Metabolomics combined with proteomics provides a novel interpretation of the compound differences among Chinese tea cultivars (Camellia sinensis var. sinensis) with different manufacturing suitabilities

Tea polyphenol mediated CsMYB77 regulation of CsPOD44 to promote tea plant (Camellia sinensis) root drought resistance

Drought stress significantly alters the metabolic homeostasis of tea plants; however, few studies have examined the role of specific metabolites, particularly tea polyphenols, in drought resistance. This study reveals that the tea polyphenol content in drought-tolerant tea cultivars tends to increase under drought conditions. Notably, in environments characterized by staged and repeated drought, changes in tea polyphenol are significantly positively correlated with drought resistance. To investigate this further, we irrigated the roots with exogenous tea polyphenols before subjecting the plants to drought. Our findings indicated that the absorptive roots of the experimental group exhibited enhanced development, improved cellular integrity, and a significant increase in peroxidase activity. A comprehensive analysis of the transcriptome and metabolome revealed that tea polyphenols are closely associated with the phenylpropanoid metabolism pathway. Notably, CsMYB77 and CsPOD44 genes were identified as highly correlated with this pathway. Overexpression experiments in Arabidopsis thaliana demonstrated that CsMYB77 promotes the expression of phenylpropanoid pathway genes, thereby enhancing drought resistance. Conversely, antisense oligonucleotide silencing of CsMYB77 decreased drought resistance in tea plants. Additional experiments, including yeast one-hybrid assays, luciferase complementation imaging, dual-luciferase assays, and electrophoretic mobility shift assays, confirmed that CsMYB77 positively regulates the expression of CsPOD44. In summary, our findings indicate that the differences in drought tolerance among tea cultivars are closely linked to phenylpropanoid metabolism. Specifically, tea polyphenols may mediate the regulatory network involving CsMYB77 and CsPOD44, thereby enhancing stress resistance by promoting root development. This study offers new insights into the breeding of drought-resistant tea cultivars.

Metabolomic analysis of volatile and non-volatile compounds in mulberry leaf white tea processed with different withering methods

With economic development and the diversification and improvement of consumption patterns, there is a growing concern about food health. Mulberry leaves, a kind of natural resource with the homology of medicinal and edible properties, contain various bioactive compounds. In this study, the key active constituents, including tea polyphenols, γ-aminobutyric acid (GABA), and 1-deoxynojirimycin (DNJ), in mulberry leaf white tea were characterized after different withering methods. Additionally, the effects of different withering methods on volatile and non-volatile compounds were analyzed using metabolomics. The findings indicated that non-volatile metabolites were primarily upregulated across all withering methods. Metabolic pathway analysis identified starch and sucrose metabolism and glycerophospholipid metabolism as the key pathways influenced.

L-Theanine Metabolism in Tea Plants: Biological Functions and Stress Tolerance Mechanisms

L-theanine, a unique non-protein amino acid predominantly found in tea plants (Camellia sinensis), plays a pivotal role in plant responses to abiotic stress and significantly influences tea quality. In this review, the metabolism and transport mechanisms of L-theanine are comprehensively discussed, highlighting its spatial distribution in tea plants, where it is most abundant in young leaves and less so in roots, stems, and older leaves. The biosynthesis of L-theanine occurs through the enzymatic conversion of glutamate and ethylamine, catalyzed by theanine synthase, primarily in the roots, from where it is transported to aerial parts of the plant for further catabolism. Environmental factors such as temperature, light, drought, elevated CO2, nutrient unavailability, and heavy metals significantly affect theanine biosynthesis and hydrolysis, with plant hormones and transcription factors playing crucial regulatory roles. Furthermore, it has been demonstrated that applying L-theanine exogenously improves other crops' resistance to a range of abiotic stresses, suggesting its potential utility in improving crop resilience amid climate change. This review aims to elucidate the physiological mechanisms and biological functions of L-theanine metabolism under stress conditions, providing a theoretical foundation for enhancing tea quality and stress resistance in tea cultivation.

Discriminating Mung Bean Origins Using Pattern Recognition Methods: A Comparative Study of Raman and NIR Spectroscopy

The feasibility of the two methodologies was confirmed to compare the results of determining mung bean origins using Raman and Near-Infrared (NIR) spectroscopy. Spectra from mung beans collected in Baicheng City, Jilin Province; Dorbod Mongol Autonomous, Tailai County, Heilongjiang Province; and Sishui County, Shandong Province, China, were analyzed. We established a traceability model using Principal Component Analysis combined with the K-nearest neighbor method to compare the efficacy of these methods in discriminating the origins of the mung beans. The total cumulative variance explained by the first three principal components from the NIR of mung beans from different origins was 99.01%, which is 6.71% higher than that derived from Raman. Additionally, the discrimination rate for mung bean origins based on NIR spectral data reached 98.67%, outperforming the Raman-based approach by 22.67%. These findings indicate that NIR spectroscopy is more effective than Raman spectroscopy is in tracing the provenance of mung beans.

Identification of a Flavanone 2-Hydroxylase Involved in Flavone C-Glycoside Biosynthesis from Camellia sinensis

Tea contains a variety of flavone C-glycosides, which are important compounds that distinguish tea cultivars and tea categories. However, the biosynthesis pathway of flavone C-glycosides in tea plant remains unknown, and the key enzymes involved have not been characterized. In this study, a liquid chromatography-mass spectrometry method to determine 9 flavone C-glycosides was developed, and the accumulation patterns of 9 flavone C-glycosides in tea plants were examined first. Then, an entry enzyme CsF2H for flavone C-glycoside biosynthesis was identified, which had four cytochrome P450-specific conserved motifs and was targeted to the endoplasmic reticulum. Correlation analysis indicated that the expression level of CsF2H was positively correlated with all contents of 9 flavone C-glycosides. The recombinant CsF2H could convert flavanone (naringenin) into the corresponding 2-hydroxyflavonone (2-hydroxynaringenin), rather than into flavone (apigenin). Heterologous coexpression of CsF2H and CsCGT1 in yeast revealed that the substrate naringenin could be enzymatically converted to flavone mono-C-glycosides vitexin and isovitexin under the catalytic control of CsF2H and CsCGT1 following dehydration. Gene-specific antisense oligonucleotide analysis suggested that suppressing CsF2H significantly reduced the levels of 9 flavone C-glycosides. Together, CsF2H is the first key enzyme that generates flavone C-glycosides through the 2-hydroxyflavanone biosynthesis pathway in tea plants.

Correlation analysis of secondary metabolites and disease resistance activity of different varieties of Congou black tea based on LC-MS/MS and TCMSP

To investigate the correlation between the difference of secondary metabolites and the disease-resistance activity of different varieties of Congou black tea. Among a total of 657 secondary metabolites identified, 183 metabolites had anti-disease activity, 113 were key active ingredients in traditional Chinese medicine (TCM), 73.22% had multiple anti-disease activities, and all were mainly flavonoids and phenolic acids. The main enriched metabolic pathways were phenylpropanoid biosynthesis, biosynthesis of secondary metabolites, flavonoid biosynthesis, and metabolic pathways. Flavonoid and phenolic acid secondary metabolites were more correlated with anti-disease activity and key active TCM ingredients. Conclusion: The types of JGY and Q601 Congou black tea of the relative contents show large differences in secondary metabolites. Flavonoid and phenolic acid secondary metabolites were identified as the primary factors contributing to the variation in secondary metabolites among different varieties of Congou black tea. These compounds also exhibited a stronger correlation with disease resistance activity.

Effects of Different Levels of Green Tea Powder on Performance, Antioxidant Activity, Egg Mass, Quality, and Cecal Microflora of Chickens

This study was conducted to investigate the effects of different levels of Green Tea Powder on the performance, egg quality, serum immune and antioxidant indices, and cecal microflora of 300-day-old Chishui black-bone chickens during the peak laying period. A total of 360 Chishui black-bone chickens were selected as the experimental animals. They were randomly allocated into four groups: the control group (CON), trial group I (T1), trial group II (T2), and trial group III (T3), each group with six replicates and 15 hens in each replicate. The control group was fed a basal diet, and the experimental groups were fed a basal diet supplemented with 0.8%, 1.6%, and 2.4% Green Tea Powder, respectively. The accommodation period was 14 d, and the experimental period was 60 d. The statistical software SPSS was used to perform a one-way analysis of variance (ANOVA) on the experimental data, and Duncan's method was used to perform multiple comparisons among groups. The results showed the following: compared with those of the control group, the average daily gain of the laying hens significantly decreased in the 1.6% Green Tea Powder group (p < 0.05); adding Green Tea Powder significantly reduced the content of malondialdehyde in the serum (p < 0.05), and the addition of 0.8% tea leaves significantly increased the immunoglobulin M and immunoglobulin A contents (p < 0.05); the egg yolk weight, eggshell thickness, eggshell strength, and yolk color of the laying hens significantly decreased in the 1.6% Green Tea Powder group (p < 0.05), and the addition of Green Tea Powder at the level of 2.4% significantly increased the percentage of umami, essential, and total amino acids (p < 0.05); and the structure of intestinal microorganisms was improved, and the abundance of Bacteroidetes and Bacteroidaceae significantly increased, while the abundance of Firmicutes and Lachnospiraceae significantly decreased (p < 0.05).

Global lysine succinylation analysis unveils post-translational regulation effect on phenylpropanoid metabolism remodeling during Lonicera japonica flower development

Lonicera japonica plays a significant role in traditional Chinese medicine and as a food source, making it a focus of studies on protein succinylation and its potential role in regulating secondary metabolism during flower development. This study aimed to clarify the regulatory mechanism of protein succinylation on phenylpropanoid-related phenotypic changes by conducting a global lysine succinylation proteomic analysis across different flowering stages. A total of 586 lysine succinylated peptides in 303 proteins were identified during early and late floral stages. Functional enrichment analysis revealed that succinylated proteins primarily participated in the tricarboxylic acid (TCA) cycle, amino acid metabolism, and secondary metabolism. The abundance of succinylated aspartate transaminase (AT), 4-coumarate-CoA ligase (4CL), and phenylalanine N-hydroxylase (CYP79A2) in phenylpropanoid metabolism varied during flower development. In vitro experiments demonstrated that succinylation increased AT activity while inhibited 4CL activity. Decreased levels of total flavonoids and phenolic acids indicated significant alterations in phenylpropanoid metabolism during later floral stages. These results suggest that succinylation of TCA cycle proteins not only influences flower development but also, together with AT-4CL-CYP79A2 co-succinylation, redirects phenylpropanoid metabolism during flower development in L. japonica.

Metabolomics applications for plant-based foods origin tracing, cultivars identification and processing: Feasibility and future aspects

Metabolomics, the systematic study of metabolites, is dedicated to a comprehensive analysis of all aspects of plant-based food research and plays a pivotal role in the nutritional composition and quality control of plant-based foods. The diverse chemical compositions of plant-based foods lead to variations in sensory characteristics and nutritional value. This review explores the application of the metabolomics method to plant-based food origin tracing, cultivar identification, and processing methods. It also addresses the challenges encountered and outlines future directions. Typically, when combined with other omics or techniques, synergistic and complementary information is uncovered, enhancing the classification and prediction capabilities of models. Future research should aim to evaluate all factors affecting food quality comprehensively, and this necessitates advanced research into influence mechanisms, metabolic pathways, and gene expression.

GC-MS Combined with Proteomic Analysis of Volatile Compounds and Formation Mechanisms in Green Teas with Different Aroma Types

Aroma is one of the key factors for evaluating the quality of green tea. A tender aroma (NX) and floral-like aroma (HX) are two types of high-quality aroma of green tea. In this work, the different aroma types of baked green tea were classified by sensory evaluation. Then, seven tea samples with a typical tender or floral-like aroma were selected for further volatile component analysis by GC-MS. A total of 43 aroma compounds were identified in two different aroma types of baked green tea samples. The PCA showed that linalool, geraniol, 3-hexenyl butyrate, and 3-hexenyl hexanoate were the major volatiles contributing to the HX. On the other hand, most of the alcohol volatiles, such as 1-octanol, 1-octen-3-ol, 1-dodecanol, 1-hexadecanol, phenylethyl alcohol, benzyl alcohol, aldehydes and some hydrocarbons contributed more to the NX. In addition, the chemical composition analysis showed that the content of free amino acids was higher in NX green tea samples, while the content of catechins was relatively higher in HX tea samples. A proteomic analysis revealed that most of the enzymes involved in VPBs pathways, such as phenylalanine ammonialyase, peroxidase, and shikimate-O-hydroxycinnamoyl transferase, were more abundant in NX than in HX tea samples. These results laid a foundation for the aroma formation mechanism of different aroma types of baked green tea and provided some theoretical guidance for the breeding of specific aroma varieties.

Characterization of CsUGT73AC15 as a Multifunctional Glycosyltransferase Impacting Flavonol Triglycoside Biosynthesis in Tea Plants

Flavonol glycosides, contributing to the health benefits and distinctive flavors of tea (Camellia sinensis), accumulate predominantly as diglycosides and triglycosides in tea leaves. However, the UDP-glycosyltransferases (UGTs) mediating flavonol multiglycosylation remain largely uncharacterized. In this study, we employed an integrated proteomic and metabolomic strategy to identify and characterize key UGTs involved in flavonol triglycoside biosynthesis. The recombinant rCsUGT75AJ1 exhibited flavonoid 4'-O-glucosyltransferase activity, while rCsUGT75L72 preferentially catalyzed 3-OH glucosylation. Notably, rCsUGT73AC15 displayed substrate promiscuity and regioselectivity, enabling glucosylation of rutin at multiple sites and kaempferol 3-O-rutinoside (K3R) at the 7-OH position. Kinetic analysis revealed rCsUGT73AC15's high affinity for rutin (Km = 9.64 μM). Across cultivars, CsUGT73AC15 expression inversely correlated with rutin levels. Moreover, transient CsUGT73AC15 silencing increased rutin and K3R accumulation while decreasing their respective triglycosides in tea plants. This study offers new mechanistic insights into the key roles of UGTs in regulating flavonol triglycosylation in tea plants.

Literature Review of Proteomics Approach Associated with Coffee

As a significant crop growing all across the world, coffee is mostly produced in the bean belt of our global atlas. Worldwide variations in environmental conditions are causing a decline in the yield and quality of coffee varieties. Coffee production is the main emphasis of several traditional breeding techniques. But conventional breeding methods are not sufficient to tackle the problems related to coffee. The field of genomics, which includes transcriptomics, proteomics, and metabolomics, has made great paces in the last ten years. Proteomics is a well-known technique used to enhance the growth, yield, breeding, and quality of different plants under stable and shifting environments. The regulation of specific enzymes, genes, protein expression, modification, translation, and other features played an important role in the enhancement of important plants. However, relatively less research on the proteomics approach for coffee has been published in the last few years. For this reason, some of the most important aspects of proteome profiling for coffee plants have been covered in this review, including growth, the somatic embryo technique, altitude, environmental adoption, drought, and the role that proteins and important enzymes play in the flavor and taste of coffee. This review can aid in the breeding of new cultivars and improve coffee attributes. Furthermore, the present literature can pave the way for proteomics research on coffee.

Extensive targeted metabolomics analysis reveals the identification of major metabolites, antioxidants, and disease-resistant active pharmaceutical components in Camellia tuberculata (Camellia L.) seeds

Sect. tuberculata plant belongs to the Camellia genus and is named for the "tuberculiform protuberance on the surface of the ovary and fruit". It is a species of great ornamental value and potential medicinal value. However, little has been reported on the metabolites of C. tuberculata seeds. Therefore, this study was conducted to investigate the metabolites of C. tuberculata seeds based on UPLC/ESI-Q TRAP-MS/MS with extensively targeted metabolomics. A total of 1611 metabolites were identified, including 107 alkaloids, 276 amino acids and derivatives, 283 flavonoids, 86 lignans and coumarins, 181 lipids, 68 nucleotides and derivatives, 101 organic acids, 190 phenolic acids, 10 quinones, 4 steroids, 17 tannins, 111 terpenoids, and 177 other metabolites. We compared the different metabolites in seeds between HKH, ZM, ZY, and LY. The 1311 identified different metabolites were classified into three categories. Sixty-three overlapping significant different metabolites were found, of which lignans and coumarins accounted for the largest proportion. The differentially accumulated metabolites were enriched in different metabolic pathways between HKH vs. LY, HKH vs. ZM, HKH vs. ZY, LY vs. ZY, ZM vs. LY and ZM vs. ZY, with the most abundant metabolic pathways being 4, 2, 4, 7, 7 and 5, respectively (p < 0.05). Moreover, among the top 20 metabolites in each subgroup comparison in terms of difference multiplicity 7, 8 and 13. ZM and ZY had the highest phenolic acid content. Ninety-six disease-resistant metabolites and 48 major traditional Chinese medicine agents were identified based on seven diseases. The results of this study will not only lead to a more comprehensive and in-depth understanding of the metabolic properties of C. tuberculata seeds, but also provide a scientific basis for the excavation and further development of its medicinal value.

Metabolomics investigation of the chemical variations in white teas with different producing areas and storage durations

In this study, we employed nontargeted metabolomics and quantitative analysis to explore the variations in metabolites among white teas from different production areas and with varying storage durations. A total of 83 compounds exhibited differential levels between Zhenghe and Fuding white tea, 89 between Zhenghe and Jinggu, and 75 between Fuding and Jinggu white tea. Concerning the storage of white tea, the concentrations of flavanols, dimeric catechins, and amino acids decreased over time, while N-ethyl-2-pyrrolidone-substituted flavanols (EPSFs), caffeine, adenosine monophosphate (AMP), and adenosine increased. Galloylated flavanols showed a higher propensity to form EPSFs with theanine compared to nongalloylated flavanols during storage. Theanine and epigallocatechin gallate were more inclined to generate S-configuration EPSFs during storage in Fuding and Jinggu white tea samples, while R-configuration EPSFs were more readily formed in Zhenghe white tea samples. This study offers a comprehensive understanding of the changes in metabolites during the storage of white tea.

Physicochemical properties, antioxidant activities and comprehensive phenolic profiles of tea-macerated Chardonnay wine and model wine

A new type of flavored wine was produced by macerating either green tea or black tea into Chardonnay wine and model wine respectively, where the physicochemical properties (pH, titratable acidity, color) were modulated. Significant (p < 0.05) increases of total phenolic content and antioxidant activity (assessed by DPPH, FRAP and ABTS assays) were also observed in the tea macerated wines. A total of 160 phenolic and non-phenolic compounds were identified by HPLC-DAD-ESI-QTOF-MS/MS, where 55 phenolics were newly found in the tea macerated Chardonnay wine. The interaction between wine and tea phenolics led to additional 29 phenolic compounds and 4 non-phenolic compounds that were not found in either Chardonnay wine or tea. Catechin and epigallocatechin gallate were the most abundant phenolic compounds and contributed to the improved antioxidant activities. This study provided a promising prospect of tea as a novel additive in the production of flavored wine with enhanced functionalities.

Varietal Authenticity Assessment of QTMJ Tea Using Non-Targeted Metabolomics and Multi-Elemental Analysis with Chemometrics

In this paper, a combination of non-targeted metabolomics and multi-element analysis was used to investigate the impact of five different cultivars on the sensory quality of QTMJ tea and identify candidate markers for varietal authenticity assessment. With chemometric analysis, a total of 54 differential metabolites were screened, with the abundances significantly varied in the tea cultivars. By contrast, the QTMJ tea from the Yaoshan Xiulv (XL) monovariety presents a much better sensory quality as result of the relatively more abundant anthocyanin glycosides and the lower levels of 2'-o-methyladenosine, denudatine, kynurenic acid and L-pipecolic acid. In addition, multi-elemental analysis found 14 significantly differential elements among the cultivars (VIP > 1 and p < 0.05). The differences and correlations of metabolites and elemental signatures of QTMJ tea between five cultivars were discussed using a Pearson correlation analysis. Element characteristics can be used as the best discriminant index for different cultivars of QTMJT, with a predictive accuracy of 100%.

Comprehensive applications of metabolomics on tea science and technology: Opportunities, hurdles, and perspectives

With the development of metabolomics analytical techniques, relevant studies have increased in recent decades. The procedures of metabolomics analysis mainly include sample preparation, data acquisition and pre-processing, multivariate statistical analysis, as well as maker compounds' identification. In the present review, we summarized the published articles of tea metabolomics regarding different analytical tools, such as mass spectrometry, nuclear magnetic resonance, ultraviolet-visible spectrometry, and Fourier transform infrared spectrometry. The metabolite variation of fresh tea leaves with different treatments, such as biotic/abiotic stress, horticultural measures, and nutritional supplies was reviewed. Furthermore, the changes of chemical composition of processed tea samples under different processing technologies were also profiled. Since the identification of critical or marker metabolites is a complicated task, we also discussed the procedure of metabolite identification to clarify the importance of omics data analysis. The present review provides a workflow diagram for tea metabolomics research and also the perspectives of related studies in the future.

Exogenous tannic acid relieves imidacloprid-induced oxidative stress in tea tree by activating antioxidant responses and the flavonoid biosynthetic pathway

Pesticide stress on plants is receiving increased scrutiny due to its effect on plant secondary metabolism and nutritional quality. Tannic acid (TA) is a natural polyphenolic compound showing excellent antioxidant properties and is involved in alleviating stress. The present study thoroughly investigated the effects and mechanism of exogenous TA on relieving imidacloprid (IMI) stress in tea plants. Our research found that TA(10 mg/L) activated the antioxidant defense system, enhanced the antioxidant ability, reduced the accumulation of ROS and membrane peroxidation, and notably promoted tea plant tolerance to imidacloprid stress. Additionally, TA boosted photosynthetic capacity, strengthened the accumulation of nutrients. regulated detoxification metabolism, and accelerated the digestion and metabolism of imidacloprid in tea plants. Furthermore, TA induced significant changes in 90 important metabolites in tea, targeting 17 metabolic pathways through extensively targeted metabolomics. Specifically, TA activated the flavonoid biosynthetic pathway, resulting in a 1.3- to 3.1-fold increase in the levels of 17 compounds and a 1.5- to 63.8-fold increase in the transcript level of related genes, such as ANR, LAR and CHS in this pathway. As a potential tea health activator, TA alleviates the oxidative damage caused by imidacloprid and improves the yield and quality of tea under pesticide stress.

Non-targeted metabolomics characterization of flavor formation of Lichuan black tea processed from different cultivars in Enshi

Nine tea cultivars planted in Enshi were selected and processed into "Lichuan black tea". Sensory evaluation showed that cultivar had the greatest influence on taste and aroma quality, including sweetness, umami and concentration of taste, as well as sweet and floral fragrances of aroma. The non-volatile and volatile components were identified by UPLC-Q-TOF/MS and GC-MS, and PCA analysis showed good separation between cultivars, which could cause the difference in quality. Baiyaqilan, Meizhan and Echa 10 had a floral aroma, with obvious difference in their aromatic composition from other cultivars. Moreover, Echa 10 also had a strong sweet aroma. The key aroma components in Echa 10 (with the largest cultivation area) were further investigated by GC-O-MS combined with odor activity value (OAV) analysis, included β-damascenone, phenylethylaldehyde, nonenal, geraniol, linalool, jasmonone, (E)-2-nonenal, β-cyclocitral, (E)-β-ocimene, methyl salicylate, β-ionone, 2,6,10,10-tetramethyl-1-oxaspiro[4.5]dec-6-ene, citral, β-myrcene, nerol, phenethyl alcohol, benzaldehyde, hexanal, nonanoic acid, and jasmin lactone.

Decoding the Chemical Signatures and Sensory Profiles of Enshi Yulu: Insights from Diverse Tea Cultivars

Enshi Yulu, a renowned Chinese steamed green tea, is highly valued for its unique sensory attributes. To enhance our comprehensive understanding of the metabolic variation induced by steaming fixation, we investigated the overall chemical profiles and organoleptic quality of Enshi Yulu from different tea cultivars (Longjing 43, Xiapu Chunbolv, and Zhongcha 108). The relationships between sensory traits and non-volatiles/volatiles were evaluated. A total of 58 volatiles and 18 non-volatiles were identified as characteristic compounds for discriminating among the three tea cultivars, and the majority were correlated with sensory attributes. The "mellow" taste was associated with L-aspartic acid, L-asparagine, L-tyrosine, L-valine, EGC, EC, and ECG, while gallic acid and theobromine contributed to the "astringent" taste. "Kokumi" contributors were identified as L-methionine, L-lysine, and GCG. Enshi Yulu displayed a "pure" and "clean and refreshing" aroma associated with similar volatiles like benzyl alcohol, δ-cadinene, and muurolol. The composition of volatile compounds related to the "chestnut" flavor was complex, including aromatic heterocycles, acids, ketones, terpenes, and terpene derivatives. The key contributors to the "fresh" flavor were identified as linalool oxides. This study provides valuable insights into the sensory-related chemical profiles of Enshi Yulu, offering essential information for flavor and quality identification of Enshi Yulu.

Characterization of the Sensory Properties and Quality Components of Huangjin Green Tea Based on Molecular Sensory-Omics

Huangjin green tea (HJC) is one of the most famous regional green teas in China, and has gained attention for its unique flavor. Research on HJC has focused mainly on the synthesis of L-theanine, with fewer studies concentrating on sensory characteristics. In this study, molecular sensory science techniques, including color analysis, gas chromatography-ion mobility spectrometry, and E-tongue, were used to characterize the sensory properties of HJC, with Fuding Dabai and Anji Baicha teas used as conventional and high amino acid controls, respectively. The sensory characteristics and main quality components of HJC lie somewhere between these two other teas, and somewhat closer to the conventional control. They were difficult to distinguish by color, but significant differences exist in terms of volatile organic compounds (VOCs), E-tongue values on bitterness and astringency, and their contents of major taste components. VOCs such as (E)-2-octenal, linalool, ethyl acrylate, ethyl acetate, and 2-methyl-3-furanethiol were found to be the main differential components that contributed to aroma, significantly influencing the tender chestnut aroma of HJC. Free amino acids, tea polyphenols, and ester catechins were the main differential components responsible for taste, and its harmonious phenol-to-ammonia ratio was found to affect the fresh, mellow, heavy, and brisk taste of HJC.

The Integration of Metabolomics, Electronic Tongue, and Chromatic Difference Reveals the Correlations between the Critical Compounds and Flavor Characteristics of Two Grades of High-Quality Dianhong Congou Black Tea

Tea's biochemical compounds and flavor quality vary depending on its grade ranking. Dianhong Congou black tea (DCT) is a unique tea category produced using the large-leaf tea varieties from Yunnan, China. To date, the flavor characteristics and critical components of two grades of high-quality DCT, single-bud-grade DCT (BDCT), and special-grade DCT (SDCT) manufactured mainly with single buds and buds with one leaf, respectively, are far from clear. Herein, comparisons of two grades were performed by the integration of human sensory evaluation, an electronic tongue, chromatic differences, the quantification of major components, and metabolomics. The BDCT possessed a brisk, umami taste and a brighter infusion color, while the SDCT presented a comprehensive taste and redder liquor color. Quantification analysis showed that the levels of total polyphenols, catechins, and theaflavins (TFs) were significantly higher in the BDCT. Fifty-six different key compounds were screened by metabolomics, including catechins, flavone/flavonol glycosides, amino acids, phenolic acids, etc. Correlation analysis revealed that the sensory features of the BDCT and SDCT were attributed to their higher contents of catechins, TFs, theogallin, digalloylglucose, and accumulations of thearubigins (TRs), flavone/flavonol glycosides, and soluble sugars, respectively. This report is the first to focus on the comprehensive evaluation of the biochemical compositions and sensory characteristics of two grades of high-quality DCT, advancing the understanding of DCT from a multi-dimensional perspective.

Study on taste quality formation and leaf conducting tissue changes in six types of tea during their manufacturing processes

This study fristly investigated the taste quality formation and leaf conducting tissue changes in six types of Chinese tea (green, black, oolong, yellow, white, and dark) made from Mingke No.1 variety. Non-targeted metabolomics showed the vital manufacturing processes (green tea-de-enzyming, black tea-fermenting, oolong tea-turning-over, yellow tea-yellowing, white tea-withering, and dark tea-pile-fermenting) were highly related to their unique taste formation, due to different fermentation degree in these processes. After drying, the retained phenolics, theanine, caffeine, and other substances significantly impacted each tea taste quality formation. Meanwhile, the tea leaf conducting tissue structure was significantly influenced by high processing temperature, and the change of its inner diameter was related to moisture loss during tea processing, as indicated by its significant different Raman characteristic peaks (mainly cellulose and lignin) in each key process. This study provides a reference for process optimization to improve tea quality.

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.

Integrating Metabolomics and Proteomics Technologies Provides Insights into the Flavor Precursor Changes at Different Maturity Stages of Arabica Coffee Cherries

The metabolic modulation of major flavor precursors during coffee cherry ripening is critical for the characteristic coffee flavor formation. However, the formation mechanism of flavor precursors during coffee cherry ripening remains unknown. In the present study, a colorimeter was employed to distinguish different maturity stages of coffee cherry based on the coffee cherry skin colors, and proteomics and metabolomics profiles were integrated to comprehensively investigate the flavor precursor dynamics involved in Arabica coffee cherry ripening. The data obtained in the present study provide an integral view of the critical pathways involved in flavor precursor changes during coffee cherry ripening. Moreover, the contributions of critical events in regulating the development of flavor precursors during the four ripening stages of coffee cherries, including the biosynthesis and metabolism pathways of organic acids, amino acids, flavonoids, and sugars, are discussed. Overall, a total of 456 difference express metabolites were selected, and they were identified as being concentrated in the four maturity stages of coffee cherries; furthermore, 76 crucial enzymes from the biosynthesis and metabolism of sugars, organic acids, amino acids, and flavonoids contributed to flavor precursor formation. Among these enzymes, 45 difference express proteins that could regulate 40 primary amino acids and organic acids flavor precursors were confirmed. This confirmation indicates that the metabolic pathways of amino acids and organic acids played a significant role in the flavor formation of Arabica coffee cherries during ripening. These results provide new insights into the protease modulation of flavor precursor changes in Arabica coffee cherry ripening.

Characterization of 35 Masson pine (Pinus massoniana) half-sib families from two provinces based on metabolite properties

Plant metabolism is an important functional trait, and its metabolites have physiological and ecological functions to adapt to the growth environment. However, the physiological and ecological functions of metabolites from different provinces of the same plant species are still unclear. Therefore, this study aimed to determine whether metabolites from different provinces of Masson pine (Pinus massoniana Lamb.) have the corresponding metabolic traits. The gas chromatography–mass spectrometry technique and metabonomic analysis methods were used to characterize 35 Masson pine half-sib families from two provinces. A total of 116 metabolites were putatively identified in 35 families of Masson pine, among which the average content of organic acids was the highest, followed by saccharides and alcohols, and phosphoric acids. Comparative analysis of metabolite groups showed that organic acids, amines, and others were significantly different between the Masson pine families from Guangxi and Guizhou provinces. Six differential metabolites were found between the provinces from Guizhou and Guangxi, namely caffeic acid, L-ascorbic acid, gentiobiose, xylitol, d-pinitol, and β-sitosterol. The most significantly enriched pathways among differentially expressed metabolites between the two provinces were steroid biosynthesis, phenylpropanoid biosynthesis, glutathione metabolism, pentose and glucuronate interconversions. Overall, the results showed that Masson pine half-sib families from different geographical provinces have different metabolite profiles and their metabolites are affected by geographical provenance and growth environment adaptability. This study revealed that the breeding of Masson pine families from different provinces changed the metabolite profiles, providing a reference for the multipurpose breeding of Masson pine.

Study on the Suitability of Tea Cultivars for Processing Oolong Tea from the Perspective of Aroma Based on Olfactory Sensory, Electronic Nose, and GC-MS Data Correlation Analysis

The oolong tea aroma is shown to consist of cultivar aroma and technical aroma in this study based on the aroma differences between oolong tea products of cultivars of different suitability, as determined by correlation analysis of olfactory, sensory, electronic nose, and GC-MS data. Human senses were significantly affected by the aroma components, which included eight terpene metabolites (β-Ocimene, (Z)-Furan linalool oxide, linalool, (3E)-4,8-Dimethyl-1,3,7-nonatriene, (E)-Pyranoid linalool oxide, γ-Elemene, Humulene, (Z,E)-α-Farnesene), three carotenoid metabolites (β-Ionone, (Z)-Geranylacetone and 6-methyl-5-Hepten -2-one), three lipid metabolites ((Z)-3-Hexenyl (Z)-3-hexenoate, Butanoic acid hexyl ester, and (Z)-Jasmone), four amino acid metabolites (Methyl salicylate, Geranyl isovalerate, indole, and Phenylethyl alcohol), and six thermal reaction products (2-Pentylfuran, Octanal, Decanal, (E,E)-2,4-Nonadienal, (Z)-2-Decenal, and (E)-2-Undecenal). Meanwhile, several aroma compounds (such as (E)-Nerolidol and α-Farnesene), mainly comprising the “technical aroma” formed in the processing mode, were noted to be less closely related to cultivar suitability. This study sheds light on the aroma characteristics of different tea cultivars for oolong tea processing.

Dynamic Changes of Volatile Compounds during the Xinyang Maojian Green Tea Manufacturing at an Industrial Scale

Xinyang Maojian (XYMJ) is one of the premium green teas and originates from Xinyang, which is the northernmost green tea production area in China. The special geographic location, environmental conditions, and manufacturing process contribute to the unique flavor and rich nutrition of XYMJ green tea. Aroma is an important quality indicator in XYMJ green tea. In order to illustrate the aroma of XYMJ green tea, the key odorants in XYMJ green tea and their dynamic changes during the manufacturing processes were analyzed by headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). A total of 73 volatile compounds of six different chemical classes were identified in the processed XYMJ green tea samples, and the manufacturing processes resulted in the losses of total volatile compounds. Among the identified volatile compounds, twenty-four aroma-active compounds, such as trans-nerolidol, geranylacetone, nonanal, (+)-δ-cadinene, linalool, (Z)-jasmone, cis-3-hexenyl butyrate, cis-3-hexenyl hexanoate, methyl jasmonate, and β-ocimene, were identified as the key odorants of XYMJ green tea based on odor activity value (OAV). The key odorants are mainly volatile terpenes (VTs) and fatty acid-derived volatiles (FADVs). Except for (+)-δ-cadinene, copaene, cis-β-farnesene, (Z,E)-α-farnesene and phytol acetate, the key odorants significantly decreased after fixing. The principal coordinate analysis (PCoA) and the hierarchical cluster analysis (HCA) analyses suggested that fixing was the most important manufacturing process for the aroma formation of XYMJ green tea. These findings of this study provide meaningful information for the manufacturing and quality control of XYMJ green tea.