrogen (TVB-N) index of hairtail surimi fermented by Monascus for 0-5 h met the requirements of the national standard. Among them, the 1 h group showed the best gel quality, which detected a total of 138 volatile substances, including 20 alcohols, 7 aldehydes, 12 olefins, 4 phenols, 12 alkanes, 8 ketones, 15 esters, 6 acids, 16 benzenes, 4 ethers, and 8 amines, as well as 26 other compounds. In addition, the dominant fungal microorganisms in the fermentation process of MFHS were identified, and a Spearman correlation analysis showed that 16 fungal microorganisms were significantly correlated with the decrease in fishy odor substances in the fermented fish and that 8 fungal microorganisms were significantly correlated with the increase in aromatic substances after fermentation. In short, Monascus fermentation can eliminate and reduce the fishy odor substances in hairtail fish, increase and improve the aromatic flavor, and improve the quality of hairtail surimi gel. These findings are helpful for revealing the mechanism of the quality formation of fermented surimi and provide guidance for the screening of starter culture in the future.

The Relationship between Microbial Community Succession and Flavor Formation during the Natural Fermentation of Hongqu sufu.

To study the diversity of microbial flora in Hongqu sufu and analyze the characteristics of special flavor compounds, this study took self-made Hongqu sufu as the research object. Dynamic changes in sufu during fermentation were studied. High-throughput sequencing (HTS) was used to analyze changes in the diversity of fungal and bacterial communities during fermentation. The results showed that at the phylum level, the dominant fungal phyla were identified, Mucormyces and Ascomycetes. The dominant bacterial phyla were Proteobacteria and Firmicutes. At the genus level, the dominant fungal genera were identified as Actinomucor, Monascus, and Aspergillus. The dominant bacterial genera were Pseudomonas, Aneurimibacillus, Sphingobacterium, and Bacillus. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with technology that can dynamically change flavor compounds was explored to investigate the correlation between microbiota and flavor compounds. In different stages of fermentation, 75 main volatile organic compounds were identified, including seven alcohols, four acids, 16 alkanes, 14 olefins, seven kinds of aldehydes, two kinds of ketones, 10 kinds of esters, one kind of phenol, one kind of sulfur-containing compound, one benzene, and 12 other compounds. The correlation analysis between flora and flavor compounds showed that the fungi genera Alternaria and Pichia were significantly correlated with most flavor compounds. Bacteria genera including Weissella, Hafnia-Obesumbacterium, and Leuconostoc had a strong positive correlation with ethyl oleate.

Identification of Volatile Markers during Early Zygosaccharomyces rouxii Contamination in Mature and Immature Jujube Honey.

Osmotolerant yeasts are considered one of the major contaminants responsible for spoilage in honey. To address the signature volatile components of jujube honey contaminated by Zygosaccharomyces rouxii, headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and chemometrics analyses were used to analyze the variation of volatile substances during early contamination of mature and immature jujube honey. Undecanal, methyl butyrate, methyl 2-nonenoate, methyl hexanoate, and 2-methyl-3-pentanone were identified as signature volatiles of jujube honey contaminated with Z. rouxii. In addition, methyl heptanoate, 2,6,10-trimethyltetradecane, and heptanal were identified as potential volatile signatures for immature jujube honey. The R2 and Q2 of OPLS-DA analyses ranged from 0.736 to 0.955, and 0.991 to 0.997, which indicates that the constructed model was stable and predictive. This study has demonstrated that HS-SPME-GC-MS could be used to distinguish Z. rouxii-contaminated jujube honey from uncontaminated honey based on variation in VOCs, and could provide theoretical support for the use of HS-SPME-GC-MS for the rapid detection of honey decomposition caused by Z. rouxii, which could improve nutritional quality and reduce economic losses.

Volatile, Microbial, and Sensory Profiles and Consumer Acceptance of Coffee Cascara Kombuchas.

Given the substantial world coffee production, tons of coffee fruit cascara rich in bioactive compounds are discarded annually. Using this by-product to produce potentially healthy and acceptable foods is a sustainable practice that aggregates value to coffee production and may help improve people's lives. This study aimed to elaborate kombuchas from coffee cascara tea, evaluate their microbial profile, and monitor the changes in the volatile profile during fermentation, together with sensory attributes and acceptance by consumers from Rio de Janeiro (n = 113). Arabica coffee cascaras from Brazil and Nicaragua were used to make infusions, to which black tea kombucha, a Symbiotic Culture of Bacteria and Yeasts (SCOBY), and sucrose were added. Fermentation of plain black tea kombucha was also monitored for comparison. The volatile profile was analyzed after 0, 3, 6, and 9 days of fermentation via headspace solid phase microextraction GC-MS. A total of 81 compounds were identified considering all beverages, 59 in coffee cascara kombuchas and 59 in the black tea kombucha, with 37 common compounds for both. An increase mainly in acids and esters occurred during fermentation. Despite the similarity to black tea kombucha, some aldehydes, esters, alcohols, and ketones in coffee cascara kombucha were not identified in black tea kombucha. Potential impact compounds in CC were linalool, decanal, nonanal, octanal, dodecanal, ethanol, 2-ethylhexanol, ethyl acetate, ethyl butyrate, ethyl acetate, β-damascenone, γ-nonalactone, linalool oxide, phenylethyl alcohol, geranyl acetone, phenylacetaldehyde, isoamyl alcohol, acetic acid, octanoic acid, isovaleric acid, ethyl isobutyrate, ethyl hexanoate, and limonene. The mean acceptance scores for cascara kombuchas varied between 5.7 ± 0.53 and 7.4 ± 0.53 on a nine-point hedonic scale, with coffee cascara from three-day Nicaragua kombucha showing the highest score, associated with sweetness and berry, honey, woody, and herbal aromas and flavors. The present results indicate that coffee cascara is a promising by-product for elaboration of fermented beverages, exhibiting exotic and singular fingerprinting that can be explored for applications in the food industry.

HS-SPME-GC-MS analysis of Cyprus vineyard soil for VOCs determination

In line with green chemistry principles, a headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) method was developed and optimized to study the profile of biogenic volatile organic compounds (BVOCs) in soil samples from vineyards. The 75 µm CAR/PDMS fiber was selected for the identification of BVOCs in soil. The analytical method showed very good linearity (R2 ≥ 0.9914), sensitivity, and precision. Subsequently, soil matrix effect (ME) was examined on the BVOCs emission, through combined standard addition and internal standard (IS) calibration curves. The validated and optimized method was further applied in real soil samples from three vineyard areas of Cyprus (Omodos, Polemi, and Agros). Thirty-eight BVOCs were identified in total; among them acetone (0.65–5.96 μg/kg), hexane (0–0.50 μg/kg), heptane (0–0.18 μg/kg), trichloromethane (0.13–0.21 μg/kg), 1,2-dichloropropane (0.05–1.37 μg/kg), cyclohexane (0–0.26 μg/kg), benzene (0–0.51 μg/kg), toluene (0–0.54 μg/kg), p-xylene (0.15–0.97 μg/kg), and 1,3-di-tert-butyl-benzene (7.91–29.55 μg/kg) were quantified. The results revealed that the sampling vineyard location affects the BVOCs emissions in each soil. Also, vineyard elevation, soil pH, Ca, N, Zn, and Fe showed a significant correlation with the BVOCs emissions, which explains why vineyard soil regions are distinguished from each other, concluding that sample from Agros is the most abundant in BVOCs emissions.

Evaluation and comparison of physicochemical properties, volatile substances, and microbial communities of leaf mustard (Brassica juncea var. multiceps) under natural and inoculated fermentation.

Due to the uncontrolled fermentation process and unstable quality of naturally fermented leaf mustard, inoculated fermentation is receiving more attention. Here, the physicochemical properties, volatile compounds, and microbial community in leaf mustard under natural fermentation (NF) and inoculated fermentation (IF) were analyzed and compared. The contents of total acid, crude fiber, and nitrite of leaf mustard were measured. Headspace-solid phase microextraction-gas chromatography-mass spectrometry and orthogonal projection on latent structure-discriminant analysis were used to analyze the differences of volatile compounds in NF and IF leaf mustard. Moreover, Illumina MiSeq high-throughput sequencing technology was employed to reveal the composition of microbiota. The results showed that the nitrite content in leaf mustard after IF (3.69mg/kg) was significantly lower than that after NF (4.43mg/kg). A total of 31 and 25 kinds of volatile components were identified in IF and NF, respectively. Among the detected compounds, 11 compounds caused the differences between IF and NF leaf mustard. The results of inter-group difference analysis showed that there were significant differences in fungal flora between IF and NF samples. Saccharomycetes, Kazachstania, and Ascomycota were the landmark microorganisms in IF leaf mustard and the landmark microorganisms in NF were Mortierellomycota, Sordariomycetes, and Eurotiomycetes. The abundance of probiotics (such as Lactobacillus) in IF leaf mustard (51.22%) was higher than that in NF (35.20%) and the abundance of harmful molds (such as Mortierella and Aspergillus) was opposite. Therefore, IF leaf mustard showed the potential to reduce the content of nitrite and harmful molds and increase the beneficial volatile compounds and probiotics. PRACTICAL APPLICATION: Leaf mustard of inoculated fermentation (IF) showed better fermented characteristics than natural fermentation in terms of lower nitrite content, greater beneficial volatile substances, and better potential for increasing probiotics and reducing harmful molds. These results provided a theoretical basis for IF leaf mustard and contributed to the industrial production of fermented leaf mustard.

Electrospinning composites of polyvinylidene fluoride - carbon black on solid phase microextraction fibers for enhanced detection of volatile organic compounds by gas chromatography-mass spectrometry

Urine contains volatile organic compounds (VOCs) that can be a source of biomarkers for different medical conditions. Headspace solid phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC–MS) is the gold standard for VOC detection but is time-consuming and expensive. Gas sensors on the other hand are portable and provide rapid results, but qualification of sensing layers is tedious as VOCs need to be tested individually. Our previous study showed that dip coating SPME fibers, using them to extract VOCs from urine and analyzing them by GC–MS is a tool to rapidly characterize sensing elements. The current study aims to extend these findings to demonstrate that HS-SPME GC–MS can identify how electrospinning can enhance the detection of VOCs due to the increased surface area. Herein, previously optimized suspensions of polyvinylidene fluoride-carbon black (PVDF-CB) were deposited on SPME fiber substrates through dip coating and electrospinning, used to extract VOCs from urine and were subject to GC–MS. Electrospinning parameters (applied voltage, flow rate and duration) were optimized, which showed that an applied voltage of 17 kV and a flow rate of 0.25 mL/hr was optimal for electrospinning fibers with 1.5 µm diameter, high coverage and little to no beading. SPME fibers electrospun with PVDF-CB for 10 min were compared to dip coated fibers, and the results showed electrospun fibers had increased efficiency to extract an abundant number of VOCs in urine. These VOCs were enriched when sampled by the electrospun fiber by factors ranging from 1.5 – 5.5. Results also showed that the electrospun fibers had significantly higher reproducibility (p-value < 0.001) relative to dip coated fibers. In summary, electrospinning has the capability of fabricating more sensitive SPME fibers relative to dip coating, and therefore may be utilized in the future for an array of different applications including but not limited to VOC biomarker discovery.

Multivariate regression modelling for gender prediction using volatile organic compounds from hand odor profiles via HS-SPME-GC-MS.

The efficacy of using human volatile organic compounds (VOCs) as a form of forensic evidence has been well demonstrated with canines for crime scene response, suspect identification, and location checking. Although the use of human scent evidence in the field is well established, the laboratory evaluation of human VOC profiles has been limited. This study used Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) to analyze human hand odor samples collected from 60 individuals (30 Females and 30 Males). The human volatiles collected from the palm surfaces of each subject were interpreted for classification and prediction of gender. The volatile organic compound (VOC) signatures from subjects' hand odor profiles were evaluated with supervised dimensional reduction techniques: Partial Least Squares-Discriminant Analysis (PLS-DA), Orthogonal-Projections to Latent Structures Discriminant Analysis (OPLS-DA), and Linear Discriminant Analysis (LDA). The PLS-DA 2D model demonstrated clustering amongst male and female subjects. The addition of a third component to the PLS-DA model revealed clustering and minimal separation of male and female subjects in the 3D PLS-DA model. The OPLS-DA model displayed discrimination and clustering amongst gender groups with leave one out cross validation (LOOCV) and 95% confidence regions surrounding clustered groups without overlap. The LDA had a 96.67% accuracy rate for female and male subjects. The culminating knowledge establishes a working model for the prediction of donor class characteristics using human scent hand odor profiles.

HS-SPME-GC-MS Untargeted Analysis of Normal Rat Organs Ex Vivo: Differential VOC Discrimination and Fingerprint VOC Identification.

The investigation of volatile organic compounds (VOCs) in human metabolites has been a topic of interest as it holds the potential for the development of non-invasive technologies to screen for organ lesions in vivo. However, it remains unclear whether VOCs differ among healthy organs. Consequently, a study was conducted to analyze VOCs in ex vivo organ tissues obtained from 16 Wistar rats, comprising 12 different organs. The VOCs released from each organ tissue were detected by the headspace-solid phase microextraction-gas chromatography-mass spectrometry technique. In the untargeted analysis of 147 chromatographic peaks, the differential volatiles of rat organs were explored based on the Mann-Whitney U test and fold change (FC > 2.0) compared with other organs. It was found that there were differential VOCs in seven organs. A discussion on the possible metabolic pathways and related biomarkers of organ differential VOCs was conducted. Based on the orthogonal partial least squares discriminant analysis and receiver operating characteristic curve, we found that differential VOCs in the liver, cecum, spleen, and kidney can be used as the unique identification of the corresponding organ. In this study, differential VOCs of organs in rats were systematically reported for the first time. Profiles of VOCs produced by healthy organs can serve as a reference or baseline that may indicate the presence of disease or abnormalities in the organ's function. Differential VOCs can be used as the fingerprint of organs, and future integration with metabolic research may contribute to the development of healthcare.

Effect of Protease Combined with Heat Treatment on the Volatile Composition and Aroma Quality in Liqueur Wine.

The aim of this paper was to compare the effects of two clarification methods, protease combined with heat treatment and bentonite, on the aroma quality of liqueur wines, and to identify and analyze the overall differences between the basic components and volatile aroma compounds of liqueur wines after the two treatments by chemical analysis, headspace-solid-phase microextraction-gas chromatography/mass spectrometry (HS-SPME-GC/MS), and orthogonal partial least squares discriminant analysis (OPLS-DA). The results showed that total acidity, volatile acidity and pH in liqueur wines after protease combined with heat treatment were not significantly different from those of the blank control, and the ability to remove proteins was equal to that of the bentonite treatment. A total of 58 volatile aroma compounds were detected by HS-SPME-GC/MS. Compared with the blank control group (44 species, total 108.705 mg/L), 52 (83.233 mg/L) and 50 (120.655 mg/L) aroma compounds were detected in the bentonite and protease combined with heat treatments, respectively. Compared with the control and bentonite treatment, the protease combined with heat treatment significantly increased the total content of aromatic compounds in liqueur wines, and the types and contents of olefins, furans and phenols were higher. Among them, the compounds with major contributions in the protease combined with heat treatment were ionone, β-damascenone, 3-methyl-1-butanol, alpha-terpineol and limonene, which helped increase the content of terpenoids and enhance the floral and fruit aroma of the wine. Meanwhile, linalool, diethyl succinate, 2-methyl-3-heptanone, butanal diethyl acetal, hexanal and n-octanol were six compounds with high content of aromatic compounds unique to liqueur wines after protease combined with heat treatment. The sensory evaluation results were consistent with the results of aromatic compound detection, and the overall quality was better. The results may provide a reference for further exploration of protease-based clarifiers suitable for liqueur wines.

Integrated volatile compounds and non-targeted metabolomics analysis reveal the characteristic flavor formation of proteins in grouper (Epinephelus coioides) during cold storage

Microorganisms, lipids, and proteins always interact in a complex way in the fish matrix, which becomes a hindrance to evaluate the quality of the individual factors affecting them. In order to investigate the relationship between protein deterioration and volatile compounds (VOCs) in grouper during cold storage, the myofibril protein (MP) was used as a single-factor study to exclude microorganisms and lipids effects. The oxidation and degradation of MP during storage at 4 ℃ were evaluated, including MP content, total sulfhydryl content, carbonyl content, spatial structure and microstructure. Headspace-solid phase microextraction- gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the VOCs of grouper MP, and a total of 7 key VOCs were selected, including three ketones (2-nonanone, 2-undecanone and 2-tridecanone), three esters (methyl butyrate, methyl palmitate and methyl ester 9-octadecenoic acid) and one alcohol (3-methyl-1-butanol). At the same time, a non-targeted metabolomics method based on UPLC-Q-Extractive Orbitrap was used to investigate the changes in metabolites during MP storage. A total of 107 up-regulated differential metabolites and 7 down-regulated metabolites were annotated, and 6 metabolic pathways highly related to proteins were screened. Spearman correlation analysis showed that 7 key VOCs are associated with the biosynthesis and metabolism of ornithine and lysine. And a possible solution to protein deterioration in grouper was proposed, which provided a reference for improving protein quality and regulating flavor formation during cold storage of grouper at source.

A useful species identification and quality control using volatile patterns of ssajuari-ssuk and sajabal-ssuk (Artemisia princeps Pamp. cv. ssajuari and Artemisia princeps Pamp. cv. sajabal; Korean mugwort) according to air-drying term by fast gas chromatography with uncoated surface acoustic wave sensor.

Ssajuari-ssuk and sajabal-ssuk have many clinical benefits. It is difficult to discriminate between these two species based on general characteristics aside from the shapes of the leaves. Thus, species identification and quality control between ssajuari-ssuk and sajabal-ssuk are of great concern in plant science and clinical therapy. The aim of this study is to determine whether fast gas chromatography with uncoated surface acoustic wave sensor (GC-SAW) can be a useful technique for performing species identification and quality control using volatile patterns of ssajuari-ssuk and sajabal-ssuk air-dried for 4months and 2years and 4months. Fast GC-SAW sensor provides second unit analysis, simple, on-line measurements that do not require pretreatment of the sample and rapid sensory information. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to confirm the identification of the volatiles and compared to fast GC-SAW sensor. In air-dried sajabal-ssuk, the concentration of 1,8-cineole was higher than that in air-dried ssajuari-ssuk, while the level of α-thujone was considerably lower than that of air-dried ssajuari-ssuk. Each of ssajuari-ssuk and sajabal-ssuk air-dried for 4months and 2years and 4months has its own characteristic volatile pattern owing to its individual chemotypes or chemical compositions. Consequently, the fast GC-SAW sensor can be a useful technique for species identification and quality control using volatile patterns of ssajuari-ssuk and sajabal-ssuk air-dried for 4months and 2years and 4months. This method can be used for the standardisation of quality control using volatile patterns of herbal medicines.

Based on HS-SPME-GC-MS combined with GC-O-MS to analyze the changes of aroma compounds in the aging process of Citri Reticulatae Pericarpium

Citri Reticulatae Pericarpium (CRP) is a very well-known foodstuff. It can not only be drunk directly like tea, but also be used as a condiment for cooking food. This study used headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), gas chromatography-olfactometry-mass spectrometry (GC-O-MS), and sensory evaluation to analyze and evaluate CRP over the six-year aging process (2, 5, 10, 15, 20, and 25 years). HS-SPME-GC-MS identified 93 volatile components, while GC-O-MS detected 42 aroma compounds. The results indicated that the aroma intensity (AI) of the spicy, woody, and herbal aroma compounds remained unchanged, while those with citrus and fruity notes gradually decreased and even disappeared with extended storage time, which could explain the unique CRP aroma. Orthogonal partial least squares discriminant analysis (OPLS-DA) showed that the CRP in the six-year aging process was clearly divided into three groups: young-aged samples (2Y), middle-aged samples (5Y and 10Y), and old-aged samples (15Y, 20Y, and 25Y). In addition, combining sensory evaluation and GC-O-MS fully reflected the changes during the different CRP aging stages. This study confirmed the potential of combining GC-O-MS and OPLS-DA as a reliable analytical selection technique to distinguish CRP age. Finally, 13 key aroma compounds were screened using VIP >1 and p < 0.05, including isopulegol, dodecanal, and α-calacorene.

Deciphering the brewing process of Cantonese-style rice vinegar: Main flavors, key physicochemical factors, and important microorganisms

Cantonese-style rice vinegar is one of the most important Chinese rice vinegars and is quite popular all over the southeast coast of China, especially in Guangdong. This study identified 31 volatile compounds, including 11 esters, 6 alcohols, 3 aldehydes, 3 acids, 2 ketones, 1 phenol, and 5 alkanes, using headspace solid-phase microextraction–gas chromatography–mass spectrometry. Six organic acids were detected by high performance liquid chromatography. The ethanol content was detected by gas chromatography. During acetic acid fermentation, physicochemical analysis showed that the initial concentrations of reducing sugar and ethanol were 0.0079 g/L and 23.81 g/L, respectively, and the final value of total acid was 46.5 g/L, and the pH value was stable at 3.89. High-throughput sequencing was used to identify the microorganisms, and Acetobacter, Komagataeibacter, and Ralstonia were the top three bacterial genera. Quantitative real-time polymerase chain reaction revealed patterns that were different from those of high-throughput sequencing. The co-occurrence network of microorganisms and the correlation analysis between microorganisms and flavor substances indicate that Acetobacter and Ameyamaea played crucial roles as the main functional AAB, and the failure of Cantonese-style rice vinegar fermentation can be attributed to the abnormal increase in Komagataeibacter. Microbial co-occurrence network analysis indicated that Oscillibacter, Parasutterella, and Alistipes were the top three microorganisms. Redundancy analysis disclosed that total acid and ethanol were the key environmental factors influencing the microbial community. Fifteen microorganisms closely related to the metabolites were identified using the bidirectional orthogonal partial least squares model. Correlation analysis showed that these microorganisms were strongly associated with flavor metabolites and environmental factors. The findings of this study deepen our understanding of the fermentation of traditional Cantonese-style rice vinegar.