Abstract
The effects of tannin on the properties of gelatin jelly were investigated. The addition of tannic acid to gelatin sol at pH 3-6 has similar effects on the gelation of gelatin sol as the addition of fruits juice, coffee or black tea. The results obtained are as follows.
1) When gelation sol was added to tannic acid and adjusted to pH 5, the turbidity of sol was increased, and gelation was inhibited. But the gel formation of gelatin sol containing 10 mg% tannic acid at pH 3 and 6 or 100 mg% tannic acid at pH 6 was more faster than the sol which contains no tannic acid.
2) By warming and mixing the gelatin sol well, part of the precipitation by tannic acid was dissolved and gel formation was less inhibited.
3) As the gelatin sol added to apple juice or coffee was near to pH 5, inhibitory effect of tannin on gel formation was observed. Gelatin sol added to black tea, however, was easy to gelatinize, probably because it was near to pH 6 and contained less amount of tannin.
