Michael Stang

Emulsification in High-Pressure Homogenizers

High‐pressure homogenizers are frequently employed for the homogenization of low‐viscosity emulsions containing a proportion of disperse phase which is not too high. High‐pressure homogenizers essentially consist of a high‐pressure pump and a homogenizing nozzle. The design of the homogenizing nozzle influences the flow of the emulsion in the nozzle itself and hence the results of droplet disruption. It is shown which mechanism in frequently used homogenizing nozzles is usually responsible for disruption. Experimental results reveal the effects of the dispersed phase content and the viscosity of the disperse and continuous phases in different nozzles. The results can be explained on the basis of the mechanisms of disruption. Finally, the homogenizing nozzles presented are directly compared with one another.

Adsorption kinetics of emulsifiers at oil—water interfaces and their effect on mechanical emulsification

Abstract The bursting membrane method of measuring the adsorption of emulsifier molecules at oil—water interfaces is presented. For the emulsifiers dodecyl alcohol-10-glycol ether, a whey protein concentrate and egg yolk the adsorption kinetics are measured. It is shown that this method is applicable to determine the adsorption kinetics. Oil—water emulsions have been prepared with the above-mentioned emulsifiers. The influence of the adsorption kinetics of these emulsifiers on the emulsification result is shown.

Jet agglomeration and dynamic adhesion forces

Abstract Jet agglomeration has been used in the food industry for several years to produce agglomerates with favourable instant properties from fine powders. In a jet agglomeration plant, freely moving, wetted particles are made to collide with each other to form agglomerates. Agglomeration occurs if the relative kinetic energy of the particles can be dissipated by the viscous liquid layers on their surfaces. This size enlargement process can only be understood if the forces between the colliding particles, called dynamic adhesion forces, can be described. Following a description of the jet agglomeration process, an indirect approach to this problem is presented which uses an experimental set-up allowing determination of the adherence probability of spheres colliding with wetted surfaces.