Critical Review on Hydrodynamic Cavitation as an Intensifying Homogenizing Technique for Oil-in-Water Emulsification: Theoretical Insight, Current Status, and Future Perspectives

In the recent decade, hydrodynamic cavitation (HC) emerged as a promising and effective homogenization technique for preparing oil-in-water (O/W) nanoemulsion. This technique has presented several advantages: size reduction to the nanoscale, long-term kinetic stability, and high energy efficiency. However, in the reported literature, the physical and chemical stability has not been considered to define the quality of the prepared emulsions using HC. Therefore, it is now essential to understand the effect of several geometrical and operating parameters of HC on the physical and chemical stabilities of the prepared emulsions to cover their broader applications. This review attempts to answer this question through a critical analysis of previously reported work. This review gives an overview of the mechanism of cavitationally assisted emulsification, disruptive forces involved in the emulsification process, operating parameters affecting the emulsion stability, and the current research in this area. This review elucidates the possible HC-induced lipid degradation pathway during emulsification which has been overlooked so far. The possible mechanisms and operating conditions affecting the lipid oxidation during HC-assisted emulsification are presented. Some effective strategies and recommendations for obtaining the optimum operating parameters are presented. Future perspectives and directions for further investigations in this area are also discussed.