Unlocking the secrets of Qingzhuan tea: A comprehensive overview of processing, flavor characteristics, and health benefits

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.