## 3 Non-Thermal Technologies in Food Processing
### Ultrasounds
#### 3.1.1 Application in Fruits and Vegetables  
Generally for fresh and slightly processed fruits and vegetables, juices, and purees, changes in color, a drop of microbial load, enzyme inactivation, and enhancements in drying characteristics have been noticed [76, 77, 78]. US can be used as pre-treatment prior  
Figure 3: US bath (**a**) and US probe (**b**). Adapted from [56]. to fruits and vegetables drying, since it increases the drying kinetics, in particular if an osmotic solution is employed during the process [4]. This appears with strawberry, papaya, pineapple, pomegranate, guava, and melon. In distilled water, a water loss can occur with apple or papaya. On the other side, banana, mushrooms, strawberry, and melon gain water during US treatment [4]. It has been demonstrated that for strawberries, a 5 min cleaning step with US can efficiently reduce 16 pesticide residues by 91.2% [6]. Similarly, for lettuce surfaces, US with frequencies of 20, 40, and 60 kHz can be used to remove 92.31% of abamectin b1 (AB), 89.36% of alphamethrin (AL), and 95.25% of emametcin benzoate (EB) after 8 min of ultrasonic cleaning without showing any changes in nutritional properties [76]. The ultrasound technology has gained much attention due to its inhibitory effect on browning enzymes thanks to the capability of breaking the cell membranes [5]. In particular, it has been discovered that ultrasound in combination with temperature and high pressure is more effective against polyphenol oxidase (PPO) [53]. In Oriental sweet melon, for 5 mL of juice, [PERSON] et al. [79] estimated 65% of inactivation of polyphenol oxidase. As well as with 10 mL extract of Satsuma mandarin, 63.7% of PPO was deactivated [80]. Still talking about enzyme inactivation, [PERSON] et al. demonstrated that in fresh pineapple, the activity of phenylalanine ammonia lyase increases substantially, whereas the polyphenol oxidase and polyphenol peroxidase (POD) have a drop in relation to the control group [81]. Similarly, pineapple juice had its content of PPO reduced after 10 min of US treatment as well as a viscosity decline of 75% [82]. PPO decreased also on fresh cut potatoes after a treatment of 5 min with US. The degree to which pH is affected reduced with longer treatments, but no change in color was noticed; a 10 min treatment has been revealed to damage the potatoes' cell [83]. US has been shown also to assist other techniques, for example extraction. Antioxidant, carotenoids, phenols, anthocyanins, aromas, and natural dyes can be extracted easier from pomeranate, tomatoes, garlic, and grape seeds in combination with US. This happens also with herb and spices and oleaginous seeds from which oil extraction is faster [84]. The sonication of fruit juices involves an enhancement of their quality as well as an increase of shelf life due to a reduction in spoilage microorganisms. In particular, an exposition to US produces in grapreruit juices an enhancement of total antioxidant capacity, ascorbic acid, flavonoids and flavonoids, and total phenolics. Furthermore, also apple juice has been studied under US influence, which cause a rise in total carotenoids, viscosity, minerals such as Na, K, and Ca, and of the concentration of sugar and polyphenolic compounds after a treatment of 60 min at 20 \({}^{\circ}\)C [85]. Similarly for orange, sweet lime, carrot, and spinach juices, a US sterilization treatment retains most of the nutrients compared to the classic thermal pasteurization [86]. In addition, for Cape gooseberry juice, color values, total phenols, ascorbic acid, carotenoids, and retinol activity equivalent (RAE) have been evaluated after US treatment. Researchers showed a significant decreases in the chromaticity as well as a yellowing in all the juice samples sonicated. Likewise, the other studies registered important increases in total phenols, RAE value, and carotenoids and their availability [87]. US has found application as a pre-treatment for sweet potatoes prior to frying.