Red-blue monochromatic and composite light withering modulates flavor and aroma profiles of white tea: A combined GC-IMS, E-nose, HPLC and sensory analysis.

White tea production is highly dependent on withering conditions, with traditional methods relying on natural sunlight, which is often hindered by inclement weather in tea-growing regions. Artificial light withering offers a promising solution to enhance tea quality by modulating metabolic pathways. This study investigated the effects of monochromatic (red and blue) and composite red-blue light (RB1:1, RB1:3, RB3:1) withering on the sensory characteristics, chemical composition, and volatile compounds of white tea, compared to indoor natural withering (CK). The light treatments were applied during the first 12 h of withering, followed by 12 h of natural indoor withering. Sensory evaluation revealed that red-dominant treatments (RL, RB3:1) scored was the highest in aroma and taste, while blue-dominant treatments (BL, RB1:3) darkened tea infusions and increased redness and yellowness. Red light withering significantly reduced tea polyphenols by 12.79% and elevated free amino acids by 6.24%. Blue light withering decreased total catechin content by 9.72%, flavonoids by 37%, and caffeine by 8.3%, while increasing soluble sugars by 49.15%. GC-IMS and PCA analysis distinguished volatile profiles, with red-dominant treatments enhancing floral and fruity aromas (benzaldehyde, 2-acetyl-5-methylfuran) and blue-dominant treatments promoting fresh, sweet flavor (linalool oxide and γ-terpinene). These findings demonstrate that artificial light withering, particularly red-blue composite light, optimizes white tea quality by altering key biochemical components and volatile compounds. The study provides a theoretical foundation for improving white tea processing through tailored light spectra, offering practical solutions for consistent high-quality production under variable weather conditions.