Quality Analysis and Comprehensive Evaluation of Guizhou Export Black Tea

To evaluate the quality of Guizhou export black tea and establish a comprehensive quality evaluation system, this study analyzed 21 Guizhou export black tea samples based on sensory evaluation and physical and chemical index determinations. Core indicators were identified through correlation, principal component, and cluster analyses. The entropy weight method was then used to determine their values and weights, ultimately constructing a quality evaluation system for export black tea. Results revealed that Guizhou export black tea had certain distinctive sensory characteristics. Specifically, Congou Black Tea was found to be characterized by its sweet and mellow taste with a flowery and fruity aroma, whereas Broken Black Tea had a distinct heavy and mellow flavor accompanied by bright red liquor. Based on analyses, this study obtained average values of 6.20%, 5.71%, 63.63%, and 37.33% for the moisture content, total ash, water-soluble ash ratio, and water extract of export black teas, respectively, all of which comply with both domestic and international standards. However, at 8.45%, the mean tea polyphenols content determined in this study falls below the standard limit of 9%. Moreover, strong correlations were detected between the physical and chemical indicators, and based on principal component analysis, three major components were identified with a cumulative variance contribution of 70.686%. In addition, six core quality indicators were screened out, tea polyphenols, theaflavins, water-soluble ash ratio, moisture content, water extract, and total ash, among which, water-soluble ash ratio (22.078%), moisture content (19.267%), and total ash (18.428%) emerged as key factors determining the quality of Guizhou export black tea. This comprehensive evaluation enabled the establishment that Guizhou Congou Black Tea had a significantly better quality compared to Brocken Black Tea. Consistent with the results of sensory evaluation, the following quality ranking for the different tea types was obtained: Spiral (CS)>long-shape (CL)>curly (CC)>fanning (BF)>broken (BB). These findings will provide a scientific reference for the quality control of export black tea in Guizhou.