Multi-omics study on the flavor quality of summer Lvbaoshi green tea under different spreading times

Lvbaoshi (LBS) is a high-grade green tea from Guizhou, China. Its lower quality made from summer tea leaves leads to reduced economic value. The impact of spreading duration, a key processing parameter, on summer LBS quality is still unknown. Here, we conducted integrated metabolic and transcriptomic analyses to comprehensively elucidate how spreading duration affects summer LBS quality. Sensory evaluation indicated that spreading for 6–8 h led to enhanced quality of summer LBS. The increased theanine and soluble sugar contents might contribute to the enhanced umami and sweet tastes, and the decreased caffeine and catechins were responsible for the reduced bitterness and astringency. Volatile components (geraniol and linalool, etc.) with floral, fruity, and chestnut scents increased, while those ( (Z) -3-hexen-1-ol, etc.) with grassy odors declined, resulting in enhanced aroma quality. IAA and ABA were positively correlated with the variations in theanine, geraniol and linalool contents, and SA was positively related to the alterations in caffeine, tea polyphenols, and ECG contents. Transcriptomic analysis indicated that genes related to secondary metabolic pathways (e.g., flavonoids, caffeine, and theanine) and hormone signal transduction play vital roles in regulating the content variations of quality-related components. WGCNA demonstrated that key transcription factors are involved in regulating the dynamic metabolic alterations during spreading. These findings present mechanistic insights into how spreading duration affects summer LBS quality, providing a theoretical basis for its processing parameter optimization and quality improvement.