*Acoustic and Thermal Analysis of Food DOI: http://dx.doi.org/10.5772/intechopen.108007*



#### **Table 1.**

*Advantages and disadvantages of conventional and conventional ultrasound-assisted dehydration systems.*

Regarding the applicability status of dehydration technology, we must say that ultrasound-assisted dehydration is mainly done at the laboratory level, which is used to study the dehydration kinetics and physicochemical, microbiological, structural, and rehydration characteristics of some foods [20]. Ultrasound-assisted dehydration systems are based on conventional dehydration techniques that are assisted by ultrasound waves resulting in different methods, such as ultrasoundassisted convective dehydration [21], ultrasound-assisted osmotic dehydration [22], ultrasound-assisted vacuum dehydration [23], and ultrasound-assisted freeze dehydration [24]. In ultrasound-assisted dehydration systems, ultrasound waves are used to increase the dehydration rates or decrease the dehydration temperature, since these waves strongly accelerate mass transfer maintaining food quality.

On the other hand, with respect to commercial alternatives, it can be stated that some ultrasound-assisted systems are beginning to emerge, such as the one used for dehydration of heat-sensitive biological materials and food processing. Some examples of these commercial systems include the following:


4.Ultrasound applied to food processing as yogurt fermentation, extraction of flavors and bioactive compounds, milk homogenization, sugar crystallization for confectionery, edible oils hydrogenation, honey liquefaction, juices stabilization, wine and liquor aging, accelerated ice cream freezing, batter aeration, chocolate crystallization and conching, and meat tenderization [28, 29].

Therefore, in this work, we focus on sound–assisted convection dehydration systems, which could reduce dehydration time and cost by at least 30% compared to conventional methods [30] for food dehydration. Furthermore, it should be noted that these dehydration systems are not harmful to humans as microwave, gamma radiation, or electromagnetic field pulses systems; therefore, they can be applied in the food industry for safety reasons [31, 32]. Thereby, it is important to study, analyze, and understand the food acoustic-thermal behavior when dehydrated by using an ultrasound-assisted convection dehydration system. In this regard, we presented a guide to determine and apply the most influential spectral components of ultrasound waves on food under dehydration in an ultrasound-assisted dehydration system for increasing the temperature of food under dehydration. For this purpose, we have defined two case studies; in the first one, we study and analyze the thermo-acoustic behavior of apple samples, and in the second study case, we consider tomato samples. In both case studies, food samples are immersed in ultrasound waves and they are radiated using one and three transducers. With these case studies, after identifying the intensity and frequency of the ultrasound waves that have the greatest influence on the dehydration process of each food, we intended to observe the temperature changes experienced by food samples while they are being dehydrated. In this way, this work allows us to find the best conditions for food acoustic radiation avoiding structural and nutritional damage to the food. Also, in this guide, we show how to apply the finite element method to simulate and analyze the thermal and acoustic behavior of foods under dehydration inside the dehydration chamber of an ultrasound-assisted system.

The rest of the chapter is organized as follows. Section 2 describes some scientific works related to the analysis of ultrasound-assisted food dehydration systems. Section 3 describes the two case studies for which the thermo-acoustic analysis was performed, the used configurations for the dehydration chamber, the food composition and properties, a brief overview of transducers and acoustic waves, and the selected simulation environment. Section 4 provides the acoustic and thermal mathematical model used for the thermo-acoustic analysis by the finite element method, the spatial behavior of the ultrasound waves inside the dehydration chamber, and the temporal behavior of the temperature change in the food samples. Section 5 shows the opportunities for future work when ultrasound–assisted convection systems are used in food dehydration. Finally, Section 6 is devoted to conclusions and work perspectives.
