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20 pages, 4384 KiB

Open AccessArticle

Relationship between the Grade and the Characteristic Flavor of PCT (Panyong Congou Black Tea)

by Chenxi Gao, Yan Huang, Jing Li, Shiheng Lyu, Zhihui Wang, Feng Xie, Yuqin Luo, Fan Zhang, Zhidan Chen and Weijiang Sun

Foods 2022, 11(18), 2815; https://doi.org/10.3390/foods11182815 - 13 Sep 2022

Cited by 18 | Viewed by 2574

Abstract

Panyong Congou black tea (PCT) is one of the most representative and historically famous Congou black teas in China and has been gaining more and more attention for its beneficial health properties. Currently, four grades of PCT are available, based on the raw [...] Read more.

Panyong Congou black tea (PCT) is one of the most representative and historically famous Congou black teas in China and has been gaining more and more attention for its beneficial health properties. Currently, four grades of PCT are available, based on the raw leaf materials and consumer palatability. The chemical profiles distinguishing different grades of PCT are yet to be defined, nor has the relationship with grade been evaluated. In the present study, chemometric analysis showed that epigallocatechin (EGC), catechin (C), polyphenols, gallic acid (GA), and free amino acids are grade related bio-markers of PCT. These compounds are associated with the sweet and mellow aftertaste of PCT. A total of 34 volatile components were identified, of which the three component types with the highest relative percentages were alcohols (51.34–52.51%), ketones (27.31–30.28%), and aldehydes (12.70–13.18%). Additionally, our results revealed that sweet floral and fruity aromas were positively correlated with six volatile organic compounds (VOCs), 1-pentanol, propyl hexanoate, linalool, cyclohexanone, hexanal, and 2,5-dimethylpyrazine. Clear discrimination was achieved using orthogonal projections to latent structures discriminant analysis (OPLS-DA). The findings provide vital information on the characteristic flavor of each grade of PCT. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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16 pages, 3054 KiB

Open AccessArticle

Dynamic Changes of Volatile Compounds during the Xinyang Maojian Green Tea Manufacturing at an Industrial Scale

by Peng Yin, Jing-Jing Wang, Ya-Shuai Kong, Yao Zhu, Jun-Wei Zhang, Hao Liu, Xiao Wang, Gui-Yi Guo, Guang-Ming Wang and Zhong-Hua Liu

Foods 2022, 11(17), 2682; https://doi.org/10.3390/foods11172682 - 2 Sep 2022

Cited by 17 | Viewed by 2977

Abstract

Xinyang Maojian (XYMJ) is one of the premium green teas and originates from Xinyang, which is the northernmost green tea production area in China. The special geographic location, environmental conditions, and manufacturing process contribute to the unique flavor and rich nutrition of XYMJ [...] Read more.

Xinyang Maojian (XYMJ) is one of the premium green teas and originates from Xinyang, which is the northernmost green tea production area in China. The special geographic location, environmental conditions, and manufacturing process contribute to the unique flavor and rich nutrition of XYMJ green tea. Aroma is an important quality indicator in XYMJ green tea. In order to illustrate the aroma of XYMJ green tea, the key odorants in XYMJ green tea and their dynamic changes during the manufacturing processes were analyzed by headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). A total of 73 volatile compounds of six different chemical classes were identified in the processed XYMJ green tea samples, and the manufacturing processes resulted in the losses of total volatile compounds. Among the identified volatile compounds, twenty-four aroma-active compounds, such as trans-nerolidol, geranylacetone, nonanal, (+)-δ-cadinene, linalool, (Z)-jasmone, cis-3-hexenyl butyrate, cis-3-hexenyl hexanoate, methyl jasmonate, and β-ocimene, were identified as the key odorants of XYMJ green tea based on odor activity value (OAV). The key odorants are mainly volatile terpenes (VTs) and fatty acid-derived volatiles (FADVs). Except for (+)-δ-cadinene, copaene, cis-β-farnesene, (Z,E)-α-farnesene and phytol acetate, the key odorants significantly decreased after fixing. The principal coordinate analysis (PCoA) and the hierarchical cluster analysis (HCA) analyses suggested that fixing was the most important manufacturing process for the aroma formation of XYMJ green tea. These findings of this study provide meaningful information for the manufacturing and quality control of XYMJ green tea. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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14 pages, 1704 KiB

Open AccessArticle

Effects of Three Different Withering Treatments on the Aroma of White Tea

by Huiting Wu, Yuyu Chen, Wanzhen Feng, Shanshan Shen, Yuming Wei, Huiyan Jia, Yujie Wang, Weiwei Deng and Jingming Ning

Foods 2022, 11(16), 2502; https://doi.org/10.3390/foods11162502 - 19 Aug 2022

Cited by 40 | Viewed by 4431

Abstract

White tea (WT) is a slightly fermented tea, and withering is a critical step in its processing. The withering treatment can affect white tea’s aroma; different treatments’ effects were investigated in this study. White tea was withered indoors (IWT), in a withering-tank (WWT), [...] Read more.

White tea (WT) is a slightly fermented tea, and withering is a critical step in its processing. The withering treatment can affect white tea’s aroma; different treatments’ effects were investigated in this study. White tea was withered indoors (IWT), in a withering-tank (WWT), or under sunlight (SWT). Quantitative descriptive analysis (QDA) results showed that SWT had a more obvious flower aroma, and WWT had a more pronounced grassy aroma. Volatile compounds were extracted and subsequently detected with solvent-assisted flavor evaporation (SAFE) and headspace solid-phase microextraction (HS-SPME) combined in addition to gas chromatography–mass spectrometry (GC-MS). A total of 202 volatile compounds were detected; 35 of these aroma-active compounds met flavor dilution (FD) factor ≥ 4 or odor activity value (OAV) ≥ 1. The nine key potent odorants for which both conditions were met were dimethyl sulfide, 2-methyl-butanal, 1-penten-3-one, hexanal, (Z)-4-heptenal, β-Myrcene, linalool, geraniol, and trans-β-ionone. These results were used with QDA to reveal that SWT had a stronger floral aroma mainly due to an increase of geraniol and linalool. Moreover, WWT had a stronger grassy aroma mainly due to increased hexanal. The results could be used to select processing methods for producing white tea with a superior aroma. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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14 pages, 2126 KiB

Open AccessArticle

Distinguishing Different Varieties of Oolong Tea by Fluorescence Hyperspectral Technology Combined with Chemometrics

by Yan Hu, Youli Wu, Jie Sun, Jinping Geng, Rongsheng Fan and Zhiliang Kang

Foods 2022, 11(15), 2344; https://doi.org/10.3390/foods11152344 - 5 Aug 2022

Cited by 13 | Viewed by 2563

Abstract

Oolong tea is a semi-fermented tea that is popular among people. This study aims to establish a classification method for oolong tea based on fluorescence hyperspectral technology(FHSI) combined with chemometrics. First, the spectral data of Tieguanyin, Benshan, Maoxie and Huangjingui were obtained. Then, [...] Read more.

Oolong tea is a semi-fermented tea that is popular among people. This study aims to establish a classification method for oolong tea based on fluorescence hyperspectral technology(FHSI) combined with chemometrics. First, the spectral data of Tieguanyin, Benshan, Maoxie and Huangjingui were obtained. Then, standard normal variation (SNV) and multiple scatter correction (MSC) were used for preprocessing. Principal component analysis (PCA) was used for data visualization, and with tolerance ellipses that were drawn according to Hotelling, outliers in the spectra were removed. Variable importance for the projection (VIP) > 1 in partial least squares discriminant analysis (PLS–DA) was used for feature selection. Finally, the processed spectral data was entered into the support vector machine (SVM) and PLS–DA. MSC_VIP_PLS–DA was the best model for the classification of oolong tea. The results showed that the use of FHSI could accurately distinguish these four types of oolong tea and was able to identify the key wavelengths affecting the tea classification, which were 650.11, 660.29, 665.39, 675.6, 701.17, 706.31, 742.34 and 747.5 nm. In these wavelengths, different kinds of tea have significant differences (p < 0.05). This study could provide a non-destructive and rapid method for future tea identification. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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11 pages, 2159 KiB

Open AccessArticle

Mellow and Thick Taste of Pu−Erh Ripe Tea Based on Chemical Properties by Sensory−Directed Flavor Analysis

by Sihan Deng, Xinru Zhou, Haiyu Dong, Yongquan Xu, Ying Gao, Baijuan Wang and Xiaohui Liu

Foods 2022, 11(15), 2285; https://doi.org/10.3390/foods11152285 - 31 Jul 2022

Cited by 8 | Viewed by 2901

Abstract

The mellow and thick taste is a unique characteristic of pu−erh ripe tea infusion, and it is closely related to the chemical composition of pu−erh ripe tea, which is less studied. This paper clarifies and compares the chemical composition of pu−erh ripe tea [...] Read more.

The mellow and thick taste is a unique characteristic of pu−erh ripe tea infusion, and it is closely related to the chemical composition of pu−erh ripe tea, which is less studied. This paper clarifies and compares the chemical composition of pu−erh ripe tea to that of the raw materials of sun−dried green tea, and uses membrane separation technology to separate pu−erh ripe tea into the rejection liquid and the filtration liquid. The results show that microorganisms transformed most physicochemical components, except caffeine, during the pile fermentation. It was found that total tea polyphenols, soluble proteins, total soluble sugars, theabrownin, and galloylated catechins became enriched in the rejection liquid, and the rejection liquid showed a more obvious mellow and thick characteristic. Taste interactions between crude protein, crude polysaccharide, and theabrownin were determined. They illustrated that the mellow and thick taste of pu−erh ripe tea with the addition of theabrownin increased from 4.45 to 5.13. It is of great significance to explore the chemical basis of the mellow and thick taste in pu−erh tea for guiding the pu−erh tea production process and for improving the quality of pu−erh tea. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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15 pages, 1657 KiB

Open AccessArticle

Effects of Fermentation Temperature and Time on the Color Attributes and Tea Pigments of Yunnan Congou Black Tea

by Jiayi Zhu, Jinjin Wang, Haibo Yuan, Wen Ouyang, Jia Li, Jinjie Hua and Yongwen Jiang

Foods 2022, 11(13), 1845; https://doi.org/10.3390/foods11131845 - 23 Jun 2022

Cited by 19 | Viewed by 3367

Abstract

Yunnan Congou black tea (YCBT) is a typical black tea in China, and is rich in theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). However, the influence of the fermentation temperature and time on the liquor and appearance color and the correlation between the [...] Read more.

Yunnan Congou black tea (YCBT) is a typical black tea in China, and is rich in theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). However, the influence of the fermentation temperature and time on the liquor and appearance color and the correlation between the tea pigments and its color attributes remain unclear. We investigated the effects of the fermentation temperature and time on the color attributes and tea pigments of YCBT. A low fermentation temperature was beneficial to maintain a bright orange-red liquor color and promote the accumulation of TFs and TRs. In contrast, a high temperature gave the liquor a glossy appearance and was beneficial for the formation of TBs. A correlation analysis showed that the 10TFRB index best represented the contribution of tea pigments to the quality of black tea. Moreover, TRs and TBs content prediction models were established based on the liquor L and H values, where the former value can be used as an important index to judge the fermentation process. This study will further enrich the theory of black tea processing chemistry and provide technical support for the precise and directional production of black tea. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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16 pages, 3373 KiB

Open AccessArticle

Non-Targeted Metabolomics Analysis Revealed the Characteristic Non-Volatile and Volatile Metabolites in the Rougui Wuyi Rock Tea (Camellia sinensis) from Different Culturing Regions

by Kai Xu, Caiyun Tian, Chengzhe Zhou, Chen Zhu, Jingjing Weng, Yun Sun, Yuling Lin, Zhongxiong Lai and Yuqiong Guo

Foods 2022, 11(12), 1694; https://doi.org/10.3390/foods11121694 - 9 Jun 2022

Cited by 41 | Viewed by 4013

Abstract

Rougui Wuyi Rock tea (WRT) with special flavor can be affected by multiple factors that are closely related to the culturing regions of tea plants. The present research adopted non-targeted metabolomics based on liquid chromatography–mass spectrometry (LC-MS) and gas chromatography–mass spectrometry (GC-MS), aroma [...] Read more.

Rougui Wuyi Rock tea (WRT) with special flavor can be affected by multiple factors that are closely related to the culturing regions of tea plants. The present research adopted non-targeted metabolomics based on liquid chromatography–mass spectrometry (LC-MS) and gas chromatography–mass spectrometry (GC-MS), aroma activity value method (OAV), and chemometrics to analyze the characteristic metabolites of three Rougui WRTs from different culturing regions. The results of sensory evaluation showed that the three Rougui Wuyi Rock teas had significantly different flavor qualities, especially in taste and aroma. Rougui (RG) had a heavy and mellow taste, while cinnamon-like odor Rougui (GPRG) and floral and fruity odor Rougui (HGRG) had a thick, sweet, and fresh taste. The cinnamon-like odor was more obvious and persistent in GPRG than in RG and HGRG. HGRG had floral and fruity characteristics such as clean and lasting, gentle, and heavy, which was more obvious than in RG and GPRG. The results of principal component analysis (PCA) showed that there were significant metabolic differences among the three Rougui WRTs. According to the projection value of variable importance (VIP) of the partial least squares discriminant analysis (PLS–DA), 24 differential non-volatile metabolites were identified. The PLSR analysis results showed that rutin, silibinin, arginine, lysine, dihydrocapsaicin, etc. may be the characteristic non-volatiles that form the different taste outlines of Rougui WRT. A total of 90 volatiles, including aldehydes, alcohols, esters, and hydrocarbons, were identified from the three flavors of Rougui WRT by using GC-MS. Based on OAV values and PLS-DA analysis, a total of 16 characteristic volatiles were identified. The PLSR analysis results showed that 1-penten-3-ol, α-pinene, 2-carene, β-Pinene, dehydrolinalool, adipaldehyde, D-limonene, saffron aldehyde, and 6-methyl-5-hepten-2-one may be the characteristic volatiles that form the different aroma profile of Rougui WRT. These results provide the theoretical basis for understanding the characteristic metabolites that contribute to the distinctive flavors of Rougui WRT. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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14 pages, 3116 KiB

Open AccessArticle

Effect of Strobilanthes tonkinensis Lindau Addition on Black Tea Flavor Quality and Volatile Metabolite Content

by Jinjie Hua, Jia Li, Wen Ouyang, Jinjin Wang, Haibo Yuan and Yongwen Jiang

Foods 2022, 11(12), 1678; https://doi.org/10.3390/foods11121678 - 7 Jun 2022

Cited by 8 | Viewed by 2463

Abstract

The characteristic aroma of Chinese black tea (BT) produced in summer usually lacks intensity and persistence, reducing consumer acceptance and market demand. Strobilanthes tonkinensis Lindau (STL) possesses excellent biological characteristics, making it a promising novel tea ingredient. We investigated the effects of different [...] Read more.

The characteristic aroma of Chinese black tea (BT) produced in summer usually lacks intensity and persistence, reducing consumer acceptance and market demand. Strobilanthes tonkinensis Lindau (STL) possesses excellent biological characteristics, making it a promising novel tea ingredient. We investigated the effects of different addition methods and concentrations for the novel additive STL on the sensory quality of BT. A 20:1500 g/g addition to rolled tea leaves was identified as the best BT with STL (BoS) treatment. We identified 141 volatile metabolites (VMs) for the first time in STL, with high alcohol, ester, ketone, enyne, alkyne, and alkane contents. Partial least-squares discriminant analysis distinguished the samples and revealed 28, 26, and 14 differential VMs in STL vs. BoS, BT vs. STL, and BT vs. BoS comparisons, respectively. Using a combination of Venn, multiple experiment viewer, and odor activity value analysis, 16 key differential VMs were identified. Compared to BT, the 1-octen-3-ol, 1-hexanol, 1-dodecanol, (E)-3-hexen-1-ol, phenylethyl alcohol, and 2-methoxy-3-(2-methylpropyl)-pyrazine contents in BoS were 394.7%, 53.6%, 34.1%, 24.4%, 9.9%, and 5.7% higher, respectively. BoS combined the aromatic properties of BT and STL into a sweet and glutinous rice flavor. The results provide theoretical support for future research and development of novel BT-based products. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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14 pages, 2412 KiB

Open AccessEditor’s ChoiceArticle

Comparative Analysis of Volatile Compounds in Tieguanyin with Different Types Based on HS–SPME–GC–MS

by Lin Zeng, Yanqing Fu, Jinshui Huang, Jianren Wang, Shan Jin, Junfeng Yin and Yongquan Xu

Foods 2022, 11(11), 1530; https://doi.org/10.3390/foods11111530 - 24 May 2022

Cited by 38 | Viewed by 3978

Abstract

Tieguanyin (TGY) is one kind of oolong tea that is widely appreciated for its aroma and taste. To study the difference of volatile compounds among different types of TGY and other oolong teas, solid-phase microextraction–gas chromatography–mass spectrometry and chemometrics analysis were conducted in [...] Read more.

Tieguanyin (TGY) is one kind of oolong tea that is widely appreciated for its aroma and taste. To study the difference of volatile compounds among different types of TGY and other oolong teas, solid-phase microextraction–gas chromatography–mass spectrometry and chemometrics analysis were conducted in this experiment. Based on variable importance in projection > 1 and aroma character impact > 1, the contents of heptanal (1.60–2.79 μg/L), (E,E)-2,4-heptadienal (34.15–70.68 μg/L), (E)-2-octenal (1.57–2.94 μg/L), indole (48.44–122.21 μg/L), and (E)-nerolidol (32.64–96.63 μg/L) in TGY were higher than in other varieties. With the increase in tea fermentation, the total content of volatile compounds decreased slightly, mainly losing floral compounds. Heavily fermented tea contained a higher content of monoterpenoids, whereas low-fermentation tea contained higher contents of sesquiterpenes and indole, which could well distinguish the degree of TGY fermentation. Besides, the volatiles analysis of different grades of TGY showed that the special-grade tea contained more aroma compounds, mainly alcohols (28%). (E,E)-2,4-Heptadienal, (E)-2-octenal, benzeneacetaldehyde, and (E)-nerolidol were the key volatile compounds to distinguish different grades of TGY. The results obtained in this study could help enrich the theoretical basis of aroma substances in TGY. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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14 pages, 1905 KiB

Open AccessArticle

Effects of Hydrogen Peroxide Produced by Catechins on the Aroma of Tea Beverages

by Jie-Qiong Wang, Ying Gao, Dan Long, Jun-Feng Yin, Liang Zeng, Yan-Qun Xu and Yong-Quan Xu

Foods 2022, 11(9), 1273; https://doi.org/10.3390/foods11091273 - 27 Apr 2022

Cited by 5 | Viewed by 2497

Abstract

Hydrogen peroxide has a significant effect on the flavor of tea beverages. In this study, the yield of hydrogen peroxide in (–)-epigallocatechin gallate (EGCG) solution was first investigated and found to be significantly enhanced under specific conditions, and the above phenomenon was amplified [...] Read more.

Hydrogen peroxide has a significant effect on the flavor of tea beverages. In this study, the yield of hydrogen peroxide in (–)-epigallocatechin gallate (EGCG) solution was first investigated and found to be significantly enhanced under specific conditions, and the above phenomenon was amplified by the addition of linalool. Then, an aqueous hydrogen peroxide solution was added to a linalool solution and it was found that the concentration of linalool was significantly reduced in the above-reconstituted system. These findings were verified by extending the study system to the whole green tea infusions. The results suggested that the production of hydrogen peroxide in tea beverages may be dominated by catechins, with multiple factors acting synergistically, thereby leading to aroma deterioration and affecting the quality of tea beverages. The above results provided a feasible explanation for the deterioration of flavor quality of green tea beverages with shelf life. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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16 pages, 3222 KiB

Open AccessArticle

Metabolomics Combined with Proteomics Provide a Novel Interpretation of the Changes in Flavonoid Glycosides during White Tea Processing

by Xuming Deng, Hu Shang, Jiajia Chen, Jun Wu, Tao Wang, Yiqing Wang, Chensong Zhu and Weijiang Sun

Foods 2022, 11(9), 1226; https://doi.org/10.3390/foods11091226 - 24 Apr 2022

Cited by 21 | Viewed by 3443

Abstract

In this study, nonvolatile metabolomics and proteomics were applied to investigate the change mechanism of flavonoid glycoside compounds during withering processing of white tea. With the extension of withering time, the content of the main flavonoid glycoside compounds significantly decreased, and then the [...] Read more.

In this study, nonvolatile metabolomics and proteomics were applied to investigate the change mechanism of flavonoid glycoside compounds during withering processing of white tea. With the extension of withering time, the content of the main flavonoid glycoside compounds significantly decreased, and then the flavonoid aglycones and water-soluble saccharides contents increased. However, the change trends of these compounds were inconsistent with the expression pattern of related biosynthesis pathway proteins, indicating that the degradation of flavonoid glycosides might exist in the withering process of white tea. One co-expression network that was highly correlated with variations in the flavonoid glycosides’ component contents during the withering process was identified via WGCNA. Further analysis revealed that the degradation of flavonoid glycosides may be related to the antioxidant action of tea leaves undergoing the withering process. Our results provide a novel characterization of white tea taste formation during processing. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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14 pages, 1272 KiB

Open AccessArticle

Discriminant Analysis of Pu-Erh Tea of Different Raw Materials Based on Phytochemicals Using Chemometrics

by Shao-Rong Zhang, Yu Shi, Jie-Lin Jiang, Li-Yong Luo and Liang Zeng

Foods 2022, 11(5), 680; https://doi.org/10.3390/foods11050680 - 25 Feb 2022

Cited by 4 | Viewed by 2509

Abstract

Pu-erh tea processed from the sun-dried green tea leaves can be divided into ancient tea (AT) and terrace tea (TT) according to the source of raw material. However, their similar appearance makes AT present low market identification, resulting in a disruption in the [...] Read more.

Pu-erh tea processed from the sun-dried green tea leaves can be divided into ancient tea (AT) and terrace tea (TT) according to the source of raw material. However, their similar appearance makes AT present low market identification, resulting in a disruption in the tea market rules of fair trade. Therefore, this study analyzed the classification by principal component analysis/hierarchical clustering analysis and conducted the discriminant model through stepwise Fisher discriminant analysis and decision tree analysis based on the contents of water extract, phenolic components, alkaloid, and amino acids, aiming to investigate whether phytochemicals coupled with chemometric analyses distinguish AT and TT. Results showed that there were good separations between AT and TT, which was caused by 16 components with significant (p < 0.05) differences. The discriminant model of AT and TT was established based on six discriminant variables including water extract, (+)-catechin, (−)-epicatechin, (−)-epigallocatechin, theacrine, and theanine. Among them, water extract comprised multiple soluble solids, representing the thickness of tea infusion. The model had good generalization capability with 100% of performance indexes according to scores of the training set and model set. In conclusion, phytochemicals coupled with chemometrics analyses are a good approach for the identification of different raw materials. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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11 pages, 1477 KiB

Open AccessArticle

Characterization and Quantitative Comparison of Key Aroma Volatiles in Fresh and 1-Year-Stored Keemun Black Tea Infusions: Insights to Aroma Transformation during Storage

by Meng Tao, Wenli Guo, Wenjun Zhang and Zhengquan Liu

Foods 2022, 11(5), 628; https://doi.org/10.3390/foods11050628 - 22 Feb 2022

Cited by 11 | Viewed by 2640

Abstract

The aroma of Keemun black tea (KBT) changes during storage. We investigated key aroma volatiles of fresh KBT (FKBT) and KBT stored for 1 year. Through gas chromatography–olfactometry–mass spectrometry/aroma extract dilution analysis (GC-O-MS/AEDA), 27 aroma volatiles with a flavor dilution (FD) value ≥16 [...] Read more.

The aroma of Keemun black tea (KBT) changes during storage. We investigated key aroma volatiles of fresh KBT (FKBT) and KBT stored for 1 year. Through gas chromatography–olfactometry–mass spectrometry/aroma extract dilution analysis (GC-O-MS/AEDA), 27 aroma volatiles with a flavor dilution (FD) value ≥16 were quantitated. In odor activity value (OAV) analysis, the two samples had nearly the same key aroma volatiles; (Z)-methyl epijasmonate was the exception. Dimethyl sulfide, 3-methylbutanal, 2-methylpropanal, and linalool had especially high OAVs. Except for β-damascenone, volatiles with OAVs > 1 had higher concentrations in FKBT, which revealed that most key aroma compounds were lost during storage. Sweet, malty, floral, and green/grassy aromas corresponded directly to certain compounds. Lastly, the addition test indicated that the addition of several key aroma volatiles decreasing during storage could enhance the freshness of KBT aroma, which may be a potential to control the aroma style of KBT or other teas in industry. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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16 pages, 2102 KiB

Open AccessArticle

Comparative Analysis of Purine Alkaloids and Main Quality Components of the Three Camellia Species in China

by Wen Zeng, Zhen Zeng, Jie Teng, Dylan O’Neill Rothenberg, Mengzhen Zhou, Ronghui Lai, Xingfei Lai, Wenfang Zhao, Dan Li, Changyu Yan and Yahui Huang

Foods 2022, 11(5), 627; https://doi.org/10.3390/foods11050627 - 22 Feb 2022

Cited by 9 | Viewed by 2733

Abstract

Tea (Camelliasinensis var. sinensis) is a widely consumed caffeine-containing beverage, however the Camellia genus also includes other species, which are consumed as tea in their local growing regions. Presently, HPLC analysis assessed 126 unique Camellia germplasms belonging to three Camellia [...] Read more.

Tea (Camelliasinensis var. sinensis) is a widely consumed caffeine-containing beverage, however the Camellia genus also includes other species, which are consumed as tea in their local growing regions. Presently, HPLC analysis assessed 126 unique Camellia germplasms belonging to three Camellia species, C. sinensis var. pubilimba Chang (Csp), C. gymnogyna Chang (CgC) and C. crassicolumna Chang (CcC). Theobromine was the predominant purine alkaloid in all species, representing over 90% of purine alkaloids in Csp and CgC, and 50% in CcC. Significant variability existed in purine alkaloid patterns both between and within species, and some germplasms possessed highly unique alkaloid profiles. Sensory evaluation and quality composition analysis of green tea products produced from the three Camellia species suggested their unsuitability for use in tea production due to their unpalatable flavor. The results of this study revealed the differences in purine alkaloids and main quality components between Camellia species and tea, which contributed to understand why tea, rather than other Camellia species, has become a popular beverage in the world after long-term artificial selection. In addition, unique alkaloid profiles suggest usefulness of these germplasm resources in future breeding of decaffeinated tea plant varieties and alkaloid metabolism research. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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17 pages, 7341 KiB

Open AccessArticle

Tieguanyin Oolong Tea Extracts Alleviate Behavioral Abnormalities by Modulating Neuroinflammation in APP/PS1 Mouse Model of Alzheimer’s Disease

by Hyunuk Kang, Hui Zhou, Yushan Ye, Jiangfan Yang, Zhonghua Liu, Puming He, Bo Li, Yuanyuan Wu, Yaomin Wang and Youying Tu

Foods 2022, 11(1), 81; https://doi.org/10.3390/foods11010081 - 29 Dec 2021

Cited by 8 | Viewed by 2832

Abstract

Alzheimer’s disease (AD) is a common neurodegenerative disease; tea components have important neuroprotective effects. This article explores the effects and mechanisms of Qingxiang Tiguanyin (Tgy-Q), Nongxiang Tieguanyin (Tgy-N), and Chenxiang Tieguanyin (Tgy-C) extracts on APP/PS1 AD model mice. Morris water maze and new [...] Read more.

Alzheimer’s disease (AD) is a common neurodegenerative disease; tea components have important neuroprotective effects. This article explores the effects and mechanisms of Qingxiang Tiguanyin (Tgy-Q), Nongxiang Tieguanyin (Tgy-N), and Chenxiang Tieguanyin (Tgy-C) extracts on APP/PS1 AD model mice. Morris water maze and new object recognition experiments show that Tieguanyin extracts can effectively enhance the cognitive ability of APP/PS1 mice. H&E staining, Nissl staining, and immunohistochemical staining show that Tieguanyin extracts make nerve cell boundaries and nucleoli become clearer, relieve nucleus pyknosis, and effectively reduce Aβ1-40 and Aβ1-42 in the hippocampus and cortex. They also restore the morphology of microglia and astrocytes. In addition, Tieguanyin extracts can balance the oxidative stress level in the brain of APP/PS1 mice by improving the antioxidant capacity. Western blot results show that Tieguanyin extracts can reduce the expression of NF-κB p65, TNF-α, IL-1β, IL-6, COX-2, and iNOS in mouse brain, which demonstrates that Tieguanyin extracts improves cognitive ability by alleviating inflammation. This article demonstrates for the first time that Tieguanyin extracts can inhibit the excessive activation of the NF-κB p65 signaling pathway and improve the antioxidant capacity in the cerebral cortex and hippocampus, to improve the cognitive ability of APP/PS1 mice. Our results shed light into the beneficial of Tieguanyin tea extracts on preventing and alleviating AD diseases. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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12 pages, 3022 KiB

Open AccessArticle

Adsorption Equilibrium and Thermodynamics of Tea Theasinensins on HP20—A High-Efficiency Macroporous Adsorption Resin

by Jianyong Zhang, Hongchun Cui, Jinjin Xue, Wei Wang, Weiwei Wang, Ting Le, Lin Chen, Ulrich H. Engelhardt and Heyuan Jiang

Foods 2021, 10(12), 2971; https://doi.org/10.3390/foods10122971 - 2 Dec 2021

Cited by 6 | Viewed by 2045

Abstract

The separation and preparation of theasinensins have been hot spots in the field of tea chemistry in recent years. However, information about the mechanism of efficient adsorption of tea theasinensins by resin has been limited. In this study, the adsorption equilibrium and thermodynamics [...] Read more.

The separation and preparation of theasinensins have been hot spots in the field of tea chemistry in recent years. However, information about the mechanism of efficient adsorption of tea theasinensins by resin has been limited. In this study, the adsorption equilibrium and thermodynamics of tea theasinensins by a high-efficiency macroporous adsorption HP20 resin were evaluated. The adsorption of theasinensin A, theasinensin B, and theasinensin C on HP20 resin were spontaneous physical reaction processes. Adsorption processes were exothermic processes, and lowering the temperature was beneficial to the adsorption. The Freundlich model was more suitable to describe the adsorption of tea theasinensins. The adsorption equilibrium constant and maximum adsorption capacity of theasinensin A were significantly higher than theasinensin B and theasinensin C, which indicated that the adsorption affinity of theasinensin A was stronger than that of theasinensin B and theasinensin C. The phenolic hydroxyl groups and intramolecular hydrogen bonds of theasinensin A were more than those of theasinensin B and theasinensin C, which might be the key to the resin’s higher adsorption capacity for theasinensin A. The HP20 resin was very suitable for efficient adsorption of theasinensin A. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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Review

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28 pages, 20306 KiB

Open AccessReview

Recent Advances in Analytical Methods for Determination of Polyphenols in Tea: A Comprehensive Review

by Mu-Fang Sun, Chang-Ling Jiang, Ya-Shuai Kong, Jin-Lei Luo, Peng Yin and Gui-Yi Guo

Foods 2022, 11(10), 1425; https://doi.org/10.3390/foods11101425 - 13 May 2022

Cited by 32 | Viewed by 7004

Abstract

Polyphenols, the most abundant components in tea, determine the quality and health function of tea. The analysis of polyphenols in tea is a topic of increasing interest. However, the complexity of the tea matrix, the wide variety of teas, and the difference in [...] Read more.

Polyphenols, the most abundant components in tea, determine the quality and health function of tea. The analysis of polyphenols in tea is a topic of increasing interest. However, the complexity of the tea matrix, the wide variety of teas, and the difference in determination purposes puts forward higher requirements for the detection of tea polyphenols. Many efforts have been made to provide a highly sensitive and selective analytical method for the determination and characterization of tea polyphenols. In order to provide new insight for the further development of polyphenols in tea, in the present review we summarize the recent literature for the detection of tea polyphenols from the perspectives of determining total polyphenols and individual polyphenols in tea. There are a variety of methods for the analysis of total tea polyphenols, which range from the traditional titration method, to the widely used spectrophotometry based on the color reaction of Folin–Ciocalteu, and then to the current electrochemical sensor for rapid on-site detection. Additionally, the application of improved liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) were emphasized for the simultaneous determination of multiple polyphenols and the identification of novel polyphenols. Finally, a brief outline of future development trends are discussed. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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16 pages, 1297 KiB

Open AccessReview

Tea Polyphenols Prevent and Intervene in COVID-19 through Intestinal Microbiota

by Qiao Xiang, Lu Cheng, Ruilin Zhang, Yanan Liu, Zufang Wu and Xin Zhang

Foods 2022, 11(4), 506; https://doi.org/10.3390/foods11040506 - 10 Feb 2022

Cited by 11 | Viewed by 4545

Abstract

Although all countries have taken corresponding measures, the coronavirus disease 2019 (COVID-19) is still ravaging the world. To consolidate the existing anti-epidemic results and further strengthen the prevention and control measures against the new coronavirus, we are now actively pioneering a novel research [...] Read more.

Although all countries have taken corresponding measures, the coronavirus disease 2019 (COVID-19) is still ravaging the world. To consolidate the existing anti-epidemic results and further strengthen the prevention and control measures against the new coronavirus, we are now actively pioneering a novel research idea of regulating the intestinal microbiota through tea polyphenols for reference. Although studies have long revealed the regulatory effect of tea polyphenols on the intestinal microbiota to various gastrointestinal inflammations, little is known about the prevention and intervention of COVID-19. This review summarizes the possible mechanism of the influence of tea polyphenols on COVID-19 mediated by the intestinal microbiota. In this review, the latest studies of tea polyphenols exhibiting their own antibacterial and anti-inflammatory activities and protective effects on the intestinal mucosal barrier are combed through and summarized. Among them, (−)-epigallocatechin-3-gallate (EGCG), one of the main monomers of catechins, may be activated as nuclear factor erythroid 2 p45-related factor 2 (Nrf2). The agent inhibits the expression of ACE2 (a cellular receptor for SARS-CoV-2) and TMPRSS2 to inhibit SARS-CoV-2 infection, inhibiting the life cycle of SARS-CoV-2. Thus, preliminary reasoning and judgments have been made about the possible mechanism of the effect of tea polyphenols on the COVID-19 control and prevention mediated by the microbiota. These results may be of great significance to the future exploration of specialized research in this field. Full article

(This article belongs to the Special Issue Advances on Tea Chemistry and Function)

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