Modelling acidified emulsion gels as Matryoshka composites: Firmness and syneresis

The effect of the key ingredients of a low-fat acidified emulsion gel (amount of protein, amount and type of fat, amount of thickener) on firmness and syneresis were studied with fixed ingredients but widely varying compositions (up to 35% fat containing up to 90% solid fat on fat phase, and the relative phase volume of the protein phase (from buttermilk powder) being up to 44%, relative to the phase volume of the locust bean gum containing thickener phase). It is shown that the firmness and syneresis data can be successfully analysed in terms of a new model that incorporates the hierarchical 'nesting' of structures in low-fat acidified emulsion gels: (i) Bi-continuous polysaccharide/protein phase separation-based structure; (ii) (Protein-covered) oil droplets dispersed in protein phase; (iii) Fat crystals dispersed in oil droplets. Firmness is modelled by a set of recursive power-law relations between firmness F(T) and concentration of the structuring components, reflecting the nested structure of these 'Matryoshka' composites. The fitting parameters are within the range expected based on literature data for simpler systems. Syneresis is modelled by a Darcy-type equation, which incorporates the firmness model in turn. The success of the modelling is taken to be a confirmation of the occurrence of hierarchical nesting of microstructures in these low-fat acidified emulsion gels, while the approach is flexible enough to be applied to other (similar) complex composites. (c) 2012 Elsevier Ltd. All rights reserved.