Theoretical and experimental study of the fractal nature of the structure of casein gels

Abstract

Casein gels consist of particulate disordered structures, formed by aggregation of casein micelles. The aggregation leads to flocs of a fractal nature, which form a gel as soon as the occupy the total volume. A model was developed to describe gel formation and structure usnig the concept of fractal geometry. Parameters derived from this model were compared with experimental results concerning the structure and related properties. The model was in good agreement with the dependence of the permeability or rheological properties, such as the storage modulus of the gels, on the volume fraction of casein, and with the dependence of the turbidity of the gel on wavelength. It is shown that acid casein gels can be described very well as a collection of fractal clusters with a fractal dimensionality, D, of 2.3. Rennet-induced casein gels appeared to lose their fractal behaviour due to microsyneresis. Consequently, the model was not fully valid for the latter gels.