Investigation on the Contents of Tannin and Total Nitrogen of Market Black Tea

We have investigated the tannin and total nitrogen contents of the market black teas.Tannin was estimated by three methods, i. e. Lowenthal, nepherometric, and alkaline permanganate method, and total nitrogen by micro-Kjeldahl method.As the result, it was found that a very close correlation was observed between the tannin content and the qualities of tea, especially color of liquor, taste, and color of infused leaf. And also total nitrogen has closely correlated with the qualities of tea, but less than tannin.Among the tannin values estimated by the three methods, very close correlationships were observed.