Comparison of volatile profiles and bioactive components of sun-dried Pu-erh tea leaves from ancient tea plants on Bulang Mountain measured by GC-MS and HPLC

Formulation analysis of functional fragrance via polar-gradient extraction method and chemometrics pattern recognition

In this study, characteristic components of 15 natural flavors was analyzed by the polar-gradient extraction (PGE) technique in combination with GC-MS and chemometrics pattern recognition. The obtained results were utilized for the traceability of 4 functional fragrance formulations. The optimal PGE system consisting of 5 different polar solvents, was developed based on similarity-intermiscibility theory. Four chemometrics pattern recognition models including PCA, HCA, PLS-DA, and OPLS-DA were constructed based on the characteristic component database constituting 15 natural flavors. These models were used to trace 4 functional fragrance formulations. The experimental results obtained were found to be satisfactory and accurate. The combination of PGE technique and chemometric pattern recognition methods provides theoretical guidance for the analysis of characteristic components of natural flavors and the traceability of functional fragrance formulations. This approach can be promoted in various fields such as food, traditional Chinese medicine, and cosmetics.

Changes in sensory characteristics, chemical composition and microbial succession during fermentation of ancient plants Pu-erh tea

"Ancient tea plants" are defined as tea trees > 100 years old, or with a trunk diameter > 25 cm; their leaves are manufactured to high - quality, valuable ancient plants pu-erh tea (APPT). In this study, a fermentation of APPT were developed, and outstanding sweetness of APPT infusion was observed. During fermentation, the content of soluble sugars, theabrownins (p < 0.05), as well as 41 metabolites were increased [Variable importance in projection (VIP) > 1.0; p < 0.05 and Fold-change (FC) FC > 2]; While relative levels of 72 metabolites were decreased (VIP > 1.0, p < 0.05 and FC < 0.5. Staphylococcus, Achromobacter, Sphingomonas, Thermomyces, Rasamsonia, Blastobotrys, Aspergillus and Cladosporium were identified as dominant genera, and their relative levels were correlated with contents of characteristic components (p < 0.05). Together, changes in sensory characteristics, chemical composition and microbial succession during APPT fermentation were investigated, and advanced the formation mechanism of its unique quality.

The Characteristic Aroma Compounds of GABA Sun-Dried Green Tea and Raw Pu-Erh Tea Determined by Headspace Solid-Phase Microextraction Gas Chromatography-Mass Spectrometry and Relative Odor Activity Value

We aim to improve the product quality of GABA raw Pu-erh tea during development and processing. In this study, headspace solid-phase microextraction gas chromatography-mass spectrometry technology combined with relative odor activity evaluations was used to compare the volatile compounds of GABA sun-dried green tea and GABA raw Pu-erh tea. Sensory evaluation showed a higher aroma score of GABA raw Pu-erh tea than that of GABA sun-dried green tea, with significant differences in aroma type and purity. A total of 147 volatile compounds of 13 categories were detected, which differed in composition and quantity between the two teas. 2-Buten-1-one,1-(2,6,6-trimethyl-1,3-cyclohexadien-1-yl)-,(E)- and beta.-myrcene largely contributed to the aroma formation of both teas. Five volatile compounds were screened as potential markers for tea aroma. Metabolic pathway analysis showed that monoterpenoid biosynthesis may be beneficial to the formation of flowery and fruity aromas in the teas. We suggest that the findings of this study may provide important guidance for the processing and optimization of GABA tea.

Insights into the key quality components in Se-Enriched green tea and their relationship with Selenium

Selenium-enriched green tea (Se-GT) is of increasing interest because of its health benefits, but its quality components obtained limited research. In this study, Enshi Se-enriched green tea (ESST, high-Se green tea), Pingli Se-enriched green tea (PLST, low-Se green tea), and Ziyang green tea (ZYGT, common green tea) were subjected to sensory evaluation, chemical analysis, and aroma profiling. Chemical profiles in Se-GT were consistent with the taste attributes of the sensory analysis. 9 volatiles were identified as key odorants of Se-GT based on multivariate analysis. Correlations between Se and quality components were further assessed and highly Se-related compounds contents in these three tea samples were compared. The results showed that most amino acids and non-gallated catechins were highly negatively correlated with Se, while gallated catechins exhibited strong positive correlation with Se. And there were strong and significant associations between the key aroma compounds and Se. Moreover, 11 differential markers were found between Se-GTs and common green tea, including catechin, serine, glycine, threonine, l-theanine, alanine, valine, isoleucine, leucine, histidine, and lysine. These findings provide great potential for quality evaluation of Se-GT.

Characterization of Key Odor-Active Compounds in Sun-Dried Black Tea by Sensory and Instrumental-Directed Flavor Analysis

The aroma profile of sun-dried black tea (SBT) was identified by headspace solid–phase microextraction (HS–SPME) coupled with gas chromatography–mass spectrometry (GC–MS) and gas chromatography–olfactometry (GC–O). A total of 37 scents were captured by using the GC–O technique, and 35 scents with odor intensities ranging from 1.09 ± 1.93 to 9.91 ± 0.29 were identified. Twenty-one compounds were further identified as key odor-active compounds with odor activity values (OAVs) greater than or equal to one. These key odor-active compounds were restructured with their detected concentrations, and the aroma profile of the selected SBT sample was successfully imitated to a certain extent. An omission test was performed by designing 25 models and confirmed that (E)-β-damascenone, β-ionone, dihydro-β-ionone, linalool, and geraniol were the key odor-active compounds for the aroma profile of SBT. Meanwhile, phenylethyl alcohol, (E)-2-decenal, hexanal, and methyl salicylate were also important to the aroma profile of SBT. This study can provide theoretical support for the improvement of the aroma quality of sun-dried black tea.

HPLC and high-throughput sequencing revealed higher tea-leaves quality, soil fertility and microbial community diversity in ancient tea plantations: compared with modern tea plantations

BACKGROUND

Ancient tea plantations with an age over 100 years still reserved at Mengku Town in Lincang Region of Yunan Province, China. However, the characteristic of soil chemicophysical properties and microbial ecosystem in the ancient tea plantations and their correlation with tea-leaves chemical components remained unclear. Tea-leaves chemical components including free amino acids, phenolic compounds and purine alkaloids collected from modern and ancient tea plantations in five geographic sites (i.e. Bingdao, Baqishan, Banuo, Dongguo and Jiulong) were determined by high performance liquid chromatography (HPLC), while their soil microbial community structure was analyzed by high-throughput sequencing, respectively. Additionally, soil microbial quantity and chemicophysical properties including pH, cation exchange capacity (CEC), soil organic matter (SOM), soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali-hydrolyzable nitrogen (AN), available phosphorous (AP) and available potassium (AK) were determined in modern and ancient tea plantations.

RESULTS

Tea-leaves chemical components, soil chemicophysical properties and microbial community structures including bacterial and fungal community abundance and diversity evaluated by Chao 1 and Shannon varied with geographic location and tea plantation type. Ancient tea plantations were observed to possess significantly (P < 0.05) higher free amino acids, gallic acid, caffeine and epigallocatechin (EGC) in tea-leaves, as well as soil fertility. The bacterial community structure kept stable, while fungal community abundance and diversity significantly (P < 0.05) increased in ancient tea plantation because of higher soil fertility and lower pH. The long-term plantation in natural cultivation way might significantly (P < 0.05) improve the abundances of Nitrospirota, Methylomirabilota, Ascomycota and Mortierellomycota phyla.

CONCLUSIONS

Due to the natural cultivation way, the ancient tea plantations still maintained relatively higher soil fertility and soil microbial ecosystem, which contributed to the sustainable development of tea-leaves with higher quality.

Comparative metabolomics provides novel insights into the basis of petiole color differences in celery (Apiumgraveolens L.)

Plant metabolites are important for plant development and human health. Plants of celery (Apiumgraveolens L.) with different-colored petioles have been formed in the course of long-term evolution. However, the composition, content distribution, and mechanisms of accumulation of metabolites in different-colored petioles remain elusive. Using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), 1159 metabolites, including 100 lipids, 72 organic acids and derivatives, 83 phenylpropanoids and polyketides, and several alkaloids and terpenoids, were quantified in four celery cultivars, each with a different petiole color. There were significant differences in the types and contents of metabolites in celery with different-colored petioles, with the most striking difference between green celery and purple celery, followed by white celery and green celery. Annotated analysis of metabolic pathways showed that the metabolites of the different-colored petioles were significantly enriched in biosynthetic pathways such as anthocyanin, flavonoid, and chlorophyll pathways, suggesting that these metabolic pathways may play a key role in determining petiole color in celery. The content of chlorophyll in green celery was significantly higher than that in other celery cultivars, yellow celery was rich in carotenoids, and the content of anthocyanin in purple celery was significantly higher than that in the other celery cultivars. The color of the celery petioles was significantly correlated with the content of related metabolites. Among the four celery cultivars, the metabolites of the anthocyanin biosynthesis pathway were enriched in purple celery. The results of quantitative real-time polymerase chain reaction (qRT-PCR) suggested that the differential expression of the chalcone synthase (CHS) gene in the anthocyanin biosynthesis pathway might affect the biosynthesis of anthocyanin in celery. In addition, HPLC analysis revealed that cyanidin is the main pigment in purple celery. This study explored the differences in the types and contents of metabolites in celery cultivars with different-colored petioles and identified key substances for color formation. The results provide a theoretical basis and technical support for genetic improvement of celery petiole color.

Impact of Drying Processes on the Nutritional Composition, Volatile Profile, Phytochemical Content and Bioactivity of Salicornia ramosissima J. Woods

Salicornia ramosissima J. Woods is a halophyte plant recognized as a promising natural ingredient and will eventually be recognized a salt substitute (NaCl). However, its shelf-life and applicability in several food matrices requires the use of drying processes, which may have an impact on its nutritional and functional value. The objective of this study was to evaluate the effect of oven and freeze-drying processes on the nutritional composition, volatile profile, phytochemical content, and bioactivity of S. ramosissima using several analytical tools (LC-DAD-ESI-MS/MS and SPME-GC-MS) and bioactivity assays (ORAC, HOSC, and ACE inhibition and antiproliferative effect on HT29 cells). Overall, results show that the drying process changes the chemical composition of the plant. When compared to freeze-drying, the oven-drying process had a lower impact on the nutritional composition but the phytochemical content and antioxidant capacity were significantly reduced. Despite this, oven-dried and freeze-dried samples demonstrated similar antiproliferative (17.56 mg/mL and 17.24 mg/mL, respectively) and antihypertensive (24.56 mg/mL and 18.96 mg/mL, respectively) activities. The volatile composition was also affected when comparing fresh and dried plants and between both drying processes: while for the freeze-dried sample, terpenes corresponded to 57% of the total peak area, a decrease to 17% was observed for the oven-dried sample. The oven-dried S. ramosissima was selected to formulate a ketchup and the product formulated with 2.2% (w/w) of the oven-dried plant showed a good consumer acceptance score. These findings support the use of dried S. ramosissima as a promising functional ingredient that can eventually replace the use of salt.

Phenolic profile of jujube fruit subjected to gut microbiota fermentation and its antioxidant potential against ethyl carbamate-induced oxidative damage

OBJECTIVES

To evaluate the composition of bioactive substances and the antioxidant effects of jujube fruit under gut microbiota fermentation (GMF), and the inhibitory effect on cytotoxicity caused by ethyl carbamate (EC).

METHODS

Changes in the contents of flavonoids, polyphenols, total sugars, and reducing sugars of jujube fruit after GMF (0, 2, 6, 12, 24, and 48 h) were determined. The oxidation resistance of fermented jujube fruits (from 0 to 48 h fermentation) was evaluated using in vitro 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) and ferric reducing antioxidant power (FRAP) assays. Inhibitory effects of 48 h-fermented jujube fruit at various concentrations (0.25, 0.50, 1.00, and 2.00 mg/mL) on EC-treated toxicity and DNA damage of Caco-2 cells were estimated using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and nuclear staining assays, respectively. Effects of different concentrations of jujube fruit on EC-treated Caco-2 cells' intracellular reactive oxygen species (ROS), glutathione (GSH) levels, and mitochondrial membrane potential (MMP) were also evaluated.

RESULTS

Jujube fruit has rich bioactive components after GMF and shows strong antioxidant capacity. Fermented jujube fruit can inhibit the cytotoxicity and DNA damage of Caco-2 cells caused by EC and reduce intracellular ROS generation, as well as restoring GSH and MMP.

CONCLUSIONS

Fermented jujube fruit extracts produced by GMF still contain biologically active substances which retain biological activity and antioxidation capabilities.

Differentiating Pu-erh raw tea from different geographical origins by 1 H-NMR and U-HPLC/Q-TOF-MS combined with chemometrics

Pu-erh tea is believed to be a beneficial beverage for health due to its many kinds of pharmacological effects. Nevertheless, detailed information related to differences in metabolites of Pu-erh raw tea from different geographical origins remains scarce. In this study, 43 elements were found in water-soluble components of Pu-erh raw tea by highly sensitive ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (U-HPLC/Q-TOF-MS). The characteristic groups of 29 metabolites from nondestructive proton nuclear magnetic resonance (¹ H-NMR) spectroscopy were assigned. The variables contributed largely to the origin classification, mainly including valine, threonine, chlorogenic acid, quinic acid, epiafzelechin, and gallic acid ester, were screened out by sparse partial least squares discriminant analysis (sPLS-DA) method. This study provided a feasible and rapid technique for distinguishing Pu-erh tea from different areas by ¹ H-NMR combined with sPLS-DA.

Identification and similarity analysis of aroma substances in main types of Fenghuang Dancong tea

Fenghuang Dancong tea covers the oolong tea category and is widely acknowledged for its unique floral and honey flavor. In order to characterize the volatile components in nine different aroma types of Fenghuang Dancong tea, the Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC- MS) were employed. In addition, the similarity analysis and cluster analysis (CA) were performed to compare the aroma characteristics and establish the correlation between the nine types of teas. The principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) method were employed to determine the volatile components with a high contribution to the overall aroma of each type of tea. The results presented a total of 122 volatile aroma components including 24 kinds of alcohol, 23 kinds of esters, 15 kinds of olefins, 12 kinds of aldehydes, 12 kinds of ketones, 13 kinds of alkanes and 23 kinds of other components from the nine types of Fenghuang Dancong tea. Of these volatile aroma components, 22 types were common with linalool, dehydrolinalool, linalool oxide I, linalool oxide II, etc. The similarity of the nine types of Fenghuang Dancong tea was found between 46.79% and 95.94%. The CA indicated that the nine types of Fenghuang Dancong tea could be clustered into four categories when the ordinate distance reached to 10. The PCA demonstrated that decane, octadecane, 2,2,4,6,6-pentamethylheptane, dehydrolinalool, geraniol and nerol were the important aroma components to Fenghuang Dancong Tea. OPLS-DA proved that 2,2,4,6,6-pentamethylheptane, dehydrolinalool, phenylacetaldehyde, nerolidol, linalool oxide I and hexanal were the key differential compounds between the various types of tea samples. This study provides a theoretical basis for characterizing the volatile aroma components in the main types of Fenghuang Dancong tea as well as the similarity and correlation between various types of Fenghuang Dancong tea.

Analysis of nicotine-induced metabolic changes in Blakeslea trispora by GC-MS

Blakeslea trispora is a natural source of carotenoids, including β-carotene and lycopene, which have industrial applications. Therefore, classical selective breeding techniques have been applied to generate strains with increased productivity, and microencapsulated β-carotene preparation has been used in food industry (Li et al., 2019). In B. trispora, lycopene is synthesized via the mevalonate pathway (Venkateshwaran et al., 2015). Lycopene cyclase, which is one of the key enzymes in this pathway, is a bifunctional enzyme that can catalyze the cyclization of lycopene to produce β-carotene and exhibit phytoene synthase activity (He et al., 2017).

Physicochemical Aspects and Sensory Profiles as Various Potential Factors for Comprehensive Quality Assessment of Nü-Er-Cha Produced from Rhamnus heterophylla Oliv

Nü-Er-Cha, produced from the leaves of Rhamnus heterophylla Oliv., is known as an herbal tea and used in the treatment of bleeding, irregular menstruation and dysentery. A method was developed for the quality assessment of herbal tea, Nü-Er-Cha, adopting physical parameters, chemical constituents and sensory profiles as various potential factors. Their inner relationship was mined by multivariate statistical analysis tools, and the three factors were integrated by a technique for order preference by a similarity to ideal solution (TOPSIS) approach to comprehensively analyze the characters of Nü-Er-Cha. Viscosity was also introduced to the physical parameter determination besides conductivity, pH and color. Seven common peaks of eight batches of Nü-Er-Cha were marked by a high performance liquid chromatography (HPLC) fingerprint. They were further identified by HPLC mass spectrometry/mass spectrometry (HPLC-MS/MS) as hydroxybenzoic acids and flavanol glycosides. Fifty trained members participated in the sensory evaluation. Significant correlations between total sensory scores and conductivity, viscosity as well as pH were observed, a relatively innovative result for the quality assessment of herbal teas. The common peaks, belonging to hydroxybenzoic acids and flavanol glycosides, were mainly related to the color of infusions and leaves. The result of the TOPSIS analysis showed that S3 and S4 ranked as the top two in the comprehensive quality assessment. This may be related to rhamnetin triglycoside with a galactose/glucose and two rhamnoses, which had a higher peak response in S3 and S4 than that in the other samples. The present study may contribute to a better understanding of the relationship regarding physical properties, chemical composition and sensory profiles, and it may supply ideas for the comprehensive quality assessment of the herbal tea Nü-Er-Cha.