Abstract
The determination of vitamin C in semi-fermented tea by the usual indophenol titration method is apt to lead the result erroneous, since the judgement of the end-point is much affected by the deep orange or brown color of the extract. By use of the indophenol-butanol method (colorimetric method), however, this obstacle is removed, and moreover it can be applied to the rapid estimation of plenty of samples. The results obtained with seven semi-fermented tea samples by use of both the usual indophenol titration method and the indophenol-butanol method were compared with those obtained by Roe's standard hydrazine method carried out on the same samples. It became clear that the results by the indophenol-butanol method were in good accordance with those by Roe's standard hydrazine method, while relatively higher values were obtained by the usual indophenol titration method. The vitamin C contents of the seven semi-fermented teas were within the range of 60-110mg%, the vitamin C contents of Pouchong tea samples being somewhat higher than those of Oolong tea samples.
