Abstract
The effects of cations on rheological and thermal properties of κ-carrageenan gels were examined. κ-Carrageenan CS-47 and KCl, NaCl, CaCl2, and MgCl2 as cations added were employed. Viscoelasticities, texture parameters, heats during phase transition of 0. 75 and 1. 5 % concentration gels and mineral content of κ-carrageenan were measured by using creep meter, rheolometer, differential scanning calorimeter and atomic absorption specctrophotometer.
EH showed maximum values at 0. 2-0. 3 M of KCl for 0. 75 % concentration gels and 0. 1-0. 4 M of KCl for 1. 5 % concentration gels and was significantly decreased with an increase in the concentration of KCl. A similar tendency was recognized for hardness. These gels gave creep compliance-time plots characteristic of viscoelastic behaviour. Heats during phase transition became largest at 0. 1-0. 3 M for 0. 75 % gels and decreased with an increase in the concentration of KCl. The gels containing KCl at more than 0. 1 M showed two significant peaks. Any significant changes were not recognized in the gels containing NaCl, CaCl2, and MgCl2. The κ-carrageenan after dialysis did not form gels. It was evident that potassium ion took part in the gel formation of κ-carrageenan. This fact was ascertained by both rheological and thermal measurements.
