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Dark tea is one of the most popular types of tea, in order to sort out the research process of dark tea, this paper using CiteSpace visualization analysis software, based on China National Knowledge Infrastructure (CNKI) database and Web of Science (WOS) database, 3436 Chinese and 617 English literatures were screened and analyzed by visualizing the information of authors, keywords, research institutions, countries and published journals. It is found that the number of dark tea literature is increasing, which is now in the stage of rapid development. The Chinese researches are earlier than English researches. Tea in Fujian and Journal of Agricultural and Food Chemistry were the Chinese and English journals with the highest publication volume of dark tea. The study of dark tea forms a number of research groups represented by scholars, scholar representatives included LIU Zhonghua, LÜ Caiyou and ZHOU Hongjie, etc. The research institutions are mainly agricultural colleges and tea research institutes, and the institutions with more in-depth research results are Yunnan Agricultural University, Hunan Agricultural University and Anhui Agricultural University. China is the most influential Country in dark tea research, followed by The United States of America and Japan. Chinese literature focused on the mechanism of dark tea quality formation, microorganisms, aroma composition, while English literature pays more attention to the pharmacological research, and the research of dark tea's intervention efficacy on metabolic diseases such as diabetes, atherosclerosis is still the a hotspot of dark tea research in the future.

The chemical composition, quality characteristics, antioxidant activity, and "golden flower" fungi morphology of Fu brick tea from Hunan, Hubei, Shaanxi, Guizhou, and Zhejiang provinces of China had been researched in this study. The results revealed significant differences in the contents of chemical components in different Fu brick tea (P

Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and sensory evaluation were used to investigate the aroma characteristics of different dark tea products (Fu brick tea, Dark brick tea, Tibetan tea, Liupao tea, and Tianjian dark tea). Sensory evaluation results showed that the aroma characteristics of the five dark tea samples differed remarkably. Fungal and stale aromas were the major aroma profiles of Fu brick tea. Results showed that, Liupao tea had obvious persistent areca-like and stale aromas, Tibetan tea had a persistent stale aroma, and Dark brick tea exhibited a pure aroma feature. Furthermore, Tianjian dark tea showed a persistent smoked aroma. The following rank order of the score of the sensory evaluation in the five dark teas was observed: Tibetan tea (91.35) > Fu brick tea (90.15) > Dark brick tea (89.05) > Liupao tea (88.85) > Tianjian dark tea (86.33). A total of 56 volatile compounds were identified in the five dark teas. The composition and content of aroma components varied significantly among the different dark teas. Contents of the volatile compounds in the five dark teas with the following rank order: Fu brick tea (6355.30 μg/L) > Tibetan tea (5858.73 μg/L) > Dark brick tea (5789.71 μg/L) > Tianjian dark tea (4801.37 μg/L) > Liupao tea (3740.14 μg/L). Multivariate statistical analysis and odor activity values analyses showed that 1,2,3-trimethoxybenzene was the characteristic volatile component of the stale aroma of Tibetan tea. (E,E)-2, 4-decadienal, (E,E)-2, 4-nonadienal, citral I, citral II, hexanal, and methyl salicylate contributed to the fungal aroma of Fu brick tea, while 1,2,3-trimethoxybenzene was the key contributor to the stale aroma of Fu brick tea. In Liupao tea, (+)-cedrol was a major contributor to the areca-like aroma. (E,E)-2, 4-decadienal, (E,E)-2, 4-nonadienal, hexanal, and phytol were the main contributors to the pine-smoked aroma of Tianjian dark tea. The pure aroma of Dark brick tea was formed by the comprehensive action of many volatile components, including benzene ethanol, neroltertiary alcohol II, and oxidized linalool I. This study would provide a statistical basis for exploring the aroma quality of different types of dark teas.

White tea is a unique kind of micro-fermented tea in China. In order to explore the quality differences of different types of white tea, ten samples including Baihaoyinzhen, Baimudan, Gongmei, Shoumei and New White tea were selected for high performance liquid chromatography (HPLC) detection of catechins, gas chromatography-mass spectrometry (GC-MS) detection of aroma components and sensory evaluation, combining with multivariate statistical analysis such as analysis of variance and OPLS-DA. The results showed that the content of catechins in different types of white tea varied greatly, the total catechin content of Gongmei was the highest and that of Shoumei was the lowest, which were 66.84 and 32.66 mg/g respectively, and a total of fifty aroma substances were detected in all white tea, the main aroma components consisted of hexanal, (E)-2-hexenal, benzaldehyde, linalool and its oxides (I, II). The aroma composition and content of Baihaoyinzhen, Baimudan, Gongmei and Shoumei were different from those of the New White tea. Among them, eight aroma components such as (E)-2-pentenoaldehyde and 2-heptanone existed in a large number in the four traditional white tea, but they were not detected in the New White tea. Through multi-component chemometric analysis, it was found that there were significant differences in catechins and aroma metabolites between Baihaoyinzhen, Baimudan, Gongmei and New White tea, but there was little difference between Shoumei and New White tea. This study preliminarily proved the quality differences of different types of white tea, which provided a theoretical basis for the regulation of white tea flavor quality.

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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.)

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.)