High-Pressure Homogenization in Emulsion Processing

High-pressure homogenization is a well established unit operation for producing fine emulsions by forcing a premixed fluid through a narrow gap or valve at pressures typically ranging from 100 to 2 000 bar. Within the disruption zone, intense shear, extensional stresses and cavitation act in concert to break dispersed-phase droplets down to micrometre or even nanometre scale. Key performance indicators include mean droplet diameter, polydispersity and product stability, all of which depend on operating pressure, valve geometry, emulsifier concentration and flow regime. Laminar-to-turbulent transitions govern the energy dissipation profile and influence droplet break-up rates, while repetitive passes offer diminishing returns once a threshold droplet size is reached. Applications span dairy and plant-based beverages, pharmaceuticals, cosmetics and advanced materials for which control over interfacial area and droplet size distribution is critical. Recent advances integrate computational fluid dynamics with population balance models to predict droplet size evolution, support digital-twin development and guide design optimisation towards lower energy consumption and reduced equipment wear.

Research from Nature Portfolio

Investigation of laminar versus turbulent flow in a high-pressure homogenizer has revealed that laminar conditions yield a higher rate of droplet size reduction with increasing pressure and a minimum in polydispersity, whereas turbulent flow can diminish break-up efficiency for perfluorocarbon nanoemulsions unless sufficient emulsifier is liberated by concurrent liposomal disruption. A sucrose-gradient approach enabled separate analysis of liposomes and emulsion droplets, showing that both species reduce at similar rates under laminar flow, but droplet break-up in turbulence relies on available surface-active species. Repeated homogenization cycles become ineffective beyond a certain point, as aggregation and coalescence counteract further size reduction.

Research from all publishers

A scaled-model study of turbulent droplet breakup demonstrated that experimental amplification of high-pressure homogenizer orifices preserves key non-dimensional numbers, allowing direct observation of breakup phenomena. Visual evidence confirmed that turbulence intensity and eddy scales control droplet disintegration, and that findings at macroscopic scale can be transferred to industrial micro-scale operations, informing gap geometry optimisation.

High-speed imaging of cavitating versus non-cavitating flows in an optically accessible orifice revealed that cavitation drives breakup further downstream and yields larger residual droplets compared with cavitation-free conditions at equal energy input. This work clarifies local effects of vapour bubble dynamics on droplet deformation and highlights the need to balance cavitation control for optimal emulsion quality.

Comparative computational fluid dynamics of two common valve designs—outward radial and inward radial flow—showed that at moderate pressures the traditional outward design imparts higher turbulent stress, while at extreme pressures the inward design benefits from elevated gap-exit velocities. The study quantified trade-offs between dissipation volume and velocity, offering guidance for valve selection and customisation based on target pressure ranges and desired droplet size distributions.

High-Pressure Homogenization in Emulsion Processing publication trend

The graph below shows the total number of articles in high-pressure homogenization in emulsion processing across all publications each year (not limited to Nature Index journals).

Technical terms

Emulsion: A dispersion of one immiscible liquid as droplets within another, stabilised by surface-active agents.

High-pressure homogenization: A mechanical process in which fluids are forced through narrow gaps at elevated pressures to reduce droplet or particle size.

Cavitation: The formation and collapse of vapour bubbles in a liquid under rapid pressure changes, contributing to droplet deformation and breakup.

Reynolds number: A dimensionless parameter expressing the ratio of inertial to viscous forces, used to characterise laminar or turbulent flow regimes.

Polydispersity: A measure of the breadth of droplet size distribution within an emulsion, typically expressed as a coefficient of variation.

Valve geometry: The shape and configuration of the homogenizer gap or disruption unit, which dictates local shear and extensional stress fields.

References

1. Laminar and turbulent flow effects in high-pressure homogenization of liposomes and perfluorocarbon nanoemulsions. Scientific Reports (2024).
2. Scaling of Droplet Breakup in High-Pressure Homogenizer Orifices. Part II: Visualization of the Turbulent Droplet Breakup. ChemEngineering (2021).
3. Does Cavitation Affect Droplet Breakup in High‐Pressure Homogenization? Insights into Local Effects. Chemie Ingenieur Technik (2021).
4. A hydrodynamic comparisons of two different high-pressure homogenizer valve design principles: A step towards increased efficiency. Chemical Engineering Research and Design (2022).