Abstract: One fresh leaf with one bud from the Bixiangzao tea cultivar harvested in summer were made into yellow tea by the conventional process, sequentially involving spreading, fixation, rolling, piling and drying. This study aimed to explore the dynamic changes of the main quality components during yellow tea processing for the purpose of providing useful information for improvement of the current yellow tea processing technology and its quality. The contents of tea polyphenols, catechins, amino acid, water extract, soluble sugar, caffeine and flavonoids were detected in samples from 11 representative processing points. At the same time, sensory evaluation and aroma quality components were analyzed. The results showed that during the processing of yellow tea, the contents of tea polyphenols, total catechins, water extract, soluble sugar, caffeine and flavonoids decreased gradually, which were 30.12%, 24.08%, 10.97%, 61.34%, 33.20% and 25.55%, respectively lower in dried tea than in fresh tea leaves. By contrast, the content of free amino acid increased by 19.46% compared with fresh tea leaves and the contents of tea polyphenols, caffeine, flavonoids and amino acid similarly increased during the spreading process. The relative contents of alcohols, ketones, olefins and esters in dried tea were reduced by 17.18%, 5.51%, 5.77% and 2.10%, respectively, compared with fresh tea leaves, while the relative contents of aldehydes and phenolic compounds were increased by 35.35% and 4.06%, respectively. Among the processing steps, the taste quality of yellow tea was mainly influenced by spreading and piling. The contents of amino acids were increased with the extension of spreading time, and the piling process could convert ester catechins into simple catechins and produced theaflavin at the same time, the main contributors to the formation of yellow tea’s alcohols, refreshing taste and “yellow soup and yellow leaves” quality. The taste quality was better when the piling time was 8 h; the aroma quality was mainly impacted by the spreading, piling and drying process.

Key words: tea processing, yellow tea, taste quality, aroma quality, dynamic changes