A combined drying process involving hot air and roasting for improving summer congou black tea quality

The present study aim to investigate the effects of three drying processes on the flavor-related compounds and sensory quality of summer black tea. A total of 234 flavonoids and 1200 volatile compounds were identified in tea samples by using UPLC-MS/MS and HS-SPME-GC-MS, respectively. It was found that the combining hot-air and roasting drying process increased the level of epigallocatechin, epicatechin, gallic acid, theaflavins, and umami and sweet amino acids in tea samples. Conversely, the contents of epigallocatechin gallate, caffeine, kaempferol and acylated kaempferol glycosides, and quercetin and acylated quercetin glycosides were found to decrease. Analysis of the volatile compounds revealed that combined drying process enhanced the contents of volatile substances with sweet, nutty, and floral properties while reducing those with green attributes. Sensory evaluation results showed that the combined drying process improved the mellow taste and pure aroma, decreased the bitterness and astringency, and weakened the unpleasant flavor of summer black tea. Overall result indicated that the combined drying process could improve the flavor quality of summer black tea. This study may provide data support and feasible strategies for improving summer congou black tea quality.