Fat structure in ice cream: A study on the types of fat interactions

This study investigated the type of fat interactions that lead to fat structuring in ice cream, and the effect of droplet shape on the interactions. These include fat crystal-induced partial coalescence, protein-induced (bridging) flocculation, coalescence or a combination of effects. The mechanisms by which SDS and EDTA dissociate fat aggregates could further our understanding of fat structuring. SDS reverses partially coalesced droplets while EDTA re-disperses flocculated ones. Ice cream formulations were designed to favor different kinds of aggregation. The ice creams were prepared with blends of solid (palm kernel oil) and liquid (high oleic sunflower oil) fat (0, 40, 80 or 100% solid fat at whipping temperature) in the presence of 0.15% unsaturated (UM) or saturated monoglyceride (SM). Treatment of ice cream with SDS at temperatures preserving the fat crystals revealed large decreases in particle size. This verified the existence of substantial amounts of partial coalescence as the fat structuring mechanism. The influence of EDTA was lacking, exposing the absence of flocculation in the fat structure. This was further evidenced by inhibited aggregation in the absence of monoglyceride. Some coalescence occurred, dominating in ice creams devoid of solid fat. Transmission electron microscopy images showed a unique type of shape for droplets adsorbed with unsaturated monoglyceride; these droplets partially coalesced to a larger extent than conventional SM-stabilized droplets.