Combination of steam and ultrasound kills bacteria within just 1-2 seconds

Combined steam-ultrasound treatments are usually no longer than just two seconds.

At such fast rates, the disinfection or decontamination with steam and ultrasound combined reaches up to 7-8 logs on non-food products and up to 2-4 logs on certain food products. The catalyzing effect of ultrasound accelerates heat from the steam to the surface of any object. This results in an instant increase in temperatures on the surface. The decontamination or disinfection treatment is halted before heat penetrates the product and causes unwanted thermal damages.

The “catalyzing” effect of ultrasound disrupts heat restricting air layers that protects the bacteria on the surface

The zone of air closest to the surface serves as a protective mantel, restricting vapour and heat exchange across the surface, a layer often referred to as the laminar sublayer.

surface with laminar layer without ultrasound

Ultrasound sets the air of the laminar zone in a state with intensified molecular oscillations, resulting in a destruction of the protective characteristics of the laminar sublayer. Hot steam is then able to reach microstructures and pits in the surface and secure rapid heat transfer. The continuous pumping of new steam creates a fast, substantial flux of heat to the surface structure.

surface laminar layer with ultrasound

Microorganisms are killed more rapidly with steam-ultrasound compared to steam treatment without ultrasound

The small size of microorganisms make them particularly sensitive to the concentrated steam treatment. Microbe elimination happens so quickly that the depth of heat entrance into the surface of the product is kept at a minimum. The treatment can be stopped before the surface is thermally damaged. The processing time in a SonoSteam treatment are for some applications even shorter than one second. The method gently handles the decontamination of heat sensitive products, such as fresh and processed food products, where sensory changes are not acceptable.

Real simulation of ultrasound waves disrupting the heat restricting laminar boundary air layer

This video is a real simulation of ultrasound waves, which are cutting through the different layers of air and disrupting the heat-restricting stagnant air right above any object.

The green and yellow moving areas are the turbulence air. The closest we get to an object, the darker becomes the colors and the lower are the air velocities. The very dark blue area represents the boundary laminar air layer.

The time rate must be significantly reduced in order to be able to show the super fast ultrasound waves.  In this time frame, turbulence and the boundary layer does not change and thus looks as it is frozen. The sound waves push the boundary layer aside and allow heat to reach the surface rapidly.

Learn more about the benefits of the SonoSteam treatment