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The Chinese proverb “One mountain, one flavor” reflects that raw pu-erh tea (RPT) from different tea-producing mountains (TPMs) possesses distinct flavor profiles. However, limited research has been conducted on the chemical composition underlying distinct flavor profiles. In this study, sensory evaluation and main phytochemical compositions revealed diverse aromas of RPTs from 26 TPMs. A total of 225 volatile compounds were analyzed qualitatively and quantitatively by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry, including hydrocarbon compounds, ketones, alcohols, and aldehydes. Furthermore, twenty-one common key odor-active compounds, potentially influencing the regional flavor, were identified by gas chromatography-olfactometry and odor activity value. Multivariate statistical analysis showed that geographical factors—longitudes, latitudes, counties, and elevations—account for 37.02 % of the aroma profile variance, implying the possible influence of other potential factors. The study results serve as a reference for a better understanding of the correlation between the RPT flavor characteristics and geographical attributes in TPMs.

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Copyright of Modern Food Science & Technology is the property of Editorial Office of Modern Food Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Volatile constituents are critical to the flavor of tea, but their changes in raw Pu-erh tea (RAPT) during storage have not been clearly understood. This work aimed to investigate the volatile composition and their changes at various storage durations. The volatile profile of RAPT was determined using headspace solid-phase microextraction in combination gas chromatography–mass spectrometry. A total of 130 volatile compounds were identified in RAPT samples, and 64 of them were shared by all samples. The aroma attributes of RAPT over a storage period ranging from 0 to 10 years were assessed through the combination of odor activity value (OAV), aroma characteristic influence(ACI) value, and multivariate statistical analysis. The results revealed that RAPT exhibited a distinct floral and fruity aroma profile after storage for approximately 3–4 years. A notable shift in aroma was observed after 3–4 years of storage, indicating a significant turning point. Furthermore, the likely notable shift after 10 years of storage may signify the second turning point. According to the odor activity value (OAV ≥ 100), eight key volatile compounds were identified: linalool, α-terpineol, geraniol, trans-β-ionone, α-ionone, (E,E)-2,4-heptadienal, 1-octanol, and octanal. Combining OAV (≥100) and ACI (≥1), five compounds, namely linalool, (E,E)-2,4-heptadienal, (Z)-3-hexen-1-ol, 2,6,10,10-tetramethyl-1-oxaspiro [4.5]dec-6-ene, and octanal, were identified as significant contributors to the aroma. The results offer a scientific foundation and valuable insights for understanding the volatile composition of RAPT and their changes during storage. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Volatile constituents are critical to the flavor of tea, but their changes in raw Pu-erh tea (RAPT) during storage have not been clearly understood. This work aimed to investigate the volatile composition and their changes at various storage durations. The volatile profile of RAPT was determined using headspace solid-phase microextraction in combination gas chromatography–mass spectrometry. A total of 130 volatile compounds were identified in RAPT samples, and 64 of them were shared by all samples. The aroma attributes of RAPT over a storage period ranging from 0 to 10 years were assessed through the combination of odor activity value (OAV), aroma characteristic influence(ACI) value, and multivariate statistical analysis. The results revealed that RAPT exhibited a distinct floral and fruity aroma profile after storage for approximately 3–4 years. A notable shift in aroma was observed after 3–4 years of storage, indicating a significant turning point. Furthermore, the likely notable shift after 10 years of storage may signify the second turning point. According to the odor activity value (OAV ≥ 100), eight key volatile compounds were identified: linalool, α-terpineol, geraniol, trans-β-ionone, α-ionone, (E,E)-2,4-heptadienal, 1-octanol, and octanal. Combining OAV (≥100) and ACI (≥1), five compounds, namely linalool, (E,E)-2,4-heptadienal, (Z)-3-hexen-1-ol, 2,6,10,10-tetramethyl-1-oxaspiro [4.5]dec-6-ene, and octanal, were identified as significant contributors to the aroma. The results offer a scientific foundation and valuable insights for understanding the volatile composition of RAPT and their changes during storage.

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chinese Institute of Food Science & Technology / Zhongguo Shipin Xuebao is the property of Journal of Chinese Institute of Food Science & Technology Periodical Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objective] In order to explore the correlation between the content changes of three flavonol compounds in Pu'er raw tea in different storage years and the identification of Pu'er raw tea. [Method] The raw Pu'er tea with different storage years (2006-2015) was used as the research material, and the myricetin, quercetin and kaempferol in the tea samples were determined by High Performance Liquid Chromatography (HPLC). The content of the most abundant flavonols, cluster analysis and correlation analysis were used to explore the correlation between the content of the 3 flavonols and the total amount of flavonoids and the storage year. [Results] With the extension of storage years, the contents of myricetin, quercetin and kaempferol all showed an upward trend. Among them, the content of myricetin was 0.36~3.19 mg/g, and the content of quercetin was 2.40~10.17 mg/g. Kaempferol is 2.00~7.35 mg/g, and the total amount of flavonoids is 12.87~51.99 mg/g. Using cluster analysis, the tea samples can be divided into 2 large clusters, the first cluster includes tea samples from 2006 to 2008, and the second cluster is tea samples from 2009 to 2015; correlation analysis found that the total amount of flavonoids and quercetin The correlation between kaempferol and kaempferol is the strongest, and the closer the storage years are, the stronger the correlation between tea samples. [Conclusion] The content of flavonols and the total amount of flavonoids in the tea samples of Pu'er tea in different years can be used as indicators for the identification of Pu'er tea. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The authenticity of the geographical origin of agricultural products has received widespread attention. Tea tree varieties, processing processes and origins influence the quality and price of raw pu-erh tea (RPT). This study distinguished RPT from 10 different production areas through headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with orthogonal partial least squares–discriminant analysis (OPLS-DA) model and machine learning algorithms. Among the thirty-five types of common volatiles identified, pentanal, heptanal, naphthalene, cedrol, and 2,6-di- tert -butylbenzoquinone were considered the key differential compounds distinguishing the 10 different production areas of the RPT samples through the screening of variable importance in projection values of the OPLS-DA and coefficient weights of the linear discriminant analysis function. Among them, heptanal and 2,6-di- tert -butylbenzoquinone had the highest content in West of Bingdao and the lowest content in Nannuoshan. The random forest algorithm achieved a discrimination accuracy of 98.4% based on the discrimination of five key compounds in 63 RPT samples. The random forest model was demonstrated to be reliable and valid by using receiver operating characteristic curves (area under the curve = 0.7603). The study results serve as a reference for the differentiation of 10 production areas of RPT. • Identification of 35 common volatile compounds from 63 raw pu-erh tea samples. • There was strong correlation between production sites and volatile compounds. • 5 Key difference compounds were found to distinguish between the 10 regions. • A prediction model was established for the origin of raw pu-erh tea. [ABSTRACT FROM AUTHOR]

Herein, we reported a detailed profiling of soluble components of two fermented varieties of Chinese green tea, namely raw and ripe pu-erh. The identification and quantification of the main components was carried out by means of mass spectrometry and UV spectroscopy, after chromatographic separation. The antioxidant capacity towards different radical species, the anti-microbial and the enzyme inhibition activities of the extracts were then correlated to their main constituents. Despite a superimposable qualitative composition, a similar caffeine content, and similar enzyme inhibition and antimicrobial activities, raw pu-erh tea extract had a better antioxidant capacity owing to its higher polyphenol content. However, the activity of raw pu-erh tea seems not to justify its higher production costs and ripe variety appears to be a valid and low-cost alternative for the preparation of products with antioxidant or antimicrobial properties.

Steeping process is an important factor for aroma release of tea, which has rarely been investigated for the aroma changes of raw Pu-erh tea (RAPT). In addition, the comprehensive aroma characteristics identification of RAPT infusion is necessary. In this study, GC-IMS coupled with principal component analysis (PCA) was used to clarify the difference of volatile profiles during the steeping process of RAPT. Furthermore, the volatiles contained in the RAPT infusion were extracted by three pretreatment methods (HS-SPME, SBSE, and SAFE) and identified using GC-O-MS. According to the odor activity value, 28 of 66 compounds were categorized as aroma-active compounds. Aroma recombination and omission experiments showed that "fatty", "green", "fruity", and "floral" are considered to be the main aroma attributes of RAPT infusion with a strong relationship with 1-octen-3-one, 1-octen-3-ol, ( E )-2-octenal, β-ionone, linalool, etc. This study will contribute a better understanding of the mechanism of the RAPT steeping process and volatile generation.

Cup aroma refers to the volatiles emitted from an empty cup after tea infusion. In this study, gas chromatography–olfactometry (GC–O) and the odor activity value (OAV) approach were employed to investigate the composition of fermented soybean-like cup aroma from raw Pu-erh tea. Further, the aroma recombination and omission tests were performed, and the results demonstrated that 2-methylbutyric acid, acetic acid, 4-methyl-3-penten-2-one, ethyl isobutyrate, nonanoic acid, and phenylacetic acid exhibited relatively high aroma intensities (AI) and OAVs among the 12 odor-active compounds that were detected in the fermented soybean-like cup aroma. The aroma recombination, which was performed employing the 12 odorants with AI ≥1 successfully mimicked the overall aroma profile of the fermented soybean-like cup aroma. The omission test revealed that 2-methylbutyric acid contributed significantly to the fermented soybean-like cup aroma. And the enantiomeric ratio (ER) of the (S)- to (R)-forms of 2-methylbutyric acid was 67:33. [Display omitted] • Volatiles and aroma profiles were different in cup aroma and infusion. • A mixture of 12 aromas was defined as key aroma of fermented soybean-like cup aroma. • 2-Methylbutyric acid contributed the most to the fermented soybean-like cup aroma. • The (S)-2- methylbutyric acid was the predominant configurations. [ABSTRACT FROM AUTHOR]

This study aimed to explore the relationship between the processing type and the flavor in raw Pu-erh tea (RPT). Liquid chromatography−mass, gas chromatography-mass spectrometry, and multivariate analyses were employed to measure the component of RPT and to determine the changes in the flavor evolution of RPT at processing type. Sensory evaluation indicated that the processing type enhanced the flavor of the RPT. Based on 12 detected taste-active compounds, PCA and heat map analysis showed the average content of 4 catechins (ECG、EGCG, EC, EGC) in RPTs was 132.27 mg/g, which was 21.19 mg/g less than sun-dried tea (SDT). Astringency and bitterness of RPT can be reduced by processing type. A total of 52 volatile compounds were perceived and 4 volatile components were identified as essential compounds related to PLS-DA (VIP >1, P < 0.05), including phytol, linalool, cis -geraniol, and trans -geraniol, which increased from 62.27% in SDT to 66.25% in brick tea, which significantly contributes to the floral flavor of brick tea. The findings presented in this thesis add to our understanding of the relationship between the processing type and the flavor of RPT. • Processing type played a vital role in flavor formation of RPT. • Processing type could reduce the astringency and bitterness in RPT. • The floral aroma of brick tea was enhanced. • Phytol, linalool, and cis -geraniol contributed to the floral aroma of brick tea. [ABSTRACT FROM AUTHOR]

Volatile compounds largely contribute to the aroma of raw pu-erh tea (RPT). However, the changes of volatile composition during manufacturing are unclear. This work characterized 58 volatile compounds in the RPT samples collected from withering, de-enzyming, sun-drying, and autoclaving–compressing stages. Results show that de-enzyming and autoclaving–compressing have large effects on the volatile composition, with the total volatile contents sharply decreased by 76.68% and 35.77%, respectively. After de-enzyming, the relative content of aldehydes increased by 4.68-fold, whereas that of alkenes decreased by 2.65-fold; thus, the attractive fatty aroma must be enhanced while weakening the unpleasant grassy aroma. The volatile composition would be greatly changed by autoclaving–compressing, which is a special step for RPT production but rarely studied before. These findings revealed the changes of the volatile composition of RPT during manufacturing, especially de-enzyming and autoclaving–compressing, which are important for the formation of the aroma characteristics of RPT. Image 1 • The changes of volatiles of raw pu-erh tea during manufacturing were studied. • A total of 58 volatiles were identified by GC-MS assisted by chemometrics. • Total volatile contents decreased greatly during manufacturing process. • De-enzyming increase the relative content of aldehydes but decrease alkenes. • Autoclaving–compressing have important effects on the volatile composition. [ABSTRACT FROM AUTHOR]

Contents of catechins, flavonoids, purine alkaloids and amino acids in raw Pu-erh teas (RPTs) of a storage time scale below 10 years and old RPTs stored in Yunnan and Guangdong Province, were determined by HPLC. Tea quality improved highly significantly (p < 0.01) after 8 years of storage through sensory evaluation. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) could classify RPTs into 3 categories (new, chen and old tea group, respectively) completely based on detected compounds. Gallic acid (GA), (−)-epicatechin gallate (ECG), (−)-epigallocatechin gallate (EGCG), (−)-gallocatechin gallate (GCG), (−)-epigallocatechin, (−)-gallocatechin, l -tyrosine, l -theanine, l -glutamic acid, l -asparagine and l -valine with highly significant (p < 0.01) variations could discriminate the storage time. The highly significant (p < 0.01) increase of GA might be attributed to the hydrolyzation of ECG, EGCG and GCG by existed microbes in the storage. Kaempferol and myricetin contents were increased highly significant (p < 0.01) during the storage. Hot-humid storage environment accelerated the degradation of ester catechins, l -theanine, l -asparagine, l -alanine and l -valine, and the accumulation of GA, kaempferol and quercetin. This study helps to reveal quality and chemical change rules of RPTs during the storage. • PCA and HCA divide RPTs of different storage time into three categories. • Catechins, amino acids decreased and flavonoids increased significantly (p < 0.01). • Marker compounds like GA, EGCG and Thea can distinguish the storage time. • Hot-humid condition accelerated ester catechins degradation, flavonoids accumulation. [ABSTRACT FROM AUTHOR]

Herein, we reported a detailed profiling of soluble components of two fermented varieties of Chinese green tea, namely raw and ripe pu-erh. The identification and quantification of the main components was carried out by means of mass spectrometry and UV spectroscopy, after chromatographic separation. The antioxidant capacity towards different radical species, the anti-microbial and the enzyme inhibition activities of the extracts were then correlated to their main constituents. Despite a superimposable qualitative composition, a similar caffeine content, and similar enzyme inhibition and antimicrobial activities, raw pu-erh tea extract had a better antioxidant capacity owing to its higher polyphenol content. However, the activity of raw pu-erh tea seems not to justify its higher production costs and ripe variety appears to be a valid and low-cost alternative for the preparation of products with antioxidant or antimicrobial properties. [ABSTRACT FROM AUTHOR]

Raw Pu-erh tea (RPT) needs ageing before drinking. However, the influence from environment and time of storage on chemical profile and flavor of RPT is unclear. In this study, the RPTs stored in wet-hot or dry-cold environment for 1-9 years were assessed using metabolomics based on UHPLC-Orbitrap-MS and global natural product social (GNPS) feature-based molecular networking as well as electronic tongue measurement. The results exhibited that the chemical profiles of RPTs were similar at an early stage but started to differentiate from each other at the 5th and the 7th year in wet-hot and dry-cold environments. The discriminating features including N -ethyl-2-pyrrolidinone-substituted flavan-3-ols (flavoalkaloids), unsaturated fatty acids, lysophosphatidylcholines, flavan-3-ols, amino acids, and flavonol- O -glycosides among the three chemical profiles were discovered and analyzed by means of multivariate statistics, GNPS multilibraries matching, and SIRIUS calculation. The metabolomic data were consistent with the results obtained through electronic tongue measurement.