Analysis of non-volatile and volatile metabolites during Ziziphus jujube leaf black tea processing via widely targeted metabolomics

Ziziphus jujube leaf black tea (BT-ZJL) have received extensive attention for their rich bioactive components. However, flavor formation and chemical changes during BT-ZJL processing are not well understood. This study was based on the analysis of non-volatile and volatile components of BT-ZJL using widely targeted metabolomics. Results indicated the presence of 1099 non-volatile metabolites. By screening for differentially expressed metabolites, we found the abundance of metabolites increased greatly after fermentation, and the non-volatile substances remained relatively stable during the drying process. Total polyphenols reached the maximum after fermentation, which was 25.72% dry weight. The alkaloid content was 30.65 mg/g in BT-ZJL, which was higher than traditional black tea. In addition, 755 volatile metabolites were identified, which are associated with the taste, aroma, color, and quality of BT-ZJL. The current results provide guidance and a theoretical basis for BT-ZJ processing that takes into account the desired quality and components.