Flower-centric temperature control: Optimizing osmanthus black tea aroma via environmental temperature regulation of floral vitality and enzymatic responses.

The temperature parameter of scenting process, which governs the vitality of fresh flowers and the release of floral volatiles, is still empirically determined. Here, we investigate how environmental temperature regulates osmanthus vitality and enzymatic activity to shape the aroma quality of osmanthus black tea (OBT). Results showed that the moderate-temperature (25 °C and 30 °C) exhibited superior sensory quality, accompanied by slower water loss and delayed wilting of osmanthus, which favored aroma retention during scenting. Carotenoid cleavage dioxygenase (CCD) content peaked (1268 U/g), associating with the accumulation of β-ionone (a typical floral aroma), while β-glucosidase (β-GC) activity gradually increased with rising temperature, contributing to the formation of esters such as γ-decalactone (fruity aroma). Volatile profiling revealed that 30 °C promoted the accumulation of multiple key volatile compounds (linalool, β-ionone, and γ-decalactone), resulting in the highest total volatile content and overall odor activity value (OAV). In contrast, low temperature (20 °C) maintained flower freshness but limited aroma-related enzymatic responses and volatile accumulation. High temperature (35 °C) caused rapid petal dehydration (over 73% water loss within 4 h) and premature withering, inhibiting aroma release and reducing total volatile content. Overall, these findings establish 30 °C as the optimal environmental temperature for scenting OBT and provide a flower-centric, physiologically grounded strategy for temperature control.