Influence of binary emulsifier blends on the thermal and shear sensitivity of a model oil-in-water emulsion

The controlled crystallization of oil-in-water emulsions offers a pathway to the rational design of functional foods with novel textures. Emulsifiers with different chemical structures may be used to tailor the fat crystal size and spatial distribution within emulsions. Here, we investigated the thermal and shear sensitivity of a model oil-in-water emulsion consisting of hydrogenated palm kernel oil (HPKO) and binary blends of emulsifiers containing oleic acid citrem (OA-citrem), stearic acid citrem (SA-citrem), or a sucrose ester (S170), dispersed within an aqueous phase consisting of water. We hypothesized that these emulsifiers would affect fat crystallization within the bulk of the droplet and/or at the oil-water interface, with notable improvements in stability to temperature fluctuations and shear depending on their molecular structure. Use of OA-citrem induced droplet aggregation, leading to the low thermal and shear stability of the HPKO emulsion. We ascribed this behaviour to its inability to control for the destabilizing effects of the HPKO crystals that grew within the dispersed droplets. The SA-citrem enhanced emulsion low-shear resistance and robustness to temperature-cycling via the formation of a solid shell around the dispersed oil phase. The S170 associated with the HPKO triglycerides and modified their crystallization behaviour which led to a smaller HPKO crystal size within the dispersed droplets, thereby enhancing emulsion stability against temperature-cycling. It was the binary blend of SA-citrem and S170 that offered the highest stability as the SA-citrem interfacial film that formed at the oil-water interface as well as the small HPKO crystal size resulting from the presence of the S170 led to both resistance against shear and temperature-cycling. These results demonstrated that the design of food emulsions using a targeted emulsifier blend may be used to optimize the functionality of oil-in-water emulsions.