Multiomics Analysis of the Drying Time Regulation on Selenomethionine Accumulation and Flavor Compound Changes in Selenium-Enriched Black Tea

Tea (<i>Camellia sinensis</i> (L.)O. Kuntze) converts inorganic selenium into organic selenium, including selenomethionine (SeMet). Drying improves tea flavor, but the thermal mechanism by which drying time affects flavor compounds and proteins in selenium-enriched black tea remains unclear. 98 different flavor components and 87 proteins were identified by metabolomics and proteomics at 12-54 min of hot-air drying (70 °C, 7.0-0.1% moisture). Amino acid biosynthesis and glutathione metabolic pathways were significantly affected under heat. Key flavor compounds (SeMet, cysteine, serine, etc.) and proteins (methionine synthase, etc.) were maintained at high abundance. SeMet peaked at 36 min (1.23 mg kg^-1), which increased by 19.4, 17.1, 16.0, and 61.8% compared with 12, 24, 48, and 54 min (1.03, 1.05, 1.06, and 0.76 mg kg^-1, respectively). Optimal drying (70 °C for 36 min; 3.0% moisture) minimized thermal degradation losses of flavor components like SeMet, providing a theoretical basis for maintaining the high-quality of tea.