Lower critical concentration temperature as thermodynamic origin of syneresis: Case of kappa-carrageenan solution

Polysaccharide ubiquity is trimmed for applications of low syneresis impact. This syneresis may be crucial for specific applications that are very sensitive to gel dimension stability, namely, 3D scaffolds for cell culture for disease diagnosis and tissue engineering. We hypothesized that the syneresis origin results from the kappa-carrageenan (kC) polysaccharide thermodynamic instability, and we demonstrated this by measuring the critical (coil-to-coil contact) concentration as a function of temperature. The impact of 5 mM, 10 mM and 15 mM KCl salt on the critical concentration of the solution and the lower critical concentration temperature (LCCT) were particularly investigated. For the kC polysaccharide, the gelation temperature (Tg) falls at temperatures below the LCCT, which explains the shrinking or syneresis reaction of the polysaccharide gels. The gap between Tg and LCCT would be the thermomotive force of the syneresis of many colloidal gels. •It exists a lower critical concentration temperature (LCCT) for kappa-carrageenan (kC) suspensions.•The gelation temperature (Tg) of the solutions was found below their LCCT.•The Tg and LCCT increase with the potassium concentration.•Cooling the kC suspensions from the LCCT to Tg causes syneresis.