Abstract:

This study was conducted to determine the main chemical components, the composition of catechins and free
amino acids, major mineral elements and flavor components of selected samples of Mengding yellow bud by combined use
of conventional analysis, high performance liquid chromatograph (HPLC), flame atomic absorption spectroscopy (FAAS)
and gas chromatography-mass spectrometry (GC-MS). The results showed that tea infusion of Mengding yellow bud
contained abundant chemical substances with a total content as high as (42.73±1.22)%. In addition, the tea infusion tasted
mellow and refreshing, had a sweet aftertaste and was bright yellow in color. The content of caffeine was (4.98 ± 0.34)%,
and the total catechin content was 12.91%, with epigallocatechin (EGC), catechin (C), epicatechin (EC), gallocatechin
gallate (GCG) and epigallocatechin gallate (EECG) accounting for 2.56%, 0.08%, 0.50%, 3.10% and 6.67%, respectively.
The total amino acid content was (4.55 ± 0.88)%, and the total soluble sugar content was (5.01 ± 0.53)%. However, the
total chlorophyll content was as low as (1.03±0.27) mg/g and the contents of both chlorophyll a and chlorophyll b were
also low, only (0.74 ± 0.20) and (0.29 ± 0.07) mg/g, respectively. The relative contents of theaflavins (TFs), thearubigins
(TRs) and theabrowns (TBs), the characteristic components of fermented tea, were (0.12±0.04)%, (2.32±0.42)% and
(2.75±0.56)%, respectively. A total of 10 mineral elements were detected in the tea infusion, such as the macro-elements K
(16.16 g/kg), Mg (1.73 g/kg) and Ca (0.55 g/kg) and the micro-elements Mn, Na and Zn, which were at significantly lower
levels, 368.80, 190.00 and 88.80 mg/kg, respectively. A total of 69 kinds of aroma components were detected, with alcoholsbeing the most predominant, including 22 compounds (together accounting for 31.69% of the total volatile compounds).
The observed great differences in the measured contents of the major components between Mengding yellow bud samples
from different manufacturers may result from the facts that the current production of Mengding yellow bud relies only on
the traditional experience and lacks technical parameters and modern processing technology and that the chemistry and
mechanism of quality formation of the tea have not yet been systematically researched.

Key words: Mengding yellow bud, yellow tea, components, content and composition, analysis