A Rising Star in Dark Teas: The Processing, Microorganisms, Chemicals, Bioactivities, and Safety of Qingzhuan Tea

Qingzhuan tea (QZT), as a kind of representative dark tea, is a daily necessity for people in the high-cold and high-fat diet areas of northwest China, having many health effects such as weight loss, lipid reduction, and antioxidant ability. The production of QZT has a history of more than 1000 years, which originated in Yangloudong, Chibi City, Hubei Province. QZT is typically produced by subjecting sun-dried raw green tea to various processes, including pile fermentation, drying, autoclave formation, and aging. Pile-fermentation, as the key step of processing QZT, will form abundant microorganisms to generate extracellular enzymes, which leads to a series of biochemical transformations in intrinsic chemicals. The unique sensory and nutritional properties of QZT are formed through dynamic changes of microorganisms. Meanwhile, there are still potential risks of food safety to be resolved in the processing of QZT. This paper reviews the history, manufacturing, microorganisms, chemical composition, health benefits, and safety of QZT. We first demonstrate the panorama of QZT and discuss the opportunities and challenges in the future. However, the understanding of QZT has not been integrated, and a more comprehensive study is requisite to reveal the association between consumption of QZT and human health and further illuminate the future of QZT-derived products.