Theaflavin Content Research Articles

Effects of tea and coffee on tooth discoloration

Tooth discoloration because of dietary habits is a serious concern, particularly from tea and coffee consumption. This study investigated the effects of these beverages on tooth discoloration, focusing on their key chemical components. Bovine enamel specimens were immersed in green and black tea samples and Arabica and Robusta coffee samples for 1–72 h. High-performance liquid chromatography analyzed catechins, theaflavins, and chlorogenic acids, while spectrophotometry measured discoloration. Multiple regression analysis (significance at p < 0.05) revealed that all beverages caused significant tooth discoloration, with black tea showing the most pronounced effect because of its theaflavin content.

High-throughput screening, “protein–metabolite” interaction, and hypoglycemic effect investigations of α-amylase inhibitors in teas using an affinity selection-mass spectrometry method

Tea is consumed worldwide and can reduce the risk of diabetes whereas the hypoglycemic compounds in tea remain unclear. Herein, the chemical compositions comparison and inhibition assays indicated that the inhibitory effect of tea against α-amylase was positively related with the enzyme-mediated oxidation degree of tea and black teas containing high contents of theaflavins exhibited the strongest in vitro inhibitory effect. Affinity selection-mass spectrometry-based high-throughput screening revealed that four theaflavins specifically bind to α-amylase. Compared to other compounds, theaflavins showed one order of magnitude higher in vitro inhibitory effects; thus, theaflavins are possibly the dominant α-amylase inhibitors in tea. A series of “α-amylase–theaflavins” interaction studies jointly demonstrated that theaflavins noncompetitively inhibit α-amylase activity by interacting with the amino acid residues of α-amylase and then inducing changes in the secondary structure. Furthermore, theaflavins (10 mg/kg/d) and black tea extracts (100 mg/kg/d) exhibited comparable hypoglycemic effects as acarbose in diabetic mice.

Effect of tea green leafhopper (Empoasca onukii Matsuda) sucking on the quality of Oriental Beauty

AbstractThis study aimed to investigate the effects of tea green leafhopper damage on the sensory quality and metabolite composition of Oriental Beauty by using tea leaves from different varieties of tea plants and processing factories. The results indicated that tea green leafhopper damage could reduce bitterness and increase the level of fruity aroma, which was related to the content changes of catechin components and alcohol substances. Furthermore, the tea green leafhopper salivary treatment experiment revealed that the decrease of catechin content and increase of theaflavin content were mainly influenced by the action of saliva and mechanical injury, and changes in volatile components such as linalool oxidation were responsible for the alteration in aroma. These findings provide a theoretical reference for the aroma formation and quality improvement of Oriental Beauty.

Re-rolling treatment in the fermentation process improves the taste and liquor color qualities of black tea

Fermentation is a vital process occurred under the premise of rolling affecting black tea quality. Theoretically, re-rolling during fermentation will remodel the biochemical conditions of tea leaves, and thus influence black tea quality. Herein, we studied the effect of re-rolling on black tea taste and liquor color. Sensory evaluation showed that re-rolling significantly weakened the astringency taste and improved the redness and luminance of liquor. With re-rolling, the color attributes of a* and L* and the contents of theaflavins and thearubigins were significantly improved. Metabolomics analysis showed that the contents of 110 non-volatile compounds were significantly different among black teas with different rolling treatments. In summary, re-rolling accelerated the oxidation of polyphenols into pigments, the hydrolysis of proteins into amino acids, and the metabolism of alkaloids, organic acids, glycosidically-bound volatiles, and lipids during the fermentation period. Our study provided a novel and simple way to improve black tea quality.

Effects of Pulsed Electric Field Pretreatment on Black Tea Processing and Its Impact on Cold-Brewed Tea.

This study applied pulsed electric fields (PEFs) to accelerate the withering and drying processes during cold-brewed black tea production. PEF pretreatment was administered at 1.0, 1.5, and 2.0 kV/cm electric field strengths, combined with varying withering times from 8 to 12 hr. During the 12-hour withering process, the redness value (a*) and total color change (∆E) of PEF-treated leaves significantly increased (p < 0.05). Furthermore, the homogenous redness of tea leaves during fermentation depended on the PEF strength applied. In addition, PEF pretreatment remarkably reduced the drying time, up to a 50% reduction at a 2.0 kV/cm field strength. Additionally, the 2.0 kV/cm PEF-pretreated black tea exhibited a notable 42% increase in theaflavin (TF) content and a 54% increase in thearubigin (TR) content. Sensory evaluation scores were highest for black tea that received PEF pretreatment at 2.0 kV/cm. These findings highlight the significant potential of PEFs in enhancing the efficiency of withering and drying processes while positively impacting the physicochemical and sensory properties of cold-brewed black tea.

The Impact of Different Withering Process Conditions on the Bioactivity and Quality of Black Tea from Azorean Camellia sinensis

The objective of this study was to investigate the variability of natural bioactive compounds, such as catechin, theaflavin, total phenolic content (TPC), and total flavonoid content (TFC), of Azorean black tea (Camellia sinensis L., O. Kuntze) as well as its antioxidant activities according to different withering times. The TPC, TFC, free radical scavenging activity (FRSA), ferric reducing antioxidant power (FRAP), and ferrous-ion-chelating (FIC) activities were determined by colorimetric methods, and catechin and theaflavin contents were analyzed by high-pressure liquid chromatography (HPLC). The FRSA shows similar results for the withering range of 6 to 16 h (hours). For FRAP, the best results were observed at 16 h, and for FIC, the highest value was at 20 h. The TPC and TFC showed the highest value at 9 h and the lowest at 20 h. For the total theaflavins, the highest results were obtained after 12 h of withering, and the lowest values were obtained at 16 and 20 h. According to the different withering times, the highest value of total catechin levels was at 12 h, while the lowest value was observed at 20 h. Regarding caffeine content, all samples presented similar results, with the exception of the 12 h time point. In conclusion, the best withering times were observed in the range of 9 to 16 h, showing decreased values at 20 h, with the exception of FIC.

서리피해 찻잎 활용 홍차의 성분 함량 및 맛 분석

The yield of premium green tea is reduced when the plants are exposed to abnormally low temperatures caused by climate change. In particular, the damage caused by frost is severe. All frost-damaged tea leaves are discarded after pruning. This study was conducted to partially reduce the decrease in farm household income caused by frost damage using these damaged tea leaves for black tea processing. Frost-damaged tea leaves were harvested in May 2022 and processed into black tea. The changes in the component content were investigated by analyzing the catechin, caffeine, theaflavin, and free amino acids and performing taste analysis using an electronic tongue. The total catechin content was 0.24% and 1.06% in the undamaged and frost-damaged black tea, respectively. The C (catechin) content was particularly high at 0.81% in the frost-damaged black tea. The caffeine levels in undamaged and frost-damaged black tea were 0.84% and 0.42%, respectively, showing an approximately 50% reduction of the caffeine content by frost damage. The total theaflavin content in undamaged and frost-damaged black tea was 0.24% and 0.13%, respectively. The total free amino acid content in undamaged and frost-damaged black tea was 714 mg/100 g and 1,122 mg/100 g, respectively, of which the γ-aminobutyric acid content in undamaged and frost-damaged black tea was 16.9 mg/100 g and 140.4 mg/100 g, respectively. Taste analysis using the electronic tongue revealed high AHS and CPS sensor values in undamaged black tea and high CTS, PKS, NMS, and SCS sensor values in frost-damaged black tea.

Antioxidant Capacity of Black Tea Obtained Using Tyrosinase and Tannase Treatment

Black tea has a lower antioxidant capacity than other teas, such as green tea, white tea, and oolong tea. Tannase and tyrosinase can be used as a treatment to improve the quality of black tea infusion. Tannase has been reported to be an effective way to enhance antioxidant activity in black tea infusion. Meanwhile, tyrosinase could produce higher theaflavin content than thearubigin. Research about Ready-to-Drink (RTD) black tea preparation with the addition of tannase and tyrosinase to fresh tea leaves before pasteurization has not been reported. This study aimed to find a good combination of tannase (1 mg/ml) and tyrosinase (111; 446; 1785 U/ml) to produce high antioxidant activity of RTD black tea. The results showed that higher tyrosinase concentration decreased the antioxidant activity (DPPH and reducing power), epicatechin (EC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG) content yet increased the theaflavin content and theaflavin (TF)/thearubigin (TR) ratio in the tannase-tyrosinase treated black tea. Still, the highest concentration of tyrosinase (1785 U/ml) in tannase-tyrosinase black tea produces higher antioxidant activities, gallic acid, EC, and EGC content than commercial black tea and tyrosinase without tannase-treated black tea. Thus, the combination of tannase (1 mg/ml) and tyrosinase (1785 U/ml) could be the best treatment to produce high-antioxidant black tea.

Effects of Key Components on the Antioxidant Activity of Black Tea.

Many components (such as tea polyphenols, catechins, theaflavins, theasinensins, thearubigins, flavonoids, gallic acid, etc.) in black tea have antioxidant activities. However, it is not clear which components have a greater influence on the antioxidant activity of black tea. In this study, the antioxidant activity and contents of tea polyphenols, catechins, theaflavins, thearubigins, theabrownins, TSA, total flavonoids, amino acids, caffeine, and total soluble sugar were analyzed in 51 black teas. Principal component analysis (PCA), orthogonal partial least-squares discrimination analysis (OPLS-DA), and the correlation analysis method were used for data analysis. The results showed that catechins in tea polyphenols were the most important components that determine the antioxidant activity of black tea. Among them, epicatechin gallate (ECG), epi-gallocatechin gallate (EGCG), epicatechin (EC), and epi-gallocatechin (EGC) were significantly positively correlated with the antioxidant activity of black tea, and theabrownin was negatively correlated with the antioxidant activity of black tea. Furthermore, this study analyzed the correlation between the changes in catechin and its oxidized polymers with antioxidant activity during black tea fermentation; it verified that catechins were significantly positively correlated with the antioxidant activity of black tea, and theabrownin showed a negative correlation. And the antioxidant activity of catechins and their oxidation products in vitro and their correlation in black tea processing were used as validation. This study provides a comparison method for comparing the antioxidant activity of black tea.

The Integration of Metabolomics, Electronic Tongue, and Chromatic Difference Reveals the Correlations between the Critical Compounds and Flavor Characteristics of Two Grades of High-Quality Dianhong Congou Black Tea.

Tea's biochemical compounds and flavor quality vary depending on its grade ranking. Dianhong Congou black tea (DCT) is a unique tea category produced using the large-leaf tea varieties from Yunnan, China. To date, the flavor characteristics and critical components of two grades of high-quality DCT, single-bud-grade DCT (BDCT), and special-grade DCT (SDCT) manufactured mainly with single buds and buds with one leaf, respectively, are far from clear. Herein, comparisons of two grades were performed by the integration of human sensory evaluation, an electronic tongue, chromatic differences, the quantification of major components, and metabolomics. The BDCT possessed a brisk, umami taste and a brighter infusion color, while the SDCT presented a comprehensive taste and redder liquor color. Quantification analysis showed that the levels of total polyphenols, catechins, and theaflavins (TFs) were significantly higher in the BDCT. Fifty-six different key compounds were screened by metabolomics, including catechins, flavone/flavonol glycosides, amino acids, phenolic acids, etc. Correlation analysis revealed that the sensory features of the BDCT and SDCT were attributed to their higher contents of catechins, TFs, theogallin, digalloylglucose, and accumulations of thearubigins (TRs), flavone/flavonol glycosides, and soluble sugars, respectively. This report is the first to focus on the comprehensive evaluation of the biochemical compositions and sensory characteristics of two grades of high-quality DCT, advancing the understanding of DCT from a multi-dimensional perspective.

RNA Methylome Reveals the m6A-mediated Regulation of Flavor Metabolites in Tea Leaves under Solar-withering

The epitranscriptomic mark N6-methyladenosine (m6A), which is the predominant internal modification in RNA, is important for plant responses to diverse stresses. Multiple environmental stresses caused by the tea-withering process can greatly influence the accumulation of specialized metabolites and the formation of tea flavor. However, the effects of the m6A-mediated regulatory mechanism on flavor-related metabolic pathways in tea leaves remain relatively uncharacterized. We performed an integrated RNA methylome and transcriptome analysis to explore the m6A-mediated regulatory mechanism and its effects on flavonoid and terpenoid metabolism in tea (Camellia sinensis) leaves under solar-withering conditions. Dynamic changes in global m6A level in tea leaves were mainly controlled by two m6A erasers (CsALKBH4A and CsALKBH4B) during solar-withering treatments. Differentially methylated peak-associated genes following solar-withering treatments with different shading rates were assigned to terpenoid biosynthesis and spliceosome pathways. Further analyses indicated that CsALKBH4-driven RNA demethylation can directly affect the accumulation of volatile terpenoids by mediating the stability and abundance of terpenoid biosynthesis-related transcripts and also indirectly influence the flavonoid, catechin, and theaflavin contents by triggering alternative splicing-mediated regulation. Our findings revealed a novel layer of epitranscriptomic gene regulation in tea flavor-related metabolic pathways and established a link between the m6A-mediated regulatory mechanism and the formation of tea flavor under solar-withering conditions.

The molecular mechanisms of quality difference for Alpine Qingming green tea and Guyu green tea by integrating multi-omics.

Harvest time represents one of the crucial factors concerning the quality of alpine green tea. At present, the mechanisms of the tea quality changing with harvest time have been unrevealed. In the current study, fresh tea leaves (qmlc and gylc) and processed leaves (qmgc and gygc) picked during Qingming Festival and Guyu Festival were analyzed by means of sensory evaluation, metabolomics, transcriptomic analysis, and high-throughput sequencing, as well as their endophytic bacteria (qm16s and gy16s). The results indicated qmgc possessed higher sensory quality than gygc which reflected from higher relative contents of amino acids, and soluble sugars but lower relative contents of catechins, theaflavins, and flavonols. These differential metabolites created features of light green color, prominent freshness, sweet aftertaste, and mild bitterness for qmgc. Flavone and flavonol biosynthesis and phenylalanine metabolism were uncovered as the key pathways to differentiate the quality of qmgc and gygc. Endophytic bacteria in leaves further influence the quality by regulating the growth of tea trees and enhancing their disease resistance. Our findings threw some new clues on the tea leaves picking to pursue the balance when facing the conflicts of product quality and economic benefits.

Neuroprotective effects of fermented tea in MPTP-induced Parkinson's disease mouse model via MAPK signaling-mediated regulation of inflammation and antioxidant activity

Parkinson’s disease (PD) is a neurodegenerative disorder that is characterized by dopaminergic neuronal damage. In this study, three tea extracts from Hadong, Korea, were evaluated in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity damage model (C57BL/6 mice) for their therapeutic effects against PD: green tea (GT), semi-fermented tea (SFT), and fermented tea (FT). Theaflavin content in the teas increased but catechin content decreased with the degree of fermentation. In addition, SFT showed the highest theanine and γ-aminobutyric acid contents. SFT at a concentration of 25 μg/mL showed the highest activity in the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay among all samples. Furthermore, the 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid radical scavenging activity of 25 μg/mL SFT was higher than that of l-ascorbic acid. Fermented tea suppressed the expression of inflammatory cytokines, such as interleukin-6, tumor necrosis factor-alpha, inducible nitric oxide synthase, cyclooxygenase-2, and macrophage-1, as well as inhibited overexpression of apoptotic signals, including p-53, cleaved caspase-3, and poly (ADP-ribose) polymerase-1. Moreover, GT, SFT, and FT regulated the MPTP-induced oxidative stress-related factors, including superoxide dismutase, glutathione-S-transferase, and nicotinamide adenine dinucleotide phosphate oxidase 4. Fermented tea also alleviated MPTP-induced behavioral impairment and dopaminergic neuronal damage and reduced α-synuclein levels. These results indicate that fermented tea is effective for the treatment of neuro-inflammatory, neuro-apoptotic, and neuro-oxidative disorders.

Pear polyphenol oxidase enhances theaflavins in green tea soup through the enzymatic oxidation reaction

AbstractPolyphenol oxidase (PPO) is a necessary medium for converting catechins into theaflavins in tea. This study aimed to provide an efficient and cost‐effective method for the purpose of developing a tea beverage rich in four main theaflavins (TFs) by optimizing the key factors affecting the enzymatic oxidation reaction to produce TFs. Autumn green tea (AT) soup was mixed with pear PPO crude enzyme solution and then reacted for different time at varying reaction temperatures, pH, ratios of tea soup to crude enzyme solution, and ratios of tea to water. The content of TFs in tea beverage was monitored by UPLC‐Q‐Orbitrap‐MS/MS to select the optimal process parameters to produce the maximum TFs. The TFs content after the reaction increased 968.49 times compared with that before the reaction. The results showed that the use of the enzymatic oxidation reaction of pear PPO crude enzyme solution to improve the TFs in AT soup was efficient. This method helped regulate the strong bitter and astringent taste sensation in AT, and it is unnecessary to purify the PPO enzyme source. This method is expected to be a breakthrough to use AT to produce high TFs tea beverages in a cost‐effective way with high value.

국내육성 차 품종별 홍차의 유효성분과 품질 특성 비교

This study was conducted to obtain basic data for the oxidated characteristics of tea cultivars in Korea. In particular, three kinds of cultivated green teas of Korea, namely Chamnok, Keumsull, and Beachwisull, were oxidized by the traditional sunburn Jaeksal method of Hadong area, Korea, and the oxidized teas were analyzed for their free amino acid content, taste, and aroma. When compared with landrace, a traditional tea cultivar of Korea, and used as a control in this study, the theaflavin content of the three kinds of teas in this study was higher, but their caffeine and free amino acid contents were lower. Furthermore, the total catechin content was the highest in Beachwisull (3.04 %) and the lowest in Chamnok (0.18 %). Likewise, the theaflavin content was the highest in Chamnok (0.54 %). Finally, astringency and taste after astringency were most significant in Beachwisull, and greenishness was the highest in Keumsull.

Dynamic changes in the diversity and function of bacterial community during black tea processing

Among all types of tea, black tea is produced in the largest amount worldwide, and its consumption is still increasing. Enzymatic fermentation is considered majorly contribute to quality formation of black tea, and the information about the roles of bacterial community in black tea processing is scarce. This study aimed to analyze the dynamic changes in composition, structure, and function of microbial communities during black tea processing and reveal the roles of bacterial community in black tea processing. Results showed that the genera Sphingomonas and Variovorax were dominant throughout the processing of black tea. Prediction function analysis of bacterial community showed that the mean proportions of glucuronoarabinoxylan endo − 1,4 − beta − xylanase, aminopeptidase B, phosphoserine phosphatase, homoserine O-acetyltransferase, glycolysis related enzymes, pyruvate dehydrogenase, tricarboxylic acid cycle related enzymes, and glyoxylate bypass were significantly elevated in the rolling and fermentation stages. The contents of amino acids, soluble sugar, theaflavins, thearubigins, and theabrownins increased greatly during the rolling and fermentation processes. Redundancy and Pearson’s correlation analyses showed that the relative abundance of bacteria was closely related to the contents of water extract, tea polyphenols, epigallocatechin, epicatechin gallate, catechin gallate, thearubigins, theaflavins, and theabrownins. Overall, the findings provided new insights into the variation of bacterial community during black tea processing and improved our understanding of the core functional bacteria involved in black tea processing.

Study into the chemical changes of tea leaf polyphenols during japanese black tea processing

During the processing of black tea, enzymatic oxidation converts tea catechins into a complex mixture of oxidative products, including theaflavins, and thearubigins. In this study, ultra-performance liquid chromatography was carried out to analyze the tea extracts collected after each processing stage to clarify the quantitative changes in these compounds during black tea processing. It was found that the catechin content was significantly reduced during processing, and in particular between the later rolling and fermentation periods. In contrast, the variation in the theaflavin content was negatively correlated with the catechin content. Twenty-three compounds containing the known catechins dimers and flavonol glycosides were identified by liquid chromatography–mass spectrometry (LC-MS). In addition, 45 components whose contents increased significantly between the late rolling and late fermentation stages were extracted using principal components analysis by LC-MS. It was considered that due to the catechin-like units present in these components, they likely contribute to thearubigin production during black tea processing.

건조방식에 따른 홍차의 성분과 맛 차이

The traditional black tea, called Jeaksal, has made by the method of oxidation under sunlight and consumed in the Hadong region from the past. This study compared the ingredients and quality (taste) of black tea according to drying methods. The highest and lowest levels of the caffeine were obtained in the black tea sun drying (BTSD, 1.93%), and black tea shade drying (BTSHD, 1.73%), respectively, as opposed to the highest total catechin levels in the BTSD (3.31%) and the lowest in the BTSHD (0.78%). The highest theaflavin content was detected in the black tea (BT) (control, 0.66%). We further confirmed that the free amino acid content decreased with delayed drying time and temperature. Total free amino acid was detected by the highest value in BTSD with 24.91 mg/g, but by lowest value in BTSHD with 11.45 mg/g. In the shade drying 'Jeaksal' sour, bitter and astringent taste were strongly detected, whereas salty, umami, richness (after-umami) taste were weakly measured. BT and black tea pot drying (BTPD) has a similar taste pattern overall because of the same pot-drying method.

Characterization and Analysis of Polyphenols in Green and Black Tea Brands Available in Commercial Market of Pakistan

In present study, the quality of commercial brands of green and black tea available in Pakistan was analyzed on the basis of phenolic contents. Total phenolic content was analyzed through spectrophotometric measurement using the ferrous Tartrate method. Individual catechins along with gallic acid and caffeine were determined using HPLC-UV. TPC of green tea was found to be higher than black tea. Among green tea brands, Lipton Clear Green showed higher TPC than Tapal Gulbahar. Both green and black tea polyphenols showed higher solubility in the aqueous acetone (50%, v/v) compared towater. (-)-EGCG was detected as the most abundant catechins in all green and black tea samples. Theaflavin content of Lipton Yellow Label and Vital was significantly higher than Tapal Family Mixture and Tetley. Based on catechins and theaflavins content, Lipton Clear Green, Lipton Yellow Label, and Vital Tea were considered to be of higher quality than other brands.

Application of Electronic Nose to Predict the Optimum Fermentation Time for Low-Country Sri Lankan Tea

The fermentation stage is vital during the black tea manufacturing process to produce the best-quality tea. The oxidation of tea biochemical compounds results in the appearance of characteristic smell peaks during the fermentation stage. These subtle changes in tea aroma are hard to detect unless one is a trained personnel. Here for the first time, we applied e-nose to monitor the fermentation process of Sri Lankan low-country tea. In this study, detection of smell peaks during fermentation was conducted by a custom-made e-nose (Digi-Nose) with four gas sensors. Singular value decomposition (SVD) is applied to eliminate the noise and dimensionality reduction in the sensor responses observed. The prediction of the time of appearance of smell peaks was conducted with a support-vector machine (SVM). Finally, theaflavin content with time was compared to validate the optimum fermentation times observed with an e-nose.