Thermal measurements of curdlan in aqueous suspension during gelation

Differential scanning calorimetry (DSC) measurements of curdlan in aqueous suspension were carried out in a temperature range of 40–200°C by using silver pans with and without heat treatment, respectively. Silver pans with heat treatment were heated at 200°C and then cooled. Heating DSC curves of curdlan in aqueous suspension showed an endothermic peak around 60°C and were identical below 120°C, but quite different above 120°C. A large exothermic peak was observed at 140–190°C in a heating DSC curve when a non-heated pan was used, whereas a small endothermic peak was observed at 140–160°C and no exothermic peak was observed at higher temperatures when a heated pan was used. It was suggested that the large exothermic peak was attributed to an interaction between the non-heated silver pan and water above 120°C. Only the endothermic peak at 140–160°C reflected the reality of the thermal property of curdlan in aqueous suspension, which was caused by the melting of the curdlan gel formed.