RHEOLOGICAL PROPERTIES OF MIXED GELS OF KAPPA-CARRAGEENAN WITH GALACTOMANNAN

The rheological properties of 1-1.5% kappa-carrageenan gels mixed with galactomannan, i.e., locust bean gum, tara gum, and guar gum, in ratios of 7:3 and 1:1 were investigated by measuring the temperature dependence and the courses of dynamic viscoelasticity and static viscoelasticity. The addition of small amounts of locust bean gum and tara gum to kappa-carrageenan changed the rheological properties of the original to a firmer and more elastic gel. Measurements of the storage modulus (G') and loss modulus (G'') showed that kappa-carrageenan formed the basic network structure of the gel, while locust bean gum and tara gum strengthened this network structure. kappa-Carrageenan showed a synergistic effect with locust bean gum and tara gum, but not with guar gum, which was caused by the difference of the constituent ratio of galactose to mannose in the three gums. Significant differences in the network structures of mixed gels of kappa-carrageenan and the three gums were apparent by observing with a scanning electron microscope.