Dual-frequency sonication for disrupting the self-assembled casein nanoparticles

Ultrasound as a source of energy belongs either to low frequency (16-100 kHz) for power ultrasound or medium frequency (100 kHz-1 MHz) for sonochemical ultrasound. Because of the emitted frequency, mechanisms underlying the effects of ultrasound at each range differ from the other one to some extent, resulting in different applications. It is interesting in definite cases to have cavitational reactors in which power and sonochemical ultrasounds are simultaneously applied. In the present study, casein nanoparticles were self-assembled in phosphate buffer and an approach based on dual-frequency sonication of casein solutions by 130 and 24 kHz ultrasounds was elaborated for disrupting the particles. A synergism was observed between sonochemical and power ultrasounds in disrupting the nanoparticles, leading to a much lower turbidity for casein solutions. Dual-frequency sonication by 130 and 24 kHz ultrasounds was more effective than sonication by 35 and 24 kHz ultrasounds. This is again, attributed to the synergism between sonochemical and power ultrasounds.