## 3 Non-Thermal Technologies in Food Processing  
### Ultrasounds  
Ultrasound (US) waves used in food applications can be categorized into low-intensity and high-intensity class. The low-intensity or high-frequency ultrasound waves have a typical frequency greater than 100 kHz and intensities below 1 W/cm\({}^{2}\) and are defined as diagnostic waves due to their ability to evaluate the structure and physicochemical properties of the food product both during processing and storage [51]. The high-intensity and low-frequency ultrasound waves have frequency ranges from 20 to 100 kHz, and intensities are in the range of 10 to 1000 W/cm\({}^{2}\). Differently from low-intensity US, this type of US is considered disruptive, since it produces significant modifications on the physical, biochemical, and mechanical properties of food products [52]. US produces bubbles that undergo collisions. Consequently, these generate cavitation phenomena, resulting in high temperature and pressure up to 5000 K and 50 MPa, respectively [53]. Hence, changes in the pH, stress, temperature, and pressure are caused by these strong explosions and high temperatures. In addition, these changes in an enzyme environment can imply the inactivation of enzymes due to the modifications in the enzyme structure caused by destruction of van der Waals binding and hydrogen bonding, which result in loss of enzyme activity [54; 55]. Commonly used devices that produce US are the US probe and US bath, as represented in Figure 3.  
Considering all the non-thermal processes, US can be regarded as very versatile. In fact, used alone or in combination with other methods, this technology can ensure high process yields and positive results on the quality of foods. US can significantly assist several industrial processes such as filtration, freezing, separation, drying, emulsion, thawing, brining, oxidation, homogenization, meat tenderization, sterilization, and extraction thanks to their capability of improving energy and mass transfer, mixing, and retention of food characteristics as well as reducing thermal and concentration gradients [56; 57; 58; 59; 60; 61]. Additionally, if ultrasounds are applied previous to drying, an enhancement in drying kinetics is always observed, implying a positive effect on the drying process and a reduction in total energy consumption [4, 5]. Furthermore, if the product it is not soaked in a liquid medium, the loss of hydrophilic nutrients and compounds is reduced [62]. In the freezing-related process, high-intensity US helps to control the size and the size distribution of the ice crystals as well as enhance the efficiency of the freezing and the quality of the frozen food, reducing at the same time the process time [59, 63]. This non-thermal technique has been also studied as a method to control the nucleation of a crystallization process, in particular for chocolate, honey, fats, and frozen foods [64]. Moreover, the antioxidant [65], antitumoral [66], anticoagulant [67], and antiinflammatory [68] properties of ultrasound-treated polysaccharides from vegetables, plants, and fungi have been analyzed, as well as nanoparticles production from food polysaccharides [69, 70]. In addition to all the good aspects of this emerging food treatment, there are some conditions that cause negative impacts on foods, for example color [71], antioxidants [72], and polysaccharides modifications [73] as well as degradation of fats, radicals formation, and oxidation [74] in high content lipid foods, in particular during emulsification, homogenization, cutting, and extraction steps [75]. From here on, we will present the method of operation and the manifold studies that investigate and utilize US. The tool most used in the generation of ultrasound is a transducer that transforms electrical signals into acoustic energy of the desired intensity. Magnetostrictive and piezoelectric are the two type of transducers largely used for the production of ultrasound waves. Magnetostrictive transducers behave as electroacoustic transducers to create the ultrasonic waves.