RHEOLOGICAL PROPERTIES OF AQUEOUS AGAROSE‐GELATIN GELS

ABSTRACT Melting temperatures were determined for 1‐5% agarose gels, 7.5‐40% gelatin gels and mixed gels of different concentrations of the two hydro‐colloids. The dynamic viscoclastic constants were also quantified at 0.05 HZ for mixed gels containing 0.5% agarose and 2.5–20% gelatin. In single component gels, the melting temperature increased with hydrocolloid concentration. The melting temperature of gelatin gels was lower than that of agarose gels (22–31°C vs 69–80°C) and less concentration dependent. The melting temperature of mixed gels was more similar to that of agarose gels at low (2.5–6.25%) gelatin concentrations and more similar to that of gelatin gels at high (7.5–20%) gelatin concentrations. The storage modulus decreased with increasing temperature indicating that the thermal rupturing of the noncovalent crosslinks in the gels was stronger than the entropic behavior of the network. The temperature dependence of the storage modulus and of the dynamic viscosity increased with gelatin concentration. Based on these results and on the determination of the activation energy it is concluded that, in mixed agarose/gelatin gels, the two species form individual networks which interfere with one another at high concentrations.