Analysis of fluoride level in tea leachate from Shijiazhuang City from 2017 to 2019 / 中华地方病学杂志

ABSTRACT

Objective:To understand the content of fluorine in tea leachate in Shijiazhuang City.Methods:From 2017 to 2019, different varieties of tea (including 7 varieties of green tea, scented tea, dark tea, oolong tea, black tea, white tea, and yellow tea) with high sales volume were purchased at the Shijiazhuang Tea Market. The fluoride content in tea was determined by fluoride ion selective electrode method through different soaking time (5, 10, 15, 20 min) and soaking times (1, 2, 3 times).Results:A total of 82 tea samples were detected, including 25 kinds of green tea (30.49%), 5 kinds of scented tea (6.10%), 11 kinds of dark tea (13.41%), 17 kinds of oolong tea (20.73%), 15 kinds of black tea (18.29%), 7 kinds of white tea (8.54%) and 2 kinds of yellow tea (2.44%). After soaking for 20 min, the fluorine contents in tea leachate of green tea, oolong tea, black tea, and dark tea (40.63, 65.43, 26.39, 58.90 mg/kg) were significantly higher than those in 5 min(23.09, 32.24, 15.77, 32.00 mg/kg, P < 0.05). Taking the fluorine content of the tea leachate soaking for 20 min as the total fluorine content, oolong tea was the highest, with a median of 65.43 mg/kg; black tea was the lowest, with a median of 26.39 mg/kg; The fluorine contents of oolong tea, dark tea and scented tea were significantly higher than that of black tea( P < 0.05). With the increase of soaking times of green tea, oolong tea, black tea, dark tea and white tea, the fluorine contents in tea leachate decreased significantly ( P < 0.05). Conclusions:In this study, the content of fluorine in the oolong tea is the highest, and the lowest is black tea. It is suggested that local residents in Shijiazhuang should drink black tea.