Graded shaking intensity in oolong tea processing links in-process volatile responses with finished-tea volatile outcomes

Shaking is a critical operation in oolong tea manufacturing that drives aroma formation, yet its quantitative effects remain insufficiently defined. This study systematically evaluated nine shaking intensities (6–54 cycles, at 6-cycle intervals) to determine how volatile organic compounds (VOCs) and catechins, representing complementary process-state responses, changed across manufacturing stages and how in-process VOC states were associated with the final-product volatile profile under the selected analytical preparation. Most characteristic VOCs differed significantly from the pre-shaking condition after 18–24 shaking cycles, with additional significant changes often detected between treatments separated by 6–12 cycles. Hexyl hexanoate, ( Z )-3-hexenyl hexanoate, ( E )-2-hexenyl hexanoate, and β-ocimene were strongly associated with shaking intensity and served as effective markers for discriminating among shaking levels. VOC profiles immediately after shaking, particularly linalool and linalool oxides, provided predictive information for VOC states during subsequent setting stages and for the final-product volatile profile. Fatty acid-derived volatiles and catechins showed persistent negative covariation throughout processing, indicating coordinated but pathway-distinct responses to shaking-induced wounding and oxidative progression rather than a direct biosynthetic relationship. Rather than defining a single optimal treatment, this study establishes a cycle-resolved quantitative framework linking graded shaking intensity to downstream volatile and phenolic responses and identifies operational windows associated with green-fresh or floral-fruity aroma tendencies. These findings provide an evidence-based foundation for adaptive and style-oriented control of oolong tea manufacture.