Abstract:

The aim is to analyze the effects of different drying methods on the quality and aroma of raw dark tea and provide data basis for improving the quality of raw dark tea. This study explored the combined drying effects of three traditional drying methods for raw dark tea: sunlight drying, drying and fried drying, and analyzed the differences in sensory quality, main biochemical components, tea pigments, amino acid components and aroma component contents of raw dark tea under different combined drying methods. The results showed that the combination of ‘drying+ fried drying’ had the highest sensory evaluation score (87.10 points). The contents of water extract, tea polyphenols, catechins, caffeine, and theaflavins were the highest in the ‘fried drying+ fried drying’ group, reaching 45.96%, 28.81%, 15.53%, 4.13% and 0.08% respectively, while the contents of amino acids, soluble sugars, thearubigin and theabrownin were lower, at 2.49%, 7.38%, 1.00% and 0.71% respectively. The ‘sunlight drying+ sunlight drying’ treatment had the highest contents of soluble sugars, thearubiging and theabrownins, reaching 10.97%, 1.78% and 1.10% respectively, while the contents of polyphenols, catechins, and theaflavins were lower, at 21.47%, 12.04% and 0.02% respectively. The ‘drying + sunlight drying’ treatment had the lowest contents of water extract and caffeine, at 39.92% and 2.33% respectively, while the ‘drying + fried drying’ method had the highest level of amino acids, at 3.84%. The contents of various free amino acids showed a consistent trend with the total amount of free amino acids. Analysis of aroma components showed that the relative contents of alcohols, aldehydes and ketones were relatively high under different treatments, reaching 37.57%-50.54%, 9.42%-22.78% and 9.53%-16.59% respectively, but different combined drying methods had different effects on the contents of alcohols, aldehydes and ketones in raw dark tea. 17 substances such as β-linalool, benzaldehyde, 1-octen-3-ol and β-ionone had relative contents of 1% or more in raw dark tea, accounting for 71.48%-80.33% of the relative contents of aroma components in each treatment. In conclusion, the raw dark tea prepared by the method of initial drying with drying (2 h, 60℃) and final drying with fried drying (160-180℃) showed the best sensory quality, and each quality component was more coordinated.

Key words: raw dark tea, combined drying, aroma, quality, components, sensory