Taste Modulation of White Tea by Red/Blue-LED-Assisted Withering Revealed via Non-Volatile Metabolomics

Background: Red/blue- light-emitting diode (LED)-assisted withering provides a controllable spectral input to steer tea quality, yet metabolite-level evidence linking spectrum composition to quantitative taste phenotypes in white tea remains insufficient. Methods: Fresh leaves were withered under supplemental red/blue LEDs—S0, S1, S2, S3, S4, and S5—and the resulting white teas were evaluated by quantitative descriptive analysis (QDA), untargeted metabolomics, weighted gene co-expression network analysis (WGCNA), and high-performance liquid chromatography (HPLC) quantification of caffeine, gallic acid, and eight catechin monomers. Results: Red/blue-mixed spectrum enhanced the overall sensory quality relative to the incandescent lamp; S3 maximized sweetness and freshness, whereas S4 minimized bitterness and astringency and achieved the highest overall score. Untargeted metabolomics showed the largest deviation for S0 vs. S4. A total of 18 common metabolites were identified between the S0 and light-supplemented withering treatments, dominated by saccharides and related derivatives. WGCNA linked a saccharide-centered module to higher sweetness/freshness/smoothness and a lipid-oxylipin-centered module to stronger bitterness/astringency. HPLC independently confirmed that S4 contained the lowest catechins and caffeine, supporting its reduced bitter/astringent attributes. Conclusions: Overall, the application of mixed red-blue spectra offered a promising approach to enhancing the palatability of white tea by coordinately intensifying saccharide metabolism while simultaneously suppressing key bitter and astringent components. Our study provided a scientific basis for standardizing white tea processing to enhance sensory quality.