Ultrasonic Extraction and its Working Principle

Ultrasonic extraction is the preferred technique to isolate bioactive compounds from botanicals. Sonication achieves a complete extraction and thereby superior extract yields are obtained in a very short extraction time. Being such an efficient extraction method, ultrasonic extraction is cost- and time-saving, whilst resulting in high-quality extracts, which are used for food, supplements and pharmaceuticals.

Ultrasonic Extraction

Ultrasonic extraction is used in the food, nutritional supplement and pharmaceutical industry to release bioactive compounds such as vitamins, polyphenols, polysaccharides, cannabinoids and other phytochemicals from botanicals. The ultrasound-assisted extraction is based on the working principle of acoustic or ultrasonic cavitation.

How Does Acoustic Cavitation Work?

Ultrasonic extraction is achieved when high-power, low-frequency ultrasound waves are coupled into a slurry consisting of botanical material in a solvent. High-power ultrasonic waves are coupled via a probe-type ultrasonic processor into the slurry. Highly energetic ultrasound waves travel through the liquid creating alternating high-pressure / low-pressure cycles, which results in the phenomenon of acoustic cavitation. Acoustic or ultrasonic cavitation leads locally to extreme temperatures, pressures, heating/cooling rates, pressure differentials and high shear forces in the medium. When cavitation bubbles implode on the surface of solids (such as particles, plant cells, tissues etc.), micro-jets and interparticlular collision generate effects such as surface peeling, erosion, particle breakdown, sonoporation (the perforation of cell walls and cell membranes) and cell disruption. Additionally, the implosion of cavitation bubbles in liquid media create macro-turbulences and micro-mixing. Ultrasonic irradiation represents an efficient way to enhance mass transfer processes, since sonication results in cavitation and its related mechanisms such as micros-movement by liquid jets, compression and decompression in the material with the subsequent disruption of cell walls, as well as high heating and cooling rates.
Probe-type ultrasonicators can generate very high amplitudes, which is necessary to generate impactful cavitation. Hielscher Ultrasonic manufactures high-performance ultrasonic extractors, which can easily create amplitudes of 200µm in continuous 24/7 operation. For even higher amplitudes, Hielscher offers specified high-amplitude sonotrodes (probes).
Pressurizable ultrasonic reactors and flow cells are used to intensify the cavitation. With increasing pressures, cavitation and cavitational shear forces become more destructive and improve thereby the ultrasonic extraction effects.

Ultrasonic extraction is based on acoustic cavitation and its hydrodynamic shear forces

Effects of Ultrasonic Extraction

Ultrasonic Cell Disruption and Increase of Mass Transfer
Ultrasound can assist extraction processes both through cell disruption and by enhancing mass transfer in the boundary layer surrounding the solid matrix.
Sonoporation, the perforation of cell walls and membranes, enhances the permeability of the cell walls and membranes and is often an intermediate step before cells are disrupted completely by sonication.
The mechanical effects of ultrasound-induced cavitation, such as heat and pressure differentials, shock waves, shear forces, liquid jets and micro streaming, intensify the penetration of the solvent into the cell interior and improves the mass transfer between cell and solvent so that the intercellular materials are transferred into the solvent.

Ultrasonic extraction from plant cells: the microscopic transverse section (TS) shows the mechanism of actions during ultrasonic extraction from cells (magnification 2000x) [resource: Vilkhu et al. 2011]

Ultrasonic Extraction Equipment

Hielscher Ultrasonics processors are high-performance extraction systems, which are simple and safe to operate. In accordance on your raw material, process capacities and output target, Hielscher offers you the most suitable ultrasonicator. Our product portfolio ranges from compact, powerful hand-held ultrasonicators over bench-top system to fully-industrial ultrasonic units capable to process several tons per hour.
Hielscher Ultrasonics extractors can be used for batch and continuous inline extraction and can be used in combination with any solvent.
Various accessories such as sonotrodes (probes) of various sizes and shapes, booster horns, flow cells with various volumes and geometries, pluggable temperature and pressure sensors and many other gadgets are available to assemble the ideal ultrasonic setup for your extraction process.
All our digital models are equipped with intelligent software, which allows you to adjust, monitor, and set extraction parameters. Due to the precise control over amplitude, sonication time and duty cycles, optimum process results such as superior yield and highest extract quality can be achieved. The automatic data recording of the sonication process are the bases for process standardization and reproducibility / repeatability, which are required for Good Manufacturing Practices (GMP).

Hielscher Ultrasonics industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators: