RHEOLOGICAL PROPERTIES OF PECTATE GELS

Creep compliance measurements were made on calcium pectate gels using a paralled plate viscoelasto-meter. Linear viscoelastic behaviour was observed and the response was consistent with a model containing a Maxwell element in series with three Voigt elements. When gels were prepared with the calcium level necessary for maximum gel strength a linear relationship was found between the reciprocal of the creep compliance and the square of the polysaccharide concentration.
The rheological behaviour of pectate gels had many similarities to gels prepared from alginates containing a high proportion of guluronic acid residues. However, pectate gels were more sensitive to calcium ions than alginate gels and at high calcium levels the Newtonian viscosity of the pectate gel was much higher than that found for the alginates. These differences have been interpreted in terms of the structure and molecular weight of the two polymers.