# Effects of Five Different Withering Methods on the Composition and Quality of Congou Black Tea
## 3 Results
### Effects of Different Withering Methods on the Composition of Catechins  
Catechins are important polyphenolic compounds found in tea leaves, and their individual composition and content significantly affect the taste and quality of tea. During the processing of black tea, catechins serve as important conversion substances for the formation of theflavirus and thearubigins, which are closely related to the color and taste of black tea. The research results of [PERSON] et al. [24] showed that epicatechin and epigallocatechin only have a bitter taste, without astringency, whereas gallocatechin gallate and epigallocatechin gallate have both bitter and astringent tastes. [PERSON] et al. [25] used inhalation-exhalation techniques to demonstrate that ester-type catechins in tea are the main substances responsible for the astringency of tea, with epigallocatechin gallate in particular contributing the most. As the main components of tea infusion flavor substances, various catechins vary in composition and content, resulting in different flavors of tea infusion. In this study, catechin (C), epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (ECG), and epigallocatechin gallate (EGCG) were detected. The contents of the catechin components obtained via the five withering methods are shown in Figure 3. Among them, in the SNW, the content of C was the highest at 0.179%, which was significantly different from those of the other withering methods. In the NAW treatment, the content of EC was the highest at 0.25%, which was significantly different from those in the other three withering treatments, except for WAW (\(p<0.05\)). The EGC content in NAW was highest at 0.55% and significantly different from that in SHW (\(p<0.05\)). ECG and EGCG had the lowest contents in SHW at 1.00% and 0.48%, respectively, and were significantly different from those in the other four treatment methods (\(p<0.05\)). The ECG and EGCG contents were highest in SNW at 2.04% and 1.48%, respectively. Among the five withering methods, SHW had the lowest content of all the catechin fractions, which may be related to the oxidation of polyphenic substances during the shaking process, followed by NAW, and SNW had the highest content of all the fractions. Combining Figure 1A with Figure 4, the lower tea polyphenol content but higher ester catechin content might be the reason for the lighter flavor but astringent taste of the WAW treatment. Figure 4: Bubble diagram of the catechin compositions of different withering methods. Effects of Different Withering Methods on Tea Pigments and Correlation Analysis with Other Nonvolatile Substances  
Theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs) are not only key substances that contribute to the color of infusion and infused leaves [26], but also strongly correlate with the flavor of tea. Additionally, they are important bioactive compounds in black tea [27]. TF are the main components that impart a bright red color to teainfusion, and they also affect the concentration, strength, and freshness of the flavor of black tea [28]. TRs constitute the main component that gives black tea its red color, with a certain level of astringency and a sweet and mellow taste. TBs cause the tea liquor to appear dark brown and taste bland, which is the main reason for the dark color of black tea. Therefore, in the processing of black tea, it is advisable to preserve more TFs and TRs while reducing the accumulation of TBs. Among the five withering methods, there was no significant difference in the contents of TFs (Figure 5A), but SHW had the highest content at 0.24%. There were significant differences in the contents of TRs and TBs (Figure 5B) (\(p<0.05\)), with SHW having the highest TR content at 8.69% and SNW having the lowest at 6.50%. SHW also had the highest TB content at 8.25%, while WAW had the lowest at 5.230%. The total ratio of TFs and TRs to TBs is an important factor in assessing the quality of black tea.