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21 pages, 4531 KiB

Open AccessArticle

Flavor Characteristics of Sun-Dried Green Tea in Different Regions of Yunnan: Metabolite Basis and Soil Influencing Factors

by Miao Zhou, Xiujuan Deng, Qiaomei Wang, Zhenzhen Wei, Xinhua Wang, Wenxia Yuan, Limei Li, Man Zou, Weihao Liu, Shijie Lu, Yubo Sheng and Baijuan Wang

Foods 2025, 14(7), 1280; https://doi.org/10.3390/foods14071280 (registering DOI) - 7 Apr 2025

Abstract

To elucidate the regional flavor characteristics of sun-dried green tea (SDT) and their underlying influencing factors, a comprehensive analysis was conducted using metabolomics and flavoromics approaches. This study systematically examined SDT samples and their corresponding tea garden soils from 13 distinct regions in [...] Read more.

To elucidate the regional flavor characteristics of sun-dried green tea (SDT) and their underlying influencing factors, a comprehensive analysis was conducted using metabolomics and flavoromics approaches. This study systematically examined SDT samples and their corresponding tea garden soils from 13 distinct regions in Yunnan Province. The results revealed that the SDT samples could be classified into two distinct groups based on their flavor profiles. Compared to the regions of Pa Sha (PS), Bang Dong (BD), Dong Ban Shan (DBS), Dong Guo (DG), Su Hu (SH), Gua Feng Zhai (GFZ), and Wu Liang Shan (WLS), the regions of Xin Nong (XN), Ba Ka Nuan (BKN), Mang Ang (MA), Man Nuan (MN), Bing Dao (BDao), and Bin Shan (BS) exhibited a significant upregulation of the tea polyphenols (TP)/free amino acids (FAA) ratio. The former group was characterized by a sweet mellow taste, while the latter displayed a stronger taste profile. Furthermore, the analysis of volatile compounds demonstrated that geraniol and linalool were significantly upregulated in the PS, BD, DBS, DG, BS, and BDao regions, which were associated with tender and floral aromas. In contrast, isophorone, 2-pentyl furan, 1-octanol, D-limonene, and benzaldehyde were markedly enriched in the XN, BKN, MA, MN, SH, GFZ, and WLS regions, contributing to sweet and honey-like aromatic profiles. Altitude and mineral element phosphorus are potential key factors affecting the regional flavor differences in SDT. Specifically, SDT cultivated at higher altitudes and in soils with elevated available phosphorus content exhibited a greater likelihood of accumulating sweet mellow and floral compounds. This study provides scientific evidence for understanding the characteristic flavor profiles of SDT across different regions, offering valuable insights into the factors contributing to regional flavor differentiation in tea production. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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15 pages, 3041 KiB

Open AccessArticle

Effect of Drying Methods on Aroma Profiling of Large-Leaf Green Tea (Camellia sinensis var. Assamica) Determined by HS-SPME-GC-MS

by Zhengfei Luo, Linlong Ma, Yangtao Zhang, Yanhong Liu, Rui Yang, Xuean Dai, Tiantian Wang, Changmi Lv, Lifeng Zuo, Yanli Liu, Dan Cao, Haibo Yuan, Longfeng Yu and Xiaofang Jin

Foods 2025, 14(7), 1275; https://doi.org/10.3390/foods14071275 (registering DOI) - 5 Apr 2025

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Abstract

Drying methods play a crucial role in the formation of green tea aromas. This study investigated the aroma characteristics and volatile component profiles of large-leaf green tea under hot-air drying, pan-fired drying, and sun drying. The results revealed significant differences in the sensory [...] Read more.

Drying methods play a crucial role in the formation of green tea aromas. This study investigated the aroma characteristics and volatile component profiles of large-leaf green tea under hot-air drying, pan-fired drying, and sun drying. The results revealed significant differences in the sensory aroma characteristics and volatile components of the large-leaf green tea among the three drying methods. The pan-fire-dried green tea (PDGT) exhibited a distinct roasted aroma, while the hot-air-dried green tea (HDGT) and sun-dried green tea (SDGT) displayed a faint scent and lasting aroma characteristics, with the SDGT additionally featuring a noticeable sun-dried odor. A total of 48 differential volatile components were identified, among which β-Ionone, (E)-β-Ionone, 2,2,6-Trimethylcyclohexanone, Dihydroactinidiolide, BenzeneacetAldehyde, 2-Pentylfuran, 1,1,6-Trimethyl-1,2-dihydronaphthalene, δ-Cadinene, β-Myrcene, Geranylacetone, o-Cymene, 6-Methyl-5-hepten-2-one, (E)-β-Ocimene, and BenzAldehyde were identified as the primary contributors to the aroma differences among the three large-leaf green teas. Additionally, 43 differential volatile compounds were found to be significantly correlated with at least one of the aroma types (floral, sweet, green, faint scent, nutty, or roasted). The findings of this study provide a theoretical foundation for understanding the formation of aroma qualities in large-leaf green tea and offer valuable insights for improving its aromatic characteristics. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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13 pages, 8253 KiB

Open AccessArticle

Predicting the Degree of Fresh Tea Leaves Withering Using Image Classification Confidence

by Mengjie Wang, Yali Shi, Yaping Li, Hewei Meng, Zezhong Ding, Zhengrui Tian, Chunwang Dong and Zhiwei Chen

Foods 2025, 14(7), 1125; https://doi.org/10.3390/foods14071125 - 25 Mar 2025

Viewed by 125

Abstract

Rapid and non-destructive detection methods for the withering degree of fresh tea leaves are crucial for ensuring high-quality tea production. Therefore, this study proposes a fresh tea withering degree detection model based on image classification confidence. The moisture percentage of fresh tea leaves [...] Read more.

Rapid and non-destructive detection methods for the withering degree of fresh tea leaves are crucial for ensuring high-quality tea production. Therefore, this study proposes a fresh tea withering degree detection model based on image classification confidence. The moisture percentage of fresh tea leaves is calculated by developing a weighted method that combines confidence levels and moisture labels, and the degree of withering is ultimately determined by incorporating the standard for wilted moisture content. To enhance the feature extraction ability and classification accuracy of the model, we introduce the Receptive-Field Attention Convolution (RFAConv) and Cross-Stage Feature Fusion Coordinate Attention (C2f_CA) modules. The experimental results demonstrate that the proposed model achieves a classification accuracy of 92.7%. Compared with the initial model, the detection accuracy was improved by 0.156. In evaluating the predictive performance of the model for moisture content, the correlation coefficients (Rp), root mean square error (RMSEP), and relative standard deviation (RPD) of category 1 in the test set were 0.9983, 0.006278, and 39.2513, respectively, and all performance were significantly better than PLS and CNN methods. This method enables accurate and rapid detection of tea leaf withering, providing crucial technical support for online determination during processing. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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14 pages, 9146 KiB

Open AccessArticle

Magnesium Regulation Increases the Content of Characteristic Volatile Compounds and Enhances the Intensity of Odor Characteristics in Tea Tree Leaves

by Jianghua Ye, Qiqi Weng, Yulin Wang, Weiting Cheng, Junbin Gu, Qi Zhang, Bitong Zhu, Qiyan Liu, Xiaoli Jia, Juanying Wang and Haibin Wang

Foods 2025, 14(6), 1043; https://doi.org/10.3390/foods14061043 - 19 Mar 2025

Viewed by 185

Abstract

Magnesium plays an important role in regulating the growth and quality of tea trees. However, the effect of magnesium regulation on changes in the aroma quality of tea tree leaves remains unknown. In this study, the volatile compounds of tea leaves under different [...] Read more.

Magnesium plays an important role in regulating the growth and quality of tea trees. However, the effect of magnesium regulation on changes in the aroma quality of tea tree leaves remains unknown. In this study, the volatile compounds of tea leaves under different magnesium concentrations were determined to obtain the characteristic volatile compounds that changed significantly and their odor characteristics and to explore the effect of magnesium regulation on the aroma quality of tea leaves. The results showed that magnesium significantly enhanced the content of 15 characteristic volatile compounds in tea tree leaves, especially heptyl formate and t-geraniol. The 15 characteristic volatile compounds mainly showed five kinds of odor characteristics, such as fruity, green, floral, pungent, woody, and burnt; magnesium regulation critically increased floral, fruity, and green odor characteristics. This study lays an important foundation for the application of exogenous magnesium ions to regulate tea aroma quality. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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17 pages, 3348 KiB

Open AccessArticle

Effects of Liupao Tea with Different Years of Aging on Glycolipid Metabolism, Body Composition, and Gut Microbiota in Adults with Obesity or Overweight: A Randomized, Double-Blind Study

by Yuyang Wang, Qiang Hu, Botian Chen and Defu Ma

Foods 2025, 14(5), 866; https://doi.org/10.3390/foods14050866 - 3 Mar 2025

Viewed by 521

Abstract

Background: Liupao tea (LPT) is a traditionally fermented dark tea from Guangxi, China and the effects of different aging periods of LPT on metabolic health remain inadequately explored. Methods: This randomized, double-blind, longitudinal study enrolled 106 adults with obesity or overweight who were [...] Read more.

Background: Liupao tea (LPT) is a traditionally fermented dark tea from Guangxi, China and the effects of different aging periods of LPT on metabolic health remain inadequately explored. Methods: This randomized, double-blind, longitudinal study enrolled 106 adults with obesity or overweight who were assigned to consume LPT of different ages over a 90-day period. Participants were randomly divided into four groups, each consuming LPT that had been aged for 1 year, 4 years, 7 years, or 10 years. The metabolic parameters, body composition, and gut microbiota were assessed at baseline and after the 90-day intervention. Results: All LPT groups experienced significant reductions in systolic blood pressure (SBP) and diastolic blood pressure (DBP), with the 10-year-aged group showing the most notable SBP decrease (p < 0.001). Total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels decreased significantly in the 1-, 4-, and 10-year-aged groups (p < 0.05), while high-density lipoprotein cholesterol (HDL-C) increased in the 7-year-aged group (p < 0.05). Body weight, body fat mass (BFM), body mass index (BMI), waist circumference (WC), body fat percentage (BFP), and visceral fat area (VFA) significantly declined across all groups (p < 0.05). Gut microbiota analysis showed changes in specific genera, though overall diversity remained stable. No significant differences were found in metabolic or microbiota outcomes between the different aged groups. Conclusions: LPT consumption effectively improves blood pressure, lipid profiles, and body composition in adults with obesity without adverse liver effects. The aging duration of LPT does not significantly alter these health benefits, challenging the belief that longer-aged LPT is superior. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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20 pages, 6083 KiB

Open AccessArticle

Characteristic Changes and Potential Markers of Flavour in Raw Pu-Erh Tea with Different Ageing Cycles Analysed by HPLC, HS-SPME-GC-MS, and OAV

by Jiayi Xu, Xiujuan Deng, Yamin Wu, Miao Zhou, Cen Du, Qiaomei Wang, Yuxin Xia, Junjie He, Wenxia Yuan, Wendou Wu, Hongxu Li, Yankun Wang, Tong Li and Baijuan Wang

Foods 2025, 14(5), 829; https://doi.org/10.3390/foods14050829 - 27 Feb 2025

Viewed by 410

Abstract

To investigate the flavour evolution mechanism of raw Pu-erh tea (RPT) during storage, the volatile and non-volatile compounds of RPT with different storage years (1–10 years) from the same raw material origin, manufacturer, and storage location in Wenshan Prefecture, Yunnan Province, were systematically [...] Read more.

To investigate the flavour evolution mechanism of raw Pu-erh tea (RPT) during storage, the volatile and non-volatile compounds of RPT with different storage years (1–10 years) from the same raw material origin, manufacturer, and storage location in Wenshan Prefecture, Yunnan Province, were systematically analysed by HPLC, HS-SPME-GC-MS, and OAV. The results showed that both cluster analyses based on non-volatile and volatile compounds could classify RPT of different storage years into three ageing cycles, with key turning points in the third and eighth years of storage, which is also accompanied by the colour changing from green to orange or brown, the aroma changing from a faint scent to woody and ageing, the astringency diminishing, and the sweet and mellow increasing. Theophylline was identified as the potential marker of RPT stored 1–3 years, while (−)-catechin gallate, (−)-gallocatechin gallate, quercetin, and rutin as those for a storage of 9–10 years. The volatile compounds indicate a general trend of an initial increase followed by a decrease. Forty-four key aroma compounds (OAV ≥ 1) were identified. Eucalyptol, β-Caryophyllene, 2-Amylfuran, Copaene, Estragole, and α-Terpinene originated as potential markers for RPT stored 1–3 years, while (Z)-Linalool oxide (furanoid), α-Terpineol, Terpinen-4-ol, and cis-Anethol were for RPT stored 8–10 years. This study revealed the flavour characteristics and quality changes of RPT over the course of storage, and constructed a sensory flavour wheel, providing theoretical underpinnings for the quality control and assessment of RPT. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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16 pages, 3883 KiB

Open AccessArticle

Influence of Different Shaping Techniques on the Aroma Quality and Volatile Metabolites of Green Tea Revealed by Gas Chromatography Electronic Nose and Gas Chromatography–Tandem Mass Spectrometry

by Jiahao Tang, Jiajing Hu, Xianxiu Zhou, Qiwei Wang, Yongwen Jiang, Haibo Yuan, Yujie Wang and Yanqin Yang

Foods 2025, 14(5), 816; https://doi.org/10.3390/foods14050816 - 27 Feb 2025

Viewed by 488

Abstract

The shaping process is recognized as a crucial step in the manufacturing of green tea. However, its influence on aroma quality remains unclear. In this study, the effects of four shaping techniques, including flat green tea (FGT), straight green tea (SGT), phoenix green [...] Read more.

The shaping process is recognized as a crucial step in the manufacturing of green tea. However, its influence on aroma quality remains unclear. In this study, the effects of four shaping techniques, including flat green tea (FGT), straight green tea (SGT), phoenix green tea (PGT), and curled green tea (CGT), on the aroma quality and volatile metabolites of green tea were investigated by gas chromatography electronic nose (GC-E-Nose) and gas chromatography–tandem mass spectrometry (GC-MS/MS). The findings indicated that distinct shaping processes significantly influenced the development of the aroma quality and aroma components of green tea. The PGT processing facilitated the attainment of superior aroma quality of green tea. In total, 60 volatile components were identified by GC-MS/MS, with 54 of these compounds being consistently detected across four different shaping techniques. In particular, the PGT processing method was effective in yielding elevated levels of alcohols, esters and ketones. Moreover, 20 key odorants were screened out, with (E,E)-2,4-decadienal, (E,E)-2,4-nonadienal, phenylethyl alcohol, and benzeneacetaldehyde proven to be substantial contributors to the overall aromas of green tea under diverse shaping procedures. These key odorants were primarily derived from lipid degradation and the Maillard reaction. GC-E-Nose served as a significant adjunct to sensory evaluation, enabling the swift differentiation of green tea samples that have undergone various shaping processes. These findings offer both theoretical and technical perspectives that may guide the creation of innovative green tea products distinguished by their unique shapes. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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15 pages, 3089 KiB

Open AccessArticle

The Combination of Shaking and Yellow-Light Withering Promote the Volatile Aroma Components and the Aroma Quality of Black Tea

by Zeyi Ai, Shuangming Hu, Lingfei Ji, Bing Mu and Yiyang Yang

Foods 2025, 14(5), 758; https://doi.org/10.3390/foods14050758 - 23 Feb 2025

Viewed by 484

Abstract

The application of shaking during the withering process has been shown to significantly enhance the floral aroma of black tea. However, prior to this study, there was limited research on the effects of shaking combined with other withering treatments on the aroma components [...] Read more.

The application of shaking during the withering process has been shown to significantly enhance the floral aroma of black tea. However, prior to this study, there was limited research on the effects of shaking combined with other withering treatments on the aroma components of black tea. In this study, the aroma attributes of black teas processed with shaking combinations of yellow-light or high-temperature withering (YLS, HTS, and HYS) were evaluated through sensory evaluation, and the volatile composition and identification of key aroma compounds in black teas and in-process withered tea leaves were analyzed by gas chromatography–mass spectrometry (GC-MS). The results indicated that black teas subjected to different shaking combinations exhibited a distinct floral aroma with higher volatile compound content, with the YLS treatment showing the most significant aroma improvement. Eight volatile compounds with relative odor activity values (rOAV) > 1 were identified from 53 differential volatile compounds in black tea under different shaking combinations as the most important contributors to aroma quality. Linalool, trans-β-Ionone, α-cedrene, and nonanal were identified as key floral volatiles with high rOAVs. Their concentrations in YLS were notably higher compared to those in S, both in withered tea leaves (with the exception of trans-β-Ionone) and in the final dry black teas, suggesting that there may be a synergistic effect between the yellow-light withering and the shaking process in enhancing these key floral compounds. Overall, this study found that shaking combined with yellow-light withering can improve the aroma composition and quality of black tea, providing a theoretical basis and practical guidance for the production and optimization of high-aroma black tea. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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20 pages, 3624 KiB

Open AccessArticle

Insight into the Volatile Profiles and Key Odorants of Rizhao Green Tea by Application of SBSE-GC-MS, OAVs and GC-O Analysis

by Mengqi Wang, Dapeng Song, Hongxu Yin, Fengxiang Fang, Yali Shi, Hui Wang, Jiyan Li, Kunpeng Wang, Yin Zhu, Haipeng Lv and Shibo Ding

Foods 2025, 14(3), 458; https://doi.org/10.3390/foods14030458 - 31 Jan 2025

Viewed by 706

Abstract

Rizhao green tea (RZT), a renowned green tea, is cultivated in China’s northernmost tea region. Its unique environment endows it with a strong chestnut- and seaweed-like aroma. This study sought to explore the volatile profiles of RZT and pinpoint its key odorants by [...] Read more.

Rizhao green tea (RZT), a renowned green tea, is cultivated in China’s northernmost tea region. Its unique environment endows it with a strong chestnut- and seaweed-like aroma. This study sought to explore the volatile profiles of RZT and pinpoint its key odorants by employing stir bar sorptive extraction (SBSE) coupled with gas chromatography–mass spectrometry (GC-MS), determining the odor activity value (OAV), and performing gas chromatography–olfactometry (GC-O). A total of 112 volatiles were identified, and the major volatile compounds were esters (2035.25 μg/kg), alcohols (1799.02 μg/kg), alkanes (991.88 μg/kg), and ketones (691.96 μg/kg), comprising 74.91% of the total. A molecular aroma wheel was preliminarily established based on these key odorants. These insights might contribute to the scientific elucidation of the flavor chemical basis of RZT. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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12 pages, 576 KiB

Open AccessArticle

Exploring the Bioaccessibility of Roasted Japanese Green Tea: Impact of Simulated Gastrointestinal Digestion

by Wei Qin and Sunantha Ketnawa

Foods 2025, 14(2), 311; https://doi.org/10.3390/foods14020311 - 17 Jan 2025

Viewed by 1163

Abstract

In this study, the effects were explored of digestive enzymes and pH on the bioaccessibility of polyphenols, flavonoids, and antioxidant activities in Hojicha (roasted green tea, RT) infusions during simulated in vitro digestion. Roasting modifies its polyphenolic profile and reduces bitterness, making it [...] Read more.

In this study, the effects were explored of digestive enzymes and pH on the bioaccessibility of polyphenols, flavonoids, and antioxidant activities in Hojicha (roasted green tea, RT) infusions during simulated in vitro digestion. Roasting modifies its polyphenolic profile and reduces bitterness, making it a popular variation of green tea. In this study, RT was used for assessing how the roasting-induced changes influenced the tea’s bioaccessibility and stability under digestive conditions. A two-step gastrointestinal digestion model was applied to mimic real digestion. Total polyphenol content (TPC), total flavonoid content (TFC), and antioxidant activity (DPPH, ABTS, FRAP, and MIC) were measured at different digestion stages. Gastric conditions led to a 2.07-fold reduction in TPC and a 4.27-fold reduction in TFC. Digestive enzymes enhanced bioactive compound stability, with TPC and TFC bioaccessibility reaching 56% and 25% in the simulated digestion with digestive enzymes (MD) group, compared to 52% and 20% in the without digestive enzymes (WOE) group. Antioxidant activities were also better preserved, with antioxidant activity retention at 31% in the MD samples versus 19% in the WOE. These findings emphasize the key role of digestive enzymes in maintaining the antioxidant potential of roasted green tea during digestion, providing insight into future research on roasting methods and tea functionality for product development. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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13 pages, 5109 KiB

Open AccessArticle

Withering and Fermentation Affect the Transformation and Accumulation of Key Metabolites in Rougui (Camellia sinensis) for the Formation of Special Taste Characteristics

by Jianghua Ye, Yangxin Luo, Yulin Wang, Qi Zhang, Shuqi Zhang, Junbin Gu, Yankun Liao, Tingting Wang, Xiaoli Jia and Haibin Wang

Foods 2024, 13(23), 3955; https://doi.org/10.3390/foods13233955 - 8 Dec 2024

Cited by 1 | Viewed by 999

Abstract

During the production of Wuyi rock tea, withering and fermentation play a crucial role in the primary processing of the tea, greatly influencing the development of its distinct taste characteristics. In this study, Rougui (Camellia sinensis) was selected as the research [...] Read more.

During the production of Wuyi rock tea, withering and fermentation play a crucial role in the primary processing of the tea, greatly influencing the development of its distinct taste characteristics. In this study, Rougui (Camellia sinensis) was selected as the research object to investigate the effects of withering and fermentation on metabolites and taste characteristics in tea leaves. The findings revealed that a total of 1249 metabolites were detected in Rougui leaves at various processing stages, of which only 40 key metabolites were significantly altered. The process of withering and fermentation is crucial to increase the content of organic acids, plumerane, alkaloids, nucleotides and derivatives, amino acids and derivatives, and free fatty acids in the leaves of Rougui and to decrease the content of saccharides, phenolic acids, flavonols, flavones, and flavanols, which in turn enhances the mellowness, fresh and brisk taste, and aroma of tea and attenuates the saccharides, bitterness, and astringency. Withering and fermentation had the greatest effect on the bitterness and astringency of Rougui taste characteristics, followed by mellowness. It can be seen that withering and fermentation were extremely important for the development of Rougui’s special taste characteristics. The present study provides important support for optimizing Rougui processing and the formation of its special taste characteristics. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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13 pages, 5493 KiB

Open AccessArticle

Research on Rapid Detection Methods of Tea Pigments Content During Rolling of Black Tea Based on Machine Vision Technology

by Hanting Zou, Tianmeng Lan, Yongwen Jiang, Xiao-Lan Yu and Haibo Yuan

Foods 2024, 13(23), 3718; https://doi.org/10.3390/foods13233718 - 21 Nov 2024

Viewed by 831

Abstract

As a crucial stage in the processing of black tea, rolling plays a significant role in both the color transformation and the quality development of the tea. In this process, the production of theaflavins, thearubigins, and theabrownins is a primary factor contributing to [...] Read more.

As a crucial stage in the processing of black tea, rolling plays a significant role in both the color transformation and the quality development of the tea. In this process, the production of theaflavins, thearubigins, and theabrownins is a primary factor contributing to the alteration in color of rolled leaves. Herein, tea pigments are selected as the key quality indicators during rolling of black tea, aiming to establish rapid detection methods for them. A machine vision system is employed to extract nine color feature variables from the images of samples subjected to varying rolling times. Then, the tea pigment content in the corresponding samples is determined using a UV-visible spectrophotometer. In the meantime, the correlation between color variables and tea pigments is discussed. Additionally, Z-score and PCA are used to eliminate the magnitude difference and redundant information in original data. Finally, the quantitative prediction models of tea pigments based on the images’ color features are established by using PLSR, SVR, and ELM. The data show that the Z-score–PCA–ELM model has the best prediction effect for tea pigments. The Rp values for the model prediction sets are all over 0.96, and the RPD values are all greater than 3.50. In this study, rapid determination methods for tea pigments during rolling of black tea are established. These methods offer significant technical support for the digital production of black tea. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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13 pages, 4518 KiB

Open AccessArticle

Aerospace Mutagenesis Increases the Content of Characteristic Metabolites of Tea Tree Leaves and Enhances Taste Characteristics of Tea Leaves

by Jiaming Chen, Yangxin Luo, Qi Zhang, Yulin Wang, Tingting Wang, Miao Jia, Yankun Liao, Xiaoli Jia, Haibin Wang and Jianghua Ye

Foods 2024, 13(22), 3538; https://doi.org/10.3390/foods13223538 - 6 Nov 2024

Viewed by 986

Abstract

Aerospace mutagenesis can alter the physiological metabolism and growth of tea trees and affect tea leaf quality. In this study, the effect of aerospace mutagenesis on the metabolite content and taste characteristics of Dahongpao fresh leaves and raw tea were analyzed. The results [...] Read more.

Aerospace mutagenesis can alter the physiological metabolism and growth of tea trees and affect tea leaf quality. In this study, the effect of aerospace mutagenesis on the metabolite content and taste characteristics of Dahongpao fresh leaves and raw tea were analyzed. The results showed that aerospace mutagenesis had little effect on the composition and total amount of metabolites in fresh leaves and raw tea, but significantly changed the content of different metabolites. Aerospace mutagenesis improved the content of lipids, lignans and coumarins, and amino acids and derivatives, which in turn enhanced the aroma and fresh and brisk taste of fresh leaves. Aerospace mutagenesis increased the content of alkaloids, tannins, flavonoids, lignans and coumarins, amino acids and derivatives, and organic acids in raw tea, and enhanced the bitterness, mellowness, and fresh and brisk taste of raw tea. This study provides a basis for the development of aerospace mutagenesis Dahongpao tea products and the establishment of processing techniques. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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18 pages, 9791 KiB

Open AccessArticle

Profiling of Potential Anti-Diabetic Active Compounds in White Tea: An Integrated Study of Polyphenol-Targeted Metabolomics, Network Pharmacology, and Computer Simulation

by Weiwei Wu, Zhiqiang Zheng, Zhihui Wang, Chenxi Gao, Yilin Liang, Wen Zeng and Weijiang Sun

Foods 2024, 13(21), 3354; https://doi.org/10.3390/foods13213354 - 22 Oct 2024

Viewed by 1590

Abstract

Diabetes remains a critical global public health challenge, posing a growing threat to human health and well-being. White tea is a lightly fermented tea and one of the six traditional tea categories in China. Owing to its rich content of bioactive compounds such [...] Read more.

Diabetes remains a critical global public health challenge, posing a growing threat to human health and well-being. White tea is a lightly fermented tea and one of the six traditional tea categories in China. Owing to its rich content of bioactive compounds such as catechins and alkaloids, it has demonstrated potential anti-diabetic properties. However, its precise bioactive components, mechanisms of action, and relevant molecular targets require further investigation. In this study, an integrated approach combining polyphenol-targeted metabolomics, in vitro antioxidant assays, α-glucosidase inhibition tests, network pharmacology analysis, GEO database exploration, molecular docking, and molecular dynamics simulations was employed to identify the potential anti-diabetic compounds, targets, and mechanisms of white tea. The findings revealed that white tea is particularly abundant in 10 bioactive compounds, including epigallocatechin gallate, epicatechin gallate, and catechin, all of which exhibit significant anti-diabetic potential. These compounds were found to exert their effects by interacting with core molecular targets, namely cathepsin V (CTSV) and nucleotide-binding oligomerization domain-containing protein 1 (NOD1), and engaging in pathways related to signal transduction, apoptosis, and immune responses. This study establishes a strong theoretical basis for advancing white tea research and underscores new opportunities for applying natural products in diabetes therapy. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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15 pages, 2537 KiB

Open AccessArticle

Dynamic Changes in Aroma Compounds during Processing of Flat Black Tea: Combined GC-MS with Proteomic Analysis

by Cun Ao, Xiaojun Niu, Daliang Shi, Xuxia Zheng, Jizhong Yu and Yingbin Zhang

Foods 2024, 13(20), 3243; https://doi.org/10.3390/foods13203243 - 12 Oct 2024

Cited by 1 | Viewed by 1437

Abstract

Flat black tea (FBT) has been innovatively developed to alleviate homogenisation competition, but the dynamic changes in aroma components during the process remain unclear. This study employed HS-SPME-GC-MS to analyse the aroma components of tea samples from various processing stages of FBT, and [...] Read more.

Flat black tea (FBT) has been innovatively developed to alleviate homogenisation competition, but the dynamic changes in aroma components during the process remain unclear. This study employed HS-SPME-GC-MS to analyse the aroma components of tea samples from various processing stages of FBT, and to make a comparative assessment with conventional strip-like Congou black tea (SBT). Additionally, a proteomic analysis was conducted on fresh leaves, withered leaves, and frozen–thawed leaves. Significant changes were observed in the aroma components and proteins during the processing. The results of the multivariate and odour activity value analysis demonstrated that the principal aroma components present during the processing of FBT were linalool, (E)-2-hexen-1-al, methyl salicylate, geraniol, hexanal, benzeneacetaldehyde, (Z)-3-hexenyl butyrate, dimethyl sulphide, 2-methylbutanal, 2-ethylfuran, nonanal, nonanol, 3-methylbutanal, (Z)-3-hexen-1-ol, 2-pentylfuran, linalool oxide I, and β-myrcene. Freezing–thawing and final roasting are the key processing steps for forming the aroma quality of FBT. The final roasting yielded a considerable quantity of pyrazines and pyrroles, resulting in a high-fried aroma, but caused a significant reduction in linalool, geraniol, β-myrcene, and esters, which led to a loss of floral and fruity aromas. The freezing–thawing treatment resulted in an accelerated loss of aroma substances, accompanied by a decrease in the expression level of lipoxygenase and 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase. The formation of aroma substances in the linoleic acid metabolic pathway and terpenoid metabolic process was hindered, which had a negative impact on tea aroma. This study elucidates the causes of unsatisfactory aroma quality in tea products made from frozen tea leaves, providing theoretical support for the utilisation of frostbitten tea leaves, and helps us to understand the mechanism of aroma formation in black tea. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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18 pages, 12397 KiB

Open AccessArticle

Metabolite Profiling and Identification of Sweet/Bitter Taste Compounds in the Growth of Cyclocarya Paliurus Leaves Using Multiplatform Metabolomics

by Liang Chen, Dai Lu, Yuxi Wan, Yaqian Zou, Ruiyi Zhang, Tao Zhou, Bin Long, Kangming Zhu, Wei Wang and Xing Tian

Foods 2024, 13(19), 3089; https://doi.org/10.3390/foods13193089 - 27 Sep 2024

Viewed by 1326

Abstract

Cyclocarya paliurus tea, also known as “sweet tea”, an herbal tea with Cyclocarya paliurus leaves as raw material, is famous for its unique nutritional benefits and flavor. However, due to the unique “bittersweet” of Cyclocarya paliurus tea, it is still unable to fully [...] Read more.

Cyclocarya paliurus tea, also known as “sweet tea”, an herbal tea with Cyclocarya paliurus leaves as raw material, is famous for its unique nutritional benefits and flavor. However, due to the unique “bittersweet” of Cyclocarya paliurus tea, it is still unable to fully satisfy consumers’ high-quality taste experience and satisfaction. Therefore, this study aimed to explore metabolites in Cyclocarya paliurus leaves during their growth period, particularly composition and variation of sweet and bitter taste compounds, by combining multi-platform metabolomics analysis with an electronic tongue system and molecular docking simulation technology. The results indicated that there were significant differences in the contents of total phenols, flavonoids, polysaccharides, and saponins in C. paliurus leaves in different growing months. A total of 575 secondary metabolites were identified as potential active metabolites related to sweet/bitter taste using nontargeted metabolomics based on UHPLC-MS/MS analysis. Moreover, molecular docking technology was utilized to study interactions between the candidate metabolites and the sweet receptors T1R2/T1R3 and the bitter receptors T2R4/T2R14. Six key compounds with high sweetness and low bitterness were successfully identified by using computational simulation analysis, including cis-anethole, gluconic acid, beta-D-Sedoheptulose, asparagine, proline, and citrulline, which may serve as candidates for taste modification in Cyclocarya paliurus leaves. These findings provide a new perspective for understanding the sweet and bitter taste characteristics that contribute to the distinctive sensory quality of Cyclocarya paliurus leaves. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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15 pages, 5917 KiB

Open AccessArticle

Analysis of Metabolite Differences in Different Tea Liquors Based on Broadly Targeted Metabolomics

by Xiongyu Li, Miao Niu, Hongyan Yang, Xianxiu Zhou, Jianliang Ding, Yawen Xu, Caiyou Lv and Jiahua Li

Foods 2024, 13(17), 2800; https://doi.org/10.3390/foods13172800 - 3 Sep 2024

Viewed by 1070

Abstract

To expand the development of characteristic extension products of Yunnan tea and improve the utilization rate of Yunnan tea resources, in this study, we compared the metabolite composition among raw Pu-erh tea, ripe Pu-erh tea prepared with glutinous rice (according to tea to [...] Read more.

To expand the development of characteristic extension products of Yunnan tea and improve the utilization rate of Yunnan tea resources, in this study, we compared the metabolite composition among raw Pu-erh tea, ripe Pu-erh tea prepared with glutinous rice (according to tea to glutinous rice ratio of 1:3), and ripe Pu-erh tea prepared with a mixture of sorghum, rice, glutinous rice, wheat, and corn as raw materials (according to a tea to glutinous rice ratio of 1:3). Rice flavor liquor prepared with 100% glutinous rice served as a control. The raw Pu-erh tea liquor (RAWJ), ripe Pu-erh tea liquor (RIPEJ), ripe Pu-erh tea mixed grain liquor (HHLSJ), and rice-flavor liquor (MJ) were all brewed by semi-solid fermentation. The non-volatile components of the liquor samples were analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry as a broadly targeted metabolomics technique. A total of 691 metabolites were identified from the four samples. Among them, 674, 671, 633, and 667 species were detected in RAWJ, RIPEJ, HHLSJ, and MJ samples, respectively. Venn diagram analysis demonstrated 19, 21, and 14 unique metabolites in RAWJ, RIPEJ, and HHLSJ, respectively, compared with the metabolite composition of MJ. Flavonoids are the most important differential metabolite between tea liquor and rice-flavor liquor. This study provides a theoretical basis for the development of tea liquor products and offers insight into the difference in non-volatile components between tea liquor and rice-flavor liquor. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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15 pages, 6146 KiB

Open AccessArticle

Rapid Color Quality Evaluation of Needle-Shaped Green Tea Using Computer Vision System and Machine Learning Models

by Jinsong Li, Qijun Li, Wei Luo, Liang Zeng and Liyong Luo

Foods 2024, 13(16), 2516; https://doi.org/10.3390/foods13162516 - 12 Aug 2024

Viewed by 2007

Abstract

Color characteristics are a crucial indicator of green tea quality, particularly in needle-shaped green tea, and are predominantly evaluated through subjective sensory analysis. Thus, the necessity arises for an objective, precise, and efficient assessment methodology. In this study, 885 images from 157 samples, [...] Read more.

Color characteristics are a crucial indicator of green tea quality, particularly in needle-shaped green tea, and are predominantly evaluated through subjective sensory analysis. Thus, the necessity arises for an objective, precise, and efficient assessment methodology. In this study, 885 images from 157 samples, obtained through computer vision technology, were used to predict sensory evaluation results based on the color features of the images. Three machine learning methods, Random Forest (RF), Support Vector Machine (SVM) and Decision Tree-based AdaBoost (DT-AdaBoost), were carried out to construct the color quality evaluation model. Notably, the DT-Adaboost model shows significant potential for application in evaluating tea quality, with a correct discrimination rate (CDR) of 98.50% and a relative percent deviation (RPD) of 14.827 in the 266 samples used to verify the accuracy of the model. This result indicates that the integration of computer vision with machine learning models presents an effective approach for assessing the color quality of needle-shaped green tea. Full article

(This article belongs to the Special Issue Production, Quality, Flavor Characteristics and Health Benefits of Tea)

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