# Effect of Aging Time on the Composition of the Volatile Components of An-tea
## 4 Discussion  
### Aroma Components of Aged An-tea  
More than 700 types of volatile compounds have been related to tea aroma. However, only some of these play key roles in the quality of tea aroma [7]. In this study, a total of 64 volatile compounds were detected in aged An-tea, with only 20 in common to the HAS, MAS, and LAS samples (Table 6)--with ketones and aldehydes being the most common. Owing to the homogeneity of the specific \"aging aroma\" of An-tea in samples with different degrees of aging, it can be speculated that the 20 common volatile compounds from above form the material basis of its formation, with some of them potentially being essential for the \"aging aroma\" of An-tea. Of the 20 common compounds, ketones provide fragrant, fruity, and woody aroma notes; aldehydes have fragrant, herbal, and medicinal notes; alcohols have fragrant and fruity notes; hydrocarbons and esters have woody notes; and furans have fruity and fragrant notes, all of which constitute the \"background\" to the An-tea \"aging aroma\". Of the common compounds, the relative contents of linalool, \(\beta\)-ionone, safranal, benzaldehyde, 6-methyl-5-hepten-2-one, and \(\alpha\)-ionone were high. The threshold values of linalool [21], \(\beta\)-ionone [21], benzaldehyde [22], and \(\alpha\)-ionone [22] are 0.6, 0.2, 0.35, and 0.4 g/L, respectively, while that of 6-methyl-5-hepten-2-one [23] is 50 g/L. The threshold value of safranal has not yet been determined. From these results, linalool, \(\beta\)-ionone, benzaldehyde, and \(\alpha\)-ionone were considered the key compounds providing the aroma quality of aged An-tea. One study has used GC/MS to determine the volatile substances in three types of low-grade aged An-tea in Chizhou City [3]. According to this study, linolenic acid (10.15%), dibutyl phthalate (10.12%), styrene (9.43%), and linalool (9.33%) produced the characteristic aroma substances of An-tea, while \(\beta\)-ionone might also be related to the characteristics of aged tea. Therefore, it can be suggested that linalool and \(\beta\)-ionone are two key compounds in the \"aging aroma\" of An-tea. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Volatile**} & \multicolumn{2}{c}{**The First Principal**} & \multicolumn{2}{c}{**The Second Principal**} & \multicolumn{2}{c}{**The Third Principal**} \\  & \multicolumn{2}{c}{**Component**} & \multicolumn{2}{c}{**Component**} & \multicolumn{2}{c}{**Component**} \\ \cline{2-7}  & **Eigenvector** & **Loading** & **Eigenvector** & **Loading** & **Eigenvector** & **Loading** \\ \hline ketones & 0.136 & 0.937 & \(-\)0.218 & \(-\)0.339 & 0.391 & 0.087 \\ aldehydes & 0.237 & 0.936 & 0.056 & 0.351 & 0.236 & 0.020 \\ alcohols & \(-\)0.184 & \(-\)0.906 & \(-\)0.246 & \(-\)0.138 & 0.217 & 0.400 \\ esters & 0.120 & \(-\)0.703 & \(-\)0.013 & \(-\)0.609 & \(-\)0.525 & \(-\)0.367 \\ phenols & \(-\)0.245 & \(-\)0.156 & -0.137 & \(-\)0.965 & \(-\)0.052 & \(-\)0.208 \\ hydrocarbons & 0.245 & 0.504 & \(-\)0.141 & \(-\)0.792 & 0.012 & 0.346 \\ nitrogenous & \(-\)0.132 & \(-\)0.458 & 0.319 & 0.032 & 0.204 & \(-\)0.888 \\ others & 0.041 & 0.519 & 0.389 & 0.540 & 0.123 & 0.662 \\ \hline \end{tabular}
\end{table} 
Table 4: Eigenvectors and loading matrix of first three principal components. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Aging time** & **F1** & **F2** & **F3** & **F *** & **Order** \\ \hline HAS & 0.732 & 0.063 & \(-\)1.308 & 0.096 & 3 \\ MAS & 0.086 & 1.331 & 0.686 & 0.598 & 1 \\ LAS & 0.621 & \(-\)1.052 & 0.870 & 0.155 & 2 \\ CK & \(-\)1.439 & \(-\)0.342 & \(-\)0.248 & \(-\)0.849 & 4 \\ \hline \end{tabular}  
* F = F1 \(\times\) Contribution rate1 + F2 \(\times\) Contribution rate2 + F3 \(\times\) Contribution rate3, Contribution rates shown in Table 3.  
\end{table} 
Table 5: Overall scores of principal components after standardization. As well as the endogenous compounds produced by various biochemical reactions in tea, the leaves of the checker-patterned Indocalamus and bamboo baskets used for packaging An-tea also produce volatile compounds.