Total polyphenols (TP), total flavonoids (TF) and (-)-epigallocatechin gallate
((-)-EGCG) were determined in five commercial tea infusions by continuous
infusion method, using the ratio 20g of tea to 1L of water at 85±5 °C and
brewing time between 5-180 min.
This paper presents a developed HPLC method for the determination of
caffeine and theobromine in different black and green tea infusion samples,
using different infusion methods, such as infusion with and without boiling,
repeated and continuous i
nfusion. A mixture of double-distilled water and
methanol (60:40 v/v), was used as a mobile phase. In this condition, the
retention time for theobromine was three minutes and for caffeine five minutes.
Four different brands of black tea and one brand of green tea commonly
available in Syrain markets were tested to measure the level of fluoride
contained in their liquid using four different methods of infusion and utilizing
the spectrophotometer
technology: A. Infusion without boiling. B. Infusion with
boiling. C. Repeated infusion. D. Continuous infusion.
The results have indicated that the average level of fluoride in the samples
of black tea liquid is higher than the one in the green tea sample regardless of
the infusion method used. Also, it was found that the level of fluoride released
from all samples is higher when boiling them in water from 1 to 5 minutes. In
addition, it was proved that the level of fluoride in tea liquids is higher when
it’s prepared using repeated infusion, but it’s lower when the tea has been
prepared using the continuous infusion method. Tea brands (2) and (4) released
the highest level of flouride 7.37mg/L and 5.01mg/L respectively, which are
very high levels comparing to the other brands which released between 1.5mg/L
to 2.7mg/L. To prevent fluoride from reaching poising levels, the total daily
consumption of black tea liquid of brands (2) and (4) should not exceed 1.76L
and 2.58L respectively and to avoid preparing them using the repeated and
countinous infusion methods.
