Physicochemical characteristics of mixed colloidal dispersions: Models for foods containing fat and starch

Mixed colloidal dispersions, consisting of starch granules and lipid droplets, were used as model systems to represent commercial food products, such as sauces, desserts, and soups. Colloidal dispersions were prepared by mixing unheated modified starch (3.5 or 5.0 wt%) and lipid droplets (2.5, 5.0 or 8.0 wt% oil) together and then heating (90 °C for 5 min) to promote starch gelatinization. The lipid droplets were stabilized by a food-grade surfactant consisting of a mixture of diacetyl tartaric acid ester of mono-diglycerides (DATEM) and mono-diglycerides. The influence of thermal processing and composition (starch, lipid, surfactant content) on the particle size, microstructure, lightness, and shear viscosity of the model sauces was examined. There was a pronounced increase in shear viscosity upon heating, which was attributed to the swelling of the starch granules leading to a close-packed particle suspension. The shear viscosity and lightness of the colloidal dispersions increased with increasing starch and fat content, with fat droplets dominating lightness and starch granules dominating viscosity. The amount of surfactant present also influenced the rheology of the mixed colloidal dispersions, which was attributed to its ability to modify starch granule interactions. Overall, these results have important implications for designing high quality emulsion-based food products, such as soups, sauces, desserts, and beverages.