The shaping of oolong tea: not only shapes the appearance but also influences the flavor

The shaping process significantly influences oolong tea quality beyond mere physical appearance. However, its effects on specific quality attributes remain unclear. In this study, an integrated approach combining electronic tongue, electronic nose, texture analysis, high-performance liquid chromatography (HPLC), and gas chromatography-olfactometry-mass spectrometry (GC-O-MS), coupled with chemometric analysis, was employed to investigate the impacts of shaping methods on the physical properties, metabolites, and flavor of oolong tea. Distinct differences were observed between twisting-rolling (TR) and wrapping-kneading (WK) shaping methods. Strip oolong tea processed by the TR method exhibited mellow taste and floral aroma, associated with lower cellular damage, resulting in reduced contents of bitter catechins and promoted retention of benzeneacetaldehyde (floral). By contrast, pellet oolong tea processed by the WK method exhibited umami taste and fresh floral aroma, attributed to greater cellular damage (palisade tissue and vein tissue), which facilitated the maintenance of umami amino acids and nerolidol (fresh floral). The findings offer new insight into the role of shaping in the formation of oolong tea quality and provide a scientific basis for targeted quality formation through shaping process control. • WK presents the highest degree of cell disorganization, density and hardness. • WK promotes amino acid accumulation, whereas TR reduces catechins effectively. • Nerolidol enhances WK fresh floral note, benzeneacetaldehyde improves TR floral note. • WK has umami and fresh floral quality, TR has mellow and floral quality.