More and more people are starting to collect tea leaves, and "antique tea" has become popular. For example, CCTV's "Treasure Appraisal" program once showcased a basket of 1953-produced dark tea valued at 480,000 yuan.

Dark tea is a type of post-fermented tea made from steamed and compressed green tea. The "golden flowers"—Eurotium cristatum—produced during fermentation are the secret behind dark tea becoming more fragrant with age. Varieties such as Qingzhuan, Xiangjian, and Fuzhuan dark teas all contain them.

Once tea leaves are inoculated with the golden flower fungus, they undergo unique changes due to the enzymes secreted by the fungus: the total amount of aromatic substances decreases, but low-boiling-point, volatile aromas increase significantly, forming the distinctive flavor of dark tea.

Besides aroma, the golden flower fungus also enhances the nutritional quality of dark tea. For instance, vitamin A increases noticeably. Eurotium cristatum appears golden on the outside and contains vitamin precursors, such as yellow pigments like β-carotene and lutein. One β-carotene molecule can hydrolyze to form two vitamin A molecules. Therefore, the nutrients in the tea leaves combine with those from the fungus. Moreover, the precious enzymes secreted by these "molds" can break down macromolecular substances like cellulose in the tea leaves, generating low-molecular-weight edible oligosaccharides. These have effects such as promoting weight loss, cleansing the intestines, and stimulating the growth of beneficial gut microorganisms, giving dark tea excellent weight-loss properties.