Green tea, Black Tea, Yellow Tea, and Oolong tea with a fresh aroma are prone to oxidation, moisture absorption, and flavor contamination during storage, which can degrade their quality; thus, they are not suitable for long-term storage. Conversely, aged White Tea, dark tea (black tea), and heavily roasted oolong teas like Wuyi rock tea can effectively improve their flavor quality and market value through appropriate storage. Consumers should choose rationally based on the type of tea and storage conditions, combining various methods to achieve the desired storage and preservation effects.

1. Tea Storage Techniques
1.1 Enhancing the Quality of Certain Teas Through Timely Storage Aged white tea, dark tea, and heavily roasted oolong teas like Wuyi rock tea can effectively improve their flavor quality and market value through timely storage. In Fuding City, Fujian Province, the main production area for white tea, there is a saying that white tea is “a one-year tea, a three-year medicine, and a seven-year treasure.” White tea stored under suitable conditions for an extended period is believed to have better health benefits than new tea and is used as a good medicine for inflammation and cooling the body. The most suitable storage condition for white tea is in a sealed container, away from light and at room temperature.

Dark tea, as a post-fermented tea, has the characteristic of “aging improves its aroma.” As the storage years increase, the market price of aged dark tea continues to rise, and the ability of Kang brick tea to fight oxidation and clear free radicals significantly increases. Using Pu'er brick tea produced in 1996, 2002, and 2009, high, medium, and low dosage models were set up to study the inhibitory effect of Pu'er brick tea on diarrhea caused by drugs in mice. The results showed that the longer the storage time of Pu'er brick tea, the better its anti-diarrheal effect, and it has a dose-effect relationship.

Newly roasted Wuyi rock tea will retain some smokiness, and timely storage can enhance its quality. During the initial storage period, the smokiness of Wuyi rock tea gradually fades, and the sensory quality improves; in the later storage period, the taste becomes more mellow, but the sharpness of the aroma slightly decreases.
1.2 Preservation Techniques Green tea, black tea, yellow tea, and Oolong Tea with a fresh aroma are prone to oxidation, moisture absorption, and flavor contamination during storage, which can degrade their quality. From the initial use of lime and charcoal for sealed storage to the current biological preservation methods, tea storage technology has been continuously developing and improving. With the research into the mechanisms of aging and degradation in various types of tea, a series of storage and preservation techniques have been summarized based on the causes of degradation, such as low-temperature refrigeration, oxygen removal and vacuum nitrogen addition, and biological preservation methods.

(1) Low-Temperature Refrigeration Temperature significantly affects tea quality, and low temperatures can effectively slow down the oxidation of substances within the tea. Low-temperature refrigeration is currently the most widely used method in the market. Large tea companies typically store tea in cold storage (the temperature is generally set between -1°C and 8°C, with humidity below 65%). However, when removing the tea, attention must be paid to eliminating temperature differences because there is a significant difference between the temperature of the tea stored at low temperatures and room temperature, making it susceptible to dampness and spoilage due to condensation. Small merchants and households can usually choose to store tea in refrigerators or freezers for preservation. Although low-temperature refrigeration is very effective, it consumes a large amount of energy.

(2) Oxygen Removal and Vacuum Nitrogen Addition Oxygen is one of the primary factors leading to changes in tea quality, and oxygen removal and nitrogen addition can effectively isolate oxygen and prevent degradation. Currently, there are two main oxygen removal methods:
① Adding oxygen absorbers. One category includes inorganic substances such as activated carbon and active iron; another category includes organic compounds such as vitamin C and linoleic acid. Oxygen absorbers absorb the oxygen in the packaging bag to achieve the effect of oxygen removal. This method is low-cost and easy to operate, and its effect is more significant when combined with low-temperature and dry storage.
② Vacuum nitrogen addition. This involves using a vacuum packaging machine to remove oxygen and then filling the package with nitrogen gas. This method can effectively remove oxygen from the tea packaging and provide a relatively oxygen-free or low-oxygen environment for tea storage, suitable for small-package tea storage with good preservation effects.

(3) Biological Preservation Biological preservation uses the oxygen isolation and antibacterial effects of natural or artificially added microbial populations to achieve preservation and prevent quality degradation. Compared with traditional methods, this technique can maximize the retention of the original quality of tea and is safe and non-toxic. Currently, Bacillus is commonly used in tea, forming a biofilm on the surface of the tea to achieve oxygen isolation and prevent degradation.

2. Outlook Aged white tea, dark tea, and heavily roasted oolong teas like Wuyi rock tea are typically considered to have better quality and value after long-term storage, while other teas such as green tea, black tea, and yellow tea are the opposite. They are easily affected by their own characteristics and storage conditions during long-term storage, and their freshness and sensory qualities, such as taste, will continually decline over time, reducing their economic value. With the continuous development of science and technology and the deepening of tea research, emerging storage technologies continue to emerge, and tea storage and preservation technologies are developing towards being more efficient, economical, energy-saving, and eco-friendly. Moreover, tea storage and preservation do not rely solely on a single method but require the joint use of various storage and preservation techniques. Based on the specific variety of tea, sales requirements, preservation effects, and costs, the maximum synergy of various methods should be achieved to reach the ideal storage and preservation effects.

Currently, research on tea mainly focuses on the processing and fermentation processes of the six major tea categories, while research on quality changes during tea storage and storage techniques is still relatively limited, especially for yellow tea, with almost no related research. Therefore, we hope that more scholars will devote themselves to research on the chemistry of tea storage quality and storage techniques in the future.

China Tea