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As has been confirmed by several studies reported in the literature, cavitation phenomena considerably contribute to droplet breakup during emulsification in high‐pressure homogenizers. High‐pressure homogenizers can be equipped with different homogenizing valves. The question, whether cavitation is also of importance for droplet breakup in orifice valves which have been proved very efficient for some emulsion systems, has not been investigated yet and is the subject of this contribution.

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In continuous mechanical emulsification, disruption and stabilization of droplets determine the resulting droplet size and, thus, the emulsion's microstructure. Without the need of adding any stabilizer, w/o emulsions provide the possibility of a high viscosity of the continuous phase and, in consequence, of decreasing the probability of coalescence. The present work presents investigations on the production of w/o emulsions in high-pressure homogenizers: the different geometries of standard valve, microfluidizer and orifice valve are compared to each other with reference to disruption and stabilization of droplets. In the orifice valve, droplets are disrupted most efficiently; however, coalescence superimposes the disruption result to a higher extent than in the microfluidizer. On the basis of simulations of the flow pattern, the geometry of the orifice valve has been improved: the new conical valve provides for higher volumetric flow rates and a lower extent of coalescence in comparison to the orifice valve.

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