Types Of Tea Research Articles

Method development for multielement determination of halogens and sulfur in teas

Abstract Microwave-induced combustion was evaluated as a sample preparation method for several types of tea (black, green, lemon balm, boldo, and mint) for further determination of bromine, chlorine, fluorine, iodine, and sulfur by ion chromatography. Parameters such as the sample mass efficiently decomposed and the most suitable absorbing solution (ultrapure water and 25, 50, 100, and 150 mmol L−1 NH4OH) were evaluated, considering the characteristics of the analytes and the determination technique used. The maximum sample mass possible to be decomposed was 900 mg of milled tea in the form of pellets, and the absorbing solution chosen was 100 mmol L−1 NH4OH, which provided suitable stabilization of the analytes (recoveries between 95 % and 103 %). To assess the accuracy of the proposed method, a certified reference material (BCR 060, aquatic plant) was analyzed. Agreements with the certified values ranged from 101 % to 107 %. The proposed method was used to analyze tea samples and the concentrations ranged from 549 to 2,549 mg kg−1 for chlorine, 223 to 828 mg kg−1 for fluorine, and 786 to 4,023 mg kg−1 for sulfur; bromine and iodine concentrations were below the limits of quantification (42 and 80 mg kg−1, respectively) in all evaluated samples.

Medicinal cannabis tea contains variable doses of cannabinoids and no terpenes.

Tea is a recommended way of administration of prescribed cannabis plant products in Denmark. We aimed to investigate the cannabinoid and terpene doses contained in different teas. We analysed tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), and terpene concentrations in three repeated preparations of each type of tea, and in plant material. In standard tea, concentrations of THC were [median (min-max)] 9.5 (2.3-15), 19 (13-34), and 36 (26-57) μg/mL for products with a labelled content of 6.3%, 14%, and 22% total THC (THC + THCA), respectively. The CBD concentration in tea from a product labelled with 8% total CBD (CBD + CBDA) was 7.5 (1.9-10) μg/mL. Based on this, the recommended starting amount of 0.2L of the different teas would contain between 0.46 and 11.3mg THC, and 0.38 to 2.0mg CBD. Adding creamer before, but not after boiling, increased the THC and CBD concentration 2.3-4.4 and 2.1-fold, respectively. Terpenes were detected in plant material, but not in tea. The study elucidates THC and CBD doses in different teas, which may assist the clinician's choice of cannabis product. Moreover, it underscores the need for caution as administration as tea can result in exposure to different doses, even when the same cannabis product is used.

The influence of processing methods on polyphenol profiling of tea leaves from the same large-leaf cultivar (Camellia sinensis var. assamica cv. Yunkang-10): nontargeted/targeted polyphenomics and electronic sensory analysis

Tea polyphenols transform under processing methods, but a systematic study on their changes in the same large-leaf tea cultivar is lacking. Here, Camellia sinensis var. assamica cv. Yunkang-10 leaves underwent six processing methods and were assessed using optimized nontargeted (UHPLC-Q-Exactive Orbitrap-MS) and targeted (UHPLC-QqQ-MS) polyphenomics, along with molecular networking analysis. 903 and 52 polyphenolic compounds (catechins, flavones and flavonols, and phenolic acids) were respectively relatively and absolutely quantified for the first time. Dark and black teas, with the lowest polyphenol content, differed from the other four tea types, although variations existed among these four teas. However, some flavonol and flavone aglycones (e.g. kaempferol, apigenin), as well as some phenolic acids (e.g. ellagic acid, gallic acid), exhibited higher levels in dark and black teas. Correlations between polyphenolic composition and electronic sensory characteristics were observed using E-tongue and E-eye. This study enriches understanding of polyphenol profiles in Chinese teas post diverse processing.

Exploring the antioxidant realm of green tea: From extraction to fortification

AbstractGreen tea, a widely consumed beverage with a long history of traditional use has garned renewed scientific interest due to its potential health benefits. Unlike other tea types, green tea undergoes minimal oxidation and thus preserving its potent catechins and antioxidant properties. This review devels into the fascinating chemistry of green tea, exploring how processing steps like fixation and rolling, shape its distinct profile. We will further explore the potential health benefits associated with green tea consumption, acknowledging the existing research focus on tea polyphenols and aiming to provide a broader perspective on its potential health impact. Finally, the review examines the emerging application of green tea extract fortification in food matrices. This innovative approach offers exciting possibilities for enhancing food stability and sensory appeal while potentially contributing to a range of health benefits.

Can herbal teas be used as complementary therapies for kidney disorders? Results from a cross-sectional study

IntroductionChronic kidney disease (CKD) has limited treatment options and is becoming more and more common. Since apparent evidence in the literature shows that herbs may be reno-protective, we discussed different kinds of herbal tea in relation to CKD and related disorders. MethodsThis cross-sectional study was conducted in health care centres located in a region in central Iran by enroling subjects aged 18 years and older. A self-reported questionnaire was used to evaluate the frequency and type of herbal tea drinks by participants. Anthropometric characteristics were measured and blood samples were obtained using a standard procedure. The Kidney Disease Outcome Quality Initiative (K/DOQI) guideline was the reference for diagnosis of CKD. Through multiple logistic models, the association between herbal tea drinking with CKD and related disorders was examined. ResultsOverall, 3 322 subjects were examined in this study. Three types of herbal tea were consumed by the study participants including green tea, chamomile-thyme tea, and borage tea. No statistically significant consistent associations between kidney disorders, including CKD, haematuria, albuminuria, and kidney stone and consumption of these herbal preparations were identified. ConclusionOverall, this study failed to suggest any consistent association between renal function and three categories of herbal tea in adult Iranian individuals.

Functionalizing the Electrical Properties of Kombucha Zoogleal Mats for Biosensing Applications.

Kombucha is a type of tea that is fermented using yeast and bacteria. During this process, a film made of cellulose is produced. This film has unique properties such as biodegradability, flexibility, shape conformability, and ability to self-grow as well as be produced across customized scales. In our previous studies, we demonstrated that Kombucha mats exhibit electrical activity represented by spikes of the electrical potential. We propose using microbial fermentation as a method for in situ functionalization to modulate the electroactive nature of Kombucha cellulose mats, where graphene and zeolite were used for the functionalization. We subjected the pure and functionalized Kombucha mats to mechanical stimulation by applying different weights and geometries. Our experiments demonstrated that Kombucha mats functionalized with graphene and zeolite exhibit memfractive properties and respond to load by producing distinctive spiking patterns. Our findings present incredible opportunities for the in situ development of functionalized hybrid materials with sensing, computing, and memory capabilities. These materials can self-assemble and self-grow after they fuse their living and synthetic components. This study contributes to an emergent area of research on bioelectronic sensing and hybrid living materials, opening up exciting opportunities for use in smart wearables, diagnostics, health monitoring, and energy harvesting applications.

Hyperspectral image construction in different spectral bands of tea leafs for identifying the tea type using O-ConvNet-RF model

Tea, a commonly consumed beverage, is susceptible to being sold in adulterated or expired forms by third-party vendors. Hyperspectral imaging across different wavelength bands has proven to precisely assess the diverse types of tea and their corresponding financial gains. This study aims to employ a deep learning methodology in conjunction with hyperspectral imaging for efficiently classifying tea leaves. A novel approach is proposed, wherein a waveband convolutional neural network is utilized to generate hyper spectral images of tea leaf samples with enhanced resolution. The model known as optimized-convolutional neural network-random forest O- (ConvNet-RF) demonstrated exceptional performance, achieving high accuracy, impressive recall, F1 score, and notable sensitivity rate, outperforming existing alternative methods. The tea leaf types, namely green, yellow, and black, were accurately identified using a combination of the random forest (RF) model and the O-ConvNet-RF model. The tree-based classification method for the identification of tea leaves demonstrated superior performance as compared to alternative machine learning models. In general, this study presents a successful methodology for the classification of tea leaves, with potential implications for consumer processing and distributor profit analysis.

Comparison of Volatile Compounds among Four Types of Teas Analyzed Using Gas Chromatography-Ion Mobility Spectrometry.

Gas chromatography-ion mobility spectrometry (GC-IMS) is a smart method that has been applied to determine the volatile compounds in Chinese teas, but its use in comparing the volatile compounds of different types of tea has not been mentioned. In this study, the volatile compounds found in four types of samples (green, yellow, white, and black teas) made with fresh leaves of Camellia sinensis (L.) Kuntze 'Zhongcha 111' were analyzed using GC-IMS. The results showed that 93 volatile compounds were identified from our tea samples and that the average volume of aldehydes was higher than that for other compounds, especially in white tea. The different samples were successfully categorized using multivariate statistical analysis. Using partial least squares discriminant analysis (PLS-DA), we found 15 key compounds, including four differential components: (E)-2-hexenal, 2-furanmethanethio, 2-hexanol, and 1-octene. There were 29 common components, and their total content reached 386.0 μg/g. Moreover, the 3-methyl-2-butenal and dimethyl disulfide detected in the four samples were also differential compounds, varying according to the manufacturing technology. Thus, this study demonstrates that different types of teas can be discriminated easily using GC-IMS and that this is helpful to shorten the time for improving tea quality and developing new products.

Modelling pH Dynamics, SCOBY Biomass Formation, and Acetic Acid Production of Kombucha Fermentation Using Black, Green, and Oolong Teas

Kombucha is a traditional, fermented beverage made with an essential biomaterial known as SCOBY (symbiotic culture of bacteria and yeast). Three different tea types, namely black, green, and oolong, were compared in kombucha fermentation in terms of pH dynamics, the formation of SCOBY biomass, and the production of acetic acid. The rational, exponential, and polynomial models described pH dynamics with good fit, R2 > 0.98. The formation of SCOBY biomass and the production of acetic acid were modelled using sigmoidal functions, with three-parameter logistic and Gompertz models and four-parameter Boltzmann and Richards models. The F-test indicated that the three-parameter models were statistically adequate; thus, the Gompertz model was modified to present the biological meaning of the parameters. The SCOBY biomass formation rates ranged from 7.323 to 9.980 g/L-day, and the acetic acid production rates ranged from 0.047 to 0.049% acid (wt/vol)/day, with the highest values from the non-conventional substrate, oolong tea. The correlations between pH and SCOBY biomass or acetic acid using polynomial models enable the prediction of product formation in kombucha processing.

Concentration and health risk assessment of 16 rare earth elements in six types of tea in China

Rare Earth Elements (REEs) have been implicated in potential health effects. However, the health risk of REE exposure among tea drinkers in China remains poorly understood. This study aimed to characterize the concentration of REEs in different tea categories and evaluate the associated health risks for tea consumers in China. By analyzing the content of 16 REEs in 4326 tea samples from China, the exposure level of REEs to the general population was estimated. The content of these 16 REEs was similar across six types of tea, with oolong tea exhibiting the highest levels. The concentration of light rare earth elements (LREEs) in six types of tea was higher than that of heavy rare earth elements (HREEs). The daily mean and 95th percentile (P95) exposure to REEs from tea for the general population in China were 0.0328 μg/kg BW and 0.1283 μg/kg BW, respectively, which are significantly lower than the temporary acceptable daily dose (tADI). Our findings suggest that REEs from tea do not pose a known health risk to Chinese consumers.

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.

METABOLOMIC TECHNIQUE IN GREEN TEA RESEARCH: A REVIEW

Tea, consumed by two-thirds of the global population, had a production of 5.68 million tons in 2017. The cultivation and processing of tea are crucial variables that have a substantial impact on the final product. As a result, many types of tea, such as black, oolong, and green, are produced, each with its own unique flavors and health advantages. Metabolomic techniques, which employ advanced analytical methods, are employed to characterize chemical composition of tea, thereby enabling the assessment of its quality, origin, and bioactivity. This review focused on the application of these techniques to the green tea research. Analytical methods such as UPLC-MS and 1H NMR, when employed in conjunction with multivariate analysis, have proven effective in correlating green tea quality with its chemical constituents, identifying key metabolites such as EGCG, ECG, and caffeine. These metabolomic techniques permit rapid and accurate assessments, enabling the differentiation between high- and low-quality green tea and enhancing the comprehension of its chemical composition and sensory attributes. In addition, a metabolomic approach was employed, utilizing HPLC-TOF-MS, to differentiate between various types of green tea based on their bioactivities. These methods have the capacity to reveal significant variations in metabolite profiles and bioactivities. The application of multivariate analysis enabled the identification of specific bioactive cultivars, thereby demonstrating the efficacy of the technique in evaluating the health-promoting effects of different tea samples. Thus, metabolomic methods represent an optimal approach for a comprehensive and expeditious investigation of the research related to green tea.

Uptake and Transport of Selenium in a Soil–Tea Plant–Tea Infusion System: A Study of Typical Tea Plantations in a Selenium-Rich Area of China

Selenium is an important indicator for the evaluation of tea quality. However, the relationship between selenium uptake by tea plants (Camellia sinensis) and soil properties, as well as selenium transport and distribution in a tea plantation soil–tea plant–tea infusion production system, remain unclear. In this study, 12 tea plantations situated in a typical selenium-rich area of China were selected, and the characteristics and crucial factors influencing the uptake and transport of selenium were analyzed using a plantation soil–tea plant–tea infusion production system. The soil total selenium content ranged from 1.12 to 6.67 mg kg−1, with an average of 2.57 mg kg−1. The average available selenium content was 53.56 µg kg−1, and the activation rate of soil selenium was 2.27%. Soil-available selenium was significantly positively correlated with total selenium, available potassium, and soil organic matter contents, and was significantly negatively correlated with soil pH. The selenium content in old leaves ranged from 0.29 to 2.73 mg kg−1, which met the standard for selenium-rich tea, whereas only 33% of young leaves met this standard. The selenium enrichment factor was highest in the fibrous root and lowest in the young leaves. The average selenium transport factors from fibrous roots to main roots, from main roots to main stems, from main stems to lateral stems, from lateral stems to young leaves, and from lateral stems to old leaves were 0.53, 0.92, 0.67, 0.97, and 2.30, respectively. The selenium concentration of tea infusion ranged from 1.88 to 12.49 μg L−1, and the average selenium dissolution rate was 22.62% after one brewing. This study identified critical factors that influence soil-selenium availability. The selenium content in tea plant organs is indicated to be strongly associated with the selenium content in the main roots.

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.

Serum untargeted metabolomics analysis of the preventive mechanism of TAETEA Prebiotea on non-alcoholic fatty liver in rats

Pu-erh tea belongs to the six tea categories of black tea, according to the processing technology and quality characteristics, is divided into two types of raw tea and ripe tea. Raw tea is made from fresh leaves of tea as raw materials, through the process of greening, kneading, sun drying, steam molding and other processes made of tightly pressed tea. Ripe tea is made from Yunnan large-leafed sun green tea, using a specific process, post-fermentation (rapid post-fermentation or slow post-fermentation) processing of loose tea and tightly pressed tea. TAETEA Prebiotea is Puerh Ripe Tea, TAETEA Prebiotea has the effect of increasing insulin level and improving hyperglycemia in mice, and it also has the effect of regulating blood lipids, which can reduce the level of serum total cholesterol (TC) and triglycerides (TG), increase the level of high-density lipoprotein cholesterol (HDL-C), and improve the metabolism of lipids. Therefore, further experiments were conducted by us, and TAETEA Prebiotea was formulated into a suitable dose for the intervention of non alcoholic fatty liver disease (NAFLD) model rats, and at the end of the experiments, the samples of each group of experiments were analyzed and detected by the method of UHPLC-Q-Exactive LC-MS liquid-mass spectrometry methodology, and the relevant metabolites as well as metabolic pathways were analyzed by the method of Non targeted metabolomics analysis. As a result, 71 differential metabolites could be screened, of which 35 differential metabolites were up-regulated after intervention and 36 differential metabolites were down-regulated after intervention. Based on the KEGG pathway enrichment and Pathway Impact bubble diagram analysis, glycine, serine, threonine metabolism, arginine and proline metabolism, protein digestion and absorption, and central carbon metabolism in cancer may be the main metabolic pathways in which TAETEA Prebiotea exerted preventive effects on NAFLD rats, C00148 (Proline), C00300 (Creatine) and C00719 (Betaine) are the differential metabolites that play important regulatory roles.

Effect of CTC processing on quality characteristics of green tea infusion: A comparative study with conventional orthodox processing

Traditionally, green tea is manufactured using orthodox processing methods. The CTC (curl, tear, and crush) method, widely employed in black tea processing, has minimal application in green tea production. However, it exhibits potential in terms of extraction efficiency to infusion. This study investigates the CTC method for producing green tea (CGT) and compares the extraction efficiency of bioactives to infusion with orthodox green tea (OGT). Total polyphenol, catechins, caffeine, and theanine extraction efficiencies were evaluated in both CGT infusion (CGTI) and OGT infusion (OGTI), along with water extract, antioxidant activity, color parameters, and sensory attributes. Results showed the amount of the bioactive compounds extracted from 2.00 g OGT could be attained from 0.75 to 1.00 g of CGT. This indicates that CGT is 100 to 167% more efficient in terms of the contents of bioactives in the infusion than OGT. This finding corroborates the observations of higher antioxidant activity of CGT compared to OGT. CGTI achieved similar taste and color perceptions with half the amount of OGT or even less. This enhanced extraction efficiency, along with CGTI's taste and color characteristics, can facilitate its commercial production, benefiting consumers and the tea industry. Industrial relevanceThis study provides comprehensive information on CTC green tea to the tea industry, which is the first of its kind with such in-depth details. As evident, the CTC processing mode of green tea promises more affordability to its growing consumers leading to increased demand for this type of tea which will immensely benefit the tea industry.

A colorimetric sensor for rapid discrimination of tea polyphenols and tea authentication based on Rh-decorated Pd nanocubes with high peroxidase-like activity

The rapid development of nanozymes has offered substantial opportunities for the fields of biomedicine, chemical sensing, and food safety. Among these applications, multichannel sensors, with the capability of simultaneously detecting multiple target analytes, hold promise for the practical application of nanozymes in chemical sensing with high detection efficiency. In this study, Rh-decorated Pd nanocubes (Pd–Rh nanocubes) with significantly enhanced peroxidase-like activity are synthesized through the mediation of underpotential deposition (UPD) and subsequently employed to develop a multichannel colorimetric sensor for discriminating tea polyphenols (TPs) and tea authentication. Based on a single reactive unit of efficient catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine dihydrochloride (TMB), the nanozyme-based multichannel colorimetric sensor responds to each analyte in as short as 1 min. With the aid of principal component analysis (PCA) and hierarchical cluster analysis (HCA), various TPs and types of tea can be accurately identified. This work not only provides a new type of simply structured and highly active nanozymes but also develops a concise and rapid multichannel sensor for practical application in tea authentication and quality inspection.

Bioinspired integrated triboelectric electronic tongue

An electronic tongue (E-tongue) comprises a series of sensors that simulate human perception of taste and embedded artificial intelligence (AI) for data analysis and recognition. Traditional E-tongues based on electrochemical methods suffer from a bulky size and require larger sample volumes and extra power sources, limiting their applications in in vivo medical diagnosis and analytical chemistry. Inspired by the mechanics of the human tongue, triboelectric components have been incorporated into E-tongue platforms to overcome these limitations. In this study, an integrated multichannel triboelectric bioinspired E-tongue (TBIET) device was developed on a single glass slide chip to improve the device’s taste classification accuracy by utilizing numerous sensory signals. The detection capability of the TBIET was further validated using various test samples, including representative human body, environmental, and beverage samples. The TBIET achieved a remarkably high classification accuracy. For instance, chemical solutions showed 100% identification accuracy, environmental samples reached 98.3% accuracy, and four typical teas demonstrated 97.0% accuracy. Additionally, the classification accuracy of NaCl solutions with five different concentrations reached 96.9%. The innovative TBIET exhibits a remarkable capacity to detect and analyze droplets with ultrahigh sensitivity to their electrical properties. Moreover, it offers a high degree of reliability in accurately detecting and analyzing various liquid samples within a short timeframe. The development of a self-powered portable triboelectric E-tongue prototype is a notable advancement in the field and is one that can greatly enhance the feasibility of rapid on-site detection of liquid samples in various settings.

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.

Determination of organic acids for predicting sourness intensity of tea beverage by liquid chromatography-tandem mass spectrometry and chemometrics methods.

The contents of organic acids (OAs) in tea beverage and their relationship with taste intensity have not been fully understood. In this work, a rapid (10min for a single run) and sensitive (limits of quantification: 0.0044-0.4486µg/mL) method was developed and validated for the simultaneous determination of 17 OAs in four types of tea, based on liquid chromatography-tandem mass spectrometry with multiple reaction monitoring mode. The contents of 17 OAs in 96 tea samples were measured at levels between 0.01 and 11.80g/kg (dried weight). Quinic acid, citric acid, and malic acid were determined as the major OAs in green, black, and raw pu-erh teas, while oxalic acid and tartaric acid exhibited the highest contents in ripe pu-erh tea. Taking the OAs composition as input features, a partial least squares regression model was proposed to predict the sourness intensity of tea beverages. The model achieved a root-mean-square error of 0.58 and a coefficient of determination of 0.84 for the testing set. The proposed model provides a theoretical way to evaluate the sensory quality of tea infusion based on its chemical composition.