Development of a model whipped cream: Effects of emulsion droplet liquid/solid character and added hydrocolloid

Abstract

Traditional whipped dairy cream is stabilized by a rigid network of partially coalesced fat globules; it has a substantial elastic modulus, and a finite yield stress, allowing it to support its own weight under gravity; it has a very low yield strain (< 0.1%), beyond which the microstructure breaks down, leading to smooth flow with a creamy texture. Here we attempt to mimic the textural properties of whipped cream using model aerated systems of acidified protein-based emulsions where the foam structure is not stabilized by partial coalescence. Acidified caseinate-stabilized oil-in-water emulsions (30 vol% oil) containing either liquid groundnut oil or solid n-eicosane droplets were whipped to 120% overrun. Systems composed of liquid emulsion droplets gave rise to elastic foams of low rigidity and high apparent fracture strain. Replacing all the liquid droplets with crystalline droplets resulted in a considerably more brittle foam; the resulting rigidity was similar to that of whipped dairy cream. Partial replacement of liquid droplets by all-solid ones had a significant influence on the model foam properties only at high replacement fractions (75−80% or above). In some emulsions a small quantity of low-methoxyl pectin was added to generate additional protein−polysaccharide bridging interactions between the droplets during pH lowering. Regardless of the liquid/solid character of the emulsion droplets, addition of pectin increased the elastic modulus of the foam, and it also increased the yield strain. Overall, these findings suggest that the properties of these acidified caseinate-stabilized emulsion foams are dependent on both the solid/liquid character of the emulsion droplets and the nature of the interdroplet interactions.