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

Characteristic volatile compounds of white tea with different storage times using E-nose, HS-GC-IMS, and HS-SPME-GC-MS.

This paper studied the influence of storage duration on the flavor profile of white tea in detail, with samples produced between 2020 and 2023. Sensory evaluation was performed by quantitative descriptive analysis (QDA), followed by an in-depth aroma components analysis employing an electronic nose (E-nose), headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The QDA findings revealed a gradual transition in the flavor profile of white tea during storage, shifting from sweet, fruity, and floral to more herbal and stale characteristics. E-nose could well distinguish white tea with different storage times. A total of 55 and 53 volatile compounds were identified by HS-GC-IMS and HS-SPME-GC-MS, respectively. The orthogonal partial least squares-discriminant analysis models, based on HS-GC-IMS (R2Y=0.998, Q2=0.987) and HS-SPME-GC-MS (R2Y=0.984, Q2=0.993), successfully distinguished white tea samples stored for different storage times. Furthermore, 14 and 8 key compounds were screened based on the double variable criterion of one-way analysis of variance (p<0.05) and variable importance in projection (VIP) >1.2, and their content changes were also compared. It is the gradual decrease of important aroma components such as 2-hexenal, 2-methyl-2-hepten-6-one, linalool, and geraniol, which are positively correlated with sweet, fruity, and floral aromas, and the gradual increase of hexanoic acid, thiophene, propanoic acid, dimethyl disulfide, and borneyl acetate, which are positively correlated with herbal and stale flavor, that leads to the changes in flavor and aroma of white tea during storage. The results of the study provided a reference for elucidating the aroma characteristics of white tea at different storage times as well as a theoretical basis for the quality control of white tea.

Influence of Apple Juice Type on Fermentation Process and Volatile Compounds of Hard Apple Cider

Fermented apple cider is a refreshing alcoholic drink known since ancient times, and it is obtained by fermenting apple fruit juice. Using the standards of alcohol concentration (up to 8%) and carbonation, it belongs to drinks similar to beer. It can be produced using wild yeasts, but currently a fermentation starter can be purchased. This work aims to produce fermented cider using commercial pasteurized juices: clear apple juice and organic cloudy juice using commercial yeast for cider production. After fermentation, the physico-chemical characteristics of the drink were determined, alongside volatile compounds of the freshly produced ciders, as well after 1, 2, and 3 weeks of maturation. Acids, alcohols, carbonyl compounds, terpenes, esters, and volatile phenols were determined using headspace–solid phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC/MS). The results show that the fermentation was slower (14 days) in the cloudy juice in contrast to the sample produced from clear apple juice (10 days). Also, the volatile compounds related to aroma were abundantly found in the cider produced from cloudy apple juice compared to the cider produced from the clear apple juice. The conducted sensory analysis was in favor of cloudy juice.

Integrated omics profiles for exploring the potential mechanism underlying aroma formation in the terpenoid-rich aromatic plant Opisthopappus taihangensis and the bioactivity of its leaf essential oil

Opisthopappus taihangensis (Anthemideae, Asteraceae), which is rich in bioactive components, produces flowers and leaves with robust fragrances. In this study, we conducted comprehensive metabolomic and transcriptomic analyses to identify changes in terpenoid metabolites and associated gene expression across various O. taihangensis tissues (leaves, buds, and inflorescences at the exposure, initial-bloom, and full-bloom stages). We identified 1,370 metabolites using headspace solid-phase micro-extraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS), 308 of which were terpenoid metabolites. The expression of terpenoid synthesis-related genes was relatively consistent with the synthesis of terpenoid metabolites at each examined developmental stage. An analysis of gene networks governing terpenoid synthesis revealed that MCT genes (OtMCT1, OtMCT2, and OtMCT3), TPS genes (OtTPS5, OtTPS9, and OtTPS10), and OtISPS1 may be crucial for synthesizing specific metabolites in different tissues. Additionally, the essential oil extracted from leaves by water distillation showed thatthujone and camphor were the predominant components. The considerable antioxidant activity of the leaf essential oil was comparable to that of vitamin C (16 μg/mL). Notably, its antimicrobial effects against Staphylococcus aureus and Escherichia coli growth were greater than those of ampicillin and vancomycin at the same concentrations. Scanning electron microscopy images indicated that the leaf essential oil significantly disrupted bacterial cell structures. This study thoroughly analyzed the network of genes regulating terpenoid metabolites in different O. taihangensis tissues, and elucidated the antioxidant and antibacterial potential of the leaf essential oil, thus providing valuable insights for breeding, molecular characterization, and the potential application of O. taihangensis in developing useful essential oil-based natural products.

Characteristic aroma identification of differentially colored peach fruits based on HS-SPME-GC–MS

Aromatic components are vital for the flavor profile of peaches. This study investigated the aroma compounds of 20 differential peach cultivars using headspace solid-phase microextraction-gas chromatography–mass spectrometry (HS-SPME-GC–MS). A total of 82 distinct aromas were identified, comprising 6 lactones, 16 esters, 24 alcohols, 5 aldehydes, 12 ketones, and 19 other compounds. The yellow peach cultivar ‘Tropic Beauty’ exhibited the highest aroma content, whereas ‘Xiahui 5’ topped the white peaches. Furthermore, 11 key aromas were identified based on their odor activity values (OAVs), with hexanal demonstrating the highest average OAV of 1333.27. The top ten cultivars were ranked as follows: ‘Tropic Beauty’, ‘NJN76’, ‘Vega’, ‘Xiahui 5’, ‘Zhongyoujinshuai’, ‘Troubador’, ‘Flordaguard’, ‘Ruiguang 35’, ‘Jinhualu’, and ‘Xiacui’. These results lay a strong foundation for assessing peach flavor and developing breeding strategies for peach cultivars.

Rapid quantification of isovaleraldehyde in sake by HPLC with post-column fluorescent derivatisation

Why was the work done: Elevated levels of isovaleraldehyde (3-methylbutanal) in sake gives rise to an unfavourable aroma of ‘mureka’ or ‘stuffy smell’. The concentration of isovaleraldehyde is typically higher in unpasteurised than pasteurised sake. Controlling the concentration of isovaleraldehyde in unpasteurised sake remains a major challenge for quality control. As existing methods for the quantification of isovaleraldehyde in sake require specialised sample preparation, there is a need for a simple and precise method. How was the work done: High-performance liquid chromatography with fluorescence detection and post-column derivatisation (HPLC-PCD-FLD) for determining the isovaleraldehyde content in sake has been developed with optimisation of the separation of peaks and derivatisation of aldehyde compounds. The new method was compared with the established method of headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). What are the main findings: The limit of quantification of the new method was 87 µg/L, and accordingly, the HPLC-PCD-FLD method could determine the concentration of isovaleraldehyde in sake below the reported threshold level. The precision of the HPLC-PCD-FLD method for the analysis of sake containing isovaleraldehyde (&gt; threshold level) either matched or was superior to the HS-SPME-GC-MS method. Why is the work important: The new approach requires only particle removal for sample preparation, with an rapid analysis time (&lt;1 h per sample), and requires a smaller sample volume (≈ 100 µL) than the alternative method (10 mL). These improvements contribute to a simpler and more efficient workflow for routine analysis of isovaleraldehyde in the quality control of sake.

HS-SPME-GC-MS combined with multivariate statistical analysis reveals off-flavor composition and biomarker generation mechanism of whole milk powder

Milk powder is prone to producing off-flavor when it is not handled properly during production or storage. In order to identify the off-flavor compounds of whole milk powder (WMP), headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with cluster heatmap analysis was used, orthogonal partial least squares discriminant analysis (OPLS-DA) and principal component analysis (PCA) were used to investigate the off-flavor substances of whole milk powder. Cluster heatmap analysis showed that there were certain differences in the relative contents of volatiles among the eight milk powders. Further, OPLS-DA was applied to the relative contents of volatile substances in milk powders with and without unpleasant odor, a to obtain the main difference components of the 28 with variable importance in projection (VIP) greater than 1, with off-flavor substances being the main ones. Finally, the volatile compounds positively correlated with off-flavors in milk powder were screened by principal component analysis and combined with relative aroma activity values greater than 1 to identify (E)-2-hexenal and (E,E)-2,4-decadienal as the major off-flavor compounds of milk powder, and also described the mechanism of generation of (E)-2-hexenal (a marker of soya flavor) and (E,E)-2,4-decadienal (a marker of grass flavor) in milk powder. The results provide a reference for the analysis of flavor profile and possible off-flavor components of milk powder, which is beneficial for the optimization and improvement of whole milk powder.

Effect of Perilla Seeds Pretreatment on the Volatile Profile and Flavor Characteristics of Perilla Oil: Comparison of Oven, Infrared, and Microwave Heating

ABSTRACTThe effects of microwave (MW), infrared (IF), and oven heating (OH) on the volatile profile and flavor of perilla oil were investigated in this study. Physicochemical properties and Maillard reaction products of perilla oil were measured to investigate the potential pathway of flavor formation. Sensory evaluation, combined with headspace‐solid‐phase microextraction‐gas chromatography‐mass spectrometry (HS‐SPME‐GC‐MS) and electronic nose (E‐nose) techniques, was employed to determine the categories and contents of volatile compounds in perilla oil. Three heating treatments all effectively increased the content of odor‐active volatile compounds in perilla oil. Samples treated by MW contained higher concentration of heterocyclics, while samples treated using IF and OH contained more aldehydes. The content of (E,E)‐2,4‐heptadienal were highly correlated to P‐AV. The contents of pyrazines and furans were positively correlated with A420nm, particularly 2,5‐dimethyl‐pyrazine, trimethyl‐pyrazine, and 2‐pentylfuran. The content of hexanal and (E)‐2‐hexenal showed a negative correlation with the content of heterocyclic compounds. Consequently, the volatile compounds in perilla oils were generated through three potential mechanisms: lipid oxidation, the Maillard reaction, and their synergistic effect.

Stimulation of Saliva Affects the Release of Aroma in Wine: A Study of Microbiota, Biochemistry, and Participant Origin.

Saliva influences the release of aroma in the oral cavity. The composition of human saliva varies depending on stimulation and host's origin; however, the compositional differences of saliva and their influences on aroma release have not been fully evaluated. In this study, we recruited 30 healthy adults (15 Australians and 15 Chinese) and collected saliva samples at three stages: before, during, and after stimulation. Salivary samples were characterized by the flow rate, total protein concentration, esterase activity, microbiome composition by full-length 16S rRNA gene sequencing, and the ability to release aroma from wine by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Differences in salivary composition and specific wine volatiles were found between Australian and Chinese participants and among the three stimulation stages. Significant correlations between the relative abundance of 3 bacterial species and 10 wine volatiles were observed. Our results confirm the influence of participant's geographic origin and stimulation on the salivary composition, highlighting the role of salivary components, especially salivary bacteria, on the release of aroma from wine.

An Integrated Approach to Identify the Q-Markers of Banxia-Houpo Decoction Based on Nontargeted Multicomponent Profiling, Network Pharmacology, and Chemometrics.

The inherent complexity of traditional Chinese medicine (TCM) poses significant challenges in directly correlating quality evaluation with clinical efficacy. Banxia-Houpo Decoction (BHD), a classical TCM formula, has demonstrated efficacy in treating globus hystericus. However, the intricate composition of BHD, which contains both volatile and non-volatile active components, complicates efforts to ensure its consistent quality and clinical effectiveness. The aim of this study was to introduce an integrated approach that combines non-targeted multicomponent analysis, network pharmacology, and multivariate chemometrics to identify quality markers for the effective quality control of BHD. First, a nontargeted high-definition MSE method based on ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometry (UHPLC-QTOF-MS) was developed for the comprehensive multi-component characterization of BHD. Next, the quality markers of nonvolatile compounds in BHD were identified through network pharmacology analysis. Subsequently, volatile organic compounds (VOCs) in BHD samples were analyzed via headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). Finally, the orthogonal partial least squares discriminant analysis (OPLS-DA) model was applied to screen for potential markers. Based on in-house library-driven automated peak annotation and comparison with 25 reference compounds, 128 components were identified for the first time. Additionally, honokiol, magnolol, magnoflorine, 6-gingerol, rosmarinic acid, and adenosine were preliminarily identified as potential quality markers for BHD through network pharmacology analysis. By employing two complementary techniques, HS-SPME-GC-MS and HS-GC-IMS, a total of 145 volatile compounds was identified in the BHD samples. Four potential differential VOCs in the BHD samples were further identified based on the variable importance in projection (VIP ≥ 1.5) using HS-GC-IMS combined with chemometric analysis. In conclusion, this study not only contributes to establishing quality standards for BHD but also offers new insights into quality assessment and identification in the development of classical formulations enriched with volatile components.

Combined Analysis of Grade Differences in Lapsang Souchong Black Tea Using Sensory Evaluation, Electronic Nose, and HS-SPME-GC-MS, Based on Chinese National Standards.

Tea standard samples are the benchmark for tea product quality control. Understanding the inherent differences in Chinese national standards for Lapsang Souchong black tea of different grades is crucial for the scientific development of tea standardization work. In this study, Lapsang Souchong black tea of different grades that meet Chinese national standards was selected as the research object. The aroma characteristics were comprehensively analyzed through sensory evaluation, electronic nose, and HS-SPME-GC-MS (headspace solid-phase microextraction gas chromatography-mass spectrometry). The findings indicate that the higher-grade Lapsang Souchong has a higher evaluation score. The results of electronic nose analysis indicate that the volatiles with differences in tea of different grades were mainly terpenoids and nitrogen oxides. The results of HS-SPME-GC-MS analysis show that the odor characteristics of the super-grade samples are mainly floral and fruity, and these substances mainly include D-Limonene, 3,7-dimethyl-1,6-octadien-3-ol and 3-Hydroxymandelic acid, and ethyl ester. The primary aroma characteristics of the first-grade samples are floral, sweet, woody, and green, with key contributing compounds including 2-Furanmethanol, 1-Octen-3-ol, and 5-ethenyltetrahydro-α,α,5-trimethyl-cis-, 4,5-di-epi-aristolochene. The main aroma characteristics of the second-grade samples are green, herbal scent, and fruity, and the main substances include 3,7-dimethyl-1,6-octadien-3-ol, 2,3-dimethylthiophene, Dihydroactinidiolide, and Naphthalene-1-methyl-7-(1-methylethyl)-. It is worth noting that the second-grade samples contain a large amount of phenolic substances, which are related to the smoking process during processing. This study lays a solid foundation for the preparation of tea standard samples and the construction of the tea standard system.

Impact of Mild Field Drought on the Aroma Profile and Metabolic Pathways of Fresh Tea (Camellia sinensis) Leaves Using HS-GC-IMS and HS-SPME-GC-MS.

Aroma plays a pivotal role in defining tea quality and distinctiveness, and tea producers have often observed that specific drought conditions are closely associated with the formation and accumulation of characteristic aroma compounds in tea leaves. However, there is still limited understanding of the differential strategies employed by various tea cultivars in response to drought stress for the accumulation of key volatile aroma compounds in fresh tea leaves, as well as the associated metabolic pathways involved in aroma formation. In this study, two widely cultivated tea cultivars in China, Fuding Dabai (FD) and Wuniuzao (WNZ), were examined to assess the impact of mild field drought stress on the composition and accumulation of key volatile aroma compounds in fresh leaves using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) technologies. Results revealed that drought stress led to a substantial increase in the diversity of volatile compounds (VOCs) in FD, while WNZ exhibited a notable rise in low-threshold VOC concentrations, amplifying sweet, floral, fruity, and earthy aroma profiles in post-drought fresh leaves. Through partial least squares discriminant analysis (PLS-DA) of HS-GC-IMS and HS-SPME-GC-MS data, integrating variable importance projection (VIP) scores and odor activity values (OAVs) above 1, 9, and 13, key odor-active compounds were identified as potential markers distinguishing the drought responses in the two cultivars. These compounds serve as crucial indicators of the aromatic profile shifts induced by drought, providing insights into the differential metabolic strategies of the cultivars. Additionally, KEGG enrichment analysis revealed 12 metabolic pathways, such as terpenoid biosynthesis, fatty acid synthesis, cutin, suberine, and wax biosynthesis, and phenylalanine metabolism, which may play crucial roles in the formation and accumulation of VOCs in tea leaves under drought stress. These findings provide a comprehensive framework for understanding the cultivar-specific mechanisms of aroma formation and accumulation in tea leaves under mild drought conditions.

Characterization of Changes in Ripening Process of Volatile Apple Compounds Based on HS-SPME-GC-MS Analysis

The aim of this study was to identify the aromatic compounds present in different apple varieties and to gain insights into the changes in the aromatic compounds during ripening. Three apple varieties (“Red Astrachan”, “Ning Qiu”, and “Golden Delicious”) at different stages of ripening were selected for this study; their peel and pulp were analyzed via headspace solid-phase microextraction (HS-SPME)–gas chromatography–mass spectrometry (HS-SPME-GC-MS), and 30 volatile compounds were identified. The samples’ differences were analyzed using heat map cluster analysis, principal component analysis (PCA), and an independent samples t-test. The results showed that the content of aromatic compounds in the peel was higher than that in the pulp. The relative content of esters in the aromatic compounds of the three apple varieties followed the order of pulp &gt; peel and “Ning Qiu” &gt; “Golden Delicious” &gt; “Red Astrachan”. This suggests that “Ning Qiu” combines the advantages of its parents in terms of its aroma content. The highest concentrations of aroma compounds in “Red Astrachan” and “Ning Qiu” accumulate before the ripening stage, and care should be taken to choose an appropriate harvesting time according to the different needs during production. The main compounds of “Red Astrachan” are aldehydes and C8 esters, while those of “Ning Qiu” and “Golden Delicious” are alkenes and esters. After analyzing the relative odor activity values (rOAVs) of key volatile compounds and their aroma descriptors during the harvest period, acetic acid pentyl ester, butanoic acid hexyl ester, hexanoic acid hexyl ester, and 2-ethyl-1-Hexanol were found to contribute the most to the overall flavor of the peel and pulp. “Ning Qiu” combines the parental advantages of the concentrated peel of “Red Astrachan” and the astringent pulp of “Golden Delicious”, with compounds in its composition that give a pleasing aroma. Mature “Ning Qiu” fruits have a more intense aroma and fruity flavor. The development of flavor-specific varieties has provided the theoretical basis for future research in molecular hybridization, molecular-assisted breeding, and the molecular biology of apple flavor synthesis and metabolism.

Identification and Biotransformation of Volatile Markers During the Early Stage of Zygosaccharomyces rouxii and Zygosaccharomyces mellis Contamination in Acacia Honey.

To address the volatile markers and their biotransformation during the early stage of Zygosaccharomyces spp. contamination in acacia honey, headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and chemometric analyses were used to explore the variation of volatile compounds. A total of 36 and 35 volatile compounds were identified before and after contamination of Zygosaccharomyces rouxii and Zygosaccharomyces mellis, respectively. Methyl butyrate and 2-methyl-3-pentanone could be used as volatile markers of Z. rouxii and Z. mellis-contaminated honey, which were both specific products of the yeast's own fermentation. 2,5-Dimethylbenzaldehyde was identified as a volatile marker of Z. rouxii and Z. mellis-contaminated acacia honey, and it was a specific product resulting from the interaction of yeast and acacia honey. In addition, β-damascenone could be determined as a potential volatile marker after Z. rouxii-contaminated acacia honey. Methyl 2-methylbutyrate was used as a potential volatile marker in the high-concentration groups of Z. rouxii and Z. mellis. The content ranges of methyl butyrate, 2-methyl-3-pentanone, and 2,5-dimethylbenzaldehyde in four samples were 6.62-14.59, 3.15-5.42, and 52.52-215.19 μg/mL, respectively. The variation of volatile markers during the early stage of osmotolerant yeast contamination provided a theoretical basis for the use of HS-SPME-GC-MS for the rapid detection of acacia honey deterioration while reducing economic losses.

Optimization of the preparation process of Spirulina blended liquor and Spirulina fermented wine, analysis of volatile components and in vitro antioxidant study.

The optimal conditions were explored for the preparation of Spirulina blended liquor (SBL) and Spirulina fermented wine (SFW), respectively. The parameters obtaining highest alga polysaccharide were calculated by response surface methodology. The optimal conditions for SBL preparation were base liquor of 42%vol, ultrasonication time of 37-min and ultrasonic power of 80W with polysaccharide content (PC) and alcohol content (AC) of 0.2181g/L and 39.7%vol, respectively. In the case of SFW, optimum fermentation occurred at 22°C, with a 4% inoculum and 6-day period with PC and AC of 8.533g/L and 11.2%vol, respectively. Headspace solid-phase microextraction-gas chromatography-mass spectrometry was used to quantitatively analyze the volatile components of SBL and SFW. There were 32 and 40 main aroma compounds in SBL and SFW, respectively. Volatile organic compounds, including α-ionone and β-ionone, produced by Spirulina were detected in both SBL and SFW. Comparative evaluation of scavenging activity and total reducing power revealed the antioxidant capacity of SFW significantly outperformed that of SBL.

Effects of low-temperature plasma, microwave and 60Co γ-irradiation treatments on the flavor characteristics of lychee whole fruit powder

Powdering whole lychee fruit is one of the most effective methods for improving the comprehensive utilization rate of lychees. In this study, lychee whole fruit powder (LWFP) was prepared and treated with low-temperature plasma, microwave, and 60Co γ-irradiation treatments to enhance its quality. Volatile organic compounds (VOCs) were analyzed using Headspace Solid Phase Micro-extraction Gas Chromatography-mass Spectrometry (HS-SPME-GC-MS), Headspace Gas Chromatography Ion Mobility Spectrometry (HS-GC-IMS), and electronic nose (E-nose) techniques. Electronic tongue (E-tongue) analysis revealed that both sweetness and bitterness were significant taste indicators of LWFP. GC-MS analysis revealed that the predominant volatile compounds in LWFP were terpenoids and alcohols, specifically nerol, geraniol, ɑ-pinene, hexylbenzene, ɑ-caryophyllene, caryophyllene oxide, and isoamylenol. GC-IMS identified small-molecule aldehydes such as 2-methyl propanal, hexanal, propanal, and 2-methylbutanal as significant contributors to the aroma profile. Moreover, key aromatic contributors include dimethyl sulfide, 1-penten-3-one, and acetic acid. Notably, microwave treatment exerted the most significant effect on the aroma profile of lychee. In contrast, low-temperature plasma and irradiation treatments exhibited similar and consistent changes. Specifically, microwave treatment primarily increased the concentration of larger terpenoid molecules such as nerol, 1-phenylhexane, and caryophyllene oxide, whereas low-temperature plasma and irradiation had a greater impact on smaller aldehyde molecules such as hexanal and 2-methylbutanal. All treatments enriched the sweet fruity, brilliant woody, and cabbage scents of LWFP.

Characterization of the flavor profile of four major Chinese carps using HS-SPME-GC–MS combined with ultra-fasted gas chromatography-electronic nose

The four major Chinese carps are highly popular for their distinctive nutritional benefits. However, the differences in flavor among these carps remain unclear. This study investigated the flavor profiles of these carps using headspace solid-phase micro-extraction gas chromatography–mass spectrometry (HS-SPME-GC/MS) combined with ultra-fasted gas chromatography electronic nose (GC E-nose). The four major Chinese carps had high protein content (16.68–18.61 %) and low fat levels (0.42–1.29 %). A total of 45 volatile compounds were identified in these carps. Both the GC E-nose and HS-SPME-GC–MS results consistently showed significant flavor profiles differences among these carps, with Ctenopharyngodon Idella (CI) exhibiting the most pronounced distinctions compared to the other three species. Based on VIP >1 and p < 0.05, 10 key compounds including 2-Nonanone, Cyclodecanol, Eugenol, 1,3-Cyclooctadiene, etc., largely contributed to the distinctive overall flavor profile of four major Chinese carps derived mainly from amino acid and fatty acid metabolism.

The dynamic changes and correlations between biochemical properties, flavor and microbial community during fermentation of asparagus by-products

Asparagus by-products are the promising resource that urgently need to be re-valorized. This study investigated the dynamic changes in physicochemical properties, organic acids, free amino acids, volatile flavor compounds, microbial succession, and their correlations during 7-day spontaneous fermentation of asparagus by-products. Dominant organic acids (lactic acid and acetic acid) and free amino acids (Ser, Glu, and Ala) increased with fermentation time, with lactic acid reaching 7.73 ± 0.05 mg/mL and Ser increasing 56-fold after 7 days. A total of 58 volatile flavor compounds were identified using headspace solid-phase microextraction-gas chromatography–mass spectrometry (HS-SPEM/GC–MS), with esters, alcohols and acids as the main volatile flavor compounds. Fourteen volatile flavor compounds had odor activity value >1. High-throughput sequencing showed Firmicutes and Proteobacteria as the main bacterial phyla, dominated by lactic acid bacteria (Levilactobacillus, Lactiplantibacillus, Weissella). Correlation analysis revealed that five bacterial genera (Levilactobacillus, Lactiplantibacillus, Enterobacter, Pediococcus and Acetobacter) were highly correlated with organic acids, free amino acids, and volatile flavor compounds, indicating their pivotal role in forming the characteristic flavor of fermented asparagus by-products (FAPS). This study provides new insights into the flavor and microbial profile of FAPS, offering a strategy for value-added processing and industrial production.

Chemical profile and in-vitro bioactivities of three types of yellow teas processed from different tenderness of young shoots of Huoshanjinjizhong (Camellia sinensis var. sinensis)

In the present study, bud yellow tea (BYT), small-leaf yellow tea (SYT) and large-leaf yellow tea (LYT) were produced from the same local “population” variety Huoshanjinjizhong (Camellia sinensis var. sinensis), and the effects of raw material tenderness on the chemical profile and bioactivities of these teas were investigated. The results showed that 11 crucial compounds were screened by headspace solid-phase microextraction-gas chromatography–mass spectrometry from 64 volatiles in these yellow teas, among which the heterocyclic compounds showed the greatest variations. In addition, 43 key compounds including organic acids, flavan-3-ols, amino acids, saccharides, glycosides and other compounds were screened by liquid chromatography-mass spectrometry from 1781 non-volatile compounds. BYT showed the best α-glucosidase inhibitory activity and antioxidant capacity among the selected yellow teas, which might be contributed by the higher content of galloylated catechins. These findings provided a better understanding of the chemical profile and bioactivities of yellow teas.

HS-SPME-GC-MS untargeted metabolomics reveals key volatile compound changes during Liupao tea fermentation

This study used headspace solid-phase microextraction-gas chromatography–mass spectrometry and multivariate statistical analysis to comprehensively analyze the volatile components in Liupao tea samples throughout fermentation. In total, 1009 volatile organic compounds were detected and identified, including terpenoids, heterocyclic compounds, esters, ketones, hydrocarbons, alcohols, aromatics, and acids. Principal component and hierarchical cluster analyses, characterize the volatile components of Liupao tea samples were characterized at various fermentation stages. Orthogonal partial least squares discriminant analysis identified 248 differentiating compounds (VIP ≥ 1, P < 0.05, and |Log2FC| ≥ 1.0) during fermentation. K-means clustering analysis showed that 11 metabolites increased significantly throughout the fermentation process, whereas 31 metabolites decreased continuously. Annotation of these differential compounds revealed significant changes in sensory flavor characteristics in “green, sweet, fruity, floral, and woody” flavors. The results demonstrated significant variations in the volatile components of Liupao tea fermentation, along with notable changes in flavor characteristics.

Microbial Community Dynamics and Metabolite Changes during Wheat Starch Slurry Fermentation.

Wheat starch fermentation slurry is the main substrate for producing Ganmianpi, a traditional Chinese fermented wheat starch-based noodle. In the present work, the microbial population dynamics and metabolite changes in wheat starch fermentation slurry at different fermentation times (0, 1, 2, 3, and 4 days) were measured by using high-throughput sequencing analysis and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) methods. The texture and sensory properties of Ganmianpi made from fermented starch slurry are also evaluated. The results showed that Latilactobacillus curvatus and Leuconostoc citreum were the dominant bacteria in wheat starch fermentation slurry, while Saccharomyces cerevisiae and Kazachstania wufongensis were identified as the main species of fungi. With the extension of fermentation time, the reducing sugar content first increased and then decreased, when the titratable acidity content showed an increasing trend, and the nonvolatile acid was significantly higher than the volatile acid. A total of 62 volatile flavor compounds were identified, and the highest content is alcohols, followed by acids. Fermentation significantly reduced the hardness and chewiness of Ganmianpi, and increased its resilience and cohesiveness. Ganmianpi made from fermented starch slurry for two and three days showed a higher sensory score than other samples. The present study is expected to provide a theoretical basis for exploiting the strains with potential for commercial application as starter cultures and quality improvement of Ganmianpi.