Ultrasound technology: Effect of processing conditions and material on cavitation level

Ultrasound technology has been widely studied for its application in food area to improve different processes and properties of food. The most used form of application is by immersing the product in a medium placed directly or by using containers. During the ultrasound application, different conditions such as powers, media for the transmission of waves, container materials, or pressure levels have been applied. However, it has not yet been described how these conditions impact the level of acoustic cavitation. In this work, by using an ultrasound bath with 40 kHz and power levels (30% - 100%), the effect of the position of beakers, their type of material (plastic and glass), the type of medium (water and ethanol) and pressure (atmospheric and vacuum), in the acoustic cavitation level was studied. As results, the acoustic cavitation level increased as the power level increased. The position in the transducers allowed a higher level of acoustic cavitation, while the influence of the type of material in the acoustic cavitation depended on the power level. At 100% power, the acoustic cavitation decreased by more than 14% when using containers of glass, while, at 30% power level, cavitation highly increased compared to plastic containers. Regarding the medium type, at high power levels (>70%), the acoustic cavitation in water was greater than in ethanol. However, it remained similar at low power level (30%). Finally, when vacuum was used, cavitation decreased in both media, but the level of reduction was greater when the medium was water. In conclusion, the different processing conditions showed a significant impact on the level of acoustic cavitation. This must be considered when the ultrasound technology is applied since the observed effects in food will depend on this.