Phenomenological theory describing the behaviour of non-freezing water in structure formation process of polysaccharide aqueous solutions

In this study, the experimental results on annealing and subsequent cooling induced gelation obtained by the falling ball method (FBM) and differential scanning calorimetry (DSC) have been summarized. By FBM measurements, it has become apparent that the gel¯sol transition temperature, Tg¯s, increases by the annealing of the solution in the sol state. By DSC measurements, the anomalous behaviour of nonfreezing water was observed in the annealing process of the solution in the sol state, i.e. the amount of non-freezing water changed oscillationally in the initial stage of annealing and then approached a constant value. Such an observation suggested that the structure that induces gelation is formed by the homogenization of the system. It is thought that the homogenization of the system is caused by the diffusion of polysaccharide chains removed from polysaccharide molecule assemblies by the dissociation. The phenomenological equation was derived in order to describe the behaviour of non-freezing water taking into account the effect of homogenization of the system assuming that the adsorption and desorption of water molecules on polysaccharide chains takes place. It was found that a large amount of water is adsorbed in junction zones composed of polysaccharide chain assemblies.