Abstract:

We employ phosphorus molybdenumtungsten acid casein method to determine tannin content of two different products from the leaves of Pyrus betulaefolia Bge.. Tannins were extracted to be soaking at room temperature by staying overnight When the color reaction between phosphomolybdium Tungslic acid and phenolic acids was carrying through 90~120 min,absorbency of tolal phenolic acids and unabsorbable phenolic acids was delermined respectively at The wavelength of 760 nm. Tannins content is derived by spectrophotometry difference and standard curve method. Better linear relationship (r=0.997 9) exists in the range of 1~10 μg/mL. We obtain average recovery rate of 98.581% (n=6) and RSD of 0.51%. Tannins average content of unfermented leaves is 0.60%, and tannins is not detected in the leaves of fermentation under this condition.

Key words: Pyrus betulaefolia Bge., phosphorus molybdenum-tungsten acid casein, tannin, content determination