# Pasteurization of Foods with Ultrasound: The Present and the Future
## 5 Bioactive Compounds
The results for some of the products containing these pigments are presented in Table 3. In general terms, the anthocyanin content of the listed products was increased after the ultrasound treatment. Blueberry juice and spinach juice had a significant increase in anthocyanins. [PERSON] et al. [89] showed that as the ultrasound intensity gets stronger, the concentration of anthocyanins is higher. These authors mention the disruption of cell walls because of the cavitation releasing the anthocyanins into the medium. They compared this effect to using ultrasound to extract pigments with higher yields than conventional technologies. Besides, ultrasound positively affects the inactivation of peroxidase and polyphenol oxidase enzymes (as shown in Table 2). Both enzymes can naturally lead to the degradation of anthocyanins. In a Polish beverage (_Berberis amurensis_ juice), the main anthocyanin, peonidin-3-O-glucoside, showed an increase of 20% in the concentration after being processed with ultrasound (20 kHz, 140 W, 70% of amplitude, 10 min) boosting the antioxidant content of the product [94]. Carotenoids were also increased in goldenberry juice, cape gooseberry juice, mandarin juice, and spinach juice after sonication, as shown in Table 3. As part of the carotenoids, lycopene was also increased in the cape gooseberry juice. In a different study, \(\beta\)-carotene showed a significant increase in sweet potato juice after sonication. The concentration of this pigment went from 246.3 \(\mu\)g/g to 298.9 \(\mu\)g/g after 8 min of treatment (26 kHz, 0.66 W/cm\({}^{2}\)) and exhibited a high bioaccessibility (76.6%) compared to raw juice (10.3%) [95]. Like anthocyanins, carotenoids are extracted from the cell walls because of the effect of cavitation, but they are protected from enzymatic activity because of the enzyme inactivation by ultrasound. However, a threshold value of acoustic energy can damage these pigments [47,92]. Opposite to the previous bioactive compounds, the concentration of organic acids such as ascorbic acid (vitamin C) and citric acid was decreased in almost all the products presented in Table 3 after sonication. It is well known and documented the heat sensitivity of ascorbic acid [96,97], and this is one of the reasons for evaluating alternative technologies for pasteurization, mainly for citric juices, which have a high content of vitamin C. Ascorbic acid is a very unstable molecule and can be degraded because of the effect of pH, light, temperature, oxygen, and metallic catalysts [97]. During sonication, there is constant contact with oxygen, and temperature increases, mainly in the \"hot spots\" and the deposition of metallic particles from the sonotrodes. These factors can decrease ascorbic acid in the evaluated products after sonication. [PERSON] et al. [21] attributed the decrease of vitamin C in amora juice because of the oxidation process during sonication and the generation of free radicals interacting with the ascorbic acid. Similar findings were reported by [PERSON] et al. [92] during the sonication of cape gooseberry juice. If the processing is conducted under atmospheric conditions, oxygen will be part of the process leading to the oxidation and decrease of the ascorbic acid. In other products, ultrasound (42 kHz) was tested in a different type of honey and its bioactive compounds, such as total phenols, antioxidant capacity, and flavonoids, showed a significant increase after processing for a few minutes (5-15 min). Additional studies in sonicated honey exhibited increased antibacterial activity, mainly for _Salmonella typhimurium_[98]. Camel and bovine milk were successfully treated with ultrasound (20 kHz, 105-210 W, 5-10 min), reducing total plate count and Staphylococcus counts with no viable cells after the strongest treatments. The study also investigated the effect of sonication on the protein of both kinds of milk, showing no degradation in this macromolecule.