Apparatus for emulsion production in small scale and under controlled shear conditions

In this article, a rotor-stator apparatus for the production of 5 g batches of emulsion is introduced. Special attention was paid to the design of the apparatus and its construction, ensuring close tolerances in all machined parts. The size of the dispersing gap was 500 mum. The need to prepare small quantities of homogeneous emulsion formulations containing costly ingredients formed the impetus for this work. We present a set of emulsion production experiments using a model mayonnaise recipe with a weight percentage of dispersed oil of 80%, and illustrate the effect of rotor speed on the average size and size distributions of the resulting oil droplets. These size distributions were within the same range. as a commercial mayonnaise. The maximum shear rates and corresponding shear stresses existing in the apparatus at different rotational speeds were estimated. A stabilization time related to rotor speed and geometry was also calculated. We discuss the scale-up of emulsion production, giving consideration to the length of time the shear stress is applied as well as to the magnitude of the shear stress.