Tea and Its By-Products: The Traditional and Future Drinks from Cultivation to the Cup

A special issue of Foods (ISSN 2304-8158). This special issue belongs to the section "Plant Foods".

Deadline for manuscript submissions: closed (5 August 2023) | Viewed by 31115

Special Issue Editor

College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
Interests: tea biology; tea cultivation; tea processing; tea quality and safety control
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Tea is a famous healthy drink worldwide. It is produced using the tender shoots of Camellia sinensis. There are many factors influencing the taste and flavor of tea, such as varieties, cultivation and management techniques, environment factors, and processing technology. These factors not only affect the yield of tea but also determine its flavor because of their distinct biochemical components. In terms of tea varieties, in addition to leaf size, shape, and textures, some novel varieties with white, yellow, and purple leaves have been found and cultivated. Furthermore, many tea varieties with strong stress resistance against a poor environment have been discovered. In terms of cultivation and management techniques, many methods have been applied, such as shading, pruning, fertilization, pest and disease prevention, etc. In terms of environment factors, the weather environment of the natural region and the microclimate of a tea garden contribute to the growth and quality of tea plants together. In terms of processing technology, tea includes green, yellow, white, black, oolong, and dark tea based on the fermentation degree of tea leaves. These types of tea not only have a different taste but also possess different functions with regard to human health.

The present issue on “Tea and Its By-Products: Traditional and Future Drinks from Cultivation to the Cup” aims to publish studies focused on the following areas: tea breeding, cultivation and management techniques, processing technology, quality assessment, and health benefits. The following topics are welcome:

  • Selection and breeding of tea;
  • Genetic inheritance and evolution of tea;
  • Tea physiology;
  • Tea resistance to environmental stresses;
  • Climate change impact on tea growth and production;
  • Tea cultivation methods in tea garden;
  • Soil improvement and restoration;
  • Fertilization and nutrition;
  • Soil microbiology and mineralogy;
  • Pests and diseases control;
  • Enzyme dynamics during tea processing;
  • Novel processing technology;
  • Tea chemistry, biochemistry, and medicinal properties;
  • Quality assessment and criteria;
  • Health benefits and clinical effects of tea and its extract.

Prof. Dr. Xinghui Li
Guest Editor

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Keywords

  • tea variety and breeding
  • tea cultivation
  • tea physiology
  • tea biochemistry
  • tea molecular function
  • tea manufacturing
  • tea quality assessment
  • health benefits

Published Papers (18 papers)

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Research

11 pages, 4760 KiB  
Article
The Effect of Guisangyou Tea on Abnormal Lipid Metabolism in Mice Induced by High-Fat Diet
by Yan Zhu, Xianghui Zhou, Nan Ling, Qiming Yu, Huijuan Wang and Qizhen Du
Foods 2023, 12(11), 2171; https://doi.org/10.3390/foods12112171 - 27 May 2023
Viewed by 1139
Abstract
This study was aimed to investigate the effect of Guisangyou tea (GSY tea) in improving abnormal lipid metabolism in mice with obesity induced by a high-fat diet (HFD). The results showed that intervention of the water extract of GSY tea (WE) decreased serum [...] Read more.
This study was aimed to investigate the effect of Guisangyou tea (GSY tea) in improving abnormal lipid metabolism in mice with obesity induced by a high-fat diet (HFD). The results showed that intervention of the water extract of GSY tea (WE) decreased serum levels of lipids, and positively regulated the related antioxidant enzyme activities and the inflammatory factors in the serum and liver. In the liver, the mRNA and protein expression levels of sterol regulatory element-binding proteins-1 (SREBP-1), stearoyl-CoA desaturase-1 (SCD-1), fatty acid synthase (FASN), and acetyl CoA carboxylase (ACC) related to lipid synthesis were downregulated, and the mRNA and protein expression levels of the farnesoid X receptor (FXR) and small heterodimer partner (SHP) related to bile acid production were upregulated. The results demonstrate that GSY tea can improve abnormal lipid metabolism in obese mice by improving the body’s antioxidant capacity, regulating the inflammatory state, and reducing the synthesis of lipids and increasing the production of bile acids. GSY tea can be processed and utilized as a safe and effective resource for improving abnormal lipid metabolism. Full article
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14 pages, 2622 KiB  
Article
A Nomogram Model for Predicting the Polyphenol Content of Pu-Erh Tea
by Shihao Zhang, Chunhua Yang, Yubo Sheng, Xiaohui Liu, Wenxia Yuan, Xiujuan Deng, Xinghui Li, Wei Huang, Yinsong Zhang, Lei Li, Yuan Lv, Yuefei Wang and Baijuan Wang
Foods 2023, 12(11), 2128; https://doi.org/10.3390/foods12112128 - 25 May 2023
Cited by 2 | Viewed by 982
Abstract
To investigate different contents of pu-erh tea polyphenol affected by abiotic stress, this research determined the contents of tea polyphenol in teas produced by Yuecheng, a Xishuangbanna-based tea producer in Yunnan Province. The study drew a preliminary conclusion that eight factors, namely, altitude, [...] Read more.
To investigate different contents of pu-erh tea polyphenol affected by abiotic stress, this research determined the contents of tea polyphenol in teas produced by Yuecheng, a Xishuangbanna-based tea producer in Yunnan Province. The study drew a preliminary conclusion that eight factors, namely, altitude, nickel, available cadmium, organic matter, N, P, K, and alkaline hydrolysis nitrogen, had a considerable influence on tea polyphenol content with a combined analysis of specific altitudes and soil composition. The nomogram model constructed with three variables, altitude, organic matter, and P, screened by LASSO regression showed that the AUC of the training group and the validation group were respectively 0.839 and 0.750, and calibration curves were consistent. A visualized prediction system for the content of pu-erh tea polyphenol based on the nomogram model was developed and its accuracy rate, supported by measured data, reached 80.95%. This research explored the change of tea polyphenol content under abiotic stress, laying a solid foundation for further predictions for and studies on the quality of pu-erh tea and providing some theoretical scientific basis. Full article
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20 pages, 6411 KiB  
Article
Genome-Wide Investigation and Functional Analysis Reveal That CsKCS3 and CsKCS18 Are Required for Tea Cuticle Wax Formation
by Lilai Mo, Xinzhuan Yao, Hu Tang, Yan Li, Yujie Jiao, Yumei He, Yihe Jiang, Shiyu Tian and Litang Lu
Foods 2023, 12(10), 2011; https://doi.org/10.3390/foods12102011 - 16 May 2023
Cited by 1 | Viewed by 1182
Abstract
Cuticular wax is a complex mixture of very long-chain fatty acids (VLCFAs) and their derivatives that constitute a natural barrier against biotic and abiotic stresses on the aerial surface of terrestrial plants. In tea plants, leaf cuticular wax also contributes to the unique [...] Read more.
Cuticular wax is a complex mixture of very long-chain fatty acids (VLCFAs) and their derivatives that constitute a natural barrier against biotic and abiotic stresses on the aerial surface of terrestrial plants. In tea plants, leaf cuticular wax also contributes to the unique flavor and quality of tea products. However, the mechanism of wax formation in tea cuticles is still unclear. The cuticular wax content of 108 germplasms (Niaowang species) was investigated in this study. The transcriptome analysis of germplasms with high, medium, and low cuticular wax content revealed that the expression levels of CsKCS3 and CsKCS18 were strongly associated with the high content of cuticular wax in leaves. Hence, silencing CsKCS3 and CsKCS18 using virus-induced gene silencing (VIGS) inhibited the synthesis of cuticular wax and caffeine in tea leaves, indicating that expression of these genes is necessary for the synthesis of cuticular wax in tea leaves. The findings contribute to a better understanding of the molecular mechanism of cuticular wax formation in tea leaves. The study also revealed new candidate target genes for further improving tea quality and flavor and cultivating high-stress-resistant tea germplasms. Full article
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15 pages, 2741 KiB  
Article
Metabolomics Analysis Reveals the Effect of Two Alpine Foliar Diseases on the Non-Volatile and Volatile Metabolites of Tea
by Yuhe Wan, Yuxin Han, Xinyi Deng and Yingjuan Chen
Foods 2023, 12(8), 1568; https://doi.org/10.3390/foods12081568 - 07 Apr 2023
Cited by 1 | Viewed by 1149
Abstract
Blister blight and small leaf spots are important alpine diseases that mainly attack tender tea leaves, affecting tea quality. However, there is limited information on the effect of these diseases on tea’s non-volatile and volatile metabolites. Metabolomic analysis based on UHPLC-Q-TOF/MS, HPLC and [...] Read more.
Blister blight and small leaf spots are important alpine diseases that mainly attack tender tea leaves, affecting tea quality. However, there is limited information on the effect of these diseases on tea’s non-volatile and volatile metabolites. Metabolomic analysis based on UHPLC-Q-TOF/MS, HPLC and GC/MS was used to reveal the characteristic chemical profiles of tea leaves infected with blister blight (BB) and small leaf spots (SS). Flavonoids and monolignols were non-volatile metabolites that were enriched and significantly changed. Six main monolignols involved in phenylpropanoid biosynthesis were significantly induced in infected tea leaves. The accumulation of catechins, (−)-epigallocatechin gallate, (−)-epicatechin gallate, caffeine, amino acids and theanine were significantly decreased in both diseased tea leaves, while soluble sugar, (−)-epigallocatechin and phenol-ammonia were obviously increased. Among them, the amounts of sweet and umami-related soluble sugar, sucrose, amino acids and theanine were much higher in BB, while bitter and astringent taste-related catechins and derivatives were much higher in SS. Volatiles analysis showed that volatiles content in SS and BB was significantly decreased, and styrene was significantly induced in blister blight-infected tea leaves. The results indicate that the type and amount of volatiles were highly and differentially influenced by infection with the two alpine diseases. Full article
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13 pages, 4009 KiB  
Article
Characterization of the Aroma Profiles of Guangdong Black Teas Using Non-Targeted Metabolomics
by Qiushuang Wang, Dandan Qin, Xiaohui Jiang, Kaixing Fang, Bo Li, Qing Wang, Chendong Pan, Erdong Ni, Hongjian Li, Dong Chen and Hualing Wu
Foods 2023, 12(7), 1560; https://doi.org/10.3390/foods12071560 - 06 Apr 2023
Cited by 6 | Viewed by 1839
Abstract
Guangdong black teas have diverse flavors and aromas. To explore the molecular basis of these aromas, we extracted and analyzed the volatile flavor compounds of 31 black tea samples from 7 districts (Yingde, Luokeng, Renhua, Meizhou, Chaozhou, Lianshan, and Heyuan) in Guangdong Province [...] Read more.
Guangdong black teas have diverse flavors and aromas. To explore the molecular basis of these aromas, we extracted and analyzed the volatile flavor compounds of 31 black tea samples from 7 districts (Yingde, Luokeng, Renhua, Meizhou, Chaozhou, Lianshan, and Heyuan) in Guangdong Province with headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS). Then, 135 volatile flavor compounds (VFCs) were identified and grouped into 12 classes according to their chemical structure. Notably, alcohols accounted for 31.40–44.43% of total VFCs. The score plot of supervised partial least squares-discriminant analysis (PLS-DA) revealed good discrimination for most black tea samples. Additionally, 64 compounds with variable importance in projection > 1.0 were identified as differential odorants. Through an odor activity value analysis, eight volatile compounds were identified as the key active differential VFCs: linalool, methyl salicylate, phenylethyl alcohol, p-cresol, 3-methyl-butanoic acid, geraniol, benzaldehyde, and benzeneacetaldehyde. Thus, benzeneacetaldehyde and linalool in YJ-Yingde samples, benzaldehyde in Luokeng samples with an almond-like aroma, phenylethyl alcohol in the Heyuan samples, and p-cresol and 3-methyl-butanoic acid in the Chaozhou samples were the key volatile flavor compounds that could differentiate local black teas from other black teas. These findings will enrich the research in tea aroma chemistry and provide a method for identifying the origins of Guangdong black teas. Full article
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20 pages, 8320 KiB  
Article
Metabolic Variations among Three New Tea Varieties Cultivated in Shandong, China
by Jiazhi Shen, Hui Wang, Litao Sun, Kai Fan, Xifa Zhang, Qingfu Huang, Shibo Ding, Yu Wang and Zhaotang Ding
Foods 2023, 12(6), 1299; https://doi.org/10.3390/foods12061299 - 18 Mar 2023
Cited by 2 | Viewed by 1262
Abstract
Cultivar identification is a necessary step in tea breeding programs. Rapid identification methods would greatly improve these breeding processes. To preliminarily identify the three new Lucha tea varieties (LC6, LC7, and LC17) cultivated in Shandong, we measured their main agronomic characters and biochemical [...] Read more.
Cultivar identification is a necessary step in tea breeding programs. Rapid identification methods would greatly improve these breeding processes. To preliminarily identify the three new Lucha tea varieties (LC6, LC7, and LC17) cultivated in Shandong, we measured their main agronomic characters and biochemical components. Then, we analyzed the metabolic profiles of these tea varieties and Fuding Dabaicha (FD) using a UPLC-ESI-MS/MS system. Their biochemical components indicated that the Lucha varieties had excellent varietal characteristics, with higher amino acid contents. Furthermore, secondary metabolism changed a lot in the Lucha tea varieties compared with that in the FD, with their accumulations of flavonoids and phenolic acids showing significant differences. These differential flavonoids were dominated by flavones and flavanone, flavonols, flavonoid carbonosides, and flavanols monomer. Flavanols especially, including epicatechin glucoside, epicatechin-3-(3″-O-methyl)gallate, epigallocatechin-3-O-(3,5-O-dimethyl)gallate, and epitheaflavic acid-3-O-Gallate, showed higher levels in the Lucha varieties. The phenolic acids containing caffeoyl groups showed higher levels in the Lucha varieties than those in the FD, while those containing galloyl groups showed a reverse pattern. Nitrogen metabolism, including amino acids, also showed obvious differences between the Lucha varieties and FD. The differential amino acids were mainly higher in the Lucha varieties, including 5-L-glutamyl-L-amino acid, N-monomethyl-L-arginine, and N-α-acetyl-L-ornithine. By using these approaches, we found that LC6, LC7, and LC17 were excellent varieties with a high yield and high quality for making green teas in Shandong. Full article
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19 pages, 2112 KiB  
Article
Volatilomics Analysis of Jasmine Tea during Multiple Rounds of Scenting Processes
by Cheng Zhang, Chengzhe Zhou, Caiyun Tian, Kai Xu, Zhongxiong Lai, Yuling Lin and Yuqiong Guo
Foods 2023, 12(4), 812; https://doi.org/10.3390/foods12040812 - 14 Feb 2023
Cited by 7 | Viewed by 2203
Abstract
Jasmine tea is reprocessed from finished tea by absorbing the floral aroma of jasmine (Jasminum sambac (L.) Aiton); this process is commonly known as “scenting”. Making high-quality jasmine tea with a refreshing aroma requires repeated scenting. To date, the detailed volatile organic [...] Read more.
Jasmine tea is reprocessed from finished tea by absorbing the floral aroma of jasmine (Jasminum sambac (L.) Aiton); this process is commonly known as “scenting”. Making high-quality jasmine tea with a refreshing aroma requires repeated scenting. To date, the detailed volatile organic compounds (VOCs) and the formation of a refreshing aroma as the number of scenting processes increases are largely unknown and therefore need further study. To this end, integrated sensory evaluation, widely targeted volatilomics analysis, multivariate statistical analyses, and odor activity value (OAV) analysis were performed. The results showed that the aroma freshness, concentration, purity, and persistence of jasmine tea gradually intensifies as the number of scenting processes increases, and the last round of scenting process without drying plays a significant role in improving the refreshing aroma. A total of 887 VOCs was detected in jasmine tea samples, and their types and contents increased with the number of scenting processes. In addition, eight VOCs, including ethyl (methylthio)acetate, (Z)-3-hexen-1-ol acetate, (E)-2-hexenal, 2-nonenal, (Z)-3-hexen-1-ol, (6Z)-nonen-1-ol, β-ionone, and benzyl acetate, were identified as key odorants responsible for the refreshing aroma of jasmine tea. This detailed information can expand our understanding of the formation of a refreshing aroma of jasmine tea. Full article
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13 pages, 2786 KiB  
Article
Pea-Tea Intercropping Improves Tea Quality through Regulating Amino Acid Metabolism and Flavonoid Biosynthesis
by Qingping Ma, Laichao Song, Zhanhai Niu, Ziyuan Qiu, Haiwei Sun, Zhihong Ren, Huanhuan Wu, Yu Wang, Huiling Mei, Xinghui Li and Zhaotang Ding
Foods 2022, 11(22), 3746; https://doi.org/10.3390/foods11223746 - 21 Nov 2022
Cited by 3 | Viewed by 1719
Abstract
Pea-tea intercropping is an excellent cultivation method that can improve tea quality. However, the underlying mechanism is still unclear. The present study was aimed at elucidating the mechanism of the effect of pea-tea intercropping on tea quality through a high-throughput method. Transcriptome and [...] Read more.
Pea-tea intercropping is an excellent cultivation method that can improve tea quality. However, the underlying mechanism is still unclear. The present study was aimed at elucidating the mechanism of the effect of pea-tea intercropping on tea quality through a high-throughput method. Transcriptome and metabolome analyses were conducted to identify the changes in gene expression and metabolites changes intercropping, respectively. In addition, the amino acids and catechins were detected using the LC-MS method and quantified absolutely. The results showed that total polyphenols and catechins decreased but amino acids increased in pea intercropped tea shoots. Correspondingly, genes related to amino acid metabolism and flavonoid biosynthesis were differentially expressed. For amino acid metabolism, 11 differentially expressed genes were identified, including 5 upregulated and 6 downregulated genes. Meanwhile, three genes involved in carbohydrate transport and metabolism were upregulated in pea intercropped tea plants. These genes were also involved in amino acid metabolism. For flavonoid biosynthesis, two downregulated genes were identified, which were the flavonol synthase and anthocyanidin synthase genes and followed a similar pattern to changes in catechins and polyphenols. These advances have opened new horizons for understanding the biochemical mechanisms of amino acids and flavonoids in improving tea quality in the pea-tea intercropping cultivation model. Full article
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20 pages, 2222 KiB  
Article
A Comprehensive Investigation of Macro-Composition and Volatile Compounds in Spring-Picked and Autumn-Picked White Tea
by Cheng Zhang, Chengzhe Zhou, Kai Xu, Caiyun Tian, Mengcong Zhang, Li Lu, Chen Zhu, Zhongxiong Lai and Yuqiong Guo
Foods 2022, 11(22), 3628; https://doi.org/10.3390/foods11223628 - 14 Nov 2022
Cited by 14 | Viewed by 2045
Abstract
The flavour of white tea can be influenced by the season in which the fresh leaves are picked. In this study, the sensory evaluation results indicated that spring-picked white tea (SPWT) was stronger than autumn-picked white tea (APWT) in terms of the taste [...] Read more.
The flavour of white tea can be influenced by the season in which the fresh leaves are picked. In this study, the sensory evaluation results indicated that spring-picked white tea (SPWT) was stronger than autumn-picked white tea (APWT) in terms of the taste of umami, smoothness, astringency, and thickness as well as the aromas of flower and fresh. To explore key factors of sensory differences, a combination of biochemical composition determination, widely targeted volatilomics (WTV) analysis, multivariate statistical analysis, and odour activity value (OAV) analysis was employed. The phytochemical analysis showed that the free amino acid, tea polyphenol, and caffeine contents of SPWTs were significantly higher than those of APWTs, which may explain the higher umami, smoothness, thickness, and astringency scores of SPWTs than those of APWTs. The sabinene, (2E, 4E)-2, 4-octadienal, (-)-cis-rose oxide, caramel furanone, trans-rose oxide, and rose oxide contents were significantly higher in SPWTs than in APWTs, which may result in stronger flowery, fresh, and sweet aromas in SPWTs than in APWTs. Among these, (2E,4E)-2,4-octadienal and (-)-cis-rose oxide can be identified as key volatiles. This study provides an objective and accurate basis for classifying SPWTs and APWTs at the metabolite level. Full article
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13 pages, 3024 KiB  
Article
Effect of the Presence of Stem on Quality of Oolong Tea
by Jiazheng Lin, Yuwan Wang, Lin Chen, Yunfei Yang, Zheng Tu and Yang Ye
Foods 2022, 11(21), 3439; https://doi.org/10.3390/foods11213439 - 29 Oct 2022
Cited by 3 | Viewed by 1589
Abstract
Combined with the unique processing technology of oolong tea, oolong tea with stem processing has a better flavor compared to oolong tea without stem processing. However, there is currently no available evidence to support the contribution of stems to the taste quality of [...] Read more.
Combined with the unique processing technology of oolong tea, oolong tea with stem processing has a better flavor compared to oolong tea without stem processing. However, there is currently no available evidence to support the contribution of stems to the taste quality of oolong tea. In this study, the electronic tongue, sensory evaluation method combined with liquid chromatography, and gas chromatography–mass spectrometry were used to explore the influence of the presence of stems on the flavor substances and aroma of oolong tea during processing. The results showed that the presence of stems significantly increased the umami taste of oolong tea (p < 0.05), and the content of seven free amino acids (p < 0.05), including theanine (53.165 μg/mL) and aspartic acid (3.190 μg/mL), two umami-related amino acids, significantly increased. Moreover, the content of nerolidol (2.598 μg/g) in aroma components was significantly increased. This study identifies the contribution of stems to oolong tea quality during processing. Full article
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20 pages, 4735 KiB  
Article
Dynamic Analysis of Physicochemical Properties and Polysaccharide Composition during the Pile-Fermentation of Post-Fermented Tea
by Yan Luo, Zhenjun Zhao, Hujiang Chen, Xueli Pan, Risheng Li, Dewen Wu, Xianchun Hu, Lingling Zhang, Huawei Wu and Xinghui Li
Foods 2022, 11(21), 3376; https://doi.org/10.3390/foods11213376 - 26 Oct 2022
Cited by 5 | Viewed by 1460
Abstract
Ultra-high performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS) was used to study the diversity of tea polysaccharides and the dynamic changes in the physicochemical indexes of tea samples. FT-IR spectra and the free radical scavenging ability of tea polysaccharides, during pile-fermentation [...] Read more.
Ultra-high performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS) was used to study the diversity of tea polysaccharides and the dynamic changes in the physicochemical indexes of tea samples. FT-IR spectra and the free radical scavenging ability of tea polysaccharides, during pile-fermentation of post-fermented tea, were analyzed. The results showed that 23 saccharide co mponents in tea polysaccharides were identified: these belonged to 11 monosaccharides, 5 oligosaccharides, and 6 derivatives of monosaccharides and oligosaccharides. The abundance of oligosaccharides decreased gradually, while monosaccharides, and derivatives of monosaccharides and oligosaccharides increased gradually with the development of pile-fermentation. According to the differences in polysaccharide composition and their abundance, the tea polysaccharide samples extracted from different pile-fermentation stages could be clearly classed into three groups, W-0, W-1~W-4 and W-5~C-1. The pile-fermentation process affected the yield, the content of each component, FT-IR spectra, and the DPPH free radical scavenging ability of tea polysaccharides. Correlation analysis showed that microorganisms were directly related to the changes in composition and the abundance of polysaccharides extracted from different pile-fermentation stages. The study will further help to reveal the function of tea polysaccharides and promote their practical application as a functional food. Full article
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16 pages, 2808 KiB  
Article
Multi-Metabolomics Coupled with Quantitative Descriptive Analysis Revealed Key Alterations in Phytochemical Composition and Sensory Qualities of Decaffeinated Green and Black Tea from the Same Fresh Leaves
by Jie Wang, Ying Zhang, Yan Liu, Shaorong Zhang, Linying Yuan, Yingfu Zhong, Xiuhong Wu, Juan Yang and Ze Xu
Foods 2022, 11(20), 3269; https://doi.org/10.3390/foods11203269 - 20 Oct 2022
Cited by 2 | Viewed by 1494
Abstract
The supercritical CO2-based decaffeination (SCD) method can be used to prepare decaffeinated tea, but its overall effect on the phytochemicals, volatiles, and sensory qualities of green and black teas is still unclear, and its suitability to prepare decaffeinated green and black [...] Read more.
The supercritical CO2-based decaffeination (SCD) method can be used to prepare decaffeinated tea, but its overall effect on the phytochemicals, volatiles, and sensory qualities of green and black teas is still unclear, and its suitability to prepare decaffeinated green and black teas still needs to be compared. This study revealed the effect of SCD on phytochemicals, volatiles, and sensory qualities in black and green tea prepared from the same tea leaves, and compared the suitability of preparing decaffeinated green and black teas using SCD. The results showed that the SCD could remove 98.2 and 97.1% of the caffeine in green and black tea, respectively. However, it can cause further losses of phytochemicals in green and black teas, specifically the loss of epigallocatechin gallate, epigallocatechin, epicatechin gallate, and gallocatechin gallate in green tea and the loss of theanine and arginine in green and black teas. After the decaffeination, both green and black teas lost some volatiles but also generated new volatiles. Especially, the fruit/flower-like aroma, ocimene, linalyl acetate, geranyl acetate, and D-limonene, were generated in the decaffeinated black tea, while herbal/green-like aroma, β-cyclocitral, 2-ethylhexanol, and safranal, were generated in the decaffeinated green tea. The overall acceptance of decaffeinated green tea decreased due to the substantial reduction in bitterness and astringency, while the overall acceptance of decaffeinated black tea significantly increased. Therefore, SCD is more suitable for the preparation of decaffeinated black tea. Full article
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14 pages, 1168 KiB  
Article
HS−SPME/GC−MS Reveals the Season Effects on Volatile Compounds of Green Tea in High−Latitude Region
by Jie Wang, Xiaohan Li, Ying Wu, Fengfeng Qu, Lei Liu, Baoyi Wang, Peiqiang Wang and Xinfu Zhang
Foods 2022, 11(19), 3016; https://doi.org/10.3390/foods11193016 - 28 Sep 2022
Cited by 15 | Viewed by 1922
Abstract
This study investigates the volatile compounds of green tea produced with different leaves from spring, summer, and autumn in high−latitude region. A total of 95 volatile compounds were identified by gas chromatography–mass spectrometry (GC–MS). Spring, summer and autumn green tea contained 68, 72 [...] Read more.
This study investigates the volatile compounds of green tea produced with different leaves from spring, summer, and autumn in high−latitude region. A total of 95 volatile compounds were identified by gas chromatography–mass spectrometry (GC–MS). Spring, summer and autumn green tea contained 68, 72 and 82 volatile compounds, respectively. Principal component analysis (PCA), partial least squares−discrimination analysis (PLS−DA), and hierarchical cluster analysis (HCA) classified the samples and showed the difference. And 32 key characteristic components were screened out based on variable importance in the projection (VIP) values higher than 1.0. The characteristic volatile compounds of spring green tea including 18 components, such as geranylacetone, phenethyl alcohol, geraniol, β−ionone, jasmone, 1−octen−3−ol and longifolene. 13 components such as 2−methylfuran, indole, 1−octanol, D−limonene and ethanethiol were the key compounds in summer green tea. And 2,4,6−trimethylstyrene was the major differential volatile compounds in autumn green tea. The results increase our knowledge of green tea in different seasons and provide a theoretical basis for production control of green tea. Full article
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15 pages, 2052 KiB  
Article
Characterization of the Key Aroma Compounds of Shandong Matcha Using HS-SPME-GC/MS and SAFE-GC/MS
by Ying Luo, Yazhao Zhang, Fengfeng Qu, Peiqiang Wang, Junfeng Gao, Xinfu Zhang and Jianhui Hu
Foods 2022, 11(19), 2964; https://doi.org/10.3390/foods11192964 - 22 Sep 2022
Cited by 6 | Viewed by 2246
Abstract
Shandong matcha has the quality characteristics of bright green color, seaweed-like aroma and strong, fresh and brisk taste. In order to identify the characteristic aroma components and clarify the contribution of the grinding process to the aroma of Shandong matcha. Three grades of [...] Read more.
Shandong matcha has the quality characteristics of bright green color, seaweed-like aroma and strong, fresh and brisk taste. In order to identify the characteristic aroma components and clarify the contribution of the grinding process to the aroma of Shandong matcha. Three grades of Shandong matcha and corresponding tencha material were firstly tested with sensory evaluation, and the volatile components were extracted with headspace solid-phase microextraction (HS-SPME) and solvent-assisted flavor evaporation (SAFE) and analyzed using GC–MS. The sensory evaluation results showed that high-grade matcha (M-GS) had prominent seaweed-like, fresh and roasted notes, whereas medium and low-grade matcha (M-G1, M-G2) were gradually coupled with grassy, fatty and high-fired aromas. GC–MS results showed that in the HS-SPME method, heterocyclic compounds (45.84–65.35%) were the highest in Shandong matcha, followed by terpenoids (7.44–16.92%) and esters (6.91–15.27%), while in the safe method, esters were the highest (12.96–24.99%), followed by terpenoids (10.76–25.09%) and heterocyclic compounds (12.12–17.07%). As a whole, the composition of volatile components between M-G1 and M-G2 is relatively close, and there are more differences in volatile components between them and M-GS. The volatile components unique to M-GS were screened using the odor activity value (OAV) evaluation method, with components such as 3-methyl-2-butene-1-thiol, 3-ethyl-Phenol, 2-thiophenemethanethiol, 2,4-undecadienal, (E,E)-2,6-nonadienal, (E,Z)- being evaluated. There were other differentially volatile components, that is, volatile components that coexist in the three grades of matcha, but with different concentrations and proportions. M-G1 and M-G2 contained more volatile substances with high-fired aroma, such as 2-ethyl-3-methyl-pyrazine, coumarin and 5,6,7,8-tetrahydroquinoxaline. The grinding process not only changes the appearance of tencha, but also increases the content of volatile components of matcha as a whole, enhancing the aroma and flavor characteristics of matcha. In this study, the contents of 24 volatile components in matcha were mainly increased, such as benzene, (2,2-dimethoxyethyl)-, cis-7-decen-1-al, safranal and fenchyl acetate. The dual factors of material tencha and matcha grinding technology are indispensable in forming the differences in aroma and flavor of Shandong matcha at different levels. Full article
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17 pages, 4068 KiB  
Article
A Rapid Prediction Method of Moisture Content for Green Tea Fixation Based on WOA-Elman
by Tianmeng Lan, Shuai Shen, Haibo Yuan, Yongwen Jiang, Huarong Tong and Yang Ye
Foods 2022, 11(18), 2928; https://doi.org/10.3390/foods11182928 - 19 Sep 2022
Cited by 1 | Viewed by 1768
Abstract
Fixation is the most critical step in the green tea process. Hence, this study developed a rapid and accurate moisture content detection for the green tea fixation process based on near-infrared spectroscopy and computer vision. Specifically, we created a quantitative moisture content prediction [...] Read more.
Fixation is the most critical step in the green tea process. Hence, this study developed a rapid and accurate moisture content detection for the green tea fixation process based on near-infrared spectroscopy and computer vision. Specifically, we created a quantitative moisture content prediction model appropriate for the processing of green tea fixation. First, we collected spectrum and image information of green tea fixation leaves, utilizing near-infrared spectroscopy and computer vision. Then, we applied the partial least squares regression (PLSR), support vector regression (SVR), Elman neural network (ENN), and Elman neural network based on whale optimization algorithm (WOA-ENN) methods to build the prediction models for single data (data from a single sensor) and mid-level data fusion, respectively. The results revealed that the mid-level data fusion strategy combined with the WOA-ENN model attained the best effect. Namely, the prediction set correlation coefficient (Rp) was 0.9984, the root mean square error of prediction (RMSEP) was 0.0090, and the relative percent deviation (RPD) was 17.9294, highlighting the model’s excellent predictive performance. Thus, this study identified the feasibility of predicting the moisture content in the process of green tea fixation by miniaturized near-infrared spectroscopy. Moreover, in establishing the model, the whale optimization algorithm was used to overcome the defect whereby the Elman neural network falls into the local optimum. In general, this study provides technical support for rapid and accurate moisture content detection in green tea fixation. Full article
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14 pages, 2581 KiB  
Article
Prediction of Tea Polyphenols, Free Amino Acids and Caffeine Content in Tea Leaves during Wilting and Fermentation Using Hyperspectral Imaging
by Yilin Mao, He Li, Yu Wang, Kai Fan, Yujie Song, Xiao Han, Jie Zhang, Shibo Ding, Dapeng Song, Hui Wang and Zhaotang Ding
Foods 2022, 11(16), 2537; https://doi.org/10.3390/foods11162537 - 22 Aug 2022
Cited by 14 | Viewed by 2267
Abstract
The withering and fermentation degrees are the key parameters to measure the processing technology of black tea. The traditional methods to judge the degree of withering and fermentation are time-consuming and inefficient. Here, a monitoring model of the biochemical components of tea leaves [...] Read more.
The withering and fermentation degrees are the key parameters to measure the processing technology of black tea. The traditional methods to judge the degree of withering and fermentation are time-consuming and inefficient. Here, a monitoring model of the biochemical components of tea leaves based on hyperspectral imaging technology was established to quantitatively judge the withering and fermentation degrees of fresh tea leaves. Hyperspectral imaging technology was used to obtain the spectral data during the withering and fermentation of the raw materials. The successive projections algorithm (SPA), competitive adaptive reweighted sampling (CARS), and uninformative variable elimination (UVE) are used to select the characteristic bands. Combined with the support vector machine (SVM), random forest (RF), and partial least square (PLS) methods, the monitoring models of the tea polyphenols (TPs), free amino acids (FAA) and caffeine (CAF) contents were established. The results show that: (1) CARS performs the best among the three feature band selection methods, and PLS performs the best among the three machine learning models; (2) the optimal models for predicting the content of the TPs, FAA, and CAF are CARS-PLS, SPA-PLS, and CARS-PLS, respectively, and the coefficient of determination of the prediction set is 0.91, 0.88, and 0.81, respectively; and (3) the best models for quantitatively judging the withering and fermentation degrees are FAA-SPA-PLS and TPs-CARS-PLS, respectively. The model proposed in this study can improve the monitoring efficiency of the biochemical components of tea leaves and provide a basis for the intelligent judgment of the withering and fermentation degrees in the process of black tea processing. Full article
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18 pages, 5883 KiB  
Article
Untargeted Metabolomics and Transcriptomics Reveal the Mechanism of Metabolite Differences in Spring Tender Shoots of Tea Plants of Different Ages
by Cuinan Yue, Hua Peng, Wenjin Li, Zhongfei Tong, Zhihui Wang and Puxiang Yang
Foods 2022, 11(15), 2303; https://doi.org/10.3390/foods11152303 - 02 Aug 2022
Cited by 6 | Viewed by 2051
Abstract
The metabolites in the tender shoots of the tea plant are the material basis for the determination of tea quality. The composition and abundance of these metabolites are affected by many key factors, and the tea plant’s age is one of them. However, [...] Read more.
The metabolites in the tender shoots of the tea plant are the material basis for the determination of tea quality. The composition and abundance of these metabolites are affected by many key factors, and the tea plant’s age is one of them. However, the effect of plant age on the tender shoot metabolites of tea cultivars of different genotypes is poorly understood. Therefore, we used a combination of untargeted metabolomics and transcriptomics to analyze the differential mechanism behind the differences in the metabolites of the spring tender shoots of 7- and 40-year-old tea plants of two tea cultivars of different genotypes. We found that plant age could significantly change the metabolites in the spring tender shoots of tea plants and that flavonoids, and amino acids and their derivatives, were predominant among the differential metabolites. The quantities of most flavonoids in the aged tea plants of different genotypes were upregulated, which was caused by the upregulated expression of differential genes in the flavonoid biosynthesis pathway. We further discovered that 11 key structural genes play key regulatory roles in the changes in the flavonoid contents of tea plants of different plant ages. However, the influence of plant age on amino acids and their derivatives might be cultivar-specific. By characterizing and evaluating the quality-related metabolites of tea cultivars of two different genotypes at different plant ages, we found that whether an old tea plant (40 years old) can produce high-quality tea is related to the genotype of the tea plant. Full article
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11 pages, 2033 KiB  
Article
Molecular Link in Flavonoid and Amino Acid Biosynthesis Contributes to the Flavor of Changqing Tea in Different Seasons
by Qingping Ma, Mengyao Qin, Laichao Song, Haiwei Sun, Hong Zhang, Huanhuan Wu, Zhihong Ren, Hui Liu, Gang Duan, Yu Wang and Zhaotang Ding
Foods 2022, 11(15), 2289; https://doi.org/10.3390/foods11152289 - 31 Jul 2022
Cited by 5 | Viewed by 1706
Abstract
The present study was aimed to elucidate the flavor formation mechanism of Changqing tea. High-performance liquid chromatography (HPLC) analysis showed that the total catechins of Changqing tea was 65–160 mg/g, with 16–34 mg/g non-galloyated catechins and 49–126 mg/g galloylated catechins. Tea polyphenols and [...] Read more.
The present study was aimed to elucidate the flavor formation mechanism of Changqing tea. High-performance liquid chromatography (HPLC) analysis showed that the total catechins of Changqing tea was 65–160 mg/g, with 16–34 mg/g non-galloyated catechins and 49–126 mg/g galloylated catechins. Tea polyphenols and free amino acids account for 286–312 mg/g and 35–89 mg/g, respectively. Transcriptome of Changqing tea during different seasons revealed 316, 130 and 12 DEGs in comparisons of spring vs. autumn, spring vs. summer, and summer vs. autumn, respectively. Compared to spring, the genes involved in flavonoid biosynthesis and bitter imparted amino acids were up-regulated in summer and autumn. Metabolome analysis was conducted by using HPLC-MS; the result indicated that umami and kokumi contributing amino acids were decreased in summer and autumn compared with spring. It could be concluded that the coordination of flavonoid biosynthesis and amino acids biosynthesis resulted in the special flavor of Changqing tea. Full article
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