Search Results (1,787)

Eight different types of tea bags were investigated in this work using dynamic light scattering, electrophoretic mobility and nanoparticle tracking analysis methods to determine the concentration and size of released particles from the bag materials at different temperatures and times. Infrared spectroscopy and calorimetric methods confirmed that the bag material consisted of synthetic (nylon or polypropylene) or natural polymers (cellulose). The size of the released particles lies in the range of 200 nm^–1 µm with an initial bimodal distribution and with an average diameter of about 600 nm. The concentration of released particles increases with increasing temperature and brewing time. The released particles of synthetic polymers remain quite stable and are not affected by natural enzymes, while cellulose particles are easily degraded by the proteolytic complex Morikrase. When analyzing the electrophoretic mobility, it was found that the released particles have a negative surface charge, which probably determines the absence of cytotoxicity established on the epithelial cell line Caco-2 even at the maximum values of the observed particle concentrations (14 × 10⁹ particle/L for synthetic polymers and 170 × 10⁹ particle/L for cellulose). Full article

White tea quality is primarily determined by its chemical composition, which varies significantly among cultivars. This study aimed to elucidate the chemical basis underlying quality differentiation in Baimudan white tea produced from three major Fujian tea cultivars: “Zhenghe Dabaicha” (ZHDB), “Fuan Dabaicha” (FADB), and “Fuding Dahaocha” (FDDH). Headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS), liquid chromatography–mass spectrometry (LC-MS), and quantitative descriptive analysis (QDA) were employed to characterize volatile compounds, amino acids, and saccharides. Odor Activity Values (OAVs) and Taste Activity Values (TAVs) were calculated to identify key contributors to sensory perception. Results showed that theanine, glutamic acid, asparagine, and serine were the primary contributors to umami taste, especially in ZHDB and FADB. Sweetness differences were largely due to sucrose, serine, and asparagine. OAV analysis further identified 22 critical aroma compounds: methyl salicylate, linalool, and β-ionone predominantly imparted floral notes, while β-ocimene, benzaldehyde, and geraniol enhanced sweet and fruity aromas. In contrast, (Z)-3-hexenol, (Z)-3-hexenal, and (E)-2-hexenal contributed grassy and refreshing characteristics, together defining the unique aroma profiles of each cultivar. This study provides an integrated chemical and sensory framework for understanding white tea quality variation, offering a theoretical basis for targeted flavor modulation. Full article

The effects of soil acidification on the phoD-harboring microbial community and the fractions of soil phosphorus in tea plantation soils are still unclear. In this study, tea plantations with different soil pH were used as the research object to analyze changes in soil phosphorus fractions, phoD gene abundance, phoD-harboring microbial community composition, and their relationship with tea yield and quality. The results showed that the content of tea polyphenols, caffeine, free amino acids, theanine, and tea yield decreased significantly after acidification. Moreover, the content of total phosphorus in the acidified soil also decreased significantly. Further analysis of soil phosphorus fractions showed that the acidification of the tea plantation soil resulted in a significant decrease in the content of different types of labile and moderately labile phosphorus, whereas the content of non-labile phosphorus exhibited the opposite trend. As the content of soil NaHCO₃-Po, NaOH-Po, Resin-Pi, NaHCO₃-Pi, NaOH-Pi, and HCl-Pi decreased significantly after acidification, its organic and inorganic phosphorus content also decreased significantly. Its phosphorus activation capacity decreased by 4.75% after soil acidification. Soil acidification significantly reduced the diversity of phoD-harboring microbial communities by 61.89%. Analysis of the phoD-harboring microbial community composition suggested that the microbial abundance of Acidobacteria and Proteobacteria showed a decreasing trend in acidified soils, while for Nitrospirae, Verrucomicrobia, Actinobacteria, and Planctomycetes, it showed an increasing trend. Correlation analysis showed that microorganisms with significantly decreasing abundance in tea plantation soils were significantly and positively correlated with soil pH, labile phosphorus, moderately labile phosphorus, phosphorus activation coefficients, and tea yield and quality after soil acidification. It is evident that soil acidification inhibited soil phosphorus availability by shifting phoD-harboring microbial community composition in tea plantation soils, thus affecting the yield and quality of above-ground tea leaves. Full article

This study investigates the evolution of the chemical components of kombucha aroma during refrigerated storage. Two preparation methods (MT1 and MT2) were used to produce kombucha from a 1:1 mixture of black and green tea. The bottled beverages were stored at 4 °C for three months, and changes in headspace (HS) volatiles were monitored at different time points using solid-phase microextraction (SPME) and GC-MS. A total of 68 volatile substances were identified, with alcohols, acids, and esters dominating the aroma profile. The study revealed significant changes in flavor composition during cold storage, particularly in the first two weeks, with an increase in the number of esters, acids, ketones and terpenoids, as well as the total amount of esters and alkanols. While some changes contribute to the desirable “cider-like” characteristics, others, like certain volatile acids, aliphatic aldehydes and ketones, are associated with off-flavors. These findings suggest that refrigeration alone is not sufficient to completely inhibit microbial activity in freshly prepared kombucha, highlighting the need for further research to correlate chemical changes with sensory properties to establish optimal organoleptic standards and shelf life. Full article

The impregnation and curing process of dry bushing requires the epoxy material for bushing to have a good process performance. In addition, the actual operating conditions of dry bushing put forward high requirements on the dielectric properties of the epoxy material. Amine accelerators can not only improve the technological properties of epoxy materials such as gel time and curing exothermic temperature rise by regulating the reaction rate of epoxy resin and anhydride curing agent, but also optimize the dielectric properties of epoxy materials by regulating the crosslinking density of epoxy materials. However, there are many types of amine accelerators, and the effects of amine accelerators with different nucleophilicity on epoxy materials vary greatly. In this paper, four kinds of amine accelerators with different nucleophilic ability were selected to study the influence of the nucleophilic ability of amine accelerators on the process and dielectric properties of epoxy materials. The results show that the stronger the nucleophilicity of the amine accelerator, the shorter the gel time of the epoxy mixture and the higher the exothermic temperature rise during curing, indicating a poorer processing performance. However, stronger nucleophilicity also endows the epoxy material with superior dielectric properties. Among them, the strong nucleophilic ability of TEA shortens the gel time of the material by 50% and increases the curing exothermic temperature rise by 55.3% compared with the weak nucleophilic ability of the DET epoxy system; the dielectric constant and dielectric loss of the material are reduced by 8.3% and 39.5%, respectively, and the breakdown strength is improved by 11.4%. This paper reveals the contradictory relationship between the process and dielectric performance of epoxy materials triggered by the difference in the nucleophilic ability of amine accelerators, and it also provides a new research idea for the improvement of the process and in the dielectric performance of epoxy materials for dry bushing. Full article

This study investigated the physicochemical properties of Camellia oleifera husks collected from three regions of Jiangxi Province (Ganzhou—GZ, Yichun—YC, and Jiujiang—JJ) and extracted tea saponins via microwave-assisted solvent extraction (MASE), aiming to provide a theoretical basis for the high-value utilization of this agricultural by-product. The husks from YC were rich in bioactive compounds such as tea saponins (16.29 ± 0.02%), with lower cellulose (21.05 ± 1.05%) and lignin (12.48 ± 1.14%) contents and higher hemicellulose (27.40 ± 0.80%) content. The husks from JJ exhibited abundant porosity and a larger specific surface area (40–60 mesh, 4.15 ± 0.04 m²/g). Single-factor extraction experiments indicated that the microstructure and chemical composition of Camellia oleifera husks significantly affected the extraction efficiency of saponins, tannins, and flavonoids. The optimal extraction conditions for tea saponins were established using Box–Behnken response surface methodology, with the liquid-to-solid ratio identified as the most critical factor. Optimal conditions for GZ husks were a liquid-to-solid ratio of 46.75 mL/g, ethanol concentration of 35.5%, extraction time of 6 min, and microwave power of 350 W, with the extraction yield of 7.49 ± 0.01%. Optimal conditions for YC husks were a liquid-to-solid ratio of 50.55 mL/g, ethanol concentration of 40.13%, extraction time of 6 min, and microwave power of 350 W, with the extraction yield of 16.29 ± 0.02%. Optimal conditions for JJ husks were a liquid-to-solid ratio of 47.44 mL/g, ethanol concentration of 37.28%, extraction time of 6 min, and microwave power of 350 W, with the extraction yield of 9.39 ± 0.02%. The study provides important scientific evidence for understanding the structure–function relationship of Camellia oleifera husks and offers practical guidance for developing sustainable industrial processes to convert agricultural by-products into high-value bioactive compounds, thereby promoting resource recycling and economic benefits in the Camellia oleifera industry. Full article

Scopula subpunctaria (Herrich-Schaeffer), is a significant insect pest affecting tea plantations in China; however, its thermal developmental characteristics remain inadequately understood. This study examined the immature developmental stages of S. subpunctaria under eight constant temperature regimes (13, 16, 19, 22, 25, 28, 31, and 33 °C) in controlled laboratory conditions. Results indicated an inverse relationship between temperature and the total duration of the immature stages (egg to pupa), with developmental time decreasing from 105.8 days at 13 °C to 29.3 days at 31 °C. Specifically, the developmental durations for eggs, larvae, and pupae ranged from 5.4 to 20.3 days, 15.4 to 52.3 days, and 8.1 to 33.3 days, respectively, in 13 °C to 31 °C temperature range. Using an ordinary linear model, the estimated lower developmental threshold temperatures were 8.61 °C for eggs, 8.40 °C for larvae, 9.39 °C for pupae, and 8.85 °C for the total immature stage, with corresponding thermal constants of 114.94, 302.11, 149.93, and 558.99 degree-days (DD), respectively. Comparative analysis of eleven nonlinear models revealed substantial variation in estimates of lower and upper temperature thresholds, while estimates of optimal temperatures showed minor differences. Based on statistical criteria and biological relevance, the Briere-2 model was selected to characterize egg development, the Lactin-1 model for larval development, and the Briere-1 model for pupal and total immature stages. Stage transition models for eggs, larvae, pupae, and the total immature period were constructed using a two-parameter Weibull function integrated with the respective nonlinear models. This study provides foundational insights into the thermal developmental characteristics of S. subpunctaria and offers predictive tools for forecasting stage-specific emergence in tea plantations. Full article

Aimed at addressing the increasingly serious problem of adulteration in Xihu Longjing, a catechin-targeted nano-enhanced visual and fluorescent dual-mode sensor array was constructed by nano porphyrins and quantum dots (QDs) for the precise analysis of Xihu Longjing from adjacent origins. This sensor array realizes the quantitative analysis of catechin enantiomers in Xihu Longjing through the selective combination of sensing units. It can accurately identify adjacent Xihu Longjing teas with different grades and storage times and can precisely detect samples with a low proportion of adulteration. At the same time, the flavor quality and antioxidant performance of Xihu Longjing tea can also be quantitatively evaluated. The dual-mode sensor array design proposed in this study provides a new idea for detecting minor differences in food authenticity and has significant application value for quality control in the tea industry. Full article

Accurate identification of tea plant varieties during the harvest period is a critical prerequisite for developing intelligent multi-variety tea harvesting systems. Different tea varieties exhibit distinct chemical compositions and require specialized processing methods, making varietal purity a key factor in ensuring product quality. However, achieving reliable classification under real-world field conditions is challenging due to variable illumination, complex backgrounds, and subtle phenotypic differences among varieties. To address these challenges, this study constructed a diverse canopy image dataset and systematically evaluated 14 convolutional neural network models through transfer learning. The best-performing model was chosen as a baseline, and a comprehensive optimization of the training strategy was conducted. Experimental analysis demonstrated that the combination of Adamax optimizer, input size of 608 × 608, training and validation sets split ratio of 80:20, learning rate of 0.0001, batch size of 8, and 20 epochs produced the most stable and accurate results. The final optimized model achieved an accuracy of 99.32%, representing a 2.20% improvement over the baseline. This study demonstrates the feasibility of highly accurate tea variety identification from canopy imagery but also provides a transferable deep learning framework and optimized training pipeline for intelligent tea harvesting applications. Full article

Both China and Korea have significant markets for tea; however, both the availability and preference for oolong and black oolong tea vary across the two markets. Although this difference has been highlighted in previous studies, the group differences in the two markets based on preferences and sensory perceptions have not been assessed. Therefore, this study aimed to investigate the overall oolong and black oolong tea preferences based on specific characteristics of the tea samples and the sensory perceptions of young Chinese and Korean consumers residing in South Korea. Twelve tea samples were selected for on-site evaluations. A Check-All-That-Apply (CATA) method with 20 sensory characteristics was used to identify the sensory characteristics perceived, supplemented by intensity ratings for key attributes. The CATA-Penalty analysis revealed sensory characteristics that significantly impacted overall liking. The results indicated that while Chinese and South Korean consumers exhibited some differences in overall preference trends, they shared similar preferences within specific tea categories. This reflects differences in preferences between Chinese and South Korean consumers for oolong and black oolong tea beverages and the possible impact of different cultural backgrounds on consumption habits. These findings provide insights into cross-cultural sensory preferences and the impact of the cultural background on tea beverage perception. Full article

The genus Camellia offers valuable resources for tea production, oil extraction, and ornamental purposes, and its applications are expanding beyond traditional regions due to increasing human demands and advancements in research. To explore new therapeutic resources and identify key active metabolites, we conducted a non-targeted metabolomics analysis on three camellias. We also utilized network pharmacology to identify the potential targets of key metabolites involved in anti-inflammatory, antioxidant, antibacterial, and antiviral effects. A total of 385 significantly different metabolites were identified, with organic acids and derivatives, lipids and lipid-like molecules, and phenylpropanoids and polyketides being the top three metabolite classes. Of the 71 different phenylpropanoids and polyketides identified, 54 were common across all three cultivars, while 17 were unique. Network pharmacology further identified 78 potential molecular targets associated with the four therapeutic activities under study. Seven flavonoid glycosides, two flavans, two biflavonoids/polyflavonoids, and one flavone were highlighted as key active metabolites. Notably, Camellia japonica ‘Kōshi’ emerged as a promising material for future applications. The key active ingredients may contribute to the development of novel approaches for cosmetic, food, and medicinal applications, as well as germplasm innovation for new functional camellias. Full article

Tea is a global commodity, and due to its way of preparation pesticide residues cannot be tolerated. This underlines the importance of non-chemical pest control. Kenya is the third largest global tea producer but the potential of natural enemies against tea pests is unknown. We used artificial caterpillars made of non-drying green plasticine to quantify attack rates by predators on tea canopies at different distances from plantation edges and in the nearby native forest during the wet and dry seasons in three tea-growing mountain regions of Kenya, Kericho, Gatamaiyu and Kakamega. The artificial sentinel caterpillars were readily attacked by arthropods, birds, and sporadically by small mammals. During an exposure time of 24 h, the overall attack rate was 25.0%d⁻¹. Natural enemy activity was higher in the dry (35.3%d⁻¹) than in the wet (16.7%d⁻¹) season. The highest predation pressure was measured in the native forest (41.7%d⁻¹) and gradually decreased with increasing distances into the tea plantation (to 8.3%d⁻¹ at 40 m from the edge). The rate of decrease from the forest edge towards the centre of the tea plantation was steeper for birds than for arthropods, indicating that birds were more reluctant to use this habitat. The potential for natural pest control in Kenyan tea plantations is high, but planting native trees is recommended especially if bird activity inside tea plantations is to be encouraged. Full article

Furniture surfaces are prone to the accumulation of bacteria, fungi and other micro-organisms, especially in humid environments such as kitchens and bathrooms. The antimicrobial treatment of coatings has been demonstrated to enhance the performance of wood, prolong its service life, and improve hygiene and safety. Consequently, by investigating the most effective preparation process for antimicrobial microcapsules and incorporating them into the coating, the coating can be endowed with antimicrobial properties, thereby expanding its application range. Microcapsules were prepared using a composite wall material consisting of chitosan (CS) and Arabic gum (AG), with tea tree essential oil (TTO) serving as the core material. The best CS-AG coated TTO microcapsules were prepared when the core–wall ratio was 1.2:1, the emulsifier concentration was 2%, the pH was 3, and the mass ratio of AG to CS (m_AG:m_CS) was 3:1. The m_AG:m_CS was identified as the most significant factor affecting the microcapsule yield and encapsulation rate. With the increase in m_AG:m_CS, the antimicrobial rate of the coating against Escherichia coli (E. coli) exhibited a trend of first rising and then falling, while the antimicrobial rate against Staphylococcus aureus (S. aureus) demonstrated a trend of first rising, then falling, and then rising again. The colour difference (ΔE) and gloss exhibited an overall downward trend, the light loss rate demonstrated a fluctuating upward trend, and the roughness exhibited a trend of first falling and then rising. The visible light band transmittance exhibited minimal variation, ranging from 86.43% to 92.76%. Microcapsule 14# (m_AG:m_CS = 3:1) demonstrated remarkable antimicrobial properties (E. coli 65.55%, S. aureus 73.29%), exceptional optical characteristics (light transmittance 92.12%, 60° gloss 24.0 GU), and notable flexibility (elongation at break 18.10%, modulus 0.10 GPa). The waterborne coating was modified by microcapsule technology, thus endowing the coating with antimicrobial properties and concomitantly broadening the scope of application of antimicrobial microcapsules. Full article

The contents of secondary metabolites such as tea polyphenols, amino acids, caffeine, and volatile metabolites in fresh tea leaves are key factors determining the unique flavor and health attributes of finished tea products. However, differences in varieties, cultivation practices, and environmental conditions often lead to variations in these metabolites among fresh tea leaves, thereby affecting tea quality. In order to clarify the various internal and external factors that influence the formation of the quality of fresh tea leaves and their mechanism of action. This article mainly reviews the research on fresh leaf quality in the past decade. Firstly, it clarifies the molecular basis of metabolic differences among varieties. Then, it summarizes the regulatory mechanisms of underground (soil, microorganisms) and above-ground (light, temperature, humidity) environments on key metabolic pathways, and focuses on evaluating the effects of intercropping, fertilization, and other cultivation measures on improving tea quality. This review found that the specific gene expression of varieties, the transmission of environmental signals, and cultivation interventions jointly drive the synthesis and accumulation of tea polyphenols, amino acids, caffeine, and aroma substances. However, no one has ever systematically reviewed it. Therefore, it provides certain theoretical references for improving the quality of fresh leaves. Full article

Direct Contact Membrane Distillation–Crystallization (DCMD-Cr) is a synergistic technology for zero liquid discharge (ZLD) and resource recovery from high-salinity brines. In this study, DCMD-Cr was integrated to desalinate real oilfield-produced water (PW) with an initial salinity of 156,700 mg/L. The PW was concentrated to its saturation point of 28 wt.% via DCMD, and the integrated crystallization increased the overall water recovery from 42.0% to 98.9%, with a decline in water flux and salt rejection, mainly due to vapor pressure lowering and scaling. The precipitated salts in the crystallization unit were recovered and identified using different techniques. The results indicated that 91% of the crystals are sodium chloride, and less than 5% are calcium sulfate. A techno-economic analysis (TEA) was performed to evaluate the economic feasibility of the integrated DCMD-Cr process with a 500,000 gallons per day (GDP) capacity. The results showed that the crystallization operating cost was dominant at USD 0.50 per barrel, while the capital cost was only USD 0.04 per barrel. The economic viability can be enhanced by recovering value-added byproducts and using renewable or waste heat, which can reduce the total cost to USD 0.50 per barrel. Full article