The taste quality of oolong tea generated from leaves of Camellia sinensis L. cultivated in the
same mountain area is positively correlated to the cultivation altitude, partly due to the
inverse correlation with the astringency of the tea infusion. The astringency of oolong tea
mostly results from the presence of polyphenolic compounds, mainly catechins and their
derivatives. Four catechins, (-)-epicatechin (EC) and (-)-epigallocatechin (EGC) together with
their gallate derivatives (with relatively high astringency), (-)-EC gallate (ECG) and (-)-EGC
gallate (EGCG), were detected as major compounds in oolong tea. The degrees of catechin
galloylation, designated as ECG/(EC þ ECG) and EGCG/(EGC þ EGCG), in both oolong tea
infusions and their fresh tea leaves, were found to be inversely correlated to the cultivation
altitude at 200 m, 800 m, and 1300 m. A similar inverse correlation was observed when
seven more oolong tea infusions and seven more fresh leaves harvested at altitude ranging
from 170 m to 1600 m were recruited for the analyses. Moreover, catechin contents in
oolong tea infusions were also found to be inversely correlated to the cultivation altitude. It
is proposed that catechin content and the degree of its galloylation account for, at least
partly, the inverse correlation between the astringency of oolong tea and the cultivation
altitude.