Interpreting rheological behaviour of sugar-fat mixtures as a function of solids phase volume

Abstract

Abstract Many confectionary items and food components are based on complex suspensions of hydrophilic sugar particles in a hydrophobic fat phase. We hypothesise that the rheology of these suspensions is defined by either the Maron-Pierce-Quemada (MPQ) model, which theoretically predicts the viscosity of hard spheres, or by the percolation model describing a network of attractive particles (gel). The rheology of two sugar-fat mixtures, sugar-shortening based biscuit-creams and chocolate, are characterised as a function of phase volume, particle size distribution (PSD) and emulsifier concentration. It is found that their rheological behaviour shows the formation of a network gel structure at sufficient concentration of sugar particles. We find that, upon addition of sufficient emulsifier, the suspension viscosity follows the MPQ hard sphere model, which only depends on phase volume and particle size distribution. Combining the use of the theoretical model and emulsifiers, we are able to decouple the effects of phase volume and particle size distribution from that of particle interactions. The results provide a theoretical basis for identifying levers to control the rheological behaviour of molten chocolate, biscuit-creams, and other sugar-fat based systems, which is relevant to food processing and sensory perception during consumption.