Rheokinetic model to characterize the maturation process

MARIEL L. OTTONE, MARTA B. PEIROTTI AND JULIO A. DEIBER

FOOD HYDROCOLLOIDS

ELSEVIER SCI LTD

Año: 2009 vol. 23 p. 1342 - 1350

0268-005X

Under static conditions, the maturation process of gelatin solutions may be described through a basic structural parameter evolving to the percolation value. Within a rheological framework, two asymptotic viscosities are well identified for the maturing process of gelatin solutions at the limit zero shear rate. One involves the initial solution viscosity that may be associated with the null structural parameter (the microstructure is not formed yet). The other is the percolation zero shear rate viscosity (assuming an infinite value when approaching the gel time) and corresponds to the maximum value of the structural parameter. Under flow, thixotropic theories combined with the knowledge of suspension rheology allow one to convert directly experimental data obtained as shear stress versus time for a given shear rate into the time evolution of the structural parameter. Consequently rheometric experimental data available places the search for a rheokinetic model of the structural parameter. Here, different expressions for this model are investigated, mainly those involving both the rates of structure breakdown and buildup, where the sizes of clusters are affected by the shear rate. The rate equation thus obtained may be then applied, in principle, to any arbitrary shear rate history. Numerical results of the rheokinetic model proposed in this work fit well experimental rheometric data obtained in shear flow for the maturing of different types of gelatin solutions. Experimental data obtained in this work are presented and discussed in relation to those reported previously in the literature.