Search Results (113)

Black tea is widely consumed worldwide, and its characteristic taste and color result from fermentation, where polyphenols are enzymatically oxidized to generate major pigments, including theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). This study investigated the effects of increased oxygen treatment during fermentation on the flavor attributes and chemical properties of Congou black tea. Fresh tea leaves (variety “Fuyun 6”) were subjected to four oxygen treatments: 0 h (CK), 1 h (TY-1h), 2 h (TY-2h), and 3 h (TY-3h), with oxygen supplied at 8.0 L/min. Sensory evaluation revealed that oxygen-treated samples exhibited tighter and deeper-colored leaves, a redder liquor, fuller taste, and a sweeter fragrance compared with CK. Chromatic analysis showed significant increases in redness (a*) and luminance (L*), alongside reduced yellowness (b*), indicating enhanced liquor color. Chemical analyses demonstrated elevated levels of TFs, TRs, and TBs in oxygen treatments, with TRs showing the most pronounced increase. Non-targeted metabolomics identified 2318 non-volatile and 761 volatile metabolites, highlighting upregulated flavonoids, phenolic acids, and lipids, and downregulated catechins and tannins, which collectively contributed to improved taste and aroma. Optimal results were achieved with 2–3 h of oxygen treatment, balancing pigment formation and sensory quality. These findings can provide a scientific basis for optimizing oxygen conditions in black tea fermentation to improve product quality. Full article

Polyphenol oxidase (PPO) is a metalloproteinase widely present in plant organelles that plays crucial roles in photosynthesis, pest and disease resistance, growth and development, and flower color formation. Due to the high cost and reuse difficulties of plant PPO in applications, immobilization has emerged as a key technology to improve its stability, recyclability, and reusability. Immobilized plant PPO has been widely used in environmental and detection fields. This review examines different immobilization methods and carrier materials for plant PPO and summarizes its applications in wastewater treatment, biosensor detection, food preservation, and theaflavin synthesis. Finally, current challenges and future opportunities for immobilized plant PPO are discussed. Full article

Background/Objectives: Ultraviolet B (UVB) radiation contributes significantly to skin aging and skin disorders by promoting oxidative stress, inflammation, and collagen degradation. Natural antioxidants such as theaflavins and thearubigins from Camellia sinensis L. (black tea) have shown photoprotective effects. This study aimed to optimize the extraction of theaflavins and thearubigins from black tea leaves and evaluate the efficacy of the extract against UVB-induced damage using a transfersome-based topical formulation. Methods: Extraction of theaflavins and thearubigins was optimized via response surface methodology (Box-Behnken Design), yielding an extract rich in active polyphenols. This extract was incorporated into transfersomes that were characterized for size, polydispersity, zeta potential, storage stability, and entrapment efficiency. Human dermal fibroblasts (NHDF) were used to assess cytotoxicity, protection against UVB-induced viability loss, collagen degradation, and expression of inflammatory (IL6, COX2, iNOS) and matrix-degrading (MMP1) markers. Cellular uptake of the extract’s bioactive marker compounds was measured via LC-MS/MS. Results: The transfersomes (~60 nm) showed a good stability and a high entrapment efficiency (>85%). The transfersomes significantly protected NHDF cells from UVB-induced cytotoxicity, restored collagen production, and reduced gene expression of MMP1, IL6, COX2, and iNOS. Cellular uptake of key extract’s polyphenols was markedly enhanced by the nanoformulation compared to the free extract. Conclusions: Black tea extract transfersomes effectively prevented UVB-induced oxidative and inflammatory damage in skin fibroblasts. This delivery system enhanced bioavailability of the extract and cellular protection, supporting the use of the optimized extract in cosmeceutical formulations targeting photoaging and UV-induced skin disorders. Full article

Significant research has been carried out on the applications of imaging and spectroscopy technologies for a variety of foods and agricultural products, and the technical fundamentals and their feasibilities have also been widely demonstrated in the past decade. Imaging technologies, including computer vision, Raman, X-ray, magnetic resonance (MR), fluorescence imaging, spectroscopy technology, as well as spectral imaging technologies, including hyperspectral or multi-spectral imaging, have found their applications in non-destructive tea quality assessment. Tea quality can be assessed by considering their external qualities (color, texture, shape, and defect), internal qualities (contents of polyphenols, amino acids, caffeine, theaflavin, etc.), and safety. In recent years, numerous studies have been published to advance non-destructive methods for assessing tea quality using imaging and spectroscopy technologies. This review aims to give a thorough overview of imaging and spectroscopy technologies, data processing and analyzing methods, as well as their applications in tea quality non-destructive assessment. The challenges and directions of tea quality inspection by using imaging and spectroscopy technologies for future research and development will also be reported and formulated in this review. Full article

Diabetes is one of the major non-communicable diseases whose physiological complications are linked with a higher risk of mortality amongst the adult age group of people living globally. This review article documents updated pharmacological evidence and insights into the antidiabetic mechanisms of green, black, white, oolong, and pu-erh teas via reported experimental and clinical models toward encouraging their use as a complementary nutraceutical in managing the biochemical alterations found in the onset and progression of diabetes. Peer-reviewed articles published in “PubMed”, “Google Scholar”, and “ScienceDirect” from 2010 and beyond that reported the antidiabetic, antilipidemic, and digestive enzyme inhibitory effects of the selected tea types were identified. The keywords used for the literature search comprise the common or scientific names of the tea and their corresponding bioactivity. Although teas portrayed different antidiabetic pharmacological properties linked to their bioactive components, including polyphenols, polysaccharides, and amino acids, the type of phytochemical found in each tea type depends on their processing. Green tea’s strong carbohydrate digestive enzyme inhibitory effect was linked with Ellagitannins and catechins, whereas theaflavin, a main ingredient in black tea, increases insulin sensitivity via enhancing GLUT4 translocation. Theabrownin in pu-erh tea improves FBG and lipid metabolism, while chemical components in white tea attenuate prediabetes-mediated reproductive dysfunctions by improving testicular tissue antioxidant capabilities. Based on the body of findings presented in this article, it is evident that integrating tea intake into daily food consumption routines could offer a promising practical solution to support human health and well-being against diabetes disease. Full article

This study aims to investigate the effects of theaflavins on production performance and egg quality in laying hens fed oxidized corn gluten meal while evaluating their antioxidant and anti-apoptotic effects on granulosa cells (GCs) from chicken follicles. In total, 600 Lohmann commercial laying hens, aged 64 weeks, were randomly assigned to four treatment groups: a control group, a theaflavin-supplemented group, an oxidized corn gluten meal group, and a combination group. After 8 weeks of feeding, production performance, egg quality, and antioxidant status, along with GC apoptosis and the antioxidant capacity of eggs, were measured. The results demonstrated that oxidized corn gluten meal significantly reduced production performance, antioxidant capacity, and egg quality in laying hens while increasing GC apoptosis. Theaflavin significantly enhanced egg production during weeks 5–8, along with superoxide dismutase activity in the liver, serum, and ovary, alongside egg white reducing power and egg yolk threonine content (p < 0.05). Additionally, theaflavin decreased feed conversion ratios during weeks 5–8 and 1–8, lowered egg white malondialdehyde content (p < 0.05), and inhibited GC apoptosis. In conclusion, oxidized protein reduced production performance, while theaflavin supplementation partially alleviated its adverse effects. Full article

Tea blending technology is based on finished tea. Blending fresh leaves during processing has not been proposed and investigated anywhere. This study investigates the impact of blending fresh leaves from different varieties on the flavor quality of black tea. The main taste components, including catechins, theaflavins, and free amino acids, were analyzed using HPLC, while the volatile components were analyzed using GC-MS. The results show that adding fresh Jinguanyin or Jinxuan leaves to Fudingdabai can regulate the ratio of esterified to non-esterified catechins, increase the content of theaflavins and amino acids, and positively impact the strength and freshness of the black tea. The sensory evaluation results show that the taste scores of FJG (black tea made from the blend of fresh Fudingdabai and Jinguanyin tea leaves) (92.14 ± 0.41 b) and FJX (black tea made from the blend of fresh Fudingdabai and Jinxuan tea leaves) (93.80 ± 0.19 a) are significantly higher than those of Fudingdabai (90.05 ± 0.31 d), Jinguanyin (86.10 ± 0.45 e), and Jinxuan (91.03 ± 0.26 c). Furthermore, adding fresh Jinguanyin or Jinxuan leaves to Fudingdabai can also enhance the floral compounds in the black tea, specifically phenylacetaldehyde, linalool, benzyl alcohol, and oxidized linalool (linalool-type pyran), which make important contributions to the floral aroma of the black tea. Conclusions: Blending fresh leaves for processing can enhance the sensory quality of black tea. This work proposes new insights and methods to enhance black tea sensory quality via the blending of fresh tea leaves with different varieties during processing. Full article

The pile-fermentation conditions and raw materials used play a vital role in determining the stability and quality of dark tea. In this study, sensory quality evaluation, metabolomics, and microbiomics techniques were used to investigate the effect of pile-fermentation duration on the taste quality of single-cultivar large-leaf dark tea (SLDT) and its underlying metabolite and microbial mechanisms. The study revealed that a 60-day duration resulted in a better SLDT sensory quality, with astringency and bitterness significantly reduced and sweetness increased. Catechins and theaflavins with ester structures, L-epicatechin, methyl gallate, protocatechuic acid, gallic acid, salicin, chlorogenic acid, and neochlorogenic acid were key taste metabolites contributing to the reduction of astringency and bitterness. Salicylic acid and D-sorbitol helped form the sweetness. Correlation analysis found out Aspergillus, Thermomyces, Bacillus, Staphylococcus, and Micrococcaceae were core functional microorganisms linked to these metabolites, helping to foster the higher quality of SLDT. Microorganisms shaped the taste quality of SLDT through metabolic processes and enzyme secretion during pile-fermentation. This study provided insights into the metabolite basis and microbiological mechanisms of SLDT taste formation and offered guidance for optimizing production processes to improve the stability and quality of dark tea. Full article

Theaflavins, as key bioactive compounds of black tea, are garnering increasing attention. However, research predominantly focuses on theaflavin monomers derived from the enzymatic oxidation of cis-type catechins. In this study, we identify a unique stereoisomer of theaflavin-3-gallate (TF-3-G), named isoneoTF-3-G, in black tea from Camellia ptilophylla (C. ptilophylla), which is rich in trans-catechins. IsoneoTF-3-G, a characteristic theaflavin of C. ptilophylla black tea, is formed by the oxidation of gallocatechin gallate and catechin. It exhibits a bright orange–red color and shows an [M+H]⁺ ion at m/z 717.1449 in positive electron spray ionization-mass spectrometry. Furthermore, isoneoTF-3-G demonstrates potent inhibitory effects on the proliferation of human colorectal carcinoma HCT116 cells, with a half-inhibitory concentration of 56.32 ± 0.34 μM. This study reveals that the mitochondrial pathway is involved in the apoptosis induction of HCT116 cells by isoneoTF-3-G. Specifically, isoneoTF-3-G leads to increased reactive oxygen species in HCT116 cells, decreased mitochondrial membrane potential, and the consequent release of cytochrome c from the mitochondria to the cytosol, activating caspase-9 and caspase-3, which further promotes the cleavage of poly(ADPribose) polymerase. The results of this study enhance our understanding of the composition and synthesis mechanisms of theaflavins and provide foundational evidence for the further development of isoneoTF-3-G and C. ptilophylla. Full article

At present, the heavy bitter taste, poor flavor quality and low functional activity of summer and autumn tea are the bottleneck problems restricting the low utilization rate of summer and autumn tea resources. The research and development of new products of fruit-flavored black tea is conducive to expanding the utilization of summer and autumn tea resources. Different kinds of fruit juice were added during the fermentation and processing of classic black tea, such as bananas, apples, fragrant pear and Sydney pear, in this study. The effects of fruit juice on the flavor quality and amylase inhibitory activity of fruity black tea were researched. The sensory quality, flavor chemicals and α-amylase inhibitory activity were evaluated. The results showed that the sensory evaluation scores of black tea treated with fruit juice were significantly higher than those of black tea treated without fruit juice, especially the crown pear juice. The amylase inhibition rate of black tea treated with fruit juice was significantly higher than the control treated without fruit juice (p < 0.05). The sensory evaluation scores, polyphenol oxidase activity, water extract content, soluble sugar content, free amino acid content, theaflavin content, thearubigin content and inhibition rate of amylase activity of black tea treated with pear juice were significantly higher than those of the apple and banana juices (p < 0.05), especially crown pear juice. Tea polyphenol content and theaflavin content of black tea treated with added pear juice were significantly lower (p < 0.05) than the black tea control treated with added apple juice and banana juice, especially crown pear juice. The fruity black tea treated with crown pear juice had a redder broth, more pronounced sweet fruit aroma, sweet and mellow taste and reduced astringency. Therefore, the black tea treated with crown pear juice was preferred. The research hopes to provide a theoretical basis for the research of black tea quality control and the research of summer and autumn tea resources utilization technology. Full article

Background: Black tea processing conditions significantly affect the final taste and flavor profiles, so researchers are now focusing on developing equipment and improving the appropriate processing conditions of major black tea varieties. Methods: Here, we tested the effect of four different initial drying temperatures, i.e., R65 (65 °C), R85 (85 °C), R105 (105 °C), and R125 (125 °C), on the sensory and biochemical profiles and volatilome of the black tea variety “Lishui wild” (LWV). Results: Our results indicate that both 85 and 105 °C are better than 65 and 125 °C for initial drying for 20 min. R105 had the highest sensory evaluation scores due to better shape, aroma, taste, leaf base, thearubigins, theanine, caffeine, and ratio of theaflavins + thearubigins to theaflavins. Both R85 and R105 had higher catechins than R65 and R125. The LWV volatilome consisted of esters (19.89%), terpenoids (18.95%), ketones (11.3%), heterocyclic compounds (9.99%), and alcohols (8.59%). In general, acids, aldehydes, amines, aromatics, ethers, hydrocarbons, phenols, sulfur compounds, and terpenoids accumulated in higher amounts in R85 and R105. The highly accumulated compounds in R105 were associated with green, fruity, sweet, woody, floral, hawthorn, mild, nutty, powdery, rose, and rosy flavors. The main pathways affected are secondary metabolites, sesquiterpenoid and triterpenoid biosynthesis, glycerolipid metabolism, zeatin biosynthesis, phenylpropanoid biosynthesis, ABC transport, glutathione metabolism, etc. Therefore, R105 can be used to achieve the optimal taste, flavor, and aroma of LWV. Conclusions: Overall, the presented data can be used by the tea industry for processing black tea with the most optimum volatile substances, catechins, theanine, amino acids, and other compounds. Full article

The treatment of black tea fermentation with different exogenous tannases was investigated, and processing parameters during black tea fermentation, including fermentation time, fermentation temperature, and exoenzyme amounts, were optimized, while the consumption and transformation pathways of catechins were analyzed. The results showed that tannase from Aspergillus niger was ultimately selected as the optimal enzyme to effectively increase the content of theaflavins by promoting the hydrolysis reaction and benzoylation reaction of catechins, resulting in a greater theaflavin (TF) content of 1.41%. The optimal processing conditions were found to be a fermentation time of 3 h, a fermentation temperature of 20 °C, and 1 g of tannase for 300 g of rolled tea leaves. Processing with the exogenous tannase could provide an ideal choice for the efficient utilization of summer and autumn fresh tea leaves, and could be used to develop summer and autumn black tea and to improve the content of theaflavins. It could also be used to develop deep processing of tea products with theaflavin extracts in the future. Full article

Liver cancer is one of the most prevalent cancers worldwide. The first-line therapeutic drug sorafenib offers only a moderate improvement in patients’ conditions. Therefore, an approach to enhancing its therapeutic efficacy is urgently needed. It has been revealed that hepatocellular carcinoma (HCC) cells with heightened intracellular quiescin sulfhydryl oxidase 1 (QSOX1) exhibit increased sensitivity to sorafenib. QSOX1 is a secreted disulfide catalyst, and it is widely recognized that extracellular QSOX1 promotes the growth, invasion, and metastasis of cancer cells through its participation in the establishment of extracellular matrix. Inhibiting QSOX1 secretion can increase intracellular QSOX1 and decrease extracellular QSOX1. Such an approach would sensitize HCC cells to sorafenib but remains to be established. Since (−)-epigallocatechin-3-gallate (EGCG) has been demonstrated to be an effective inhibitor of α-fetal protein secretion from HCC cells, we screened QSOX1 secretion inhibition using polyphenolic compounds. We examined eight dietary polyphenols (EGCG, quercetin, fisetin, myricetin, caffeic acid, chlorogenic acid, resveratrol, and theaflavin) and found that EGCG and quercetin effectively inhibited QSOX1 secretion from human HCC cells (HepG2 or Huh7), resulting in high intracellular QSOX1 and low extracellular QSOX1. The combination of EGCG or quercetin, both of which change the cellular distribution of QSOX1, with sorafenib, which has no influence on the cellular distribution of QSOX1, exhibited multiple synergistic effects against the HCC cells, including the induction of apoptosis and inhibition of invasion and metastasis. In conclusion, our current results suggest that dietary EGCG and quercetin have the potential to be developed as adjuvants to sorafenib in the treatment of HCC by modulating the cellular distribution of QSOX1. Full article

Lichuan black tea (LBT) is a well-known congou black tea in China, but there is relatively little research on its processing technology. Echa No. 10 is the main tea tree variety for producing LBT. This study investigated the sensory quality, flavor components, and bioactivity of Echa No. 10 Lichuan black tea (LBT) at different drying temperatures (70, 80, 90, 100, 110, 120, and 130 °C). During 80–120 °C, increasing the drying temperature enabled a higher sweet aroma concentration and enhanced the sweetness in the taste, in contrast to reducing the floral, fruity, and sweet aromas, and increasing the bitterness and astringency, at >120 °C. Additionally, with an increasing drying temperature, the contents of tea polyphenols and total catechins significantly decreased, with the theaflavins decreasing first and then increasing, and the alcohols, aldehydes, esters, and hydrocarbons increasing first and then decreasing. Meanwhile, compounds (including linalool, (Z)-linalool oxide (furanoid), (E)-linalool oxide (furanoid), cis-β-Ocimene, and methyl salicylate) contribute more to the floral and fruity aromas at <110 °C. Furthermore, low-temperature drying favors the antioxidant and inhibitory effects of the α-amylase, α-glucosidase, and glucose absorption activity. Both the tea quality and bioactivity results revealed 80–110 °C as the optimal drying temperature range for LBT. Full article

Camellia sinensis tea has received considerable attention due to its beneficial effects on health, particularly due to its antioxidant properties that are affected by several factors, which have a high influence on the final quality of black tea. The objective of this study was to investigate the biological properties of Azorean C. sinensis black tea from five different zones of tea plantation in order to select specific areas to cultivate tea rich in targeted compounds beneficial to human health. The free radical scavenging activity (FRSA), ferric reducing antioxidant power (FRAP), ferrous ion chelating (FIC) activities, total phenolic content (TPC), total flavonoid content (TFC), and tannins were determined by colorimetric methods, and catechin and theaflavin contents were analyzed by high-pressure liquid chromatography. The results indicated that samples from Zone E (341 m above the sea level) presented higher values of FRSA (EC₅₀ = 7.22 µg/mL), FRAP (EC₅₀ = 9.06 µg/mL), and FIC activities (79.83%) and higher values of total phenolics (264.76 mg GAE/g DE) and almost all catechins. For TFC, the values were very similar between zones, and for theaflavins content, Zone A showed the best levels, followed by Zone E. In general, these results clearly highlight that altitude plays a significant role in enhancing certain compounds of tea, thereby influencing its quality. Full article