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Qingzhuan tea (QZT) is classified as compressed dark tea and has been an essential daily commodity for ethnic minority communities in China's border areas. It boasts unique flavor characteristics and health benefits, captivating the attention of consumers both domestically and internationally. However, the QZT industry's historical closed nature and lengthy processing cycle have impeded a comprehensive scientific understanding and evaluation of this tea, as well as hindered the overall healthy development of the industry. This article provides a comprehensive overview of the research progress on QZT, covering defluoridation techniques, processing technology, flavor characteristics, chemical composition, microbial communities, health benefits, and their underlying mechanisms. A technology system aimed at reducing fluoride levels in tea, known as "appropriate fertilization-selection of low-fluorine tea tree varieties-control of raw material tenderness and growing period," has been proposed. Through the implementation of specific processing techniques, QZT exhibiting an orange-red infusion color, a mellow taste, and an aged aroma. During the key pile fermentation process, microorganisms release extracellular enzymes that initiate enzymatic and moist heat reactions, resulting in oxidation, hydrolysis, polymerization, and secondary metabolic conversions. These reactions serve as the underlying foundation for the distinctive sensory attributes of QZT. The regulation of microorganisms plays a vital role in attaining the desired flavor of QZT. Moreover, QZT encompasses a diverse array of bioactive constituents, which offer numerous health advantages such as antioxidative properties, anti-obesity and anti-diabetes effects, modulation of the intestinal microbiota, and alleviation of non-alcoholic fatty liver. • A systematic approach to reduce fluoride in tea is proposed. • Specific techniques are used to create Qingzhuan tea (QZT) with vibrant color, taste and aroma. • The role of microorganisms in developing QZT's sensory traits is revealed. • Diverse bioactive compounds in QZT for health benefits are highlighted. [ABSTRACT FROM AUTHOR]

[Display omitted] • Changes in characteristic aroma-active compounds occur during processing at an industrial scale. • Pile fermentation increases the proportion of olefinic aldehyde compounds. • Methoxybenzene compounds formed during pile fermentation were weakened by aging. • Olefinic aldehydes, ketones, and methoxybenzenes were the characteristic volatiles of aged fragrances. Changes in key odorants and aroma profiles of Qingzhuan tea (QZT) during its manufacture were determined using headspace solid-phase microextraction gas chromatography-mass spectrometry/olfactometry. An aroma profile was constructed to illustrate sensory changes during manufacture. The characteristic aroma of QZT was aged fragrance, which was mostly developed during pile fermentation and was enhanced during the aging and drying stages. Using volatile compounds found in the raw materials, sun-dried green tea and QZT finished product were compared by orthogonal partial least square-discriminant analysis. Among 108 detected volatiles, 19 were significantly upregulated and 15 were downregulated. (E)-β-Ionone, (E,Z)-2,6-nonadienal, 1-octen-3-one, (E,E)-2,4-heptadienal, (E,E)-2,4-nonadienal, safranal, (E)-2-nonenal, α-ionone, and 1,2,3-trimethoxybenzene were found to be significant contributors to the aged QZT fragrance, reflecting their high odor-activity values and aroma intensities. Finally, the metabolic transformation of key aroma-active compounds was systematically analyzed. This study provided a theoretical basis for improving the processing and quality of QZT. [ABSTRACT FROM AUTHOR]

The tea plant is a fluoride hyperaccumulator, and fluoride accumulation in its leaves is closely related to human health. To dissect molecular mechanisms underlying fluoride accumulation/detoxification, the leaves of tea seedlings exposed to different fluoride treatments for 30 days were sampled for physiological and proteomics analyses. The results showed that fluoride had no adverse effects on the growth of tea seedlings in spite of high content fluoride accumulation in their leaves. Through TMT coupled with UPLC MS/MS, 189 differentially accumulated proteins were quantified, of which 41 and 148 were localized in the cell wall and cellular compartments respectively. 41 cell wall proteins were mainly conductive to cell wall structure rearrangement, signaling modulation and the protection cells from damages; 148 cellular compartments proteins mainly contributed to diverse metabolisms reprogramming, energy reallocation and plant defense. Notably, upregulation of several proteins including GHs, smHSPs, DRT100, YLS2-like, primary amine oxidase, GDSL esterase/lipases and citrate synthase probably enhanced the defense of tea seedlings against fluoride. Collectively, our results presented a comprehensive proteomics analysis on the leaves of tea seedlings in response to fluoride, which would contribute to further deciphering of molecular mechanisms underlying fluoride accumulation/detoxification in tea plant. Significance The tea plant ( Camellia sinensis ) is an important economic crop with its made tea occupying up the third non-alcohol beverage in the world. Tea plant is also a fluoride hyperaccumulator with up to 98% fluoride accumulation in the leaves by initiative absorption. Due to the fact that about 40% to 90% of fluoride could be readily released into tea infusion and then absorbed by human body, overaccumulation of fluoride in tea leaves is closely related to human health. Therefore, it is very necessary to deeply dissect the mechanisms underlying fluoride accumulation/detoxification in tea plant. Previously, numerous studies were conducted to investigate fluoride specification and fluoride localization of tea plant at morphological, physiological and biochemical levels, which documented that fluoride was majorly immobilized in the cell walls and stored in the vacuoles in the form of fluoride-ligands complexes. However, the molecular mechanisms governing cell wall immobilization and vacuolar compartmentation of fluoride were still remaining unknown. Thus, a quantitative proteomics study into the leaves of tea seedlings upon exposure to fluoride was performed in current study. Our results showed that 41 and 148 of 189 differentially accumulated proteins were targeted into the cell wall and cellular compartments respectively, revealing that cell wall proteins and cellular compartments proteins played crucial roles in the response of tea seedlings to fluoride. Our results were also in good agreement with the idea that the cell wall was involved in fluoride accumulation/detoxification in tea plant. However, the functions of key interested differentially accumulated proteins need be further analyzed in follow-up work. [ABSTRACT FROM AUTHOR]