# Development of Assessment Criteria for Managing the Quality of Taishan Black Tea
## 1 Introduction  
As one of the three most-common non-alcoholic beverages, tea is highly favored by consumers for its distinctive taste and diverse aroma. The Tai'an tea area is situated in the south-central region of Shandong Province, which is primarily known for its production of Taishan green tea. Consumers are drawn to this variety because of its high aroma, strong taste, and brewing resistance [1]. However, climatic factors have led to limited spring and autumn tea production in the Tai'an tea area [2], making summer the primary season for tea cultivation. During this season, tea trees produce substances with a higher phenolic content and a stronger bitter taste, greatly impacting tea quality [3]. To enhance the value of tea tree raw materials during the summer, Taishan black tea was produced. On 22 December 2017, the former Ministry of Agriculture of the People's Republic of China officially granted registration and protection for the geographical indications for Taishan black tea, and in November 2023, 11 companies had received approval for its production and use.  
The quality of Taishan black tea is influenced by many factors, including the tea tree variety, processing technology, and production season. [PERSON] et al. [1] compared Taishan black tea harvested during the summer to existing tea varieties and reported that the quality of Taishan black tea was superior when processed by 'Fuding Dabai' and 'Qimenzhong'. Another study by [PERSON] et al. focused on 13 tea clones imported from Tai 'an, and it was observed that the ratio of phenol to ammonia in summer tea raw extracts of 'Jinxuan', 'Fuding Dabai', and 'Zhenggu Dabai' exceeded 12, resulting in excellent sensory quality, which was suitable for processing Taishan black tea. [PERSON] et al. [4] reported that the best qualities for Taishan black tea were found in the spring. The concentration of catechin compounds, including catechin (C) and epicatechin (EC), was found to be significantly higher in summer tea compared to spring black tea, reaching a level of 30.01 mg/g. Furthermore, the amino acid content in spring black tea was observed to be 3.08% greater than that in summer black tea [5]. However, due to temperature and humidity fluctuations, the fermentation of black tea was slow, leading to a noticeable greenish taste of the tea infusion. The characteristics of summer black tea, described as thick and strong, were more pronounced, and the tea soup was brilliant-red and bright. Conversely, autumn black tea leaves exhibited higher hardness, indicating insufficient fermentation and resulting in an overall quality slightly lower than that of spring and summer teas.  
The quality of Taishan black tea sold on the market is affected by many factors, and the consistency of its quality is poor. At the same time, there are also some differences between products. In order to improve and stabilize the quality of Taishan black tea, assessment criteria for managing the quality of Taishan black tea needs to be established urgently. In this work, we studied the products marketed by 15 major Taishan black tea manufacturers, and their compounds were analyzed using both national standard methods and gas chromatography-mass spectrometry. To conduct a comprehensive analysis, multivariate statistical analysis techniques, including principal component analysis, systematic clustering, and orthogonal partial least-square discriminant analysis, were employed. Aiding in this evaluation was the calculation of aroma vitality values, which helped clarify characteristic flavor components [6]. This study will evaluate the quality of Taishan black tea objectively and accurately, and provide data support for the quality judgment, standard formulation, and quality management of Taishan black tea products.