Abstract:

The aroma constituents, water extract, total polyphenols, total amino acids, total soluble sugars and three
polyphenolic pigments in Keemun black tea collected from various regions were investigated. The quality of Keemun black
tea was evaluated through chemical composition analysis combined with sensory evaluation. The results showed that the
compounds with a high probability of contribution to the Keemun black tea aroma included geramiol, linalool and linalool
oxide, benzyl alcohol, phytol, phenylacetaldehyde, trans-2-hexenal, and n-hexadecanoic acid. Keemun Maofeng black tea
had a rich aroma with fresh, delicate and sweet characteristics. Keemun Congou black tea had a rich aroma with tenacious,
fragrant and sweet characteristics. Samples of different quality grades, i.e. superfine, special grade, first class Keemun black
tea, were very similar in aroma components; however, they were very different in aroma contents. The higher the tea grade
was, the better the aroma quality was. The contents of total polyphenols and amino acids were decreased in lower-grade
tea and the taste and freshness degree of tea infusion were declined. Collectively, all the samples had the typical quality
characteristics of Keemun black tea such as fragrant aroma and mellow taste, especially the higher soluble sugar content,
which made Keemun Congou black tea from various showed sweet and mellow.

Key words: Keemun black tea, aroma constituents, chemical composition, quality