Oxygen-enriched fermentation improves the taste of black tea by reducing the bitter and astringent metabolites

Chen, Lin; Liu, Fei; Yang, Ying-Chun; Tu, Zheng; Lin, Jiazheng; Yang, Yalin; Xu, Ping

doi:10.1016/j.foodres.2021.110613

Cited by 45 publications

(28 citation statements)

References 20 publications

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“…In general, it was observed that TFs production initially increased and subsequently decreased, consistent with the results of Jiang et al 8 . and Chen et al ., 22 and lower temperatures favored high TFs and TSs production (Figs 4 and 5), which is closely associated with the changes in the catechin depletion rate and enzymatic activities at different temperatures 12 . During low‐temperature fermentation, a high PPO activity resulted in the gradual oxidation of various catechin components to TFs and TSs, whereas a low POD activity led to a lower rate of TFs polymerization to polymers, such as TRs and TBs.…”

Section: Discussionsupporting

confidence: 90%

New insights into the effect of fermentation temperature and duration on catechins conversion and formation of tea pigments and theasinensins in black tea

et al. 2021

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BACKGROUND The phenol oxidative pathway during fermentation remains unclear. To elucidate the effect of fermentation on phenol conversion, we investigated the effects of fermentation temperature and duration on the conversion of catechins and the formation of theasinensins (TSs), theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). RESULTS During fermentation, TSs formation increased initially and then decreased. Long fermentation durations were unfavorable for liquor brightness (LB) and resulted in the production of large amounts of TRs and TBs. Low fermentation temperatures (20 °C and 25 °C) favored the maintenance of polyphenol oxidase activity and the continuous formation of TFs, TSs, and TRSI (a TRs fraction), resulting in better LB and liquor color. Higher temperatures (30 °C, 35 °C, and 40 °C) resulted in higher peroxidase activity, higher oxidative depletion rates of catechins, and excessive production of TRSII (a TRs fraction) and TBs. Analysis of the conversion pathway of polyphenolic compounds during fermentation showed that, during early fermentation, large amounts of catechins were oxidized and converted to TFs and theasinensin B. As fermentation progressed, considerable amounts of theaflavin‐3′‐gallate, theasinensin A, theaflavin‐3‐gallate, theaflavin‐3,3′‐digallate, and theasinensin C were produced and then converted to TRSI; in the final stage, TRSII and TBs were converted continuously. CONCLUSION Different fermentation temperature and duration combinations directly affected the type and composition of phenolic compounds. The key conditions for controlling phenolic compound conversion and fermentation direction were 60 or 90 min and 25 or 30 °C. Our study provides insights into the regulation of phenolic compound conversion during black tea fermentation. © 2021 Society of Chemical Industry.

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Section: Discussionsupporting

confidence: 90%

New insights into the effect of fermentation temperature and duration on catechins conversion and formation of tea pigments and theasinensins in black tea

et al. 2021

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“…The reaction gradually changed from strong to moderate as fermentation continued. Thus, the quantity of catechins dropped dramatically over 0–2 h and then continued to decrease more slowly over 2–5 h [ 19 ]. Specifically, the EC component of the catechin content decreased by 96.28%, indicating that EC was the major component involved in the chemical reaction during fermentation.…”

Section: Results and Analysesmentioning

confidence: 99%

Nondestructive Testing and Visualization of Catechin Content in Black Tea Fermentation Using Hyperspectral Imaging

Dong

Yang

Liu

et al. 2021

Sensors

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Catechin is a major reactive substance involved in black tea fermentation. It has a determinant effect on the final quality and taste of made teas. In this study, we applied hyperspectral technology with the chemometrics method and used different pretreatment and variable filtering algorithms to reduce noise interference. After reduction of the spectral data dimensions by principal component analysis (PCA), an optimal prediction model for catechin content was constructed, followed by visual analysis of catechin content when fermenting leaves for different periods of time. The results showed that zero mean normalization (Z-score), multiplicative scatter correction (MSC), and standard normal variate (SNV) can effectively improve model accuracy; while the shuffled frog leaping algorithm (SFLA), the variable combination population analysis genetic algorithm (VCPA-GA), and variable combination population analysis iteratively retaining informative variables (VCPA-IRIV) can significantly reduce spectral data and enhance the calculation speed of the model. We found that nonlinear models performed better than linear ones. The prediction accuracy for the total amount of catechins and for epicatechin gallate (ECG) of the extreme learning machine (ELM), based on optimal variables, reached 0.989 and 0.994, respectively, and the prediction accuracy for EGC, C, EC, and EGCG of the content support vector regression (SVR) models reached 0.972, 0.993, 0.990, and 0.994, respectively. The optimal model offers accurate prediction, and visual analysis can determine the distribution of the catechin content when fermenting leaves for different fermentation periods. The findings provide significant reference material for intelligent digital assessment of black tea during processing.

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“…The chemical composition of tea, especially phenolic compounds, can vary according to geographic, genetic, ecological, physiological and processing factors ( Abdel Azeem et al, 2020 , Pedro et al, 2019 ). Processing plays an important role in the phenolic composition, since some compounds are evidenced only after the fermentation of the leaves ( Abdel Azeem et al, 2020 ), as well as some compounds are degraded during this process ( Chen, Liu, et al, 2021 ). An example of this are the higher levels of theanine contained in green tea (unfermented) in comparison with black tea (fully fermented) ( Abdel Azeem et al, 2020 ).…”

Section: Bioactive Composition Of Teasmentioning

confidence: 99%

“…Furthermore, reduced concentrations of secondary metabolites are also associated with amino acid degradation (to form volatile aldehydes). This degradation is the result of the oxidation reaction of catechins that consequently promote the oxidation of some phenolic acids and the reduction of astringency in flavor attributes ( Chen, Liu, et al, 2021 ).…”

Section: Bioactive Composition Of Teasmentioning

confidence: 99%

“…However, bioactive compounds profile may be modified during tea processing since the exposition of oxygen can imply on degradation of some chemical compounds. Thus, teas are classified according to their processing, where the main variation occurs in the degree of oxidation that modifies chemical and sensory characteristics ( Chen, Liu, et al, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

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Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

et al. 2021

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Oxygen-enriched fermentation improves the taste of black tea by reducing the bitter and astringent metabolites

Cited by 45 publications

References 20 publications

New insights into the effect of fermentation temperature and duration on catechins conversion and formation of tea pigments and theasinensins in black tea

New insights into the effect of fermentation temperature and duration on catechins conversion and formation of tea pigments and theasinensins in black tea

Nondestructive Testing and Visualization of Catechin Content in Black Tea Fermentation Using Hyperspectral Imaging

Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

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