Finding the optimal light quality and intensity for the withering process of fuding Dabai tea and its impact on quality formation

Abstract

This study investigates the pivotal role of withering in shaping the quality of white tea. We used a single-factor experimental design to optimize both the light quality and intensity during the withering process. Using gas chromatography-mass spectrometry (GC-MS), sensory evaluation, and physical and chemical analyses, we identified the ideal parameters as yellow light at an intensity of 5000 lx. Subsequently, we used non-targeted metabolomics and transcriptomics to analyze the mechanism of white tea quality formation at various stages of withering. The results showed significant changes to flavonoids during the withering process, with heightened F3′5′H (flavonoid3,5-hydroxylase) gene expression leading to increased levels of quercetin, myricetin, and luteolin. Conversely, the decreased catechin content was attributed to the decreased expression of most genes in the catechin synthesis pathway. The elevated levels of leucine, isoleucine, and GABA in free amino acids were due to a significant increase in the expression of the genes that synthesize them. Hormone and WGCNA analyses substantiated the importance of ABA, JA, and other key genes in shaping white tea quality during withering. These combined factors orchestrate the gradual formation of the distinctive characteristics of high-quality white tea.