Influence of elasticity on the syneresis properties of κ-carrageenan gels.

Kappa-carrageenan hydrogels spontaneously release fluid (syneresis) under certain elasticity conditions, which depend on the temperature, the salt concentration in the gel (KCl) and the polysaccharide concentration. Strong and weak gels exhibit notably weak syneresis properties. The maximum syneresis was found at intermediate elasticity where the gel was neither strong nor weak. The variation in the gel composition indicated that the fluid is released according to the thermal retraction coefficient, which depends on the elasticity. Experiments revealed a dynamic equilibrium of the syneresis process where syneresis fluid was not withdrawn. However, once the fluid was removed from the gel surface, the release of solvent starts again if the elasticity is below the compressive pressure in the gel. Therefore, swelling of the gel is suggested as an explanation for the dynamic equilibrium of the syneresis process.