Effects of Different Drying Processes on the Quality and Volatile Flavor Components of Jinmudan Tea (Camellia sinensis L.) Flowers

To explore the effect of different drying methods on the floral quality and volatile flavor compounds of Jinmudan tea flowers, three drying techniques were selected including vacuum freeze-drying (pre-freezing for 2 hours, freeze-dried for 6, 8, 10 hours, cold trap temperature −50 ℃, which were treatments 1, 2 and 3 respectively), hot air drying (the treatment time was 3, 4 and 5 hours, and the baking temperature was 75 ℃, which were treatments 4, 5 and 6 respectively), and natural drying (CK). The effects of these drying processes on sensory quality, chemical composition, amino acid profile, and volatile flavor compounds of tea flowers were analyzed. The results revealed that tea flowers dried using the vacuum freeze-drying method exhibited the best sensory quality, with a distinct honey aroma preserved. Among them, the tea flowers subjected to treatment 3 obtained the highest overall sensory evaluation score, along with higher levels of water extract, tea polyphenols, and caffeine content. Furthermore, they exhibited the highest total amino acid content, sweetness amino acid content, freshness amino acid content, and essential amino acid content. A total of 107 volatile compounds were identified across the 3 drying processes, with alcohols, alkanes, and ketones comprising the predominant volatile components. Hierarchical cluster analysis (HCA) based on principal component analysis (PCA) further classified the volatile substances into 4 groups corresponding to 3 drying methods. A partial least squares discriminant analysis (PLS-DA) model was established to select 35 volatile components with variable importance in projection (VIP) values greater than 1, indicating differential markers. Additionally, the volatile substance patchoulol was identified as unique to the CK group. In summary, vacuum freeze-drying is the most effective method for preserving the aroma and bioactive compounds of tea flowers, with treatment 3 demonstrating the optimal overall evaluation. This study provides a theoretical basis for exploring the effects of drying methods on the quality and flavor of tea flowers and their corresponding changes in volatile components.