Comprehensive analysis of pigment alterations and associated flavor development in strip and needle green teas.

Strip/needle green teas (SGT/NGT) processed using innovative technologies are in high demand; however, mechanisms behind their color and flavor have not been comprehensively studied. We aimed to reveal the dynamics of major pigmented components (carotenoids, lipids, flavonoids, and Maillard products) and their contributions to the flavor of green teas. The total content of flavonoids in SGT and NGT were 255 ± 4.51 and 201 ± 3.91 mg·g-1, respectively; these values are slightly lower than that in fresh leaves (FLs), resulting in a fresh and sweet aftertaste. In average, carotene content in SGT/NGT (24.8 µg·g-1) was higher than in FL (17.4 µg·g-1), whilst xanthophyll content (603 µg·g-1) decreased to one-half of that in FL (310 µg·g-1). Among the 218 primary metabolites, glutamine, glutamic acid, and arginine were found to accumulate and were dominate contributors for the umami and sweet taste. Notably, more than 96 volatiles were screened and revealed their correlations with carotenoids, lipids, and amino acids. Overall, the synergism between pigments and their non-enzymatic derivates' contribution to GT characterized flavor was illustrated.

Value of Combined Bone Morphogenetic Protein-2/7 Testing in the Assessment of Infected Preterm Labor.

Objective: To analyze the clinical significance of bone morphogenetic protein-2 (BMP-2) and bone morphogenetic protein-7 (BMP-7), members of the bone morphogenetic protein family, in infectious preterm birth, to provide references for future prevention and management of IPB. Methods: The study participants were 20 pregnant women with IPB admitted to between January 2022 and January 2023 (research group) and 20 concurrent normal pregnancies (control group). Serum BMP2, BMP-7 inflammatory factors were quantified. Differences in BMP2 and BMP-7 were identified. The Receiver Operating Characteristic curve analyzed the evaluation value of BMP2 and BMP-7 on infectious preterm birth and adverse pregnancy outcomes in pregnant women, and Pearson correlation coefficient determined the correlation of the two with inflammatory factors levels. Results: The research group was higher in serum BMP2 and BMP-7 levels than control group (P < .05). The joint detection by BMP2 and BMP-7 had a sensitivity of 80.00% and a specificity of 90.00% in diagnosing infectious preterm birth (P < .05), and its sensitivity and specificity in predicting adverse pregnancy outcomes in infectious preterm birth pregnant women were 100.0% and 66.67%, respectively (P < .05). According to Pearson correlation coefficient analysis, there was an obvious positive relationship between BMP-2 and BMP-7 and inflammatory factors in research group (P < .05). Conclusions: BMP-2 and BMP-7 are elevated in IPB and are linked to inflammatory factor levels. Joint detection of BMP2 and BMP-7 shows promising potential for evaluating infectious preterm birth.

Enantiomeric separation and precise quantification of chiral volatiles in Wuyi rock teas using an efficient enantioselective GC × GC-TOFMS approach.

Chiral volatiles play important roles in the formation of aroma quality of foods. To date, enantiomeric characteristics of chiral volatiles in Wuyi rock tea (WRT) and their aroma contributions are still unclear. In this study, an efficient enantioselective comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (Es-GC × GC-TOFMS) approach to separate and precisely quantitate 24 pairs of chiral volatiles in WRTs was established, and the enantiomeric distribution and aroma contribution of chiral volatiles among WRTs from four representative cultivars were investigated. Enantiomeric ratio (ER) of R-α-ionone (80%) in Dahongpao (DHP), ER of S-α-terpineol (57%) in Jinfo (JF), ERs of R-γ-heptanolactone (69%), S-γ-nonanolactone (55%), (2R, 5S)-theaspirane B (91%), concentration of S-(E)-nerolidol (313.37 ng/mL) in Rougui (RG) and concentration of R-α-ionone (33.01 ng/mL) in Shuixian (SX) were unique from other types of WRTs, which were considered as the potential chemical markers to distinguish WRT cultivars. The OAV assessment determined 7 volatile enantiomers as the aroma-active compounds, especially R-α-ionone and R-δ-octanolactone in SX, as well as S-(E)-nerolidol and (1R, 2R)-methyl jasmonate in RG contribute much to aroma formation of the corresponding WRTs. The above results provide scientific references for discrimination of tea cultivars and directed improvement of the aroma quality of WRT.

Colloidal bismuth pectin-containing quadruple therapy as the first-line treatment of Helicobacter pylori infection: A multicenter, randomized, double-blind, non-inferiority clinical trial.

BACKGROUND: Bismuth-containing quadruple therapy is an effective regimen for Helicobacter pylori (H. pylori) treatment. No head-to-head comparison trials have been conducted to evaluate the efficacy of colloidal bismuth pectin (CBP) in quadruple therapy for eradicating H. pylori. We aimed to compare the efficacy and safety of CBP quadruple therapy and bismuth potassium citrate (BPC) quadruple therapy for 14 days in the first-line treatment of H. pylori. METHODS: In this multicenter, randomized, double-blind, non-inferiority clinical trial, H. pylori-infected subjects without eradication history were randomized to receive amoxicillin 1 g twice daily, tetracycline 500 mg three time daily, esomeprazole 20 mg twice daily in combination with CBP 200 mg three time daily or BPC 240 mg twice daily for 14 days. 13 C-urea breath tests were used to access the eradication rate at least 4 weeks after treatment. RESULTS: Between April 2021 and July 2022, 406 patients were assessed for eligibility and 339 subjects were randomized. The cure rates (primary outcome) of CBP and BPC quadruple therapy were 90.5% and 92.3% (p = 0.56) by intention-to-treat analysis, respectively, and 96.1% and 96.2% (p = 1.00) by per-protocol analysis, respectively. CBP quadruple therapy was non-inferior to BPC quadruple therapy in the intention-to-treat and per-protocol analysis (p < 0.025). The frequency of adverse events and compliance were not different among the two groups (p > 0.05). CONCLUSIONS: Both CBP and BPC quadruple therapy for 14 days provide high efficacy, good compliance, and safety in the first-line treatment of H. pylori in China.

Special tea products featuring functional components: Health benefits and processing strategies.

The functional components in tea confer various potential health benefits to humans. To date, several special tea products featuring functional components (STPFCs) have been successfully developed, such as O-methylated catechin-rich tea, γ-aminobutyric acid-rich tea, low-caffeine tea, and selenium-rich tea products. STPFCs have some unique and enhanced health benefits when compared with conventional tea products, which can meet the specific needs and preferences of different groups and have huge market potential. The processing strategies to improve the health benefits of tea products by regulating the functional component content have been an active area of research in food science. The fresh leaves of some specific tea varieties rich in functional components are used as raw materials, and special processing technologies are employed to prepare STPFCs. Huge progress has been achieved in the research and development of these STPFCs. However, the current status of these STPFCs has not yet been systematically reviewed. Here, studies on STPFCs have been comprehensively reviewed with a focus on their potential health benefits and processing strategies. Additionally, other chemical components with the potential to be developed into special teas and the application of tea functional components in the food industry have been discussed. Finally, suggestions on the promises and challenges for the future study of these STPFCs have been provided. This paper might shed light on the current status of the research and development of these STPFCs. Future studies on STPFCs should focus on screening specific tea varieties, identifying new functional components, evaluating health-promoting effects, improving flavor quality, and elucidating the interactions between functional components.

Aroma characterisation of Liu-pao tea based on volatile fingerprint and aroma wheel using SBSE-GC-MS.

Liu-pao tea (LPT) has unique aroma characteristics, and is a special microbial fermented tea produced using dark raw tea (LPM) as its raw material. In this study, stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS) was applied to investigate the volatiles of 16 LPTs and 6 LPMs. Moreover, variations in volatile profiles between LPTs and LPMs were explored. Results showed that a total of 132 volatile compounds were identified from LPTs. The volatile fingerprint was constructed with a similarity ranged from 0.85 to 0.99. Furthermore, twenty-six aroma compounds were selected to depict the molecular aroma wheel of LPT. Multivariate statistical analysis revealed that the contents of 24 aroma compounds changed significantly (P < 0.05) when LPMs were processed into LPTs. These results reveal the volatile profiles of LPTs and aroma composition changes during microbial fermentation process, which might provide chemical basis of the aroma quality of LPT.

MRTCM: A comprehensive dataset for probabilistic risk assessment of metals and metalloids in traditional Chinese medicine.

Traditional Chinese medicine (TCM) is still considered a global complementary or alternative medical system, but exogenous hazardous contaminants remain in TCM even after decocting. Besides, it is time-consuming to conduct a risk assessment of trace elements in TCMs with a non-automatic approach due to the wide variety of TCMs. Here, we present MRTCM, a cloud-computing infrastructure for automating the probabilistic risk assessment of metals and metalloids in TCM. MRTCM includes a consumption database and a pollutant database involving forty million rows of consumption data and fourteen types of TCM potentially toxic elements concentrations. The algorithm of probabilistic risk assessment was also packaged in MRTCM to assess the risks of eight elements with Monte Carlo simulation. The results demonstrated that 96.64% and 99.46% had no non-carcinogenic risk (hazard indices (HI) were < 1.0) for animal and herbal medicines consumers, respectively. After twenty years of exposure, less than 1% of the total carcinogenic risk (CRt) was > 10-4 for TCM consumers, indicating that they are at potential risk for carcinogenicity. Sensitivity analysis revealed that annual consumption and concentration were the main variables affecting the assessment results. Ultimately, a priority management list of TCMs was also generated, indicating that more attention should be paid to the non-carcinogenic risks of As, Mn, and Hg and the carcinogenic risks of As and Cr in Pheretima and Cr in Arcae Conch. In general, MRTCM could significantly enhance the efficiency of risk assessment in TCM and provide reasonable guidance for policymakers to optimize risk management.

The management of Helicobacter pylori infection and prevention and control of gastric cancer in China.

Helicobacter pylori (H. pylori) infection, a type-1 carcinogen, was closely associated with gastric cancer (GC). Successfully eradicating H. pylori infection could reduce the incidence of GC. China was a country with high incidence of GC and high prevalence of H. pylori infection. Nearly half of worldwide GC new cases and deaths attributed to H. pylori infection occurred in China. H. pylori prevalence varied over time with the improvement of socioeconomic status and sanitary conditions. The knowledge of antibiotic resistance rate in time was important to guide the clinical choice of antibiotics use in the regimens. With the publication of five Chinese consensus reports on the management of H. pylori infection and the effort of public preach of H. pylori-related knowledge, the standardization of H. pylori diagnosis and treatment by clinicians was improved. Bismuth-containing quadruple therapy was widely applied in clinical practice of H. pylori eradication because of high efficacy and safety. High-dose Proton Pump Inhibitor-amoxicillin dual therapy or vonoprazan-amoxicillin dual therapy showed comparable efficacy and lower side effects than bismuth-containing quadruple therapy, which were the alternative choice. The diagnosis rate of early GC was low and distinguishing Chinese GC risk population for the further endoscopy screening was important. Efforts have been done to establish prediction models to stratify GC risk in the Chinese GC risk population. We reviewed the current situation of the management of H. pylori infection and prevention and control of GC in China here.

Analysis of oral microbiota alterations induced by Helicobacter pylori infection and vonoprazan-amoxicillin dual therapy for Helicobacter pylori eradication.

BACKGROUND: The oral cavity is considered a potential reservoir of Helicobacter pylori (H. pylori), and the imbalance of oral microbiota directly reflects the health of the host. We aimed to explore the relationship among oral microbiota, H. pylori infection, and vonoprazan-amoxicillin (VA) dual therapy for H. pylori eradication. METHODS: Helicobacter pylori-positive patients were randomized into low- or high-dose VA dual therapy (i.e., amoxicillin 1 g b.i.d. or t.i.d. and vonoprazan 20 mg b.i.d) for 7 or 10 days. H. pylori-negative patients served as normal controls. Saliva samples were collected from 41 H. pylori-positive patients and 13 H. pylori-negative patients. The oral microbiota was analyzed by 16S rRNA gene sequencing, followed by bioinformatics analysis. RESULTS: Helicobacter pylori-positive patients had higher richness and diversity and better evenness of oral microbiota than normal controls. Beta diversity analysis estimated by Bray-Curtis or weighted UniFrac showed distinct clustering between H. pylori-positive patients and normal controls. The number of bacterial interactions was reduced in H. pylori-positive patients compared with that in negative patients. Forty-one patients evaluated before and after successful H. pylori eradication were divided into low (L-VA) and high dose (H-VA) amoxicillin dose groups. The alpha and beta diversity of the oral microbiota between L-VA and H-VA patients exhibited no differences at the three time points (before eradication, after eradication, and at confirmation of H. pylori infection cure). CONCLUSION: Helicobacter pylori infection could alter the diversity, composition, and bacterial interactions of the oral microbiota. Both L-VA and H-VA dual therapy showed minimal influence on the oral microbiota.

Altered Gut Microbiota and Short-Chain Fatty Acids After Vonoprazan-Amoxicillin Dual Therapy for Helicobacter pylori Eradication.

The combination of vonoprazan (VPZ) and amoxicillin (VA therapy) has been shown to achieve acceptable eradication rates for Helicobacter pylori (H. pylori). Herein, our aim was to explore the short-term effect of VA therapy on the gut microbiota and short-chain fatty acids (SCFAs) using human fecal samples. A total of 119 H. pylori-positive patients were randomized into low- or high-dose VA therapy (i.e., amoxicillin 1 g b.i.d. or t.i.d. and VPZ 20 mg b.i.d.) for 7 or 10 days. Thirteen H. pylori-negative patients served as controls. Fecal samples were collected from H. pylori-positive and H. pylori-negative patients. The gut microbiota and SCFAs were analyzed using 16S rRNA gene sequencing and gas chromatography-mass spectrometry, respectively. The gut microbiota in H. pylori-positive patients exhibited increased richness, diversity, and better evenness than matched patients. Fifty-three patients studied before and after H. pylori eradication were divided into low (L-VA) and high (H-VA) amoxicillin dose groups. The diversity and composition of the gut microbiota among L-VA patients exhibited no differences at the three time points. However, among H-VA patients, diversity was decreased, and the microbial composition was altered immediately after H-VA eradication but was restored by the confirmation time point. The decreased abundance of Anaerostipes, Dialister, and Lachnospira induced by H-VA was associated with altered SCFA levels. VA dual therapy for H. pylori eradication has minimal negative effects on gut microbiota and SCFAs.

Comprehensive investigation on non-volatile and volatile metabolites in four types of green teas obtained from the same tea cultivar of Longjing 43 (Camellia sinensis var. sinensis) using the widely targeted metabolomics.

In this study, we produced roasted, baked, steamed, and sun-dried green tea products using the same batch of fresh tea leaves (FTL) of Longjing 43 (Camellia sinensis var. sinensis), and explored processing effects on the metabolic profiles of four types of green teas (FGTs) using the widely targeted metabolomics. Results showed that 146 differential metabolites including flavonoids, amino acids, lipids, and phenolic acids were screened among 1034 non-volatiles. In addition, nineteen differential metabolites were screened among 79 volatiles. Most of non-volatiles and volatiles metabolites changed notably in different manufacturing processes, whereas there were no significant differences (p＞0.05) in the levels of total catechins between FGTs and FTL. The transformation of metabolites was the dominant trend during green tea processing. The results contribute to a better understanding of how the manufacturing process influences green tea quality, and provide useful information for the enrichment of tea biochemistry theory.

A self-delivery chimeric peptide for high efficient cell membrane-targeting low-temperature photothermal/photodynamic combinational therapy and metastasis suppression of tumor.

Cellular barriers such as the cell membranes, lysosomes or nuclear pores of tumor cells hinder the drugs delivery and weaken the efficiency of traditional tumor therapies. Targeted destructing tumor cell membranes can quickly destroy cell homeostasis and kill cells without facing intracellular delivery barriers. Herein, we designed a self-delivery phototherapeutic chimeric peptide (CCP) for high efficient cell membrane-targeting combinational low-temperature photothermal therapy (LTPTT) and photodynamic therapy (PDT). The self-assembled CCP nanoparticles display remarkable tumor accumulation after systemic administration without additional carriers, avoiding the carriers related side toxicities. The CCPs are able to generate reactive oxygen species (ROS) and mild heat (<45 °C) locally at cell membrane and quickly induce immunogenic cell death to achieve efficient combinational LTPTT/PDT. The damage-associated molecular patterns released after cell membrane rupture effectively elicit antitumor immunity to eradicate residual tumor cells. With a single dosage and short-term near-infrared (NIR) light irradiation, CCPs significantly inhibit growth and metastasis of tumor, and prolong survival time of tumor-bearing mice. This work presents a unique cell membrane-targeting phototherapy strategy to kill tumor and suppress metastasis in an effective, safe and minimally invasive manner.

Optimization of vonoprazan-amoxicillin dual therapy for eradicating Helicobacter pyloriinfection in China: A prospective, randomized clinical pilot study.

BACKGROUND: Vonoprazan-amoxicillin (VA) dual therapy has been shown to achieve acceptable cure rates for treatment of Helicobacter pylori(H. pylori) in Japan. Its effectiveness in other regions is unknown. We aimed to explore the efficacy of VA dual therapy as first-line treatment for H. pyloriinfection in China. METHODS: This was a single center, prospective, randomized clinical pilot study conducted in China. Treatment naive H. pyloriinfected patients were randomized to receive either low- or high-dose amoxicillin-vonoprazan consisting of amoxicillin 1 g either b.i.d. or t.i.d plus VPZ 20 mg b.i.d for 7 or 10 days. 13 C-urea breath tests were used to access the cure rate at least 4 weeks after treatment. RESULTS: Three hundred and twenty-three patients were assessed, and 119 subjects were randomized. The eradication rates of b.i.d. amoxicillin for 7 and 10 days, t.i.d. amoxicillin for 7 and 10 days were 66.7% (16/24), 89.2% (33/37), 81.0% (17/21), and 81.1% (30/37) (p = .191) by intention-to-treat analysis, respectively, and 72.7% (16/22), 89.2% (33/37), 81.0% (17/21), and 81.1% (30/37) (p = .454) by per-protocol analysis, respectively. CONCLUSION: Neither 7- or 10-day VA dual therapy with b.i.d. or t.i.d. amoxicillin provides satisfied efficacy as the first-line treatment for H. pyloriinfection in China. Further optimization is needed.

Aromatic profiles and enantiomeric distributions of chiral odorants in baked green teas with different picking tenderness.

Suitable picking tenderness is an essential prerequisite for manufacturing tea. However, the influence of picking tenderness of fresh tea leaves on the aromatic components is still unclear. In this study, aromatic profiles and chiral odorants in fresh tea leaves and corresponding baked green teas with five levels of tenderness of two representative cultivars were analysed using stir bar sorptive extraction-gas chromatography-mass spectrometry. cis-Linalool oxide (furanoid) and methyl salicylate exhibited significantly increasing trends as samples of all series matured. The content of most chiral odorants was significantly high in the mature samples, and significant content variations of all enantiomers during baked green tea processing could be observed with different trends according to their precursors. In particular, the enantiomeric ratios of most chiral odorants were less influenced by the picking tenderness and processing, while drying (limonene), spreading and fixation (α-terpineol), and spreading (dihydroactinidiolide) influenced the chiral distribution of the aforementioned odorants.

Exposure assessment and risk-based limit levels evaluation of ochratoxin A in Astragali Radix in China.

Ochratoxin A (OTA) is a mycotoxin found in a variety of foods and herbal medicines, and several governmental bodies around the world have set maximum allowable levels of OTA in different foods and herbal medicines. This study aims to evaluate the health risk of OTA in Astragali Radix (AR) in China, and to evaluate the effects of different limit levels on the risk control of OTA in AR. The concentrations of OTA in 187 samples of AR were investigated, and 61 (32.6%) samples were positive. The mean, 50th and 95th percentile values of OTA in positive samples were 56.2, 5.1 and 304.5 µg/kg, respectively. A margin of exposure (MOE) approach was applied to assess the risk. Considering other food sources, long-term consumers have a relatively high risk of OTA exposure due to the ingestion of AR. Theoretical limit levels of OTA in AR were evaluated from two dimensions by weighing the costs and the benefits. The results indicated that the limit levels that might be applied to the management of OTA contamination in AR in China could be screened out through risk-based evaluation of limit levels.

Insights into crucial odourants dominating the characteristic flavour of citrus-white teas prepared from citrus reticulata Blanco 'Chachiensis' and Camellia sinensis 'Fudingdabai'.

Citrus-white teas (CWs), which possess a balanced flavour of tea and citrus, are becoming more popular worldwide; however, their characteristic flavour and odourants received limited research. Volatile components of two types of CWs prepared from Citrus reticulata Blanco 'Chachiensis' and Camellia sinensis 'Fudingdabai' were comprehensively investigated using a combination of stir bar sorptive extraction and gas chromatography-mass spectrometry (GC-MS). Ninety-nine crucial odourants in the CWs were quantified by applying GC-olfactometry/MS, significant differences were compared, and their odour activity values (OAVs) were calculated. Twenty-two odourants (in total 2628.09 and 1131.18 mg/kg respectively) were further confirmed as traditional CW (CW-A) and innovated CW (CW-B) characteristic flavour crucial contributors which all possessed > 1 OAVs, particularly limonene (72919 in CW-A) and trans-ß-ionone (138953 in CW-B). The unravelling of CWs aroma composition will greatly expanding our understanding of tea aroma chemistry and the potential aroma interactions will offer insights into tea blending technologies.

Autophagy-inhibiting biomimetic nanodrugs enhance photothermal therapy and boost antitumor immunity.

The instinctive protective stress responses of tumor cells hamper low-temperature photothermal therapy (LTPTT), resulting in tumor recurrence and metastasis. The rapid blood clearance and low-efficiency tumor enrichment of nanomedicines also decrease the efficacy of LTPTT. In this study, we fabricated coassembled photothermal agents (indocyanine green, ICG) and autophagy inhibitors (chloroquine, CQ) and red blood cell and cancer cell hybrid membrane (RCm)-camouflaged ICGCQ@RCm nanoparticles (ICGCQ@RCm NPs) to enhance tumor LTPTT. The ICGCQ@RCm NPs exhibited prolonged blood drug circulation and markedly enhanced drug accumulation in tumor tissues. The ICGCQ@RCm NPs reduced the thermal tolerance of tumor cells to sensitize ICG-mediated LTPTT by inhibiting protective autophagy. The ICGCQ@RCm NPs exerted strong immunogenic cell death (ICD) after efficient LTPTT to activate antitumor immunity. In addition, ICGCQ@RCms optimized the therapeutic efficacy by imaging-guided LTPTT, taking advantage of the near-infrared (NIR) fluorescence of ICG. Consequently, the ICGCQ@RCm NPs effectively inhibited tumors under mild LTPTT, significantly suppressed tumor metastasis and prolonged the survival time of tumor-bearing mice. Furthermore, the ICGCQ@RCm NPs showed high biosafety in vitro and in vivo. The ICGCQ@RCm NPs demonstrated tumor-targeting and imaging-guided autophagy inhibition-sensitized LTPTT using two Food and Drug Administration (FDA)-approved drugs, which have great potential for clinical application.

Fourteen-day vonoprazan and low- or high-dose amoxicillin dual therapy for eradicating Helicobacter pylori infection: A prospective, open-labeled, randomized non-inferiority clinical study.

Background and aim: We previously reported that vonoprazan-amoxicillin (VA) dual therapy for 7 or 10 days is not satisfactorily efficacious for Helicobacter pylori (H. pylori) eradication. We aimed to explore the efficacy of VA dual therapy for 14 days as a first-line treatment for H. pylori infection. Methods: This was a single center, prospective, open-labeled, randomized non-inferiority clinical study conducted in China. Treatment naïve H. pylori infected patients were randomized into two groups: 20 mg vonoprazan (VPZ) b.i.d. in combination with low-dose (1000 mg b.i.d.) or high-dose (1000 mg t.i.d) amoxicillin for 14 days. 13C-urea breath tests were used to access the cure rate at least 4 weeks after treatment. Results: A total of 154 patients were assessed and 110 subjects were randomized. The eradication rate of VPZ with b.i.d. amoxicillin or t.i.d. amoxicillin for 14 days was 89.1% and 87.3% by intention-to-treat analysis, respectively, and 94.1% and 95.9% by per-protocol analysis, respectively. The eradication rate and incidence of adverse events were not different between the two groups. Conclusion: VPZ with b.i.d. or t.i.d. amoxicillin for 14 days provides satisfactory efficacy as a first-line treatment for H. pylori infection in China.

Black tea aroma formation during the fermentation period.

The present study aimed to systematically investigate black tea aroma formation during the fermentation period. In total, 158 volatile compounds were identified. Of these, most amino acid-derived volatiles (AADVs) and carotenoid-derived volatiles (CDVs) showed significant increases, while fatty acid-derived volatiles (FADVs) and volatile terpenoids (VTs) displayed diverse changes during the fermentation period. During this time, fatty acids, amino acids, carotenoids, and glycosidically bound volatiles (GBVs, especially primeverosides) were found to degrade to form aroma components. Further, equivalent quantification of aroma showed that the intensity of green scent was notably decreased, while the intensities of sweet and floral/fruity scents were greatly increased and gradually dominated the aroma of tea leaves. AADVs and CDVs were shown to make greater contributions to the formation of sweet and floral/fruity scents than VTs. Our study provides a detailed characterization of the formation of sweet and floral/fruity aromas in black tea during the fermentation period.

Assessment of the contribution of chiral odorants to aroma property of baked green teas using an efficient sequential stir bar sorptive extraction approach.

Chiral volatile compounds are known to be distributed in teas at various enantiomeric ratios. However, the performance of each enantiomer, including aroma characteristics, aroma intensities, and contribution to the overall flavor of tea, is still unclear. In this study, aroma characteristics and intensities of 38 volatile enantiomers in standards and baked green teas with chestnut-like aroma and clean aroma were evaluated by an efficient sequential headspace-stir bar sorptive extraction (seq-HS-SBSE) approach combined with the enantioselective gas chromatography-olfactometry/mass spectrometry (Es-GC-O/MS) technique. Moreover, aroma recombination results for the two types of baked green teas using 14 chiral odorants and four achiral odorants indicated that the combinations of the detected odorants mainly contributed to the "floral", "sweet", and "chestnut-like" aromas. R-Linalool simultaneously enhanced the "floral", "sweet", and "chestnut-like" aromas; R-limonene mainly contributed to the "sweet" and "clean" aromas; and S-α-terpineol promoted the "sweet" and "floral" aromas of baked green tea.