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

Characterization of volatile organic compounds in grafted tomato plants upon potyvirus necrotic infection

A headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS) method was used to study the volatile organic compounds (VOCs) associated with the differential immune response of tomato plants infected with the recombinant strain of potato virus Y (PVYC-to), necrogenic to tomato. Analysis was carried out in UC82 (UC), a virus susceptible tomato variety, comparing the same UC plants grafted or not onto a virus tolerant tomato ecotype, Manduria (Ma); the three types of samples used for the GC-MS analysis were mock-inoculated UC/Ma plants, UC/Ma+PVYC-to and UC+PVYC-to plants; the VOCs obtained were 111. Results from symptomatic PVYC-to-infected UC plants showed a VOCs composition enriched in alcohols, fatty acid derivates, benzenoids, and salicylic acid derivatives, while in mock-inoculated UC/Ma plants VOCs were mainly characterized by methyl ester compounds. The VOC profile was in line with RNAseq data analyses, denoting that PVYC-to viral RNA accumulation and disease symptoms induce the specific transcriptional activation of genes involved in VOCs biosynthesis. Furthermore, principal component analysis highlighted that VOCs of PVYC-to-infected and mock-inoculated grafted plants were much closer each other than that of symptomatic PVYC-to-infected non-grafted UC plants. These results suggest that VOCs profiles of tomato plants are related to the viral RNA accumulation, disease intensity and graft-derived tolerance to PVYC-to infection.

Identification of volatile compounds and metabolic pathway during ultrasound-assisted kombucha fermentation by HS-SPME-GC/MS combined with metabolomic analysis

The current work combines headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS) with multivariate analysis fusion metabonomics for examining metabolite profile changes. The correlation with metabolic pathways during the fermentation of kombucha tea were comprehensively explored. For optimizing the fermentation process, ultrasound-assisted factors were explored. A total of 132 metabolites released by fermented kombucha were detected by HS-SPME-GC/MS. We employed the principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to present the relationship between aroma components and fermentation time, of which the first two principal components respectively accounted for 60.3% and 6.5% of the total variance. Multivariate statistical analysis showed that during the fermentation of kombucha tea, there were significant differences in the phenotypes of metabolites in the samples, and 25 characteristic metabolites were selected as biomarkers. Leaf alcohol was first proposed as the characteristic volatile in the fermentation process of kombucha. Furthermore, we addressed the generation pathways of characteristic volatiles, their formation mechanisms, and the transformational correlation among them. Our findings provide a roadmap for future kombucha fermentation processing to enhance kombucha flavor and aroma.

Differentiation of Mountain- and Garden-Cultivated Ginseng with Different Growth Years Using HS-SPME-GC-MS Coupled with Chemometrics.

Although there are differences in the appearance of Mountain-Cultivated Ginseng (MCG) and Garden-Cultivated Ginseng (GCG), it is very difficult to distinguish them when the samples are processed to slices or powder. Moreover, there is significant price difference between them, which leads to the widespread adulteration or falsification in the market. Thus, the authentication of MCG and GCG is crucial for the effectiveness, safety, and quality stability of ginseng. In the present study, a headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) coupled with chemometrics approach was developed to characterize the volatile component profiles in MCG and GCG with 5-,10-,15-growth years, and subsequently to discover differentiating chemical markers. As a result, we characterized, for the first time, 46 volatile components from all the samples by using the NIST database and the Wiley library. The base peak intensity chromatograms were subjected to multivariate statistical analysis to comprehensively compare the chemical differences among the above samples. MCG5-,10-,15-years and GCG5-,10-,15-years samples were mainly divided into two groups by unsupervised principal component analysis (PCA), and 5 potential cultivation-dependent markers were discovered based on orthogonal partial least squares-discriminant analysis (OPLS-DA). Moreover, MCG5-,10-,15-years samples were divided into three blocks, and 12 potential growth-year-dependent markers enabled differentiation. Similarly, GCG5-,10-,15-years samples were also separated into three groups, and six potential growth-year-dependent markers were determined. The proposed approach could be applied to directly distinguish MCG and GCG with different growth years and to identify the differentiation chemo-markers, which is an important criterion for evaluating the effectiveness, safety, and quality stability of ginseng.

Unraveling the microbial succession during the natural fermentation of grass carp and their correlation with volatile flavor formation

Complex microbial communities contribute significantly to the flavor formation of traditional fermented fish products. However, the relationship between microorganisms and flavor formation in traditional fermented grass carp products is still unclear. In this study, the diversity and succession of microbial communities and the variation of volatile compounds during natural fermentation of grass carp were analyzed using high-throughput sequencing of 16S rRNA and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. The core functional microorganism and key volatile compounds were identified, and their potential relationship was revealed using a correlation network model analysis. The microbial community analysis result showed that the microbial diversity during natural fermentation of grass carp decreased markedly with increasing fermentation time, and Lactiplantibacillus, Staphylococcus, and Enterobacter were the dominant genera in naturally fermented grass carp. HS-SPME-GC-MS analysis result showed that 45 volatile compounds were identified from fermented samples, among which 13 compounds (e.g., hexanal, heptanal, nonanal, decanal, 3-octanone, 3-methyl-1-butanol, 1-hexanol, 1-heptanol, 1-octen-3-ol, 1-octanol, ethyl acetate, 3-methyl-1-butanol acetate, and 2-methoxy-4-vinylphenol) were identified as the key volatile compounds. Additionally, the correlation network model analysis result revealed that Lactiplantibacillus showed significantly positive correlations with most of the key volatile compounds, making an important contribution to the formation of volatile flavor in naturally fermented grass carp. This study may lead to an understanding of the role of core functional microorganisms in the formation of volatile flavor during the natural fermentation of grass carp and provide some theoretical guidance for the industrial production of high-quality fermented grass carp products.

Development of a Novel Flavored Goat Cheese with Gentiana lutea Rhizomes.

Gentiana lutea rhizomes, generally used as a bittering agent in food, were harvested from two geographical sites (Massif Central: MC and Jura: J) to evaluate their potential use in the flavoring step during goat cheesemaking. Gentian flavored goat cheeses (MCGC and JGC) were elaborated by a one-night immersion of unflavored goat cheeses (CGC) into gentian-infused whey. The impregnation of gentian in goat cheeses was evaluated by chemical and sensory analysis. The chemical composition of cheeses was analyzed by HS-SPME-GC-MS (Head-Space-Solid Phase MicroExtraction-Gas Chromatography-Mass Spectrometry) for volatile compounds (alcohols, ketones, aldehydes, esters, alkenes, alkanes, acids, terpenes) and UHPLC-DAD (Ultra High-Performance Liquid Chromatography-Diode Array Detector) for gentian bitter compounds (seco-iridoids). The sensory analysis consisted of a bitterness rating and a free description of cheeses by 17 trained panelists. Results of the study highlighted that unflavored goat cheeses presented higher unpleasant notes (goaty and lactic whey) and higher amounts of hexanoic acid and toluene compared to gentian flavored goat cheeses. The bitterness of gentian flavored goat cheeses was higher compared to unflavored cheeses and could be explained by loganic acid transfer from yellow gentian to flavored cheeses. Other free descriptors of gentian flavored goat cheeses revealed more complex notes (herbal, vegetal, floral, sweet, spicy and creamy) and higher relative amounts of volatile compounds such as 3-methyl butanoic acid, 2-methyl propanoic acid, 4-methyl decane, 2,3-butanediol, ethanol, diacetyl, methyl acetate and 2-phenylethyl acetate, compared to unflavored cheeses. Phenylethyl acetate was the only volatile compound that enabled differentiation of gentian origin on gentian flavored goat cheeses. Gentian rhizomes could be considered a promising flavoring agent contributing to the olfactive and gustative complexity of flavored goat cheeses and the reduction of their goaty perceptions.

Isolation of Volatiles in Honeysuckle by Multiple Approaches with Determination by Gas Chromatography–Mass Spectrometry (GC–MS) and Headspace Solid-Phase Microextraction-Gas Chromatography–Mass Spectrometry (HS-SPME/GC–MS)

The volatile components of honeysuckle were determined using hydro-distillation (HD), water extraction coupling rectification (WER), and water extraction coupling rectification with solvent extraction (WER-SE). Gas chromatography–mass spectrometry (GC–MS) and headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME/GC–MS) identified 127 compounds. There were 27 common compounds extracted by these methods. A heatmap of the 27 common compounds indicates that WER-SE and WER were complementary approaches. In addition, 59 compounds were detected for the first time in honeysuckle. The results of this study provide a reference for the determination of volatile components in plants.

Microbial Diversity and Volatile Flavor Compounds in Tibetan Flavor Daqu.

In this study, the microbial diversity in Tibetan flavor Daqu was analyzed based on single molecule real-time sequencing (SMRT). The volatile flavor compounds in Daqu were detected using the headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). In addition, the correlation between various microbes and volatile flavor compounds was explored. Our studies indicated that the dominant bacterial genera in Tibetan flavor Daqu were Oceanobacillus, Kroppenstedtia, Virgibacillus, Enterococcus, Pediococcus, Streptomyces, Saccharopolyspora, Leuconostoc, uncultured_bacterium_f_Lachnospiraceae and Lactobacillus. The dominant fungal genera were Wickerhamomyces, Monascus, Aspergillus and Rhizomucor. 101 volatile compounds were detected in the Daqu samples, including alcohols, acids, esters, aldehydes, hydrocarbons, ketones, ethers, aromatics and pyrazines, and 10 key flavor compounds were identified using the relative odor activity value (ROAV). The results of our correlation analysis showed that Enterococcus was mainly associated with the synthesis of aldehydes such as trans-2-octenal, and uncultured_bacterium_f_lachnospiraceae was associated with the synthesis of most aldehydes. This paper has systematically investigated the physicochemical indices, microbial community structure and flavor compounds of Tibetan flavor Daqu, which is helpful in gaining a deeper understanding of the characteristics of Tibetan flavor Daqu.

GC–MS and LC-MS/MS metabolomics revealed dynamic changes of volatile and non-volatile compounds during withering process of black tea

High-performance liquid chromatography (HPLC), headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS) and ultra-high performance liquid chromatography–Q-Exactive HF-X mass spectrometer (UHPLC–Q-Exactive HF/MS) were carried out to reveal dynamic changes of volatile and non-volatile compounds during the withering process of black tea. A total of 118 volatile organic compounds (VOCs) and 648 metabolites were identified in fresh and withered tea-leaves, respectively. Among them, 47 VOCs (OAV > 1.0) for the aroma formation, and 46 characteristic metabolites (VIP > 1.50, p < 0.01) selected through orthonormal partial least squares-discriminant analysis, indicated the withering contribution during black tea processing. Overall, the withering promoted alcohols, aldehydes, phenols, heterocyclic oxygen, hydrocarbons and halogenated hydrocarbons through relevant hydrolyzation, decomposition, terpene synthesis, and O-methylation. The hydrolyzation, O-methylation, condensation and N-acylation of kaempferol glycosides, quercetin glycosides, ester catechins, and gallic acid generated the accumulation of methoxyl flavonoids and flavonoid glucosides, dihydrokaempferol, syringic acid, theaflavins, and N-acylated amino acids, respectively.

Moderate Salinity of Nutrient Solution Improved the Nutritional Quality and Flavor of Hydroponic Chinese Chives (Allium tuberosum Rottler).

Sodium chloride (NaCl), as a eustressor, can trigger relevant pathways to cause plants to produce a series of metabolites, thus improving the quality of crops to a certain extent. However, there are few reports on the improvement of nutrient quality and flavor of hydroponic Chinese chives (Allium tuberosum Rottler) by sodium chloride. In this study, five NaCl concentrations were used to investigate the dose-dependent effects on growth, nutritional quality and flavor in Chinese chives. The results show that 10 mM NaCl had no significant effect on the growth of Chinese chives, but significantly decreased the nitrate content by 40% compared with 0 mM NaCl treatment, and the content of soluble protein and vitamin C was increased by 3.6% and 2.1%, respectively. In addition, a total of 75 volatile compounds were identified among five treatments using headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME/GC-MS). Compared with the 0 mM NaCl treatment, 10 mM NaCl had the greatest effect on the quantity and content of volatile compounds, with the total content increased by 27.8%. Furthermore, according to the odor activity values (OAVs) and odor description, there were 14 major aroma-active compounds (OAVs > 1) in Chinese chives. The “garlic and onion” odor was the strongest among the eight categories of aromas, and its highest value was observed in the 10 mM NaCl treatment (OAVs = 794).Taken together, adding 10 mM NaCl to the nutrient solution could improve the nutritional quality and flavor of Chinese chives without affecting their normal growth.

Synthesis of cationic β-cyclodextrin functionalized silver nanoparticles and their drug-loading applications.

Silver nanoparticles have attracted great attention owing to their distinct physicochemical properties, which inspire the development of their synthesis methodology and their potential biomedical applications. In this study, a novel cationic β-cyclodextrin (C-β-CD) containing a quaternary ammonium group and amino group was applied as a reducing agent as well as a stabilizing agent to prepare C-β-CD modified silver nanoparticles (CβCD-AgNPs). Besides, based on the inclusion complexation between drug molecules and C-β-CD, the application of CβCD-AgNPs in drug loading was explored by the inclusion interaction with thymol. The formation of AgNPs was confirmed by ultraviolet-visible spectroscopy (UV-vis) and X-ray diffraction spectroscopy (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the prepared CβCD-AgNPs were well dispersed with particle sizes between 3-13 nm, and the zeta potential measurement result suggested that the C-β-CD played a role in preventing their aggregation in solution. 1H Nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT-IR) revealed the encapsulation and reduction of AgNPs by C-β-CD. The drug-loading action of CβCD-AgNPs was demonstrated by UV-vis and headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS), and the results of TEM images showed the size increase of nanoparticles after drug loading.

Monitoring Changes in the Volatile Compounds of Tea Made from Summer Tea Leaves by GC-IMS and HS-SPME-GC-MS.

Compared with spring tea, summer tea has the advantages of economy and quantity. However, research on the aroma characteristics of summer tea is currently limited. In this study, summer fresh tea leaves (castanopsis. sinensis, cv. Fuliangzhong) (FTLs) were processed intoblack tea (BT) and green tea (GT). The changes in the volatile compounds during the tea processing were quantified using gas chromatography-ion mobility spectrometry (GC-IMS) and head space-solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), and then analyzed on the basis of relative odor activity value (ROAV). Results showed low amounts of flavor compounds, such as linalool oxides, geraniol, and sulcatone, were found in FTLs, but after processing, high amounts of the same in BT and GT. Summer BT and GT contained characteristic compounds similar to spring tea, including linalool, geraniol, (E,E)-2,4-decdienal, β-ionone, methyl salicylate, geranyl acetone, and decanal. All these compounds have high content and ROAV values, which give the same flavor to summer teas as spring tea. This study confirmed that summer fresh tea leaves were suitable to produce black and green tea with good flavor. Monitoring changes in aroma compounds by GC-IMS coupled with GC-MS, the quality of summer tea is expected to be promoted towards the quality of spring tea by improving processing methods for valuable-tea production.

Characterization of physical properties, volatile compounds and aroma profiles of different salted egg yolk lipids

Salted egg yolks (SEY) have a desirable and unique flavor with multiple underlying applications in food processing, and their abundant lipids contribute to a creamy and pleasant aroma. However, it is important to maintain the stability of the SEY flavor, which depends to a large extent on the egg species and the processing method. This study aimed to extract different SEY lipids with conventional solvents, analyze the fatty acid composition, and screen the volatile compounds to elucidate the flavor differences between salted hen eggs and duck eggs. Compared to ethanol extraction, acetone-extracted lipids had lower acid value and viscosity, and almost had no phospholipid content. Fatty acid analysis revealed that the highest content of fatty acid in SEY lipids was oleic acid, followed by palmitic acid and linoleic acid, while there were significant variations of different SEY lipids in the fatty acid profiles. The volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS), and the overall odor was detected by the electronic nose (E-nose). A total of 27 volatile compounds were analyzed in SEY lipids and divided into 8 chemical classes. The aldehydes, furans and pyrazines were decreased, and the hydrocarbons were increased compared with untreated SEY. The combination of the physical properties and flavor evaluation of SEY lipids could provide a theoretical basis for the extension of the characteristic flavor matrix in SEY.

Preparation and Characterization of Flavored Sauces from Chinese Mitten Crab Processing By-Products

To achieve high-value utilization of Chinese mitten crab processing by-products, different types of sauces were prepared using crab legs (CLs) and crab bodies (CBs). Two processing methods, enzymatic hydrolysis and enzymatic hydrolysis coupled with the Maillard reaction, were employed to prepare these sauces. An electronic nose (E-nose) and electronic tongue (E-tongue) were used to measure the changes in the taste and odor, an automatic amino acid analyzer was used to measure the amino acid content, and a headspace solid-phase microextraction GC/MS (HS-SPME-GC/MS) was used to analyze the volatile compounds, qualitatively and quantitatively. The results showed that the sour, bitter, and other disagreeable odors of the enzymatic hydrolysis solution (EHS) were reduced following the Maillard reaction; meanwhile, the umami and saltiness were considerably enhanced. The quantity of free acidic amino acids with an umami and sweet taste in the CL and CB sauces after enzymatic hydrolysis and the Maillard reaction was substantially higher than that in the homogenate (HO). The Maillard reaction solution (MRS) produced more volatile compounds than the HO and EHS, such as aldehydes, pyrazines, ketones, etc. These compounds not only impart a unique flavor but also have antioxidant capabilities, making them a prototype for the high-value utilization of crab processing by-products.

Differential characterization of volatile components and aroma sensory properties of different types of Hehong tea (Congou black tea)

AbstractTo explore the flavour characteristics and their different molecular mechanisms of different types of Hehong tea (Gongya, GY; Congou, CG and Laocong, LC) from the perspective of dry tea, we investigated their volatile compounds and sensory aroma sub‐attribute characteristics by headspace–solid phase microextraction–gas chromatography–mass spectrometry (HS‐SPME‐GC–MS), quantitative description analysis (QDA), and chemometrics. A total of 42 volatile compounds were identified in Hehong tea, of which alcohol content was the highest, the number of esters was the largest and pyrrole showed the largest differences. The volatile components of GY and LC differed, whereas those of CG and LC were more similar. There were 34 volatile components with a significant difference in the three types of Hehong tea. We established the aroma quantitative system of Hehong tea by using QDA. We found that sweety was probably the symbolic aroma sub‐attribute of Hehong tea, and woody was the characteristic sub‐attribute of LC, and there was a certain correlation among the aroma sub‐attributes. A total of 21 volatile components importantly contributed to the aroma sub‐attributes of Hehong tea. Furthermore, we screened out 18 marker volatile compounds that may be used as important indicators for distinguishing the three types of Hehong tea. Our findings add to our understanding of the flavour characteristics and aromas of the three types of Hehong tea and provide new strategies and thoughts for the evaluation of tea flavour using dry tea.

Characterization of a novel flavored yogurt enriched in γ-aminobutyric acid fermented by Levilactobacillus brevis CGMCC1.5954

This study developed and characterized a γ-aminobutyric acid (GABA)-enriched yogurt fermented by Levilactobacillus brevis CGMCC1.5954. The GABA content in the yogurt was 147.36 mg/100 mL, which was 317.06% higher than that of the control group. Furthermore, there was a significant improvement in the aroma, hardness, adhesion, cohesiveness, and gelatinousness of yogurt. The chromatography and metabolomics analyses further confirmed the high GABA content in yogurt and its nutritional value, and the metabolic pathway for GABA production by L. brevis 54 was identified. A total of 58 volatile flavor compounds were identified using headspace solid-phase microextraction-gas chromatography-mass spectrometry, of which 2-nonanone and 2-heptanone may be responsible for the high odor score of GABA-enriched yogurt. This study developed a nutritious and unique GABA-enriched flavored yogurt, summarized the metabolic pathway of GABA, and provided a flavor fingerprint that could guide the production of specifically flavored yogurts.

The Flavor Profiles of Highland Barley Fermented with Different Mushroom Mycelium.

Highland barley was fermented with Cordyceps militaris, Stropharia rugoso-annulata, Morchella esculenta, Schizophyllum commune and Tremella sanguinea. The flavor profiles were investigated by electronic nose (E-nose), headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and sensory evaluation by train panel. Fermentation with mushroom mycelium was able to change the aroma profile of highland barley. The original strong grassy taste was reduced due to a decrease in hexanal, decanal and 2-pentylfuran, and new aromatic flavors (floral, sweet and mushroom fragrance) were acquired after fermentation. The overall flavor of the fermented highland barley varied with mushroom strains. Schizophyllum commune gave a heavier sour taste to the fermented highland barley. However, fermentation with T. sanguinea increased the content of methyl 4-methoxybenzoate making the sample difficult to accepted. Fermentation with C. militaris, M. esculenta, and S. rugoso-annulata increased the volatile contents. The high levels of 1-octen-3-ol and esters gave a strong mushroom, oily and fruity flavor. Morchella esculenta showed the best performance and the highest acceptance in the fermented highland barley. Our results suggest that fermentation with mushroom mycelium can improve the flavor of highland barley, which provides an innovative utilization of highland barley.

The Discrimination and Characterization of Volatile Organic Compounds in Different Areas of Zanthoxylum bungeanum Pericarps and Leaves by HS-GC-IMS and HS-SPME-GC-MS.

The pericarps of Zanthoxylum bungeanum (ZBP) and leaves of Zanthoxylum bungeanum (ZBL) are popular spices in China, and they have pharmacological activities as well. In this experiment, the volatile organic compounds (VOCs) of the pericarps of Zanthoxylum bungeanum in Sichuan (SJ) and its leaves (SJY) and the pericarps of Zanthoxylum bungeanum in Shaanxi (SHJ) and its leaves (SHJY) were analyzed by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The fingerprint of HS-GC-IMS and the heat maps of HS-SPME-GC-MS were established. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed. The results showed that a total of 95 components were identified, 62 components identified by HS-SPME-GC-MS and 40 components identified by HS-GC-IMS, of which 7 were the same. The analysis found that SJ and SHJ were obviously distinguished, while SJY and SHJY were not. There were considerably fewer VOCs in the leaves than in the pericarps. In the characterization of the VOCs of ZBL and ZBP, the flavor of ZBP was more acrid and stronger, while the flavor of ZBL was lighter and slightly acrid. Thirteen and eleven differential markers were identified by HS-GC-IMS and HS-SPME-GC-MS, respectively. This is helpful in distinguishing between SHJ and SJ, which contributes to their quality evaluation.

Effect of Hanseniaspora uvarum-Saccharomyces cerevisiae Mixed Fermentation on Aroma Characteristics of Rosa roxburghii Tratt, Blueberry, and Plum Wines.

Hanseniaspora uvarum, a non-Saccharomyces cerevisiae species, has a crucial effect on the aroma characteristics of fruit wines, thus, attracting significant research interest in recent years. In this study, H. uvarum-Saccharomyces cerevisiae mixed fermentation was used to ferment Rosa roxburghii Tratt, blueberry fruit wine, and plum fruit wines using either a co-inoculated or a sequentially inoculated approach. The three fruit wines' volatile aroma characteristics were analyzed by headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the mixed inoculation of H. uvarum and S. cerevisiae reduced the alcoholic content of Kongxinli fruit wine. Moreover, H. uvarum-S. cerevisiae fermented Rosa roxburghii Tratt, blueberry, and plum fruit wines and further enriched their flavor compounds. The overall flavor characteristics of sequentially inoculated fruit wines differed significantly from those fermented with S. cerevisiae alone, although several similarities were also observed. Sequential inoculation of H. uvarum and S. cerevisiae positively affected the mellowness of the wine and achieved a better harmony of the overall wine flavors. Therefore, H. uvarum-Saccharomyces cerevisiae mixed fermentation can improve the complexity of the wines' aromatic composition and empower them with a unique identity. In particular, H. uvarum-Saccharomyces cerevisiae blueberry wine produced by mixed fermentation had the widest variety and content of aroma compounds among the fermented wines. Therefore, H. uvarum-Saccharomyces cerevisiae mixed-fermentation inoculation in the three fermented fruit wines significantly increased the aroma compound variety and content, thus, enriching their aroma richness and complexity. This study is the first comparative evaluation of the aroma characteristics of different fruit wines fermented with a mixed inoculation of H. uvarum and S. cerevisiae and provides a preliminary guide for these fruit wines produced with non-Saccharomyces yeast.

The Use of Biological Sensors and Instrumental Analysis to Discriminate COVID-19 Odor Signatures.

The spread of SARS-CoV-2, which causes the disease COVID-19, is difficult to control as some positive individuals, capable of transmitting the disease, can be asymptomatic. Thus, it remains critical to generate noninvasive, inexpensive COVID-19 screening systems. Two such methods include detection canines and analytical instrumentation, both of which detect volatile organic compounds associated with SARS-CoV-2. In this study, the performance of trained detection dogs is compared to a noninvasive headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) approach to identifying COVID-19 positive individuals. Five dogs were trained to detect the odor signature associated with COVID-19. They varied in performance, with the two highest-performing dogs averaging 88% sensitivity and 95% specificity over five double-blind tests. The three lowest-performing dogs averaged 46% sensitivity and 87% specificity. The optimized linear discriminant analysis (LDA) model, developed using HS-SPME-GC-MS, displayed a 100% true positive rate and a 100% true negative rate using leave-one-out cross-validation. However, the non-optimized LDA model displayed difficulty in categorizing animal hair-contaminated samples, while animal hair did not impact the dogs' performance. In conclusion, the HS-SPME-GC-MS approach for noninvasive COVID-19 detection more accurately discriminated between COVID-19 positive and COVID-19 negative samples; however, dogs performed better than the computational model when non-ideal samples were presented.

Evaluation of Aroma Characteristics of Dried Shrimp (Litopenaeus vannamei) Prepared by Five Different Procedures.

Litopenaeus vannamei is one of the most popular shrimp species in the world and has been reported in studies on its dryness and flavor. However, the aroma characteristics of shrimps dried with different drying methods are compared in a unified way, and there are few reports on the difference in aroma of different shrimps dried. In order to clarify the difference in aroma characteristics of shrimp dried produced by different drying methods. In this study, blanched shrimp (BS) was used as a control to analyze the aroma characteristics of shrimp dried by five different procedures (SD-BFDP) samples, namely vacuum freeze-dried shrimp (VFDS), vacuum dried-shrimp (VDS), heat pump-dried shrimp (HPDS), hot air dried-shrimp (HADS) and microwave vacuum-dried shrimp (MVDS). An electronic nose (E-nose) was used to obtain the aroma fingerprint of SD-BFDP samples. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used for qualitative and quantitative analysis of volatile compounds in SD-BFDP samples. Partial least squares regression (PLSR) was used to analyze potential correlations between sensory attributes and aroma-active compounds (AACs). Partial least squares-discrimination analysis (PLS-DA) was used to screen for signature aroma compounds. The results of the E-nose showed that there were differences in the aroma fingerprints of the SD-BFDP samples, and the E-nose could distinguish the five kinds of SD-BFDP. The qualitative and quantitative results of GC-MS showed that the types and contents of the main volatile components of SD-BFDP samples were different. 15 AACs were screened from SD-BFDP based on odor activity value (OAV). The PLSR results showed good correlations between certain sensory attributes and the majority of AACs. PLS-DA results displayed that aroma attributes of SD-BFDP samples could be distinguished by six signature aroma compounds, including trimethylamine, 2,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine, nonanal, 3-ethyl-2,5-dimethylpyrazine, and octanal. These research results reveal that shrimps dried in different procedures have unique aroma characteristics, which could provide a theoretical basis for the rapid identification of aroma attributes of dried shrimps in the future. From a flavor perspective, MVD is the best drying method.