Integrative quality evaluation of tea raw material uniformity using sensory analysis, metabolomics, GC-O, and...

Although mechanical harvesting reduces labor costs, non-selective picking decreases fresh leaf uniformity, increasing the difficulty of sorting and high-value processing. This study used sensory evaluation, metabolomics, gas chromatography-olfactometry, and principal component analysis (PCA) to investigate the effects of raw material uniformity (U1 ~ U5) on tea flavor. The results show that high uniformity materials (U1 ~ U2) have floral and green aromas, with a fresh and full-bodied taste, while low uniformity materials (U4 ~ U5) are enriched with mature woody, roasted, sweet aromas and sweetness. Bitterness, astringency, and umami decrease as uniformity declines. A total of 23 key flavor compounds were identified, and their content changes were mainly related to differences in leaf maturity and drying time. In addition, PCA revealed distinct distribution patterns between U1 ~ U3 and U4 ~ U5, supporting "one bud with three leaves" as the sorting threshold between medium- and low-grade mechanically harvested fresh tea leaves.