Abstract:

The effects of pH, embedding medium and metal ion on the tannin content of reconstituted Osmunda japonica
Thunb tip under different temperatures were studied. The experimental results indicated that the removal efficiency of tannin
from reconstituted Osmunda japonica Thunb tip was good and reached a maximum level of 88.97% at pH 8–9. Increasing
the temperature favored the removal of tannin at the same pH values. One of three embedding media, β-cyclodextrins,
maltodextrin and soluble starch, was effective for removing tannin from reconstituted Osmunda japonica Thunb tip
providing a removal efficiency of over 80.76%. Along with increasing the embedding medium concentration, the content of tannin
rose at first and went down later. As the temperature increased, the content of tannin decreased at a constant concentration of
embedding medium. The tannin removal effects of different metal ions (sodium ion, potassium ion, calcium ion and magnesium
ion) on reconstituted Osmunda japonica Thunb tip were different and among them the most effective was calcium ion providing
a removal efficiency of 88.04%. With increasing metal ion concentration, the content of tannin decreased firstly and increased
subsequently. An increase in the temperature promoted tannin removal at a fixed concentration of metal ion.

Key words: Osmunda japonica Thunb tip, tannin, embedding agent, metal ion