Quality Grading of “Fubaiju” Based on Inflorescence Diameter and Content of Polyphenolic Substances

<i>Chrysanthemi</i> Flos encompasses numerous cultivars. Fubaiju (FBJ) is a subvariety of Hangbaiju introduced from Tongxiang City, Zhejiang Province. Due to the variable quality of FBJ on the market, establishing a standardized grading system is necessary. This study aimed to develop a simple and effective quality grading method for "Fubaiju" by integrating the inflorescence diameter and polyphenol content. The contents of chlorogenic acid, luteolin-7-<i>O</i>-glucoside, and 3,5-<i>O</i>-dicaffeoylquinic acid in 52 FBJ samples were determined by using UPLC-UV. The inflorescence diameter of the samples was measured, and correlation analysis was employed to examine relationships between the inflorescence diameter and polyphenol content. Samples were classified via K-means clustering based on polyphenol content and diameter, while sensory evaluation and antibacterial assays were utilized to validate the grading results. Results indicated negative correlations between the inflorescence diameter and the contents of chlorogenic acid and 3,5-<i>O</i>-dicaffeoylquinic acid. Cluster analysis categorized the samples into first-grade chrysanthemum (FGC) and second-grade chrysanthemum (SGC). FGC exhibited significantly smaller diameters and a higher polyphenol content. Electronic tongue analysis confirmed that FGC extracts possessed significantly stronger saltiness and astringency. Antibacterial tests demonstrated that FGC provided superior inhibitory effects against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> compared to SGC. This study confirms that grading FBJ quality using inflorescence diameter and key polyphenol content is feasible and effective. These findings establish a scientific foundation for standardizing the FBJ quality evaluation and provide a methodological framework for the quality control of traditional medicinal herbs.