Compound-specific hydrogen isotope analysis of lignin methoxy groups for tea provenance discrimination: Comparison with dual-water equilibration.

Cyclic cataluminescence (CCTL) is an emerging strategy that extends the principles of cataluminescence (CTL). The catalyst constitutes a critical component in CTL sensing systems. Currently, the development of innovative sensing systems and the elucidation of sensing mechanisms to enhance CTL remain significant challenges. Herein, we designed a heterogeneous electron allocator catalyst and a circulating flow system-assisted CTL for enhancing sensitivity and response speed. MgO/Y2O3 heterogeneous catalysts were employed as electron allocators and decorated on CNTs, and the resulting MgO/Y2O3/CNT catalyst was coupled with the CCTL method for the catalytic detection of multiple aldehydes. By fitting the variation of the peak intensity (In) of CCTL with time (t), the characteristic attenuation coefficient (k) value was calculated, and the k value could be used for qualitative analysis. The comprehensive k values of aldehydes contained characteristic information of tea. The k values of 61 tea samples were obtained by the CCTL method, and the k values of different tea species and origins were different from 2.0 to 41. Moreover, linear discriminant analysis and hierarchical cluster analysis were used to further process the CCTL data. This research provided a new perspective on CTL through designing a heterogeneous electron allocator catalyst and a circulating flow system.

Epigallocatechin (EGCG) is the predominant polyphenol compound of green tea. It is also reactive during processing and can form new catechin derivatives by reacting with other metabolites. In this study, two novel EGCG derivatives (EGCG-CAs) formed by conjugating caffeic acid (CA) were identified in green tea. Through the stimulated reaction, the formation of EGCG-CAs was systematically studied. The highest yield of EGCG-CAs was achieved when the initial mass ratio of EGCG to caffeic acid was 1:1 at 120 °C for 90 min. Quantitative analysis on tea samples undergoing processing revealed that EGCG-CAs were mainly formed at the fixation stage. Their contents were increased significantly after final drying. Based on sensory evaluation, it was indicated that S-configuration of 2‴ showed a higher threshold than that of R-configuration, suggesting that the methylene configuration of the caffeic acid moiety in EGCG-CA may be associated with the bitter taste threshold.

Modulator-driven pore engineering of tunable and scalable ternary ZIF-8/ZnO/Ag2O nanocomposite for electrochemical sensing of catechol oxidation marker in tea samples.

Oxides of cerium and manganese have been extensively employed in catalytic reactions due to their redox versatility. In the present study, pristine CeO2, Mn3O4 and mixed metal oxides (with Ce : Mn in ratios 2 : 1, 1 : 1 and 1 : 2) were synthesized via a facile sol-gel auto-combustion method and evaluated as polyphenol oxidase (PPO) mimics. Comprehensive structural and morphological characterization was performed using XRD, XPS, BET, TEM, SEM-EDX and EIS. Manganese doping modulated the Ce3+/Ce4+ ratio and enhanced electron transfer ability and surface area. Manganese oxide (Mn3O4) displayed the highest PPO-mimicking activity, as corroborated by structural studies. The reaction parameters, namely, pH, substrate concentration, contact time, temperature and catalytic dose, were optimized to achieve maximum activity. Michaelis-Menten kinetic studies confirmed the highest Vmax and Km for pristine Mn3O4 (Km = 0.84 mM) and the lowest for pristine CeO2 (Km = 3.48 mM), indicating enhanced substrate affinity of Mn3O4 NPs. A colorimetric sensing assay employing 3,3',5,5'-tetramethylbenzidine was used for the determination of catechol (LOD = 3.25 μM) and resorcinol (LOD = 6.9 μM) with low detection limits. Furthermore, the study was successfully extended to the detection of polyphenols in green tea and wine samples. The results correlated with the conventional Folin-Ciocalteu assay with the added advantages of fast detection, sensitivity and reusability of NPs. Thus, the present study demonstrates the potential of Mn3O4 NPs for the colorimetric detection of polyphenols.

Gallic acid (GA) modulates the flavor, aging, and fermentationdegree of traditional Chinese tea. Herein, hierarchically porous FeNi-CNF (PFeNi-CNF) nanozymes were fabricated via electrospinning and carbonization for GA detection, utilizing differential thermal decomposition kinetics of carbon precursors. The hierarchical porous structure optimizes mass transfer and facilitates active site formation, which endows PFeNi-CNF with 3.22-fold peroxidase-like activity compared to FeNi-CNF (calculated based on the absorbance values), as well as outstanding long-term stability and cycling durability. A highly selective and sensitive GA colorimetric sensor was developed with an LOD of 0.02 μM and a linear range of 0.05-3 μM. Machine learning model-assisted tea sample analysis (based on R, G, B, H, S, V values) was performed (highest accuracy of 99%), providing a fast, accurate, and convenient GA sensing platform for detection, recognition, and prediction of biosensing and food technology.

本文针对制药工程专业本科实验教学需求，设计了一套基于QuEChERS-GC-MS联用技术检测茶叶中联苯菊酯农药残留的实验方案。实验内容包括样品前处理、QuEChERS实验条件的单因素筛选和响应面法优化、GC-MS分析方法建立、茶叶样品中联苯菊酯农药残留的测定以及实验数据处理等环节，旨在培养学生综合运用现代分析技术解决实际问题的能力。通过该实验，学生可以掌握GC-MS仪器设备的基本原理和操作技能，了解真实样品中农药残留分析的完整流程，体会样品前处理对复杂体系中痕量组分分析的重要性。在单因素实验选择的QuEChERS实验条件下，茶叶样品中联苯菊酯的回收率为85.9%；在响应面法优化的QuEChERS实验条件下，茶叶样品中联苯菊酯的回收率可达90.33%。在38份茶叶样品中，有12份样品检测出了联苯菊酯，最大检出值为0.911 mg/kg，均未超出食品安全国家标准GB 2763-2021规定的茶叶中联苯菊酯的最大残留限量。本教学设计包括实验前相关内容学习、实验中操作技能训练和实验后数据分析，不仅能激发学生的学习兴趣，还能培养学生严谨的科学思维，让学生在全流程学习过程中主动面对问题，积极分析问题，设法解决问题。

Catechol, a prevalent phenolic pollutant in food products, poses a significant threat to food safety, necessitating the development of rapid and sensitive detection methods. To overcome the limitations of conventional analytical techniques, such as expensive equipment and operational complexity, electrochemical sensors have gained considerable attention owing to their rapid response and facile miniaturization. However, the rational design of sensing materials that exhibit both high sensitivity and selectivity remains a significant challenge. Herein, a series of PdCu bimetallic nanoparticles supported on reduced graphene oxide (PdCu@rGO) composites with varying Pd/Cu molar ratios was synthesized via a one-step liquid-phase reduction method. Owing to the synergistic electronic effects between Pd and Cu and the high electrical conductivity of the rGO support, the resulting nanocomposites exhibited excellent electrocatalytic activity toward catechol oxidation. At the optimal Pd/Cu molar ratio of 1:2, the fabricated Pd1Cu2@rGO/SPE sensor demonstrated a broad linear range of 0.5–500 μM, a low limit of detection of 200 nM (S/N = 3), good repeatability (RSD = 4.9%), and robust anti-interference capability. Furthermore, the proposed sensor was successfully applied to the detection of catechol in spiked green tea and fruit juice samples without complex pretreatment, achieving satisfactory recoveries of 91.0–101.4% and 98.6–104.8%, respectively. This work provides a reliable platform for the rapid, on-site screening of catechol in food matrices and offers valuable experimental insights into the rational design of bimetallic alloy–graphene heterostructures.

Aptamer-functionalized Fe3O4-BR@Hemin nanozyme for the ultrasensitive colorimetric detection toward Staphylococcus aureus.

This study investigated the effects of different brewing conditions on the sensory and chemical properties of Turkish black tea and examined the relationships among the related parameters. The brewing variables evaluated were teapot type, brewing method, teapot spout condition, brewing time, and brewing water temperature. The brewed tea samples were evaluated by seven trained panelists for colour, astringency, and flavour and analysed for major chemical quality parameters, including total phenolic content (TPC), caffeine, theaflavins (TF), thearubigins (TR), brew colour indices, and L*a*b values. A total of 2,688 cups of brewed black tea were prepared, of which 672 were control and 2,016 were test samples, and were evaluated by seven trained panelists. Among the sensory attributes, colour was the most responsive parameter, being significantly affected by teapot type and brewing water temperature (p < 0.01), whereas astringency and flavour were not significantly influenced by the tested brewing conditions. In the chemical analyses, brewing water temperature was the most influential factor, significantly affecting TPC, caffeine, TF, TR, total colour in the brew, brightness in the brew, and a* (p < 0.01). Teapot type, brewing method, teapot spout condition, and brewing time also showed selective effects on specific chemical variables. Correlation analysis further showed that sensory colour was positively associated with TPC, caffeine, TF, TR, brightness in the brew, and total colour in the brew (p < 0.01), whereas astringency and flavour showed limited or no direct associations with the analysed chemical parameters. By examining Turkish-style brewing variables together with sensory and chemical profiling, this study provides novel evidence on sensory-chemical relationships in black tea and offers practical guidance for optimising brewing conditions in research and traditional tea preparation.

Tea contains a structurally diverse family of polyphenols, and subtle variations in their molecular architecture critically influence their biochemical activity. Yet resolving such closely related analogs remains an ongoing analytical challenge. Here, we report a single-molecule structure-response framework for identifying tea polyphenols using a phenylboronic acid-functionalized nanopore. Variations in hydroxylation pattern, galloylation, and stereochemistry produce reproducible ionic current fingerprints that correspond to defined diol binding sites, allowing for unambiguous differentiation of eight structurally similar catechins. With the aid of machine-learning-based classification, an identification accuracy of 96.9% is achieved. Beyond discrimination, this platform enables rapid polyphenol profiling from tea samples within 30 min, as well as single-molecule monitoring of polyphenol-metal interactions. By establishing a direct link between electrical signatures and specific binding states, this work extends nanopore sensing from molecular detection toward real-world applications and the mechanistic interrogation of complex natural products.

Antioxidants play a crucial role in human health, yet their simultaneous identification and quantification remain a significant challenge due to their structural similarities and overlapping reductive potentials. Herein, we report a surface-dominated, tunable two-dimensional metal-organic framework (2D MOF) nanozyme array for smartphone-integrated intelligent discrimination of multiple antioxidants. Distinct from conventional 3D and bulk MOFs with limited surface sites, the ultrathin 2D structure offers highly exposed catalytic centers, facilitating rapid signal response and enhanced sensitivity. By strategically varying the metal centers, we engineered a series of 2D MOF nanozymes with metal-dependent and differentiated catalytic gradients, providing the essential cross-reactivity for multicomponent analysis. The varied inhibitory effects of antioxidants on the peroxidase-like activities of 2D MOF nanozymes generate high-dimensional colorimetric fingerprints, uniquely resolving seven antioxidant analytes. Furthermore, a smartphone-based digital platform was established for real-time RGB value extraction and then integrated with machine learning algorithms to enable on-site analysis. Such a platform achieved high performance in identifying not only individual antioxidants but also complex binary and ternary mixtures. The practical utility of the platform was further validated in juice, black tea, and wine samples, demonstrating its excellent anti-interference capability in real-world matrices. This study highlights that the surface-dominated catalytic mode of 2D MOF nanozymes not only offers a great blueprint for designing low-cost, high-throughput, and intelligent sensing platforms for antioxidant identification but also shows great promise for the development of high-fidelity sensing arrays in food safety, environmental surveillance, and precision healthcare.

Teas processed from specialty-colored tea leaves possess distinctive quality profiles shaped by their volatile and non-volatile compounds, which serve as critical metrics for evaluating tea cultivars. In this study, we comprehensively characterized the quality attributes of flat green teas produced from three tea cultivars—green-leaved ‘FDDB’, yellow-leaved ‘ZH2’, and purple-leaved ‘ZJ’—using an integrated analytical approach including sensory evaluation, widely targeted metabolomics, GC-E-nose, and HS-SPME-GC-MS. Sensory evaluation revealed distinct sensory characteristics among teas processed from the three cultivars with different leaf colors. GC-E-nose analysis further confirmed that the aroma profiles of these tea samples could be clearly distinguished based on leaf color. Metabolomic analysis identified a total of 2050 non-volatile compounds, among which 18 amino acids, 5 phenolic acids, and 4 flavonoids were pinpointed as key contributors to the unique taste profiles of infusions from ZH2 and ZJ teas. Additionally, a total of 1100 volatile compounds were detected, with 94, 75, and 90 key aroma-active compounds identified in FDDB, ZH2, and ZJ teas, respectively. Collectively, in this study, systematic analysis revealed significant differences in both volatile and non-volatile chemical compositions across the three tea cultivars. These findings provide a scientific foundation for understanding the processing suitability and quality formation mechanisms of tea cultivars with distinct leaf colors.

BackgroundCamellia sinensis, a vital cash crop in southwest China, makes Guizhou Province renowned for its premium zinc-selenium (Zn-Se)-enriched tea. While soil trace elements influence tea plant growth and quality, previous studies have predominantly focused on geochemical features, leaving gaps in understanding their distribution in tea plantations, transfer to tea plants, and specific impacts on tea quality. This study investigates trace element distribution in the rock-soil-tea system across Guizhou’s major tea-growing regions, assesses their effects on tea quality, and identifies key factors regulating soil element levels, aiming to underpin the expansion of high-quality Zn-Se tea production and sustainable regional economic development.MethodsDrawing on a prior survey of 146 surface soil (0 ∼ 20 cm) samples from Guizhou tea gardens, 36 representative tea gardens spanning 12 local tea-producing areas were chosen for field research. Soil profile samples (0 ∼ 20 cm, 20 ∼ 40 cm, 40 ∼ 60 cm) and tea leaves were collected to analyze the spatial variability of major minerals (aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), phosphorus (P), potassium (K), sulfur (S)) and trace elements (manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), germanium (Ge), selenium (Se), strontium (Sr)), as well as trace element bio-accumulation and their correlations with tea quality. Soil and rock samples were digested with aqua regia, tea samples with concentrated HNO3, and elemental concentrations were quantified using inductively coupled plasma mass spectrometry (ICP-MS).ResultsResults revealed significant spatial heterogeneity in soil trace elements (Mn, Cu, Zn, Mo, Ge, Se, Sr), with Cu and Se showing the highest variability, followed by Zn and Sr, then Mn and Mo, while Ge exhibited the least variation. In surface soils, Se concentrations ranged from 0.23 to 1.50 mg kg−1 and Zn from 33.0 to 105.6 mg kg−1; 69.4% of surface soils met Se-enriched standards, but only 33.3% reached Zn-Se-enriched levels. Strong positive correlations were detected between soil and parent rock contents of Mn, Cu, Zn, Mo, Se, and Sr, particularly for Se and Cu. Geological age and parent rock type were identified as dominant factors shaping soil Zn and Se levels, with synergistic interactions among elements further promoting their enrichment in soils. Trace element levels in tea leaves varied markedly across regions (P < 0.01), with Se showing the highest variability, followed by Zn and Sr. Biological accumulation coefficients ranked as Mn > Zn > Cu > Se > Sr > Ge > Mo. Zn and Se contents in leaves were strongly correlated with corresponding soil concentrations (P < 0.01), especially for Se. Leaf Se ranged from 0.05 to 0.54 mg kg−1, and Zn from 24.4 to 97.2 mg kg−1. Among samples, 25.0% met the threshold for Se-enriched tea and 22.2% for Zn–Se co-enriched tea, with the latter showing clear geographic clustering consistent with soil Zn and Se distribution.

In this study, an aerosol-jet-printed silver micropillar array was introduced onto the surface of a screen-printed carbon electrode (SPCE) and further coated with a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) functional film, yielding a three-dimensional hierarchical electrode for high-performance electrochemical detection of niclosamide (NA). The silver micropillar arrays form a three-dimensional microelectrode network on the working electrode surface, where the pillar tops and sidewalls markedly increase the electrochemically active area and facilitate mass transport toward the electrode interface, thereby enhancing analyte flux and amplifying the Faradaic response. In addition, PEDOT:PSS as a mixed ionic-electronic conductor, establishes a continuous and stable reaction interface on the silver-pillar scaffold, which not only improves interfacial wettability and charge/ion transport but also promotes interfacial enrichment of NA via its functionalized polymer network. Benefiting from the synergistic effects of three-dimensional structural amplification and conductive-polymer-mediated interfacial regulation, the fabricated Ag@PEDOT:PSS/SPCE sensor exhibits a good linear response over 0.01-15 μM with a limit of detection as low as 1.73 nM. Meanwhile, the sensor demonstrates excellent repeatability, reproducibility, and anti-interference performance, and it was successfully applied to the quantitative determination of NA in tap water and oolong tea samples with satisfactory recoveries and accuracy, indicating strong potential for practical applications.

Anhua dark tea, a protected geographical indication product in Hunan, China, derives its value from specific mountain micro-terroirs, including Furongshan, Gaoma Erxi, and Yuntaishan. Across these areas, micro-terroir and cultivar variations impart distinctive chemical components to the decisive raw material (locally known as Hei Mao Cha). For the authentication of these specific origins, we developed a rapid HPLC-DAD method coupled with the ATLD algorithm, enabling the quantification of caffeine and seven major flavan-3-ols within five minutes. Our method achieved satisfactory accuracy, with average recoveries of 84.73–119.88% and RMSEP values ranging from 0.28 to 4.39 μg/mL. We subsequently applied PCA and FCA, which revealed distinct clustering patterns of the tea samples by their mountain origin. Notably, Furongshan and Gaoma Erxi exhibited markedly distinct chemical profiles, while Yuntaishan showed intermediate characteristics. This integrated HPLC-DAD/ATLD protocol, coupled with non-linear t-distributed stochastic neighbor embedding (t-SNE) followed by random forest (RF) classification (validation accuracy: 85.7%), offers a practical solution for the fine-scale geographical traceability of raw dark tea, supporting quality control and providing insights into how micro-terroir shapes tea chemistry. This approach can be readily adapted for the authentication of other geographical indication products.

The warm and smooth taste, combined with the pleasant sweet aroma, are unique quality characteristics of Pingyang Huangtang (PYHT) tea. However, the potential to refine the quality through agricultural practices remains poorly explored. In this study, a one-year field experiment was conducted in the core production region of PYHT tea to assess the impacts of organic fertilizer substitution on tea quality. The experiment consisted of three fertilization regimes: T0 (pure chemical fertilizer), T1 (chemical fertilizer with rapeseed cake), and T2 (chemical fertilizer with newly organic fertilizer). Through sensory evaluation, determination of major biochemical components, and GC-MS analysis of aromatic compounds, combined with multivariate statistical methods, results showed that varied fertilization treatments significantly affected the aroma quality of PYHT tea, as indicated by T2 scoring the highest, surpassing the T0 and T1 scores, whereas no significant differences were observed in appearance, taste, liquor color, infused tea, or total score. Compared with chemical fertilization, organic fertilizer substitutes significantly reduced the total content of ammonia acids, a change primarily attributed to the decrease in the Thea, Arg, and Val levels, while the tea polyphenols and caffeine had no significant differences among treatments. GC-MS and multivariate analysis identified five key volatiles as octan-1-ol, linalool, geraniol, benzeneacetaldehyde, and δ-cadinene that differentiated the tea samples’ aroma profile. The distinct abundance patterns of these compounds are likely responsible for a fresher and more pronounced floral style of T2 tea, compared to the slightly less fresh floral notes of T0 tea and the stuffy floral expression of T1 tea. In summary, the research findings offer actionable guidelines for fertilizer application to PYHT tea production, improving aroma quality and increasing its overall market value.

Water and food safety have become increasingly important in recent years. Endocrine disrupting compounds, such as Bisphenol A (BPA) and other chemicals, mimic natural hormones and cause hormonal imbalances, leading to various health disorders. This study proposes straightforward, accurate, and sensitive dispersive liquid-liquid microextraction (DLLME) for the preconcentration of BPA before its determination by gas chromatography-mass spectrometry (GC-MS). Critical parameters affecting the extraction efficiency were optimized, including the type and amount of extractant solvent, the type and amount of dispersant solvent, buffer pH, and salt effect. The detection and quantification limits for BPA were 0.54 and 1.80 ng/mL, respectively. Calibration plot for BPA demonstrated good linearity. Recovery studies conducted with spiked bottled natural spring water and iced tea samples yielded recoveries of 91 and 97%, respectively. Various commercial demijohn and polyethylene terephthalate (PET) bottled spring water, PET and tin cola, soda, and fruit juice samples were analyzed using the optimized method.

Dietary factors play an important role in cognitive health during aging. Dark tea has shown potential cognitive benefits, but its key bioactive component and underlying mechanisms remain unclear. In a naturally aged C57BL/6J mouse model, instant dark tea (IDT) samples with different fermentation degrees were evaluated together with behavioral outcomes using composition–effect relationship analysis. This analysis identified theabrownin (TB) as the component most strongly associated with improved cognitive performance. Compared with aged controls, TB increased Y-maze spontaneous alternation from 51.91% to 71.59% and reduced escape latency on day 5 of the Morris water maze from 44.84 s to 26.59 s. In contrast, the corresponding TB-depleted fraction produced no comparable cognitive improvement. TB also alleviated hippocampal injury and neuroinflammation. Antibiotic treatment abolished the cognitive benefits of TB, whereas fecal microbiota transplantation partially restored them. Multi-omics analyses suggested that TB treatment was associated with gut microbiota remodeling and increased serum acetate and 3-hydroxybutyrate; both metabolites partially recapitulated these benefits. Together, these findings show that TB attenuates age-related cognitive decline in naturally aged mice and suggest that modulation of gut microbiota and metabolites may contribute to this effect, supporting its potential as a functional food ingredient for healthy brain aging.

Occurrence profiles of 43 minerals in different types of Tibetan tea determined by ICP-MS and the associated risk assessment