Effects of Polyhydric Alcohols on Thermal and Rheological Properties of Polysaccharide Gels

Abstract

The effects of glycerin and ethylene glycol on the elastic modulus and DSC thermograms of agarose and kappa-carrageenan gels were examined to clarify the relation between structure and properties. The elastic modulus of these gels as a function of the concentration of polyols increased up to a certain concentration and then decreased with increasing concentration of polyols. These polyols shifted the melting temperature of the gel to higher temperatures in kappa-carrageenan gels but to lower temperatures in agarose gels. The temperature dependence of elastic modulus was changed in opposite directions in agarose and kappa-carrageenan gels by the addition of polyols, and this is discussed on the basis of model consisting of junction zones which are connected by Langevin chains. It was suggested that the mean distance between junction zones became shorter in the presence of a small amount of polyols.