Shear modulus-temperature meltdown profiles of gelatin and pectin gels. A cascade theory description

In this paper, a cascade theory approach to biopolymer gelation is developed to describe variation of the shear modulus with temperature for thermoreversible gels. The broadness of this 'melting transition' is seen to depend crucially on the enthalpy of cross-linking, while the critical gel melting temperature is determined by additional factors such as the entropy of cross-linking, the polymer concentration, the molecular weight, and the number of cross-linking sites. On using the model to fit experimental data for specific gelatin and pectin systems, it was found that the behaviour of gelatin (sharp melting transition and low melting temperature) is a consequence of the large negative enthalpy and entropy of cross-linking, while, in contrast, the broad melting transition and high melting point of the pectin system are consistent with much smaller negative values for these parameters.