Black tea which contains polyphenol is important for health benefits and it is
considered as antioxidant contents .
The extraction parameters, time and temperature and kind of solvent extraction, can
Influence the polyphenol concentrations of Blac
k tea, and were investigated in this study.
The purpose of the study was to quantify the polyphenols (catechin, epicatechin,
epigallocatechin, epicatechin gallate, epigallocatechin gallate)
in different kinds of teas ( Lipton , Alrabee , Layalina ) which are available in Syria
market.The study was conducted using two types of solvents methanol 70% the adoption
of the reference method adopted ISO14502-1 and water 100% , at different extraction
times (1, 3, 5, and 10 minutes) and extraction temperatures (60°C , 70 °C , 80°C, 90°C,
100°C). the total polyphenols content was determined using the phenol reagent (Folin
Ciocalteu reagent) adoption gallic acid as standard compound
the overall content values of polyphenols have been monitoring in extracts methanol
70% and water 100% .
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.
Twenty two samples of black tea were collected from local Syrian markets
during 2009-2010 to study the quality characteristics of tea in terms of
moisture، water extract، caffeine، total ash، water soluble ash، alkalinity of
soluble ash, insoluble
ash in diluted hydrochloric acid in addition to
microscopic examination.
Results showed that all tested samples were identical to the Syrian Standard
No. 286/2003 for all above quality specifications، except for caffeine percent
which was less than the standard in 4 samples. The results also showed that
there was no adulteration with foreign plants nor exhausted tea leaves.
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.
