THE INFLUENCE OF CASEINS ON THE THEOLOGY OF IOTA-CARRAGEENAN GELS

Controlled stress oscillatory theology was used to monitor the thermoreversible gelation of 1% iota-carrageenan and mixtures of 1% iota-carrageenan and 2% sodium caseinate, alpha(s)-, beta- or kappa-casein. All samples were prepared in a 10 mmol/dm(3) imidazole-HCl buffer, pH 7.0, containing 0.01 mol/dm(3) CaCl2. The addition of each casein altered the gelation and melting characteristics of iota-carrageenan, with the effects being most pronounced on the addition of kappa-casein and least when alpha(s)- casein was added. The viscoelastic properties of formed gels were determined at 5 degrees C using both oscillatory and creep techniques. The rigidity of the iota-carrageenan gel, as measured by storage modulus and instantaneous compliance, increased on the addition of the caseins. The rigidity of gels was in the order kappa-casein/iota-carrageenan > beta-casein/iota-carrageenan > sodium caseinate/iota-carrageenan > alpha(s)-casein/iota-carrageenan > iota-carrageenan. The elasticity of the iota-carrageenan gel was more frequency dependent than the elasticity of casein/carrageenan mixed gels.