Biochemical changes in Dangui black tea in processing

Changes of biochemical composition of black tea,Dangui,in processing were investigated.The results indicated that(a) the water extract and tea polyphenols in Dangui decreased gradually;(b) the amino acids content increased in the beginning,but decreased in the later stage;(c) the ratio of polyphenols to amino acid decreased;(d) the contents of TFs,TRs and TB as well as the total amount of the three tea pigments increased gradually;(e) the total catechins content in the finished black tea decreased considerably,only 1/10 of what was in the fresh leaves;and(f) the individual catechins also decreased,with the greatest reduction on epigallocatechine gallate followed by epigallocatechine,gallocatechine gallate,epicatechine gallate,epicatechine and D,L-catechine.Sensory evaluation showed that the beverage steeped from Dangui black tea had a strong sweet note,attractive reddish color,a mellow but flavorful aroma and excellent general quality.