EFFECTS OF PH, POTASSIUM-CHLORIDE, AND SODIUM-CHLORIDE ON THE THERMALAND RHEOLOGICAL PROPERTIES OF GELLAN GUM GELS

The effects of pH on DSC curves and the breaking stress of gellan gum gels with and without NaCl or KCl were investigated. The breaking stre ss of all gels increased with decreasing pH down to pH 4. The differen ce between the breaking stress of nonheated gels and that of gels rehe ated for 2 h at 90 degrees C became larger with increasing pH. The exo thermic enthalpy (Delta H) of all samples became minimum at pH 4. The DSC cooling and heating curves for all samples did not show any peak a t pH 2. Repeated observations of DSC curves were carried out from 99.9 to 1.0 degrees C. Exothermic peaks of all gels at pH 4 and 6 shifted to lower temperatures, and the peaks of DSC heating curves of gels wit hout salt at pH 8 shifted to higher temperatures with increasing numbe rs of heating and cooling cycles.