Based on the identifications of FOG compounds on the UHPLC
and HPLC method, we analyzed 3 green tea, 2 oolong tea samples
and 3 black tea samples. The total amounts of the FOG in these teas
were 2.32–5.67 g/kg dry weight, and there is no significant difference
for the total FOG content between green tea, oolong tea and
black tea (Table 2). The highest was one black tea sample KEBT
from Kenya, but one green tea sample SBXT from China had the
similar content, and one oolong tea sample FSOT from China had
a little less content. However, we could find that the lowest was
from one green tea sample LSYW from China, and one black tea
sample ASBT from India had a lower content. It might show that
the big difference of FOG content could be sourced from the
producing area, and could be affected from some related factors
like tea cultivars, soil, rainfall and local climate. The small difference
between 2 oolong tea samples of DAOT and FSOT from the
same area in Fujian, China, might show that processing could also
influence the FOG content in some way.