Emulsification process controlled by a mixer type rheometer in O/W protein-based emulsions

• The control of the emulsifying process is carried out by a mixer-type rheometer.
• Higher agitation speed increases the emulsion viscosity but decreases droplet size.
• Increasing protein and oil concentration produce emulsions with a higher viscosity.
• Lowering the pH leads to more homogeneous emulsions with a lower viscosity.

In the present work, concentrated Oil-in-Water (O/W) emulsions were stabilized using egg albumen protein isolate as the only emulsifier. A helicoidal geometry was used and compared with a conventional one to assure an optimal emulsion preparation with that unusual geometry in order to come up with the utility of this rheometer as a valuable tool for understanding and controlling the emulsification process. The results put forward the importance of controlling the emulsification process to optimize the properties of the final emulsion and demonstrating a good agreement between in situ and off-line measurements obtained in mixer-type and conventional rheometers, respectively. Flow properties of the different emulsion prepared were measured, showing an increase in the viscosity with the agitation speed (from 10 to 16 to 114–117 Pa s), protein concentration (from 30 to 40 to 106–125 Pa s) and oil concentration (from 15 to 20 to 130–180 Pa s). Furthermore, the droplet size distribution (DSD) was also measured obtaining the influence of the different parameters with the Sauter diameter (a decrease from 20 to 30 to 7–8 μm, from 26 to 3 μm and from 17 to 24 to 8–14 μm was observed by increasing the agitation speed and the protein and oil concentration, respectively). The influence of the pH was also taken into account. Eventually, a relationship has been found that relates these properties to different composition (pH value, nature and concentration of proteins) or processing variables (agitation speed).