Mechanical Technologies: Ultrasound and Cavitation in Food Processing

Abrupt change in local pressure within a liquid medium is susceptible to break the liquid molecules cohesion, particularly when a gas is dissolved in the liquid. The created “cavity”, filled of gaseous/vaporous content is known as Cavitation. When the pressure perturbation is induced by an acoustic source, namely ultrasound, the phenomenon is then called Acoustic Cavitation. Although occurring at microscopic scale, the repletion of acoustic cavitation events presents a broad range of applications owing to the physical effects directly related to the oscillation of the bubbles, but also to their indirect chemical consequences. Nowadays, the acoustic cavitation is not only an attractive topic for fundamental research in physics and chemistry, but is recognized as a promising up-scalable solution in several fields, including agri-food. The present chapter sheds light on the applications of ultrasound and acoustic cavitation in the agri-food domain, by linking the fundamental aspects of this non-thermal process, ranging from physical to chemical effects, to the intended applications in terms of extraction, pasteurization, crystallization, synthesis and oxidation. The chapter discusses the mechanisms of action of ultrasound leading to the aforementioned applications, and emphasizes on the green and sustainable features characterizing their pathways. At the end of the present chapter, several case studies are reported from the literature in order to highlight the most promising agri-food applications harnessing the principle of acoustic cavitation, and exhibit their advantages relatively to conventional techniques, but also the challenges still facing their large-scale adoption, especially from a technological point of view.