Time–temperature studies of κ-carrageenan gelation in the presence of high levels of co-solutes

The effect of oscillatory frequency and temperature on the viscoelastic storage and loss moduli were investigated for κ-carrageenan (0.5% w/w): high co-solute (sucrose/corn syrup) (80 and 85% w/w) systems using time–temperature superposition (TTS) and the modified Cole–Cole (MCC) analysis. Thermal rheological scans (0.15 Hz) and isothermal frequency (ITF) (0.15–15 Hz) scans were performed over a temperature range of 5–85 °C, during cooling and heating. Flow behavior was characteristic of a rubber over the majority of temperatures examined. TTS failed at all temperatures for the 80% (w/w) co-solute samples, and between 25 and 85 °C for the 85% (w/w) co-solute samples. In contrast, the MCC analysis superposed ITF data over a greater temperature range, but only with data corresponding to the rubber–glass transition zone. Successful superposition occurred when the short-range relaxation of chains became overwhelmed by the response of the co-solute medium. κ-Carrageenan was proposed to form a weakly cross-linked network.