# Effect of Fermentation Humidity on Quality of Congou Black Tea
## 3 Results and Discussion
### Effects of Fermentation Humidity on Congou Black Tea Volatile Compound Composition
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Substances** & **RH55** & **RH65** & **RH75** & **RH85** & **RH95** \\ \hline Alcohols & 257.22 \(\pm\) 5.34 a & 258.88 \(\pm\) 6.44 a & 262 55 \(\pm\) 6.16 a & 266.57 \(\pm\) 16.09 a & 270.37 \(\pm\) 5.33 a \\ Alkanes \& Alkenes & 12.64 \(\pm\) 0.9 b & 12.97 \(\pm\) 0.99 b & 16.95 \(\pm\) 1.54 a & 15.79 \(\pm\) 1.58 a & 15.67 \(\pm\) 0.89 a \\ Esters & 49.21 \(\pm\) 1.29 a & 47.85 \(\pm\) 1.72 a & 48.7 \(\pm\) 3.28 a & 49.07 \(\pm\) 2.43 a & 48.85 \(\pm\) 2.12 a \\ Aldehydes \& Ketones & 93.45 \(\pm\) 0.68 b & 91.6 \(\pm\) 1.14 b & 94.99 \(\pm\) 3.89 b & 95.2 \(\pm\) 1.47 b & 98.99 \(\pm\) 1.21 a \\ Acids & 17.55 \(\pm\) 1.45 c & 17.73 \(\pm\) 0.19 c & 17.94 \(\pm\) 1.63 bc & 19.91 \(\pm\) 0.47 b & 22.33 \(\pm\) 1.37 a \\ Phenols & 5.17 \(\pm\) 0.34 ab & 5.35 \(\pm\) 0.11 a & 4.51 \(\pm\) 0.25 c & 4.52 \(\pm\) 0.19 c & 4.83 \(\pm\) 0.15 bc \\ Others & 1.65 \(\pm\) 0.07 d & 1.87 \(\pm\) 0.02 c & 4.46 \(\pm\) 0.12 a & 3.71 \(\pm\) 0.07 b & 3.81 \(\pm\) 0.11 b \\ Total & 436.88 \(\pm\) 5.90 b & 436.25 \(\pm\) 8.52 b & 450.11 \(\pm\) 7.04 ab & 454.77 \(\pm\) 20.71 ab & 464.84 \(\pm\) 6.05 a \\ \hline \hline \end{tabular} Note: Significant differences at \(p\) < 0.05 are indicated by different lowercase letters in the same row.  
\end{table} 
Table 2: Effect of fermentation humidity on the contents of different volatile species in congou black tea. (ug/g). the characteristic aromas of sweet, floral and fruity odors in congou black tea [3]. For example, linalool and its oxides are the key aromatic substances in black tea, and their content increase is associated with the up-regulated expression of the linalool synthase gene (_CsLIS_), which converts geranyl diphosphate into linalool. Additionally, \(\beta\)-glucosidase can also increase the linalool content by hydrolyzing linalool glycosides [41]. VTs such as nerol, \(\alpha\)-farnesene and linalool and its oxides act together as key active compounds to provide floral aromas to black tea [42], while \(\beta\)-cyclocitral, which is attributed to CDVs, provides fruity and faint scents to congou black tea. Based on the available reports, it can be found that substances such as linalool oxides and ionone can increase black tea floral aroma, and benzaldehyde and phenylacetaldehyde can increase its sweet aroma [40]. Combined with Table S2, all these substances were found to be most abundant in the RH95 treatment, and despite not being recognized as essential fragrance chemicals, they still contributed to the presentation of black tea's aroma. Overall, as the relative humidity of the fermentation environment increased, the content of volatile compounds in the black tea increased, leading to a rise in aroma concentration. The contents of linalool, its oxides, nerol and other substances beneficial to black tea aroma quality showed a significant increase, indicating that high relative humidity fermentation is more conducive to the formation of pleasant aromas in congou black tea, which was well supported by the sensory evaluation results. Figure 5: Proportion of different volatile species in the samples (**A**), OPLS-DA score plot of black tea with different humidity treatments (**B**), permutation test of black tea with different humidity treatments (**C**), and cluster heat map of variant aroma components of black tea under different fermentation humidity conditions (**D**).