Metabolomics and sensory analysis to investigate mechanism of floral-fruity flavor enhancement in black tea via mechanical injury during processing

This study found that slight preharvest mechanical stress (PMS) and traditional postharvest shaking (PS) significantly improved black tea (BT) flavor, especially PMS-BT, with superior floral/fruity aroma and the weakest bitterness. Key results show withering and rolling as the critical stages where the most dramatic metabolic shifts occurred, increasing bitter flavonoids alongside fruity, floral, and green aroma compounds. Processing altered 1265 non-volatile metabolites, rich in flavonoids and phenolic acids, and 664 volatile metabolites, primarily terpenoids and esters. PS- and PMS-treated leaves retained floral/fruity aroma better during later stages than untreated leaves. PMS-BT contained significantly higher levels of key floral-fruity components like ethyl (methylthio)acetate and 2-isobutylthiazole than PS-BT. This reveals the material basis, critical stages (withering, rolling), and metabolic pathways enabling PMS to enhance aroma and reduce bitterness, providing vital theoretical and practical guidance for premium floral/fruity black tea production. • PMS-BT, PS-BT had weaker bitterness and stronger sweetness and freshness than U-BT. • Both PMS and PS enhanced the floral and fruity aroma of black tea, especially PMS. • BT notably altered flavonoids, phenolic acids, terpenoids, ester in processing. • PS increased 1,2,3-Benzenetriol, .alpha.-farnesene, etc. floral-fruity DEMs. • Ethyl (methylthio)acetate, etc. gave PMS-BT the strongest floral-fruity aroma.