Improvement of the sensory characteristics of Dancong tea using a dry-heating post-treatment approach

Dancong tea is famous for floral aroma and strong, sweet aftertaste. Dry-heating post-treatment (DHP treatment) is used to decrease astringency and bitterness in oolong teas, but the effects of it on the taste and aroma profiles of Dancong teas are unknown. Here, the sensory and biochemical characteristics of two differently-scented Dancong tea varieties (YS and LH) were assessed both before and after DHP treatment. Overall, DHP treatment improved the taste and aroma of the infusions. The concentrations of theasinensins and theaflavins, which contribute to tea infusion colour and taste, varied significantly between varieties and as a result of DHP treatment. Treated samples showed a marked decrease in the abundance of volatile compounds such as alcohols, aldehydes, and ketones. Hotrienol and β-ionone were the primary aroma-active volatile components shared by all samples (both varieties, both before and after DHP treatment). DHP treatment generated β-myrcene and limonene, enhancing the characteristic Dancong aroma profiles and endowing treated samples with sweet and lemony odours, respectively. Heptanol and cis-2-heptenal were identified as the strongest contributors to the fresh, greenish aromas of untreated samples, and degraded by DHP treatment. This study offers an effective, economical, and implementable method of improving the quality of bitter, astringent teas.