Coordinated reorganization of non-volatile and volatile metabolites shapes flavor characteristics of Xinyang Maojian during processing

Abstract Xinyang Maojian (XYMJ) tea is valued for its characteristic flavor. However, the molecular and chemical processes driving quality formation during processing have not yet been clearly clarified. Here, fresh leaves and processed tea were systematically compared to elucidate processing-induced changes in key flavor-related components and antioxidant capacity. Processing markedly reduced moisture content from 66.89% to 7.12% and altered major physicochemical indices, including decreases in glucose, fructose and caffeine, alongside an increase in total flavonoids (156.65 to 173.16 mg/g). A total of 13 free amino acids were identified, with glutamic acid remaining dominant (2310.56 to 1940.03 μg/g), supporting the maintenance of umami characteristics. Metabolomic analysis identified 1611 polyphenolic compounds, with significant enrichment of flavones and flavonols, accompanied by a reduction in galloylated phenolics and anthocyanidins. Organic acid profiling revealed increased levels of aliphatic acids such as succinic and malic acids, together with a marked decrease in gallic acid. A total of 661 volatile compounds were detected, with the processing of increasing alcohols, aldehydes, ketones, and esters while reducing hydrocarbons and nitrogen-containing compounds, resulting in a shift from green and citrus-like notes to a fresher and sweeter aroma profile. Linalool, 1-penten-3-one, heptanal, 1-octen-3-one, and nonanal were identified as key aroma contributors. Processing significantly decreased the antioxidant capacity of XYMJ tea across all assays. These findings demonstrate that processing drives systematic metabolic reorganization, thereby shaping the sensory attributes and functional properties of XYMJ tea.