Tea Varieties Research Articles

Methodological approaches to gene identification of tea raw materials and raw material composition of tea-based soft drinks

Tea or tea shrub is a plant of the Camellia sinensis species, the leaves of which, previously prepared in a special way, are the traditional raw material for the production of tea products. Varietal gene identification of tea allows us to increase the level of assessment of the authenticity of tea raw materials and tea products. It is predominantly based on DNA technologies for the detection and interpretation of SNP markers (Single Nucleotide Polymorphism), represented by a wide arsenal of both expensive high-tech methods and publicly available laboratory approaches. Species gene identification of the raw material composition of tea-based soft drinks is an equally important area of research due to the risk of falsification of this type of product. The purpose of this study was to find methodological approaches to the varietal gene identification of tea raw materials and to the species gene identification of the raw material composition of tea-based soft drinks. As a result of a bioinformatics study to identify polymorphic restriction sites in the nucleotide sequences of Camellia sinensis genome loci, diagnostically significant restriction enzymes were selected that were capable of detecting SNPs and identifying tea genotypes using the analyzed markers. At the same time, 16 loci had potential for practical application, of which 11 belonged to the group of the most informative SNP markers. A post-analytical assessment of tea varieties was carried out with them regarding their genotypic affiliation and identifiability as part of solving the first task of the study. To achieve the second task, a molecular genetic approach to the species identification of the raw composition of soft drinks based on green tea was tested. The study included the analysis of experimental drinks (with natural flavoring “Lemon” and synthetic flavoring “Peach 716”), as well as commercial concentrates “TIAKVA” (based on extracts from the coarse stems of green or black tea). The methods used in the work were PCR (Polymerase Chain Reaction), RFLP (Restriction Fragment Length Polymorphism) and direct sequencing of the amplified chloroplast DNA locus. The combination of two methods (PCR and sequencing) showed its effectiveness in establishing the belonging of the analyzed nucleic acid samples to the Camellia sinensis species, the raw material base of the studied drinks and concentrates. However, to unlock the authentication potential of PCR with primers #1 and #2 combined with RFLP analysis, it will be necessary to select diagnostically significant restriction enzymes suitable for generating species-specific combinations of PCR-RFLP profiles of marker sequence.

Seasonal dynamics of phytometabolites content in Assam tea, Camellia sinensis var. assamica by LC-MS/MS: Implications for quality

The study examines the seasonal variation in phytometabolite content in Camellia sinensis var. assamica, a prevalent tea variety in Northeast India. Focusing on both bud and dormant leaf (banjhi) samples harvested during the monsoon, autumn, and winter seasons, the research aims to assist cultivators in selecting optimal harvesting times for tea production. An LC-MS/MS method was developed and validated for phytometabolite quantification. Epigallocatechin gallate (EGCG) emerged as the most abundant catechin, with concentrations ranging from 78.01±13.31–125.21±5.65 µg/mg in buds during the monsoon and decreasing to 17.86±1.22–51.11±1.21 µg/mg in winter. Banjhi leaves exhibited even higher EGCG levels, from 203.86±21.06–312.58±28.23 µg/mg in the monsoon, dropping to 74.43±15.22–97.52±8.47 µg/mg in autumn. Similarly, epicatechin gallate concentrations in buds ranged from 17.04±2.57–24.78±1.15 µg/mg in the monsoon and decreased to 5.36±0.39–11.16±1.74 µg/mg in winter, while banjhi leaves showed a decline from 63.61±1.60–72.72±1.23 µg/mg in the monsoon, dropping to 12.73±2.07–15.35±1.33 µg/mg in autumn. The study also noted seasonal variations in catechin hydrate, caffeine, gallic acid, theanine, and theaflavin. These findings underscore the importance of harvest timing for maintaining tea quality and optimizing cultivation and processing practices for sustainability amid environmental changes.

Prediction of storage years of Wuyi rock tea Shuixian by metabolites analysis.

Wuyi rock teas of different storage duration have different flavor, bioactivity, and market value, Shuixian is a main variety of Wuyi rock tea. In this study, metabolites composition of Shuixian with different storage years were analyzed using Ultrahigh Performance Liquid Chromatography-Quadrupole-Time of Flight-Mass Spectrometry (UPLC-Q-TOF-MS). A total of 1201 compounds were identified, and 104 differential compounds (VIP > 1.5) were determined. Furthermore, the results showed that five compounds exhibited a positive correlation with storage time, such as alpha-terpineol formate, carnosol, 2-phenethyl-D-glucopyranoside, Ellagic acid, and D-ribosyl nicotinic acid, while 24 compounds showed a negative correlation, such as Ethyl linoleate, leucocyanidin, cis-3-hexenyl acetate. In total, 29 signature compounds significantly correlated with storage time. These findings shed light on the patterns and mechanisms of changes in the composition of Wuyi rock tea during storage and provide a theoretical foundation for distinguishing the storage years.

Analysis and classification of tea varieties using high-performance liquid chromatography and global retention models

As a result of their metabolic processes, medicinal plants produce bioactive molecules with significant implications for human health, used directly for treatment or for pharmaceutical development. Chromatographic fingerprints with solvent gradients authenticate and categorise medicinal plants by capturing chemical diversity. This work focuses on optimising tea sample analysis in HPLC, using a model-based approach without requiring standards. Predicting the gradient profile effects on full signals was the basis to identify optimal separation conditions. Global models characterised retention and bandwidth for 14 peaks in the chromatograms across varied elution conditions, facilitating resolution optimisation of 63 peaks, covering 99.95 % of total peak area. The identified optimal gradient was applied to classify 40 samples representing six tea varieties. Matrices of baseline-corrected signals, elution bands, and band ratios, were evaluated to select the best dataset. Principal Component Analysis (PCA), k-means clustering, and Partial Least Squares-Discriminant Analysis (PLS-DA) assessed classification feasibility. Classification limitations were found reasonable due to tea processing complexities, involving drying and fermentation influenced by environmental conditions.

Effects of Photoperiod and Light Quality on Germination and Growth of Camellia sinensis 'HuangKui'.

Light, as a critical environmental factor, plays a pivotal role in photosynthesis, ultimately influencing the timing of bud flush in tea plants. However, the synergistic effects of different photoperiods and light qualities on the timing of bud flush in the albino tea cultivar 'HuangKui' (later germination variety) remain unknown. Thus, the objective of this study was to investigate the effects of different photoperiods (12L/12D, 14L/10D, 16L/8D, and 18L/6D, where L = the number of daylight hours and D = the number of hours of darkness) and ratios of red (R) to blue (B) light (R/B 1:1, R/B 1:2, R/B 1:3, and R/B 2:1) on the germination and growth of the albino tea variety 'HuangKui'. In our study, we examined how different photoperiods and red light and blue light affected tea germination and growth by investigating the timing of bud flush, photosynthesis, chlorophyll content, and growth indicators. First, our study showed that 'HuangKui' germinated 4 days, 2 days, and 1 day earlier under the 16L/8D photoperiod at the one bud and one leaf period compared with plants cultivated under the 12L/12D, 14L/10D, and 18L/6D photoperiods under light simulating the solar spectrum. Also, the growth of 'HuangKui' was maximumly promoted under the 16L/8D photoperiod treatment. Additionally, the earliest germination of 'HuangKui' was observed for the 16L/8D photoperiod under the R/B 2:1 (red/blue) treatment compared with the other treatments. Moreover, the greatest plant height, length of the new shoots, and new leaf areas were detected in the albino tea variety 'HuangKui' under R/B 2:1. Moreover, the contents of auxin (indole acetic acid, IAA) and trans-zeatin (tZ) under R/B 2:1 were significantly higher than those under the R/B 1:1 and control treatments with the 16L/8D photoperiod. Additionally, the auxin-related expression levels of CsIAA13, CsGH3.1, CsAUX1, and CsARF2 under the R/B 2:1 treatment were significantly higher than those in the control. The expression of CsARR-B, a positive regulator of cytokinin-related genes, was significantly higher under the R/B 2:1 treatment than under the control treatment, while the opposite result was found for the expression of the negative regulator CsARR-A. Therefore, the R/B 2:1 treatment with the 16L/8D photoperiod was an appropriate means of timing the bud flush for the albino tea variety 'HuangKui', which may be related to IAA or tZ signal transduction. In conclusion, our research offers a novel lighting strategy that promotes the germination and growth of albino tea cultivars.

In-depth exploration of the genomic diversity in tea varieties based on a newly constructed pangenome of Camellia sinensis.

Tea, one of the most widely consumed beverages globally, exhibits remarkable genomic diversity in its underlying flavour and health-related compounds. In this study, we present the construction and analysis of a tea pangenome comprising a total of 11 genomes, with a focus on three newly sequenced genomes comprising the purple-leaved assamica cultivar "Zijuan", the temperature-sensitive sinensis cultivar "Anjibaicha" and the wild accession "L618" whose assemblies exhibited excellent quality scores as they profited from latest sequencing technologies. Our analysis incorporates a detailed investigation of transposon complement across the tea pangenome, revealing shared patterns of transposon distribution among the studied genomes and improved transposon resolution with long read technologies, as shown by long terminal repeat (LTR) Assembly Index analysis. Furthermore, our study encompasses a gene-centric exploration of the pangenome, exploring the genomic landscape of the catechin pathway with our study, providing insights on copy number alterations and gene-centric variants, especially for Anthocyanidin synthases. We constructed a gene-centric pangenome by structurally and functionally annotating all available genomes using an identical pipeline, which both increased gene completeness and allowed for a high functional annotation rate. This improved and consistently annotated gene set will allow for a better comparison between tea genomes. We used this improved pangenome to capture the core and dispensable gene repertoire, elucidating the functional diversity present within the tea species. This pangenome resource might serve as a valuable resource for understanding the fundamental genetic basis of traits such as flavour, stress tolerance, and disease resistance, with implications for tea breeding programmes.

An insight into trichomes-deficiency and trichomes-rich black teas by comparative metabolomics: The impact of oxidized trichomes on metabolic profiles and infusion color

Tea trichomes were regarded as an essential evaluation index for reflecting tea flavor quality in terms of aroma and influence on infusion color. This study reveals the impact of golden oxidized trichomes on the color, volatile and non-volatile metabolites of black teas through comparative metabolomics combined quantitative analysis on hongbiluo (trichomes-deficiency black teas), hongjinluo (trichomes-rich black teas), and trichomes (from hongjinluo). Forty-six volatile components were detected using headspace solid-phase microextraction gas chromatography-mass spectrometry, while the results suggested that the contribution of trichomes to black teas is limited. A total of 60 marker non-volatile compounds were identified, including catechins, catechin oxidation products, flavonoid glycosides, organic acids, hydrolysable tannins and amino acids. Notably, p-coumaroyl-kaempferol glucosides, and catechin dimers demonstrated high levels in independent trichomes and showed a positive correlation with the brightness and yellow hue of black tea infusions, specifically kaempferol 3-O-di-(p-coumaroyl)-hexoside. Furthermore, results from fractional extraction analysis of separated trichomes provided that N-ethyl-2-pyrrolidinone-substituted epicatechin gallates, acylated kaempferol glycosides, and chromogenic catechins dimers, such as theaflavins, were primary color contributors in oxidized trichomes. Especially, we found that epicatechin gallate (ECG) and its derivates, 3′-O-methyl-ECG and N-ethyl-2-pyrrolidinone-substituted ECG, highly accumulated in trichomes, which may be associated with the varieties of hongbiluo and hongjinluo black teas. Eventually, addition tests were applied to verify the color contribution of trichome mixtures. Our findings employed comprehensive information revealing that golden oxidized trichomes contributed significantly to the brightness and yellow hue of black tea infusion, but their contribution to the aroma and metabolic profile is limited. These findings may contribute to the effective modulation of the infusion color during black tea production by regulating the proportion of tea trichomes or screening trichomes-rich or deficiency varieties.

Research on the influence of diverse tea varieties on disease and exercise regulation

Tea and tea beverages are popular around the world due to their unique flavors, and tea is rich in a variety of bioactive compounds such as catechins, alkaloids, and polysaccharides, which are the main contributors to its health benefits. In recent years, an increasing body of research has indicated that incorporating tea consumption into daily life exerts positive effects in combating oxidation, cardiovascular diseases, inflammation, aiding in exercise recovery, and potentially mitigating cancer risks. The relevant mechanisms of the signaling pathways involved have been extensively studied. Clinical trials have also demonstrated the potential of tea products as dietary supplements and natural medicines. In this paper, we review the health effects of tea, the steroid metabolic diseases modulated by different teas and the effects of related substances on health campaigns.

A frontier exploration of ancient craftsmanship: Effects of various tea products in traditional Chinese cuisine “tea flavored beef”

Modern science often overlooks to reveal the scientific essence of traditional crafts to promote their inheritance and development. In this work, five different types of tea products were prepared using the same variety of tea leaves referring to traditional methods. The analysis of their components and activities indicated that the processing reduced total catechin contents (from 172.8 mg/g to 48.2 mg/g) and promoted the synthesis of theaflavins (from 17.9 mg/g to 43.4 mg/g), reducing antioxidant and antimicrobial abilities of the resulting tea products. On this basis, the tea products were applied to “tea flavored beef” to reveal long-term effects. Within 15 days of storage, tea treatment showed remarkable antimicrobial and antioxidant activities on the beef. Also, the declines of sensory scores and texture of the treated beef were significantly suppressed. Meanwhile, protein degradation in the beef was inhibited, limiting the contents of various biogenic amines within relatively low levels.

Comparison of the Effect of Pruning on Plant Growth and Transcriptome Profiles in Different Tea Varieties

Although pruning contributes to the growth and development of new shoots, it is important to note that the growth potential and yield of tea varieties may differ after pruning due to genetic and environmental factors. In this experiment, 20 different varieties of tea plants were used to observe their potential for growth, shoot development, and other phenotypic indexes after pruning. The study aimed to determine the suitability of each variety for heavy pruning. It was concluded that there were obvious differences in tree strength and new growth after pruning of the different varieties, with ‘Zhongcha 302’ exhibiting the strongest growth and ‘Emei Wenchun’ showing the weakest growth. In order to understand the molecular mechanisms involved, a transcriptomic analysis was carried out on the two tea varieties. The results of the data indicate that the expression of CYP450 family was high in ‘Zhongcha 302’. In ‘Emei Wenchun’, the expression of NCED was higher than that in ‘Zhongcha 302’. The KEGG results indicate that pruning stimulates the expression of genes involved in phytohormone signalling and plant–pathogen interaction pathways in tea plants. The study offered scientific guidance for tea plant pruning suitability and preliminarily revealed the regulatory mechanism of new shoot growth in different tea plant varieties at the transcriptome level.

Dynamic Changes in Qidan Aroma during Roasting: Characterization of Aroma Compounds and Their Kinetic Fitting.

Qidan is one of the most famous varieties of Wuyi Rock tea and has a strong aroma. The aroma-active compounds in Qidan subject to different roasting times were analyzed using solid-phase microextraction two-dimensional gas chromatography-olfactometry-mass spectrometry (SPME-GC×GC-O-MS), and a total of 92 aroma-active compounds were detected. Multivariate statistical analysis showed that the roasting time had a significant effect on the aroma characteristics of Qidan, and that the key products in the Maillard reaction accumulated with the extension of the roasting time; these key products were screened out according to the calculation of the odor activity values (OAVs), from which kinetic equations were established. It was found that the levels of 2-methylbutanal, 3-methylbutanal, 2-methylpyrazine, 2-ethyl-5-methylpyrazine, and benzaldehyde increased with time, while the contents of benzeneacetaldehyde showed a tendency to first increase and then decrease. This study provides a theoretical basis for flavor quality control during Qidan processing.

Solid-State Fermentation of Ganoderma lucidum on the Soluble Sugar Metabolism of Three Summer–Autumn Black Tea Varieties

Soluble sugar is one of the important characteristic metabolites contributing to the flavor quality of tea. However, little is known about the changes and metabolic pathways of sugar in summer–autumn black tea varieties during the solid-state fermentation of Ganoderma lucidum. Therefore, this study is aimed at investigating the effects of the solid-state fermentation of Ganoderma lucidum on soluble sugar metabolism in three summer–autumn black tea varieties. In this study, we combined targeted metabolomics technology, gas chromatography-mass spectrometry, and multivariate statistical analysis to reveal the metabolic rules of 13 different sugars in three varieties of summer–autumn black tea under the action of Ganoderma lucidum. Using multivariate statistical analysis, 8 common key sugar differential metabolites were selected from the three groups of samples: D-fructose, trehalose, lactose, maltose, D-galactose, glucose, L-rhamnose, and xylitol. The eight different sugars contributed to the quality difference between Ganoderma lucidum tea and black tea in this study. To better explore the patterns of sugar changes, the metabolic pathways of 13 different sugars were screened and analyzed. The result revealed that the solid-state fermentation of Ganoderma lucidum increased the sweet characteristics and decreased the bitter characteristics of the three summer–autumn black tea varieties. In addition, these results showed that the solid-state fermentation of Ganoderma lucidum could produce lactose in tea, reduce glucose and fructose contents, and increase xylitol content. The solid-state fermentation of Ganoderma lucidum can regulate soluble sugar metabolism in three summer–autumn black tea varieties, leading to an improvement in their quality. This study has potential practical significance for regulating the flavor quality of summer–autumn tea.

Establishment of an efficient regeneration system of ‘ZiKui’ tea with hypocotyl as explants

Zikui (Camellia sinensis cv. Zikui) is a recently discovered cultivar of local purple tea in Guizhou, China. It is a purple leaf bud mutation material of Meitan Taicha (Camellia sinensis cv. ‘Meitan-taicha’) ‘N61’ strain, which is an important local germplasm resource in Guizhou. It is also a model plant for the study of anthocyanins, but the limited germplasm resources and the limitation of traditional reproduction hinder its application. Here, an efficient regeneration system is established by using hypocotyl as explants for the first time. Different plant growth regulators (PGRs) are evaluated during different regeneration processes including callus and root induction. According to our findings, using the optimal disinfection conditions, the seed embryo contamination rate is 17.58%. Additionally, the mortality rate is 9.69%, while the survival rate is measured as 72.73%. Moreover, the highest germination rate of 93.64% is observed under MS + 2.40 mg/L GA3 medium conditions. The optimal callus induction rate is 95.19%, while the optimal adventitious bud differentiation rate is 20.74%, Medium with 1.6 mg/L IBA achieved 68.6% rooting of the adventitious shoots. The survival rate is more than 65% after 6 days growth in the cultivated matrix. In summary, our research aims to establish a regeneration system for Zikui tea plants and design a transformation system for tea plant tissue seedlings. This will enable transfer of the target gene and ultimately facilitate the cultivation of new tea varieties with unique characteristics.

Jasmonates Play an Important Role in Differential Accumulation of Key Oolong Tea Aromas in Two Tea Varieties (Camellia sinensis)

Aroma is an important factor in the measurement of the quality and market value of oolong tea. However, it is hard to develop an oolong tea with good aroma quality using unsuitable tea varieties. To explore the key factors of tea varieties in the formation of oolong tea aromas, the fresh leaves of the Chungui variety (CG, suitable for oolong tea, Camellia sinensis (L.) O. Kuntze) and the Fuyun No. 6 variety (F6, unsuitable for oolong tea, Camellia sinensis (L.) O. Kuntze) were harvested and treated by withering and mechanical stress in order. Then, aroma, transcriptome, and jasmonate (JA) contents, and weighted gene co-expression network analysis (WGCNA), of samples were investigated. The contents of characteristic oolong tea aromas, including indole, (E)-β-ocimene, (E)-nerolidol, α-farnesene, and jasmine lactone, were all accumulated in much higher quantities in the CG variety after withering and mechanical stress. Accordingly, the coding genes of aroma formation synthases TSB2, OCS, NES, AFS, and LOX1, and related genes in MVA, MEP, and ALA pathways, were all much more highly activated. These differential reactions are mainly caused by the higher accumulation of jasmonates, especially methyl jasmonate, a type of important plant signal chemical, in CG after mechanical stress. WGCNA analysis indicated 34 different transcription factors from different families are predicted to be involved in this jasmonate-responsive reaction.

Characterization and Quantitation of Anthocyanins of the Pigmented Tea Cultivar TRI 2043 (Camellia sinensis L.) from Sri Lanka

Tea leaves are rich in diverse bioactive compounds. The tea accession TRI 2043 is unique due to its pigmented leaves caused by anthocyanins, clonal origin, resistance to blister blight disease, and high pubescence density. Because of its peculiarity, TRI 2043 is used to produce high-quality silver tip tea, a premium type of tea that commands high prices. This study was carried out to clarify and elucidate the types of anthocyanins in this particular accession. Four different anthocyanin species were identified and quantitated as cyanidin-3-O-β-d-galactoside and delphinidin-3-O-β-d-galactoside equivalents for leaf blades and stems of the cultivar TRI 2043. The characterization was performed by comparison with commercially available reference substances and further confirmed using ion mobility high-resolution time-of-flight-mass spectrometry (IMS-HRTOF-MS). Quantitation was carried out using ultra-high-performance liquid chromatography ultraviolet–visible detection (UHPLC-UV-vis) with cyanidin-3-O-β-d-glucoside as an internal standard. E- and Z-geometric isomers of 6-p-coumaroyl derivates of delphinidin and cyanidin-3-O-β-d-galactopyranosides were observed, and collision cross section (CCS) values were determined for all four different anthocyanidin species. The content of anthocyanins in leaf blades of cultivar TRI 2043 was 856.32 ± 41.56 µg/g dry weight, with cyanidin being the more abundant anthocyanin (69.8%). Conversely, the stem material contained an anthocyanin amount of 459.5 ± 44.7 µg/g dry weight, with a higher content of delphinidin (69.6%). In summary, an enrichment strategy using analytical membrane chromatography was established to fully elucidate and quantify the anthocyanin profile of plant samples such as the special tea variety TRI 2043.

Catechin detection in tea samples based on catechin-induced conformational changes in papain

Catechin, the major ingredient in tea that affects its taste, varies based on the tea variety, climate, and extraction techniques. Although several techniques have been developed to determine catechin levels, an easy-to-use method is still lacking. Herein, the catechin levels were determined using papain for the first time. After incubating papain with catechin, the precipitate was discarded, and the remaining catechin-enzyme complex in the supernatant was determined by UV–visible absorption spectroscopy. Upon catechin binding papain’s main absorption band (at 280 nm) was altered, reflecting conformation changes in their aromatic amino acids. It was supported by the kinetic measurements determined with N-α-benzoyl-arginine-p-nitroanilide (BAPNA) as a substrate. Complex formation between catechin and papain markedly affects the enzyme activity, resulting in the diminishes of the yellow-colored product observed at 410 nm in a concentration-dependent manner. Under the optimum conditions, the analytical curve was linear in the concentration range 0.10 – 0.80 mg/mL (r2 = 0.9893) with a detection limit of 0.44 mg/mL. This developed biosensor demonstrated long-term stability (90 days) and reproducibility with a relative standard deviation below 10%. This usefulness of papain’s conformation changes was further demonstrated in the analysis of tea infusion samples, and the recoveries are in the acceptable range (79.1–81.2%).

The quality difference in five oolong tea accessions under different planting management patterns in south Fujian of China

IntroductionOolong tea, celebrated for its significance in Chinese tea culture, was the subject of investigation in this study.MethodsFive varieties of Minnan oolong tea were sampled, each cultivated under two distinct management approaches: conventional management and natural growth methods. The study aimed to discern variations in sensory attributes, encompassing appearance and liquor color, alongside the analysis of chemical composition.Results and discussionThe results indicated that oolong tea cultivated through conventional manual management generally exhibited qualities in terms of shape and foliage appearance, in contrast to those grown naturally. However, naturally grown oolong tea tended to exhibit more favorable aroma and taste profiles compared to conventionally managed counterparts. Furthermore, the content of water extract, amino acids, polyphenols, caffeine, and other pivotal chemical constituents were typically higher in naturally grown tea varieties compared to conventionally managed ones. Conversely, catechin content was found to be more abundant in traditionally managed bushes than in those grown naturally. These findings emphasize the significance of implementing appropriate natural growth management practices to enhance the quality of Minnan oolong tea and maintain ecological sustainability.

Near-Infrared Spectroscopy Combined with Fuzzy Improved Direct Linear Discriminant Analysis for Nondestructive Discrimination of Chrysanthemum Tea Varieties.

The quality of chrysanthemum tea has a great connection with its variety. Different types of chrysanthemum tea have very different efficacies and functions. Moreover, the discrimination of chrysanthemum tea varieties is a significant issue in the tea industry. Therefore, to correctly and non-destructively categorize chrysanthemum tea samples, this study attempted to design a novel feature extraction method based on the fuzzy set theory and improved direct linear discriminant analysis (IDLDA), called fuzzy IDLDA (FIDLDA), for extracting the discriminant features from the near-infrared (NIR) spectral data of chrysanthemum tea. To start with, a portable NIR spectrometer was used to collect NIR data for five varieties of chrysanthemum tea, totaling 400 samples. Secondly, the raw NIR spectra were processed by four different pretreatment methods to reduce noise and redundant data. Thirdly, NIR data dimensionality reduction was performed by principal component analysis (PCA). Fourthly, feature extraction from the NIR spectra was performed by linear discriminant analysis (LDA), IDLDA, and FIDLDA. Finally, the K-nearest neighbor (KNN) algorithm was applied to evaluate the classification accuracy of the discrimination system. The experimental results show that the discrimination accuracies of LDA, IDLDA, and FIDLDA could reach 87.2%, 94.4%, and 99.2%, respectively. Therefore, the combination of near-infrared spectroscopy and FIDLDA has great application potential and prospects in the field of nondestructive discrimination of chrysanthemum tea varieties.

Fermented or not fermented: a comparative study of the biological activities and microbiomes of a non‐fermented green tea and a five‐year‐old fermented tea prepared from young leaves of Shan tea

SummaryCamellia sinensis var. shan is a special tea variety in Vietnam that is in high demand, especially its fermented products. This study compared the total polyphenol content (TPC), antioxidant activity, cytotoxicity, and microbiome of a green Shan tea and a five‐year‐old fermented Shan tea. Folin–Ciocalteu, DPPH and SRB assays were used for TPC, antioxidant activity and cytotoxicity evaluation. The isolated microbes were morphologically and molecularly identified. The TPC (126.59 mg g−1) and antioxidant activity (IC50 of 284.82 μg mL−1) of the green tea were significantly higher than those of the fermented tea. However, the latter showed a significantly higher cytotoxicity against liver cancer cells (inhibiting 73.84% cells at 1 mg mL−1). Notably, the green tea had a negligible number of microbes, but the fermented tea had a much richer microbiome with Aspergillus restrictus (4.7 × 104 CFU g−1), A. ruber (1.76 × 103 CFU g−1), A. pseudoglaucus (1.32 × 103 CFU g−1), A. cibarius (8.8 × 102 CFU g−1), Bacillus cereus (1.13 × 104 CFU g−1), Peribacillus frigoritolerans (4.0 × 102 CFU g−1) and B. amyloliquefaciens (2.0 × 102 CFU g−1) present. These microbes are either harmless or beneficial, except for B. cereus (can cause food poisoning at >106 CFU g−1). The fermented tea would appear to have some advantages over the green tea. However, the presence and density of B. cereus should be monitored.

Comparison of colorimetric methods for the analysis of total polyphenols in green tea extracts.

Two colorimetric methods are used to determine the total polyphenol contents of tea, namely, "the Folin-Ciocalteu method," defined by the International Organization for Standardization, and the "iron tartrate method," specified in the Standard Tables of Food Composition in Japan. In this study, we compared the Folin-Ciocalteu and iron tartrate methods using green tea extracts. When comparing the 2 methods, the sum of the 4 major catechins measured using high-performance liquid chromatography (HPLC) was regarded as the standard value. The total polyphenol contents obtained using the Folin-Ciocalteu method were closer to the HPLC value than those obtained using the iron tartrate method. However, the iron tartrate method is adequate if the current official method is improved, that is, our results suggest that the coefficients appropriate for common green tea varieties, as well as the degree and duration of cover cultivation, in the official iron tartrate method must be considered.