Exploring the combined effect of fermentation time, and first drying temperature on black tea flavor profile characterized by GC–MS and GC-IMS

Fermentation time and first drying temperature play key roles in black tea flavor quality. We investigated their combined effects on biochemical and volatile compounds (VOCs) in two cultivars. A Fermentation duration of 2.5 h followed by first drying at 95 °C was identified critical point for aroma formation, since additional fermentation and elevated drying temperature declined aroma quality. Prolonged processing decreased free amino acids, reducing sugars, and theaflavin. Gas chromatography mass spectrometry and gas chromatography-ion mobility spectrometry identified 92 and 82 VOCs, primarily alcohols and aldehydes. Key compounds, including cedrol, nonanal, trans-beta-ionone, 2,3-diethyl-5-methylpyrazine, and phenylacetaldehyde contributed to improved aroma of both cultivars subjected to 2.5 h fermentation and 95 °C drying. VOCs based hierarchical clustering revealed that, despite inherent metabolic composition differences in both cultivars the processing conditions produced distinct directional changes. This study provides new insight into dynamic variations driven by combined effect of processing parameters in different cultivars.