# Difference in Aroma Components of Black Teas Processed on Different Dates in the Spring Season
## 3 Results and Discussion
### Identification and Integral Comparison of Volatile Compounds  
To further illuminate the differences in the aroma components in black teas processed on different dates in the spring season, the volatile compounds were determined using GC-MS. In this study, a total of 71 volatile compounds were identified, consisting of 7 aromatic hydrocarbons, 7 alkenes, 18 alcohols, 21 aldehydes, 7 ketones, 8 esters, 2 heterocyclic compounds, and 1 sulfur compound (Table 2). Alcohols were the predominant category, reaching an average of 388.20 \(\mathrm{\SIUnitSymbolMicro g}\)/L and accounting for 60.98%, followed by esters (119.11 \(\mathrm{\SIUnitSymbolMicro g}\)/L, 18.63%) and aldehydes (70.35 \(\mathrm{\SIUnitSymbolMicro g}\)/L, 11.36%) (Table 2 and Figure S1). This is not consistent with previous studies [6; 10]. This discrepancy may be due to the differences in the detection method. Heterocyclic compounds were the least abundant aroma components (Table 2 and Figure S1). In terms of individual volatile compounds, according to their average content, geraniol was the most abundant volatile, followed by methyl salicate, linalool, phenylethyl alcohol, trans-linalool oxide (furanoid), benzene acetaldehyde, myrcene, nonanal, nerol, nerolidol, cis-linalool oxide (furanoid), and geraniol, etc., which is essentially consistent with the results of previous studies [6; 10; 11; 12; 13]. As shown in Table 2 and Figure 1, there were obvious differences in the content of different types of volatile compounds. The total content of volatile compounds first increased and then gradually decreased. Black teas produced on April 15 th (ZYQ-3) and March 23 rd (ZYQ-1) had the highest and lowest total content, respectively. It was reported that black tea produced in autumn had the highest content of volatile compounds, successively followed by that produced in spring and summer [15]. This implies that an appropriate temperature is conducive to the accumulation of aroma components and their precursors in fresh tea leaves, thus promoting the aroma concentration of black tea, while an excessively high temperature may bring the opposite effect. From March 23 rd to May 7 th, the temperature continues to increase. From the perspective of the total content of volatile compounds, the most suitable temperature to achieve a good black tea aroma is around April 15 th in the Hunan district, China. The changes in the content of alkenes, alcohols, and esters were consistent with that in the total content of volatile compounds. The content of aldehydes was dramatically increased on May 7 th (ZYQ-5). The content of ketones and sulfur compounds displayed an increasing trend, while the content of aromatic hydrocarbons and heterocyclic compounds showed irregular change trends. \begin{table}
\begin{tabular}{c c c c c c} \hline  & **ZYQ-1** & **ZYQ-2** & **ZYQ-3** & **ZYQ-4** & **ZYQ-5** \\ \hline Aroma description & Sweet, approaching strong & Sweet, strong and lasting & Sweet, nearby strong, lasting & Sweet, strong, with slight floral scent & Sweet, strong and lasting \\ \hline Score & 92.2 & 93.2 & 93.5 & 93.0 & 93.2 \\ \hline \end{tabular}
\end{table} 
Table 1: The sensory evaluation of the aroma quality of black teas. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**No.