**1. Introduction**

Commercially available food must have an expiration date. After that date, we should consider that food has lost a significant nutrient content, or it has been degraded by contamination to detrimental levels to human health. Different methods have been developed for food preservation. For example, dehydration, refrigeration/ freezing, fermentation, canning, pasteurization, and incorporation of chemical additives. Food dehydration is a reliable method commonly used for food preservation, based on food moisture removal, it must be performed by using energy-, cost-, and time-efficient technologies, and it must use practical methods that do not interfere with time spent on personal and professional daily activities. In this sense, it should be considered that, according to Kumar *et al.* [1] and Merone *et al.* [2], food dehydration implies energy-intensive processes approximately using 25% of the total energy consumed by the food industry. In addition, food dehydration may be a practical process with hygiene and temperature conditions. Therefore, under the demands of today's life, food dehydration must be an automatically controlled process ensuring that the food structure, content, and quality are preserved on time. In general, food dehydration systems have low efficiency, and consequently, the development of efficient systems is a relevant scientific and technological challenge [3–5]. Hence, when developing or selecting a food dehydration system, its efficiency must be evaluated considering removed moisture content and the moisture removal rate. On the other hand, energy consumption and dehydrated food quality are two critical requirements for the design, implementation, or selection of a dehydration system [6]. In this sense, ultrasound-assisted dehydration systems can be a promising alternative [7], because they can help to reduce energy consumption [8–10]. However, we must keep in mind that the internal microstructure of food could change drastically when it is immersed in ultrasound waves, reducing its resistance to water diffusion, and increasing its temperature. But, an ultrasound-assisted dehydration system could have higher energy, cost, and time efficiency than simple convection dehydration systems [11–13]. Additionally, they have been demonstrated to be reproducible processes that avoid further wastewater treatment and additional energy use [14, 15].

An overview of ultrasound waves application in other technologies for food processing can be revised in the works published in 2021 by Singla and Sit [16] and Khadhraoui *et al.* [17]. In conventional dehydration technologies combined with ultrasound systems, it is worth noting that the ultrasound-assisted dehydration systems can increase the dehydration rates or decrease the dehydration temperature since the ultrasound waves strongly accelerate mass transfer maintaining food quality. For example, in 2017, Fei *et al.* showed that ultrasound osmotic dehydration produces samples with reduced sugar, ascorbic acid, and soluble protein content at significantly higher rates than osmotic dehydration, and the food samples showed a better texture and microstructure. The ultrasound osmotic dehydration process not only retained the nutrient composition and flavor material more effectively but also improved the texture and efficiency of osmosis-treated mushrooms [18]. Complementary to the application of ultrasound waves in food dehydration systems, we can mention that, in 2016, Başlar *et al.* [19] reviewed different ultrasound-assisted dehydration processes, including convective, osmotic, vacuum, and freeze dehydration applications, as well as the various types of ultrasonic equipment used. They summarized the mechanisms, applications, advantages, disadvantages, and recent investigations of ultrasoundassisted dehydration concluding that ultrasound treatments can potentially provide significant improvement in food dehydration, as the dehydration process simultaneously accelerates heat and mass transfers in the system. In general, they showed that the dehydration methods combined with ultrasound-assisted dehydration resulted in less dehydration temperature and duration. Finally, they suggested that these two advantages in ultrasound-assisted dehydration systems may avoid the reduction effect of food quality in comparison with other dehydration techniques.

Therefore, considering the work of Başlar *et al.* [19], we have compared different dehydration systems against ultrasound-assisted versions of the same systems. In **Table 1**, we have included convective, osmotic, vacuum, and freeze dehydration systems considering that the ultrasound-assisted dehydration systems offer higher dehydration rates or lower food dehydration temperatures than conventional systems.
