###### Abstract
Thanks to the widespread use of metabolomics techniques, compounds that relate to tea flavour and quality can now be identified with greater depth and comprehensiveness. [PERSON] et al. (2023) found that aged black tea showed a decreasing trend in the pH value in the liquid of tea along with the extension of the year, which might be related to the formation and accumulation of organic acids, such as L-ascorbic acid and salicylic acid [17]. The flavour performance of sweet aroma compounds in black tea may be due to the reduction in carbohydrates and acetylation of AAs during the period of hot-air second-drying [18]. Meanwhile, 620 differential substances were detected through metabolomics techniques during the manufacturing process of \"Huangjinya\" black tea [19]. Additionally, the identification of key odorants of \"Baimaocha\" black tea from different regions revealed that  
Figure 1: The difference in the manufacturing process between traditional Cougon black tea and innovative Congou black tea (Minkehong, MKH). Traditional black tea, like Tanyang Congou black tea, is typically crafted from a single bud and one or two leaves of fresh tea. After undergoing processes including withering, rolling, fermentation, and drying, traditional Congou black tea acquires its fine, tight, and uniform appearance and bright red liquor colour, as well as a sweet, mellow taste. In contrast to traditional Congou black tea, the innovative Tanyang Congou black tea (Minkehong, MKH) tends to be made from a single bud and two or three leaves. The withering process for MKH incorporates the turning-over treatment, which is followed by rolling, light fermentation, and drying. The quality of MKH is characterized by its robust appearance, orange-red liquid colour, and sweet taste with a flowery and fruity aroma. methyl salicate, geraniol, trans-\(\beta\)-ionone, and benzeneacetaldehyde were the definitive aroma compounds [20]. Through the detection of black tea during the process of manufacturing the product, the shaping of aroma quality was a continuous process, and each stage significantly affected the concentration of volatiles [21]. In addition, [PERSON] et al. detected the accumulation of fatty-acid-derived volatiles in different stalk positions, suggesting that the maturity of fresh leaves would be an important factor influencing the quality of Jinmudan black tea [22]. These findings serve as a valuable reference for establishing quality standards for diverse black tea products, as well as guidance for the oriented processing of various grades of tea. A classification of tea grades was conducted in recent years, including green tea (such as Xihu Longjing tea [23] and Huangshan Maofeng tea [24]), oolong tea (such as Anxi Tiehuanyin tea [25], Wuyi Rougui Tea [26], and Yashi Xiang tea [27]), and even Sri Lankan tea products [28]. Additionally, related quality identification was also revealed based on standard tea samples. However, limited research has been conducted to investigate the relationship between metabolic compounds and the quality and grade standards of MKH. In this study, we used different grades of MKH standard samples as research materials. Sensory evaluation was conducted as the initial step. UPLC-MS and GC-MS were utilized to identify the non-volatile components (including catechins, AAs, caffeine, etc.) and volatile compounds in MKH. Furthermore, we identified the key differential compounds among different grades of MKH using stoichiometry combined with multivariate statistical analysis. This study aimed to provide molecular evaluation results for improving the classification of different grades of MKH, as well as act as a reference for standardized production methods and marketing strategies.