Abstract: This study describes how the rheological properties of colloidal dispersions formed by heteroaggregation of oppositely charged protein-coated lipid droplets depend on total particle concentration. Mixed-particle emulsions were formed by mixing single-particle emulsions containing either β-lactoglobulin-coated lipid droplets (ζ≈−42 mV, d43≈ 0.35 μm) or lactoferrin (LF)-coated lipid droplets (ζ≈+26 mV, d43≈ 0.32 μm). A series of single-particle and mixed-particle emulsions with different total fat contents (5% to 40%) were prepared, and their mean particle size, apparent viscosity, and shear modulus were measured. Mixed-particle emulsions (40% LF: 60%β-Lg) containing relatively high fat contents (>10%) had high viscosities and paste-like properties. These rheological characteristics were attributed to extensive particle aggregation and network formation due to electrostatic attraction between oppositely charged droplets. The viscosities of mixed-particle emulsions were much higher than those of single-particle emulsions with equivalent fat contents. Measurements of the color coordinates (L*, a*, b*) of mixed-particle emulsions with low fat contents showed that they had similar appearances as single-particle emulsions with high fat contents. This study has important implications for the creation of reduced fat foods with similar sensory qualities as higher fat foods.
Practical Application: This study describes how novel food materials can be created by mixing together negatively charged and positively charged lipid droplets. These mixed emulsions may be suitable for the creation of reduced fat products, since they have high viscosities and paste-like properties at relatively low fat contents.