Identifying key structural indicators of mechanical strength in networks of fat crystals

The mechanical properties of edible fats can be influenced by a series of factors, including the amount of solids, the polymorphism of the solid-state, as well as the microstructure of networks of polycrystalline particles created upon crystallization. This work demonstrates that for binary mixtures of the high-melting fraction of milk fat (HMF) with cocoa butter as well as for mixtures of HMF with the middle-melting fraction of milk fat, changes in the storage shear modulus (G) are mostly controlled by the solid fat content (SFC), and the material's microstructure. The SFC, in turn is a function of the phase behavior of the mixtures in the solid state. Experimental techniques used in the characterization of the different levels of structure are presented in this work. A model developed to explain mechanical properties of these materials taking into account all levels of structure is proposed. The polymorphism of the solid state did not seem to influence the mechanical properties of the fats, indicative of this material being structured as a network of weakly-attractive polycrystalline particles. Moreover, the mass fractal dimension of the network was closely related to the polymorphism of the solid state. (C) 2002 Elsevier Science Ltd. All rights reserved.