Tea storage: A not thoroughly recognized and precisely designed process

During storage, multiple biological, chemical and physical reactions occur in tea, giving rise to the alteration of tea qualities. However, tea storage technologies still remain primitive after a prolonged evolution, and approximately 70% of teas deteriorate irreversibly each year owing to improper storage. Currently, research about tea storage is mainly focused on the impact of time scale on quality, the storage condition and technology remain little noticed. In this review, the quality evolution rules, characteristic storage markers and identification technologies of six tea categories during storage were summarized for the first time. Based on the quality evolution rules, key environmental influencing factors were introduced. Meanwhile, existed methods aiming at storage, especially storage technologies based on regulating environmental factors, were reviewed. Future storage technologies were prospected combined with present advanced storage technologies in food industry. Therefore, a theoretical system of “quality evolution rules-key storage environmental factors-future storage technologies” was proposed. According to disparate storage duration-quality correlation, teas were classified into green tea, yellow tea and lightly-baked oolong tea (negative correlation), heavily-baked oolong tea, white tea, dark tea, raw Pu-er tea (positive correlation), black tea (non-linear correlation). During storage, inherent compounds in tea are susceptible to transformations influenced by environmental factors including heat, moisture, oxygen and light, thereby altering tea quality. Additionally, this review points out that there is less accumulation of studies about tea storage technology. Intelligent monitor-control technologies for environmental factors should be developed in the future.