An investigation was made for clarifying the effect of cooling conditions of gelatin sols on the gelation.
The results can be summerized as follows.
Obviously, cooling rate of the sols was much slower in refrigerator than in cold water when the samples were cooled at 5°C.
Viscosity of the standing sols measured by means of the fine-wire heating method indicated that the gelation time of the slow-cooled samples is longer than that of the fast-cooled samples, while the gelation temperature of the slow-cooling systems was higher than the others. Gelation temperature of low-temperature extracted gelatins was also much higher than that of high-temperature extracted samples.
The gelation temperature of all the samples measured by the fluidity was lower than that obtained from the fine-wire heating method.
The apparent viscosity of the stirring sols measured by the rotation method showed that the starting temperature of gelation for the low-temperature extracted gelatin was much higher than that for the high-temperature extracted one. The viscosity of the stirring sols was lower than that for standing sols in all the cases. A gap of temperature between the commencement and the final stage of gelation was influenced by the preparation temperature of gelatin samples : the samples extracted with high temperature showed a wide gap in gelation temperature.