# Improving the Sensory Quality of Black Tea by Blending Varieties During Processing
## 1 Introduction  
Black tea is widely consumed around the world due to its health benefits and rich flavors [1, 2]. Several factors influence the quality of black tea, including the variety of the tea plant, the ecological environment in which it is grown, and the processing techniques used [3, 4]. Traditional processing methods for black tea include withering, rolling, fermenting, and drying [5]. Producers often adjust these processing parameters to enhance the quality of black tea, but the change in flavor characteristics is limited. For example, _Fudingdabai_ is currently the most widely planted tea variety for producing black tea [6]. The black tea made from it has a relatively balanced flavor and aroma, but it is difficult to create a distinctive floral-scented black tea from it [7]. The unique flavor characteristics of black tea are primarily determined by the tea variety, which is influenced by the varying chemical components present in different varieties. For example, a tea variety with a high amino acid content tends to have a pronounced umami and fresh taste, while varieties rich in catechins can produce a more mellow or \"kokumi\" taste, as well as bitterness and astringency [8]. The variety of _Camellia sinensis cv. Zhuye_ is used to produce Keemum black tea and is known for its distinctive \"Keemun aroma\", which features rose-like notes. In contrast, many oolong varieties that are cooked as black tea tend to present rich floral and fruity aromas. Therefore, to address the varying quality of the teas and meet diverse consumer preferences, different varieties of cooked tea products with varying characteristics are often blended before reaching the market [9]. The blending of tea has been defined as the proper mixing of more than one variety or grade of tea from various tea estates or regions, resulting in a unique or distinctive type of tea [10]. The blending process is typically manual, where the right proportions of ingredients are selected based on their appearance, aroma, and taste. This process creates a blended tea that is soothing, desirable, palatable, and price-competitive. However, this traditional blending method requires experienced technical personnel as well as a significant amount of time and effort. Additionally, the traditional blending method is influenced by subjective factors, which makes the quality of the tea not very stable. In recent years, new technologies have been used to improve blending methods, addressing the subjective influences on the results. [PERSON] et al. [11] developed an intelligent approach using hierarchical spatial clustering-based algorithms for the blending process, which provided a universal, low-cost, and efficient blending program to aid in financial decision-making. [PERSON], [PERSON], and [PERSON] [9] employed chemometric methods to develop an algorithm for determining blending proportions, accompanied by an easy-to-use graphical interface that simplifies and accelerates the tea blending process at a lower cost. [PERSON] [12] employed Monte Carlo simulation approaches to formulate a multi-objective model for the blending problem in the tea industry. However, the advancements in blending methods often represent mere modern adaptations of traditional manual techniques without fully reforming the complex and time-consuming tea-blending process involved. Research shows that the blending of fresh leaves from different varieties of raw materials can affect the levels of tea polyphenols, theaflavins, catechins, amino acids, and aroma [13]. If fresh tea leaves of different varieties are blended based on their individual strengths in aroma, taste, and other characteristics, then the blending can be incorporated throughout the entire production process, negating the need for post-production blending. This approach streamlines operations, making the process more convenient and cost-effective.