Effect of oil droplet inhomogeneity at different length scales on mechanical and sensory properties of emulsion-filled gels: Length scale matters

We studied the effect of inhomogeneity in oil droplet distribution at different length scales on the mechanical and sensory properties of emulsion-filled food gels. Two approaches were followed to obtain an inhomogeneous distributions at different length scales: (1) clustering of o/w-emulsions by hetero-aggregation and subsequent gelation to obtain inhomogeneity at μm-scale, and (2) incorporating particles of emulsion-filled gels into emulsion-filled gel matrices with a different volume fraction of oil droplets to obtain gel-in-gels with inhomogeneity at mm-scale. Upon clustering of oil droplets at μm-scale, the Young's modulus of the gels increased by up to 60%, whereas fracture stress and strain depended on emulsifier-matrix interactions. Clustering of oil droplets affected mainly the perception of texture-related sensory attributes, such as hardness, but did not significantly affect the perception of fat-related sensory attributes. Fat-related sensory attributes, such as creaminess and melting, were dominated by emulsifier matrix interactions. For gel-in-gels, the inhomogeneous distribution of oil droplets at mm-scale did not affect Young's modulus or fracture strain. The incorporation of particles decreased the fracture stress of the gels, independently of the droplet distribution. The perception of fat-related sensory attributes changed significantly. Oiliness was lower in samples with lower oil content in the outer phase of the gel than in the inner dispersed particles, whereas coating perception increased in samples in which the oil droplet distribution was inhomogeneous, independently on whether the outer phase or the inner gel particles contained a higher oil volume fraction. Creaminess was only slightly affected. We conclude that oil droplet clustering at μm-scale can be used to modify mechanical properties and texture-related perception of emulsion-filled gels, whereas inhomogeneity at mm-scale allows altering fat-related sensations. Sensory perception can be controlled by modifying the interactions between dispersed oil droplets and matrix using different emulsifiers and by incorporating inhomogeneity in the oil droplet distribution of emulsion-filled gels at different length scales.