Headspace Solid-phase Microextraction Gas Research Articles

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.

The key odor-active components differed in cultured agarwood from two germplasms of Aquilaria. sinensis trees

To tentatively identify the key odor-active components and compare the odor profiles of cultured agarwood from ordinary and Qi-Nan Aquilaria. sinensis trees, headspace solid-phase microextraction gas chromatography-olfactometry-mass spectrometry (HS-SPME-GC–O–MS) coupled with aroma extraction dilution analysis (AEDA) were used to analyze ordinary(OA)and Qi-Nan agarwood(QNA) compared to non-resinous whitewood. From the 61 odorants found in agarwood, 20 key odor-active components were screened with flavor dilution (FD)≥ 3. Among them, FDs of cis-Eudesm-6-en-11-ol，(E)-isovalencenal and guaiol in OA were higher than those in QNA, which explained for the odor profile of stronger floral and sweet attributes in OA group at ambient temperature. When temperature became higher, low molecular weight aromatic compounds increased greatly and further differed OA and QNA. For the 2-(2-Phenylethyl) chromone derivatives(PECs)in QNA and OA were distinct and consequently pyrolyzed into different aromatic compounds. The results strongly suggested QNA and OA maintained different odor-active components, which lead to their own unique odor profiles.

Quality assessment of rose tea with different drying methods based on physicochemical properties, HS-SPME-GC-MS, and GC-IMS.

The purpose of this study is to compare the physicochemical properties and volatile flavor compounds of rose tea obtained by the methods of normal temperature drying, hot-air drying (HAD), and vacuum freeze-drying (VFD) and to evaluate the quality of rose tea. The physicochemical results showed that the content of ascorbic acid (VC) and the pH value was the highest in rose tea obtained by HAD. The contents of anthocyanin, proanthocyanidins, and total phenols were highest in rose tea obtained by VFD. However, there was no significant difference in total flavonoids between drying methods. The volatile organic compounds (VOCs) in rose tea with different drying methods were analyzed by headspace solid-phase microextraction-gas chromatography-mass spectroscopy (HS-SPME-GC-MS) and HS GC-ion mobility spectroscopy (HS-GC-IMS), and the flavor fingerprint of rose tea was established by principal component analysis (PCA). The concentration of VOCs in rose tea varied greatly with different drying methods. The main flavor compounds of rose tea were alcohols, esters, aldehydes, and terpenoids. HS-GC-IMS was used for the identification of volatile flavor compounds of rose tea, thereby helping to assess the quality of rose tea. In addition, the rose tea samples with different drying methods were well distinguished by PCA. This study deepens the understanding of the physicochemical properties and volatile flavor compounds of rose tea with different drying methods and provides a reference for the identification of rose tea with different drying methods. PRACTICAL APPLICATION: This study deepens the understanding of the physicochemical properties and volatile flavor compounds of rose tea with different drying methods and provides a reference for the identification of rose tea with different drying methods. It also provides an effective theoretical basis for consumers to buy rose tea.

Effect-Directed, Chemical and Taxonomic Profiling of Peppermint Proprietary Varieties and Corresponding Leaf Extracts

During the development of novel, standardized peppermint extracts targeting functional applications, it is critical to adequately characterize raw material plant sources to assure quality and consistency of the end-product. This study aimed to characterize existing and proprietary, newly bred varieties of peppermint and their corresponding aqueous extract products. Taxonomy was confirmed through genetic authenticity assessment. Non-target effect-directed profiling was developed using high-performance thin-layer chromatography-multi-imaging-effect-directed assays (HPTLC-UV/Vis/FLD-EDA). Results demonstrated substantial differences in compounds associated with functional attributes, notably antioxidant potential, between the peppermint samples. Further chemical analysis by high-performance liquid chromatography-photodiode array/mass spectrometry detection (HPLC-PDA/MS) and headspace solid-phase microextraction-gas chromatography-flame ionization/MS detection (headspace SPME-GC-FID/MS) confirmed compositional differences. A broad variability in the contents of flavonoids and volatiles was observed. The peppermint samples were further screened for their antioxidant potential using the Caenorhabditis elegans model, and the results indicated concordance with observed content differences of the identified functional compounds. These results documented variability among raw materials of peppermint leaves, which can yield highly variable extract products that may result in differing effects on functional targets in vivo. Hence, product standardization via effect-directed profiles is proposed as an appropriate tool.

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.

Distant heteroploid hybridization improved Hedychium floral scent, floral color and morphologcal traits

Heteroploid hybridization is an important breeding technique for producing heteropolyploids with superior traits. Hedychium is widely used in medicine and as an ornamental plant; however, the fact that no current varieties exhibit both fragrance and colorful flowers causes a bottleneck in the genetic improvement of Hedychium. In the current study, diploid Hedychium coronarium 'ZS' (with strong fragrance and white flowers) and tetraploid Hedychium coccineum 'KMH' (scentless with red flowers) were used for the reciprocal heteroploid hybridization, and the 34 flowering hybrid offspring were analyzed for ploidy and hybrid authenticity, phenotype and floral scent. In 'ZS' ♀ × 'KMH' ♂, eight hybrids were triploids, while there were nine triploids and seventeen tetraploids in 'KMH' ♀ × 'ZS'♂. Furthermore, all hybrids were true hybrids as determined by simple sequence repeat (SSR) markers, and the presence of unreduced pollen in 'ZS' flowers was confirmed. Compared with the parents, 15 morphological traits and four flower color traits of hybrid offspring were widely separated. Hierarchical clustering analysis (HCA) and principal component analysis (PCA) showed that the parents and 34 hybrids could be divided into three groups mainly depending on organ size and color intensity. Headspace solid phase microextraction–gas chromatography–mass spectrometry (HS–SPME–GC–MS) identified 16 volatile organic compounds (VOCs), all of which were widely separated in the hybrid offspring. The HCA and PCA results confirmed that the parents and 34 hybrids could be classified into three groups mainly based on linalool, (E)-β-ocimene, eucalyptol, and methyl benzoate. Partial least squares discriminant analysis (PLS-DA) revealed that morphology, floral color and floral scent differed significantly between triploids and tetraploids, and the variable importance in projection (VIP) of 14 indexes was greater than 1. Finally, this study screened four new allopolyploid germplasms (HB30, HB46, HB54 and HB61) with colorful flowers and rich floral scent. These findings suggest a new strategy for cultivating new varieties with strong fragrance and bright colors.

Development of a headspace-solid phase microextraction gas chromatography-high resolution mass spectrometry method for analyzing volatile organic compounds in urine: Application in breast cancer biomarker discovery

Background and aimBreast cancer (BC) is the leading cause of cancer-related death in females. The development of non-invasive methods for the early diagnosis of BC still remains challenge. Here, we aimed to discover the urinary volatile organic compounds (VOCs) pattern of BC patients and identify potential VOC biomarkers for BC diagnosis. MethodsUrine samples were analyzed by headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-high resolution mass spectrometry (GC-HRMS). To assure reliable analysis, the factors influencing HS-SPME extraction efficiency were comprehensively investigated and optimized by combing the Plackett–Burman design (PBD) with the central composite design (CCD). The established HS-SPME/GC-HRMS method was validated and applied to analyze urine samples from BC patients (n = 80) and healthy controls (n = 88). ResultsA total number of 134 VOCs belonging to distinct chemical classes were identified by GC-HRMS. BC patients demonstrated unique urinary VOCs pattern. Orthogonal partial least squares-discriminant analysis (OPLS-DA) showed a clear separation between BC patients and healthy controls. Eight potential VOC biomarkers were identified using multivariate and univariate statistical analysis. The predictive ability of candidate VOC biomarkers was further investigated by the random forest (RF) algorithm. The candidate VOC biomarkers yielded 76.3% sensitivity and 85.4% specificity on the training set, and achieved 76.0% sensitivity and 92.3% specificity on the validation set. ConclusionsOverall, this work not only established a standardized HS-SPME/GC-HRMS approach for urinary VOCs analysis, but also highlighted the value of urinary VOCs for BC diagnosis. The knowledge gained from this study paves the way for early diagnosis of BC using urine in a non-invasive manner.

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.

Malodorous volatile organic compounds (MVOCs) formation after dewatering of wastewater sludge: Correlation with the extracellular polymeric substances (EPS) and microbial communities

Malodorous volatile organic compounds (MVOCs) are often the key odorants in determining sludge odor character and odor impact. However, the emission characterization and generation mechanisms of MVOCs from various dewatered sludge have not been sufficiently understood partly due to the diverse and complex composition and low concentration of odorants. In this study, waste activated sludge (WAS) was collected to examine the variation of MVOC emission from sludge after different dewatering treatment in lab-scale trials. The MVOCs were measured using the electronic nose (eNose), headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS). The results showed that centrifugation treatment promoted the generation of various odorous volatiles. The identified key odorants included dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), geosmin, and p-cresol according to their odor activity values (OAVs). The effects of the enhanced dewatering on volatile production were greater than thickening, however, the key odorants of dewatered sludge using gravity thickening varied more greatly than sludges from centrifuge thickening. The distribution of extracellular polymeric substances (EPS) and variation of microbial community showed correlations with the production of key odorants. Tryptophan-like substances in the inner layer of EPS (LB-EPS and TB-EPS) were better correlated with the key odorants. The bound EPS released by centrifugation may play the role of precursor for odorous microbial volatiles. According to the predicted functions of differential microbial genera, Desulfobulbus (Desulfobacterota), Gordonia (Actinobacteriota), and Hyphomicrobium (Proteobacteria) were associated with the production of DMS, DMDS, and DMTS, while Gordonia and Hyphomicrobium were related to p-cresol production.

Investigating the Aromatic Compound Changes in Table Grape Varieties during Growth and Development, Using HS-SPME-GC/MS

This study aimed to identify the aromatic compounds present in the different aroma types of different table grape varieties and deeply understand the changes in the aromatic compounds during the growth and development process. The skin and flesh of three table grape varieties (‘Kyoho’, ‘Shine Muscat’, and ‘Ryuho’) in different growth and development stages were selected to determine their aromatic compounds using headspace solid-phase microextraction gas chromatography-mass spectrometry and principal component analysis. The results showed that the aromatic compounds of the ‘Kyoho’ and ‘Ryuho’ grapes were similar, mainly containing C6 compounds and esters, whereas ‘Shine Muscat’ was characterized by C6 compounds and terpenes. The levels of aromatic compounds in the skin were higher than those in the flesh. The content of esters in ‘Ryuho’ was significantly higher than that in ‘Kyoho’ and ‘Shine Muscat’. This showed that ‘Ryuho’ combines the advantages of the parents in its aroma composition. Selecting suitable parents for hybridization is one method for obtaining new varieties with a special aroma. This provides a theoretical basis for future molecular hybrid breeding and molecular-assisted breeding, as well as molecular biology research on aroma synthesis and metabolism in table grapes.

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.

Comparison of Volatile Compositions among Four Related Ligusticum chuanxiong Herbs by HS-SPME-GC-MS

Chuanxiong (CX, Ligusticum chuanxiong), Japanese Chuanxiong (JCX, Cnidium officinale), Fuxiong (FX, Ligusticum sinense ‘Fuxiong’), and Jinxiong (JX, Ligusticum sinense ‘Jinxiong’) are aromatic herbs used in China, Japan, and other regions. Their morphology and aromatic odor are similar, resulting in confused and mixed uses. This study compares the volatile compositions of these herbs for defining their medical uses. Headspace solid-phase microextraction–gas chromatography–triple quadrupole–mass spectrometry was employed to separate, identify, and quantify the compounds in the volatile gas of the four herbs. A total of 128 volatile compounds were identified and quantified in 23 these herbal samples. The sums of 106, 115, 116, and 120 compounds were detected in the volatile gas of CX, JCX, FX, and JX, with the mean contents of 4.80, 7.12, 7.67, and 12.0 μg/g, respectively. Types and contents of the main compounds were found to be different in the volatile gas of these herbs. The orthogonal partial least squares discriminant analysis and hierarchical clustering analysis showed the four herbs located in different confined areas or clusters. It is concluded that the volatile compositions in the four herbs are generally similar, but the contents of main volatile compounds are different. These herbs should be clearly differentiated in medical use.

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.

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.

Characterization of stale odor in green tea formed during storage: Unraveling improvements arising from reprocessing by baking

Changes in key odorants and aroma profiles of three types of green tea during storage and after baking treatment were determined using headspace solid-phase microextraction–gas chromatography–mass spectrometry/olfactometry, odor activity value (OAV) and orthogonal partial least-squares discriminant analysis. As the stale odor developed during storage, the content of aldehydes decreased, whereas the contents of ketones and heterocycles (furans, pyrroles, etc.) increased. Key odorants, including (E,E)-2,4-heptadienal, α-terpineol, (E,E)-2,4-nonadienal and (E,E)-2,4-decadienal, appeared to be mainly responsible for the stale odor. After baking treatment, the stale odor was significantly improved, the contents of aldehydes and heterocycles were significantly increased and the content of alcohols was significantly decreased. Of these, 2-pentylfuran, hexanal, nonanal and limonene, which increased after baking, contribute the green, fruity and roasted aromas of green tea, because of their high OAVs, aroma intensities and variable importance in projection values. This study has improved understanding of the chemical changes resulting in stale odor development in green tea during storage and improvements arising from baking treatment, as well as providing a theoretical basis for the improvement of storage conditions and green tea flavor.

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.

Analysis of the formation mechanism of volatile and non-volatile flavor substances in corn wine fermentation based on high-throughput sequencing and metabolomics

The purpose of this study was to reveal the relationship between core microorganisms and flavor substances in the fermentation process of corn wine. Microbial diversity, volatile and non-volatile flavor substances were detected by high-throughput sequencing (HTS), headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME/GC–MS) and gas chromatography time of flight mass spectrometry (GC-TOF-MS). High performance liquid chromatography (HPLC) was used to detect organic acids in corn wine fermentation, and its physiochemical properties were tracked. The results showed that physiochemical factors changed obviously with fermentation time. Bacillus, Prevotella_9, Acinetobacter and Gluconobacter were the predominant bacterial. Rhizopus and Saccharomyces were the dominant fungi. Acetic acid and succinic acid were important organic acids in corn wine. According to variable importance of projection (VIP) > 1 and P < 0.05, 24 volatile flavor substances with significant difference were screened out from 52 volatile flavor substances. Similarly, 25 non-volatile flavor substances with significant differences were screened out from the 97 reliable metabolites identified by 223 chromatographic peaks. Eight key metabolic pathways were enriched from 25 non-volatile flavor substances according to path influence values > 0.1 and P < 0.05. Based on Two-way Orthogonal Partial Least Squares (O2PLS) model and Pearson correlation coefficient, Saccharomyces, Rhizopus, uncultured_bacterium, Aneurinibacillus, Wickerhamomyces and Gluconobacter may be the potential volatile flavor-contributing microorganism genus in corn wine. The Pearson correlation coefficient showed that Saccharomyces was significantly positively correlated with malic acid, oxalic acid, valine and isoleucine, and Rhizopus was positively correlated with glucose-1-phosphate and alanine. These findings enhanced our understanding of the formation mechanism of flavor substances in corn wine and provided the theoretical basis for stabilizing flavor quality of corn wine.

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.