Decoding the Modulation of Temperature During Withering on the Flavor Quality and Appearance of Taiping Kuihong Black...

This study introduced freeze-withering to resolve the conflict in traditional Taiping Kuihong black tea processing, where rolling enhances flavor but damages the integrity of the leaf shape. Using sensory evaluation, high-performance liquid chromatography, and gas chromatography-mass spectrometry, the effects of three freezing treatments (-20 °C, -80 °C, and liquid nitrogen at -196 °C) were analyzed and compared with traditional withering (CK). The results demonstrated that low-temperature treatments better preserved the morphological integrity of 'two leaves and one bud.' Compared to the CK group, the -20 °C low-temperature treatment group had a significantly higher proportion of esters among the volatile compounds in Taiping Kuihong black tea. Key floral fragrance components were abundant, while grassy undertones were greatly decreased. Concurrently, this group had the highest levels of theaflavins and TF/TR ratios. The -80 °C treatment was highly effective in preserving thearubigins; however, it resulted in a less complex fragrance profile with a reduced theaflavin level. Liquid nitrogen treatment caused aberrant accumulation of theabrownins, poor aroma harmony, and the lowest theaflavin level. This study indicates that -20 °C freezing withering is the best method for harmonizing the appearance and internal quality of Taiping Kuihong, giving critical evidence for targeted processing of unique black teas.