Effect of brewing time on the amount of fluorine released from tea

Small amount of Fluoride is one of the most well-known factors being useful in controlling decay. Since high consumption of fluoride may cause fluorosis and osteoarthritis. Considering the high consumption of tea in Iran (as a national drink) and high degree content of fluoride in Iranian commonly-used teas, and considering non-awareness on the effect of brewing time on the degree of fluorine freed from tea, the present research aimed to determine the effect of brewing time on the amount of fluorine released from tea in academic year 2007-08 in Chemistry Laboratory of the Faculty of Pharmacology, Tehran University. This survey was done in experimental study. Out of 13 brands of tea in Iranian market two brands named Oghab and Doghazal which, in Iranian market in year 1386 (2007-08), were best seller brands of Iranian and foreign teas respectively were selected and three packs of each brand were purchased from three different places of Tehran City. From each type of the teas six samples were taken and brewed in different periods of time 3, 5, 15, 30, 60, and 120 minutes. In each brewing, one gram dry tea was added to 100 ml of boiling distilled water in a Teflon tea pot. For brewing tea, the tea pots were placed in a incubator at temperature of 80 degrees Celsius. When the pre-determined times passed, 10 ml tea extract was taken from each pot and filtered. Then TISAB II buffer at proportion of 1 to 1 was added to the filtered extract. The concentration of fluoride ion was measured in potentiometer method.The amount of the fluoride of tea for each brewing time and for each tea sample were studied with T-Test statistics in each section and between two teas in following up times through ANOVA Test. The average amount of fluoride in Doghazal tea was 0.77±0.04ppm and in Oghab tea was 2.6±0.11ppm. For all times, this difference was statistically meaningful (p‹0.001). The amount of fluoride freed from both brands (Oghab abd Doghazal) increased meaningfully along with increase in brewing time ((p‹0.001). As the brewing time increases, the amount of fluoride freed from tea increases. The best brewing time for tea is about 5 minutes. Furthermore, comparing Oghab tea with Doghazal tea indicates that fluorine content of Oghab tea is higher than other brand. The brewing time suggested by producing company of Doghazal tea (which has been printed on the packages) is 5 minutes which is suitable time. But the brewing time suggested for Oghab tea is 15 minutes which, as the results of this research indicates, leads to introducing of considerable amount of fluoride in the body and thus it does not seem to be advisable time for brewing tea.