Comparison of the dispersed phase coalescence mechanisms in different tablespreads.

Temperature-induced destabilization of the dispersed phase in butter and margarine was compared by following changes in droplet size (d(3,3)), solid fat content (SFC), and fat crystal spatial organization in the 28-34 degrees C range. At 28 degrees C, both butter and margarine were stable, with similar d(3,3) values (approximately 6 microm) and droplet size distributions. As the storage temperature was raised above 30 degrees C, notable droplet coalescence was observed (for example, at 32 degrees C d(3,3) values of approximately 10 microm for butter and approximately 12 microm for margarine were obtained). Dispersed phase coalescence in butter was dominated by coagulation, with the fat crystal network-limiting droplet-droplet contact until a minimum SFC was reached (approximately 2.5%). In margarine, the rate-limiting step for coalescence was the melting of Pickering crystals present around the dispersed aqueous droplets. Unlike butter, there was no sharp change in stability at a particular temperature or critical SFC. With these differences, coalescence in butter could be modeled as a 2nd-order process and as a 1st-order process in margarine. Overall, these results demonstrated that the kinetic stability of the dispersed aqueous phase in butter and margarine depends on SFC and the spatial distribution of fat crystals within the spreads.