EFFECT OF GALACTOMANNAN ADDITION ON THE THERMAL-BEHAVIOR OF KAPPA-CARRAGEENAN GELS

Gelation/melting cycles of kappa-carrageenan/galactomannan (guar, tara and locust bean gums) binary systems have been studied by measuring dynamic rheological parameters. Two experimental conditions were used, (i) the total polysaccharide concentration was kept at 1% and the kappa-carrageenan/galactomannan ratio fixed at 4:1 and (ii) the kappa-carrageenan concentration was fixed at 0.75% and the galactomannan content varied from 0% to 1.2%. A thermal hysteresis was observed for all mixed systems and was found to depend on the galactomannan used. From a comparison of the gelation temperature (T(g)) and melting temperature (T(m)) to values obtained with kappa-carrageenan alone, it was suggested that galactomannan interferes with gel structure by the formation of a secondary network provided that the M/G ratio is high enough.