EFFECT OF TETRA-ALKYL AMMONIUM BROMIDE ON THE RHEOLOGICAL AND THERMAL-PROPERTIES OF KAPPA-CARRAGEENAN AND AGAROSE GELS

Dynamic viscoelastic measurements and differential scanning calorimetry were carried out for kappa-carrageenan gels containing tetra-alkyl ammonium bromide in order to clarify the structure and functional properties of kappa-carrageenan. The dynamic Young’s modulus E′ of the gels showed a maximum as a function of concentration of tetra-alkyl ammonium bromide at around 0.2 mol l−1. At any particular temperature E max ′ decreased in the following order: E max ′(Me 4 N-)>E max ′(Et 4 N-)>E max ′(Pr 4 N-)>E max ′(Bu 4 N-). The temperatures Tm of the endothermic peak accompanying the transition from gel to sol in the heating DSC curves shifted to higher temperatures with increasing salt concentration. The order of the melting temperature of these gels was the same as in E max ′, however, the enthalpy of melting showed the reverse order. Cations with smaller dynamic hydration number n DHN increase the elastic modulus and the melting temperature of kappa-carrageenan gels more than those with larger n DHN. © 1990, The Society of Polymer Science, Japan. All rights reserved.