| dc.description.abstract | Fermented tea has been widely consumed by many countries and may be
a promising product in Vietnam. Thus, it can generate additional incomes for tea
growers. However, locally fermented tea is not well studied. Therefore, the
objectives of this study are to evaluate some basic quality parameters of a
locally fermented tea product (with different fermentation times: 2 and 5 years)
and compare them with that of non-fermented tea (green tea grown in Ha Giang
province, material of the fermented tea). Apart from this, the study also
analyzed the microbial communities in these tea samples. Total polyphenol
content and free radical scavenging capacity of tea samples, which are among
the important criteria for tea qualification, were determined by Folin-Ciocalteu
assay and DPPH assay. The microbial communities of the tea sample were
isolated by serial dilution and spread plate method. Then, they were
morphologically and molecularly identified. The total polyphenol content in the
green tea (24.98±1.64 mg/g) was significantly higher than in 2-year fermented
tea (22.99±0.94 mg/g) and 5-year fermented tea (16.15±0.57 mg/g). The
DPPH radical scavenging capacities were also recorded with the same trend, with
the IC50 values of 284.82±3.10µg/ml, 296.15±2.61µg/ml and 335.03±2.80
µg/ml for green tea, 2-year and 5-year fermented tea. These suggest that the
total polyphenol contents and DPPH scavenging abilities of tea samples were
significantly reduced during and over fermentation. Molds and bacteria were
found in all 3 samples, with 5-year fermented tea having the most species and
number of microbes. Molecular identification revealed microbes in 5-year
fermented tea, which were Bacillus cereus (1.13×104 CFU/g), Peribacillus
frigoritolerans (4.0×102 CFU/g), Bacillus amyloliquefaciens (2.0×102 CFU/g),
Aspergillus pseudoglaucus (1.32×103 CFU/g), Aspergillus ruber (1.48×103
CFU/g), Aspergillus cibarius (1.10×103 CFU/g) and Aspergillus restrictus
(2.35×104 CFU/g). Meanwhile, as the densities of microbes in 2-year fermented
tea and green tea were relatively low, they were only identified by morphological
characteristics. Based on their morphologies, the bacteria and fungi from these
two samples were putatively identified as Bacillus spp., Aspergillus sp and
Mycelia sterilia. In 2-year fermented tea, there were one Bacillus sp. (50 CFU/g),
and one Aspergillus sp. (100 CFU/g). Four Bacillus spp. and one Mycelia sterilia
were found in green tea with the densities were mostly about 50 to 150 CFU/g.
Based on the identification, the fungal and bacterial communities and densities
were specific to each tea sample. | en_US |
