The influence of caseins on the rheology of ι-carrageenan gels

Abstract

Controlled stress oscillatory rheology was used to monitor the thermoreversible gelation of 1% ι-carrageenan and mixtures of 1% ι-carrageenan and 2% sodium caseinate, α s-, β- or κ-casein. All samples were prepared in a 10 mmol/dm 3 imidazole-HCl buffer, pH 7.0, containing 0.01 mol/dm 3 CaCl 2. The addition of each casein altered the gelation and melting characteristics of ι-carrageenan, with the effects being most pronounced on the addition of κ-casein and least when α s-casein was added. The viscoelastic properties of formed gels were determined at 5°C using both oscillatory and creep techniques. The rigidity of the ι-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 κ-casein/ι-carrageenan > β-casein/ι-carrageenan > sodium caseinate/ι-carrageenan > α s-casein/ι-carrageenan > ι-carrageenan. The elasticity of the ι-carrageenan gel was more frequency dependent than the elasticity of casein/carrageenan mixed gels.