# Pasteurization of Foods with Ultrasound: The Present and the Future
## 5 Bioactive Compounds  
One of the latest and growing trends in the food industry is processing plant-based foods. These are alternative foods to standard animal products (i.e., meat, chicken, eggs, dairy, fish, seafood) but processed only from vegetable sources. The plant-based foods market showed a 3-year growth of about 54%. The sales went from 4.8 billion dollars in 2018 to 7.4 billion in 2021. Plant-based milk has been one of the main areas with strong and constant growth because of the several health benefits and innovative products. Some plant-based milk sources are sesame seeds, oats, flax, hemp seeds, upcycled barley, pea protein, cassava root, potato starch, mushrooms, bananas, cashews, coconut, macadamia nuts, pili, pistachio, pecans, walnuts, and hazelnuts [86]. Plant-based foods are often considered over-processed because of the number of processing steps and list of several ingredients required to provide the product with similar characteristics in terms of flavor, color, and texture as the animal product. Ultrasound has also been tested on plant-based food products, not only for pasteurization purposes but also to study the effect of processing on the bioactive compounds and overall quality. Almond milk, currently one of the commercial plant-based options, was tested under sonication. A comprehensive study showed that ultrasound is an excellent technology for inactivating aerobic microorganisms, yeast, molds, and enzymes. Most of the quality parameters and bioactive compounds exhibited minor variations. The cloudiness in the sonicated almond milk was increased because of the breakdown of suspended particles during the cavitation. Some of these particles in almond milk are pectin, lipids, cellulose, proteins, and hemicellulose [49]. In another plant-based product, hazelnut milk increased the total phenolic content when processed at 62.37 W/cm\({}^{2}\), 75 \({}^{\circ}\)C for 15 min. However, the soluble protein decreased by about 1%, and there was also a slight decrease in the free radical scavenging activity [50]. Ultrasound promoted better stability in hazelnut milk, showing an improvement in the stability index because of cavitation's effect in reducing the components' particle size [87]. Additional plant-based milk studied under ultrasound is peanut, coconut, soy, rice, and oat milk. Besides successful microbial inactivation, these products showed stability after processing [88]. Table 3 contains a compilation of different products treated with ultrasound and the changes in bioactive compounds. It is evident in most of the examples that ultrasound influenced the concentration of some of these. First, the total phenolic content increased in most of the reported products. Products such as amora juice, blueberry juice, and spinach juice are among the ones with a significant increase in phenolic content (139%). [PERSON] et al. [89] reported an increase in the total phenols as the intensity of the sonication treatment was increased too. Authors mention the disruption of the vegetable tissue due to the cavitation and the formation of small cavities increasing the mass transfer as responsible for a higher concentration of phenols. Total flavonoid content was also increased in some of the products listed in Table 3. Again, amora juice and blueberry juice showed the highest concentration after sonication. [PERSON] et al. [21] mentioned the release of phenolic and flavonoids from pectin and cellulose components from the cell wall and the addition of hydroxyl molecules to the aromatic ring of these compounds as the cause of an increase in the quantification. The antioxidant activity of the sonicated products presented in Table 3 was increased almost for all the items listed. That fact can be attributed because the general increase of the phenolic content in the sonicated products attributed to the previously mentioned reasons.