High-pressure homogenization as a process for emulsion formation

Emulsions find a wide range of application in industry and daily life. In the pharmaceutical industry lipophilic active ingredients are often formulated in the disperse phase of oil-in-water emulsions. Milk, butter, and margarine are examples of emulsions in daily life. In the metal processing industry emulsions are used in the form of coolants. Emulsions can be produced with different systems. In the following, the process of high-pressure homogenization is briefly compared to other common mechanical emulsification systems. To facilitate the selection of an emulsification system, the influence of the most important parameters of the emulsion formulation on the resulting mean droplet diameter in the most prevalent continuous emulsification systems is outlined. Subsequently, the most common high-pressure homogenization systems are discussed in detail. On the basis of data from the literature and own experimental results the described high-pressure homogenization systems will be compared regarding their attainable mean droplet diameter. It shows that homogenizers with a relatively simple geometry like the patented "combined orifice valve" (Kombi-Blende) attain the smallest mean droplet diameters. The advantage of the "combined orifice valve" compared to other high-pressure homogenization systems is not more efficient droplet disruption but rather more efficient droplet stabilization against coalescence immediately after the droplet breakup. The greatest research potential concerning the development of new high-pressure homogenization systems is still to be seen in improvements of droplet stabilization, i.e., the reduction of coalescence.