Modeling the rheology of gelatin gels for finite deformations. Part 1. Elastic rheological model

The rheological behavior of gelatin gels is studied through a constitutive equation derived in the literature from the classical hyperelasticity theory by using a nonlinear strain energy density. Gelatin gels are assumed to be an elastic solid here, which at a given maturation time has a degree of physical cross-links composing a permanent elastic network. It is also studied in particular: (a) the validation of the elastic rheological model proposed here in relation to the prediction of two data sets pertaining to different experimental tests (shear and simple compression) by using fixed values of rheological parameters, (b) the increase of the stress-strain nonlinearity with increasing maturation time, at a given protein concentration, (c) the evolution of the stress-strain nonlinearity with increasing gelatin concentration. It is found that gelatin gels exhibit a strong nonlinear strain energy density, which is expressed through two shear modules related to nucleation and growing of junction zones.