Unraveling the effects of shading on sensory quality, non-volatile metabolites and volatile flavor compounds of Longjing tea

Shading improves tea quality, yet the effects of different shading materials on metabolites of Longjing tea remain unclear. This study compared conventional cultivation (CK) with transparent plastic film (TPF) and black shading net (BSN) treatments in Longjing tea. BSN significantly enhanced appearance, liquor color, taste, and aroma, while TPF improved only aroma. Metabolomics showed that BSN increased the contents of certain amino acids and terpenoids but decreased catechins and flavonoids. GC–MS analyses revealed that, while BSN- and TPF-treated Longjing tea displayed greater diversity of volatile compounds, only a few key aroma compounds showed marked increases in concentration. Combined analysis of OAV values and concentrations revealed that (E)-2-hexenyl hexanoate, hexyl hexanoate, cis-3-hexenyl n-valerate, 3-carene, octanal, hexanal, nerolidol, and phenylethyl alcohol played a crucial role in enhancing the aroma quality of shade-treated tea. These findings clarify how shading regulates tea metabolites, supporting targeted cultivation for flavor-oriented production of Longjing tea. • BSN treatment significantly improved the appearance, color, taste and aroma of the Longjing tea. • TPF treatment significantly improved the aroma quality of the Longjing tea. • Both BSN-treated and TPF-treated Longjing tea increased the diversity of volatile compounds.