Influence of osmotic and weight pressure on water release from polysaccharide ionic gels

Kappa-carrageenan (kC) is a polyelectrolyte biopolymer that forms gels if the kC concentration, the salt and the temperature are adequately chosen. Actually, under certain conditions, kC gels release water in a process called syneresis. In this contribution, the syneresis of gels containing 2 g/L of kC has been studied as a function of potassium chloride concentration [KCl]. The syneresis decreases if the [KCl] is increased in the biopolymer solution (sol) before the gelation but increases if the [KCl] is increased after gelation by immersing the gels in KCl solution. The surrounding phase induces an osmotic pressure (Π), which increases if the [KCl] difference between the inside and outside of the gel increases. Swelling has been observed for negative Π. A method that enables the exudate to be removed continuously demonstrated the effect of the strain caused by the gel's own weight on syneresis. Increasing the KCl concentration in the sol promotes syneresis due to strain. The analysis of the syneresis kinetics of different systems has enabled the creation of a pressure-induced syneresis diagram. This diagram will contribute to controlling the mouthfeel of chewing products.