# Development of Assessment Criteria for Managing the Quality of Taishan Black Tea
## 4 Discussion
The characteristic aroma of black tea hinges on the interaction and coordination of different aromatic functional groups present in its diverse volatile substances. In Chinese black tea, volatile compounds are dominated by alcohols and aldehydes, with a considerable content of ketones [30]. Similar findings were observed in this study, where alcohols were the prevalent compounds in the black tea, often formed through the reduction of aldehydes or the decomposition of hydroperoxides into fatty acids [31]. A total of 231 volatile substances and 40 alcohol substances were detected in the 45 samples analyzed. The OAVs of 1-octene-3-alcohol, (1R-(1) \(\omega\)), 2. \(\alpha\), 3. \(\alpha\). )]-1, 2-dimethyl-3-(1-methyl vinyl)-cyclopentanol, \(\alpha\)-terpineol, 1-pentene-3-alcohol, shun-6-nonene-1-alcohol, anti-3-hexene-1-alcohol, 4-isopropyl-1-methylcyclohex-2-enol, and 4-terpinol exceeded 1, signifying their contribution to the overall aroma. Notably, 1-octene-3-ol, a volatile component with a greenish fragrance, was detected in most samples. Aldehydes, with lower aroma thresholds than their corresponding alcohols, play a crucial role in the aroma of black tea. Most aldehydes have greenish, malty, fatty, sweet, and floral flavors, which are usually the products of lipid auto-oxification during production [20]. In Jinjunmei, Keemun, and Dianhong, 2-methylbutanal and 3-methylbutanal showed a high degree of aroma contribution [32]. In this study, 38 aldehydes were detected, with key aroma components including 2,6,6-trimethyl-1-cyclohex-1-acetaldehyde, 3-methylbutanal, decylaldehyde, laural, valeraldehyde, isobutanal, 2,6,6-trimethyl-1, 3-cyclohexenedien-1-formaldehyde, 2-methylbutanal, cetylaldehyde, and cis-2-decenal. 3-methylbutyaldehyde, 2-methylbutyaldehyde, capric aldehyde, and isobutyraldehyde were detected in most samples. Fruity, caramel, sweet, and fruity notes were associated with 3-methylbutyaldehyde, 2-methylbutyaldehyde, capric aldehyde, and isobutyraldehyde, respectively. These aldehydes, with both having higher relative contents (Figure 5) and OAVs exceeding 1 (Table S5), significantly contributed to the flavor of the Taishan black tea. Ketones, generated through thermal oxidation and polyunsaturated fatty acid degradation, play a crucial role in the overall aroma of tea due to their relatively low aroma thresholds [31]. In this study, 24 ketones were detected, with \(\beta\)-ionone and 2-nononone emerging as the main key aroma components. Furthermore, \(\beta\)-ionone, detected in most samples, exhibits a fruity aroma, resulting from the degradation of carotenoids. It contributes a distinctive black tea aroma, playing an essential role in the overall tea aroma [33]. The results of the sensory evaluation, combined with the prevalent flavor of volatile compounds in most samples, suggest that Taishan black tea exhibits a pronounced fruity and caramel flavor. This flavor profile is primarily attributed to the high drying temperature (120 to 130 \({}^{\circ}\)C) applied during the processing of Taishan black tea, and the elevation in the drying temperature is conducive to the Maillard reaction, which enhances the tea aroma and produces fruity and caramel notes [34]. The caramelized Dianhong black tea has a similar processing process [35]. The high drying temperature of Taishan black tea can be influenced by several factors. Firstly, producers may opt to increase the drying temperature to cater to the preferences of consumers who seek a robust tea aroma. Secondly, increasing the drying temperature can reduce the production and processing time. Thirdly, producers may use high-temperature drying to address quality issues such as raw taste and astringency, which can result from uneven and inadequate tea fermentation caused by one or several stages of black tea processing. However, whether the objective is to develop fruity or caramel aromas or to rectify defects, the control of temperature appeared to be inadequately managed in some samples in this study.