The stability of aerated emulsions: Effects of emulsifier synergy on partial coalescence and crystallization of milk fat

This study investigated the effects of emulsifiers (mono- and diglycerides, Tween 80, LACTEM, and sodium stearyl lactylate), both individually and in combinations, on the partial coalescence of fat globules and fat crystallization behavior, as well as their influence on the stability of aerated emulsions (36 wt% fat). The extent of partial coalescence, solid fat content (SFC), and melting/crystallization profile of bulk anhydrous milk fat (AMF) blends were examined. Furthermore, the interfacial tension, particle size distribution, apparent viscosity, and creaming rate of the quiescent emulsions were measured, while the aeration properties, rheology, and microstructure of aerated emulsions were analyzed. Lipophilic-emulsifier formulas accelerated fat crystallization and achieved higher foam firmness, whereas mono- and diglycerides had a significant positive effect on the crystallization behavior of bulk AMF blends compared to the minor impact on emulsification. Moreover, the highly viscous emulsions that were obtained by combining more hydrophilic emulsifiers could be attributed to more partial coalescence and smaller globule particle size, especially with the inclusion of Tween 80, which was very efficient at reducing interfacial tension. The four-blend emulsifier formula produced a lower emulsion creaming rate and higher aeration activity (overrun) and its foam displayed regularly-shaped air bubbles enveloped by a fat network consisting of well-distributed fat clusters. Overall, the results showed that the choice of emulsifiers played a crucial role in the physical stability of aerated emulsions.