Preliminary tossing post-harvest: Unraveling its role in aroma enhancement of large-leaf oolong tea

Preliminary tossing, a novel step inserted before conventional oolong processing, was evaluated for its ability to enhance the aromatic compounds of high-flavor oolong tea. But the preliminary tossing of promoting the conversion and release of aroma substances is not clear. Preliminary tossing significantly enhanced the floral, fruity, and sweet aromas, without affecting taste quality. Sunlight-withering and shaking were the key steps in forming the floral-fruity aroma of OT-D, significantly increasing floral-fruity substances (1-hexanol, 3-methylbutyl acetate, benzeneacetaldehyde, 1-undecanol, trans-βocimene, 2-nitroethylbenzene, geranyl isobutyrate, and hexyl 2-methylbutanoate). Benzeneacetaldehyde, 2-nitroethylbenzene, trans-β-ocimene, and (3E,5<i>E</i>)-octa-3,5-dien-2-one made OT-D stronger floral, fruity, sweet aromas than OU-D (rOAV ≥1). (E)-Hex-2-enal, (<i>Z</i>)-hept-4-enal, 1-thiophen-2-ylethanone, 2-methoxy-3-propan-2-ylpyrazine, and 2-methoxy-phenol made the other aromas (green, nutty, fatty, woody, spicy) of OT-D significantly stronger than those of OU-D (rOAV ≥1). This study proposed a new method to enhance the suitability of different tea plant varieties, thereby promoting and developing the oolong tea industry.