# Effect of Fermentation Humidity on Quality of Congou Black Tea
## 3 Results and Discussion
### Effects of Fermentation Humidity on Congou Black Tea Taste Composition
Previous studies have revealed thearubigins as the key substances for a tea infusion's red color as well as its taste concentration and intensity, while showing theabrownins as the main substances for the formation of a tea infusion's dark brown color and its bland taste [25]. The above results suggest that high humidity fermentation could promote the conversion of theaflavins to thearubigins and theabrownins, thus reducing the astringency of the tea infusion and increasing its redness and intensity. Amino acids not only contribute to a tea infusion's umami and sweetness, but also serve as important precursors to black tea aroma formation [26]. In Figure 3E, the content of free amino acids was seen to decrease with the increase of fermentation humidity. These content changes in amino acids are related to their degradation and transformation, and limited protein hydrolysis. The increased oxidation of polyphenols during fermentation at high humidity was reported to facilitate the conversion of amino acids [27]. This phenomenon was also observed in roasting banana chips [28] and in feed production from red clover. When wild-type and low PPO-active red clover were wilted and silaged to measure their free amino acid content during processing, higher levels of free amino acids were found in the low PPO-active red clover than in the normal PPO-active wild-type plants at all stages, and the high PPO-active red clover produced more protein-phenol complexes  
Figure 3: Content of tea polyphenols (**A**), theaflavins (**B**), thearubigins (**C**), theabrownins (**D**), amino acids (**E**), soluble sugars (**F**), flavones (**G**), four main monomers (TF, TF-3-G, TF-3\({}^{\prime}\)-G, TFDG) of theaflavins and their total (**H**), and four main monomers (EGC, C, EGCG, ECG) of catechins and their total (**I**) in different treatments. Significant differences at \(p<0.05\) are indicated by different lowercase letters. during silage, thus inhibiting protein hydrolysis and reducing the contents of free amino acids [29]. With increasing fermentation humidity, total soluble sugars (TSS) had an increase of 7.7% in the RH95 treatment versus the RH55 treatment (Figure 3F). As reported by [PERSON] et al. [30], a storage environment with high humidity and low temperature can help to keep the sucrose, glucose and fructose content of zucchini at a high level. [PERSON] et al. compared TSS in straw mushrooms stored at different humidity levels and found that a high relative humidity environment was beneficial for TSS retention [31]. An increase in TSS was also shown to enhance the sweetness and mellowness of a tea infusion [32]. Therefore, high humidity fermentation could significantly improve the sweetness of a tea infusion, thus favoring the formation of quality black tea. Flavones are a kind of flavonoids, including flavones, flavonoids and flavone glycosides. In Figure 3G, their total amount was observed to fall with rising relative humidity, but no significant difference was found between 75% relative humidity and above. Studies have shown that high humidity storage environments could accelerate the decline of flavonoids in Pericrapium Citri Reticulata [33]. The same trend was also observed in the storage of strawberry and tomato peels [34; 35]. During black tea fermentation, the total amount of flavonoids was significantly reduced as a result of an enzymatic catalytic redox reaction [36]. This is consistent with in vitro simulations, which showed that when substrates extracted from fresh tea leaves were mixed with distilled water with PPO and POD solutions for fermentation, the presence of PPO could significantly reduce the content of myricetin glucoside in tea, while POD could significantly reduce the content of all flavone glycosides [37]. This indicated that the high humidity environment may accelerate the oxidation process of flavones by increasing enzyme activity.