Ultrasound assisted extraction (USAE) is an interesting process to obtain high valuable compounds and could contribute to the increase the value of some food by-products when used as sources of natural compounds. The main benefits will be a more effective extraction, thus saving energy, and also to the use of moderate temperatures, which is beneficial for heat sensitive compounds. For a successful application of the USAE, it is necessary to consider the influence of several process variables, the main ones being the applied ultrasonic power, the frequency, the extraction temperature, the reactor characteristics and the solvent-sample interaction. The highest extraction rate is usually achieved in the first few minutes, which is the most profitable period. To optimize the process, rate equations and unambiguous process characterization are needed, aspects that have often been lacking.
The use of new or non-conventional technologies widens the food processing innovation possibilities. Among technologies with a potential application, high intensity ultrasonics has emerged. Ultrasound is a mechanical wave that can affect transport phenomena. Accordingly, the effect associated to ultrasonic application will be dependent on the medium where ultrasound is travelling and on the material to be affected. In this work, ultrasonic applications in different media, such as liquid, gas and supercritical fluid, are addressed as innovative alternatives to enhance transport phenomena and highlight the main factors affecting the process.
15Food processing is in constant evolution in response to different challenges. The changes in 16 consumer tastes and the need to produce safe and high quality foods are responsible for the 17 evolution of the established food processes or the development of the new ones. In this sense,
18the introduction of new technologies could lead to a reduction of the processing time or an 19 improvement in operating conditions. These aspects are closely linked to the search for high 20 quality products that preserve the natural characteristics of foods. Another important aspect that 21 must be taken into account is the reduction of the energy needs of the processes, thereby 22 decreasing both environmental and financial costs. Ultrasound is an example of new technology 23 and its application in food processing could lead to both these areas undergoing an 24 improvement. On the one hand, ultrasound could be applied as a diagnosis technique to control 25 aspects, food product or processes. On the other hand, ultrasound could be used to improve 26 food processes by affecting the kinetics, the yield or the product quality. This work will focus on 27 the latter.
28Acoustic waves are mechanical waves that need a material medium to propagate. Usually, they
33variations is used in diagnosis applications to characterize the medium. In these applications,
34the frequency of the waves is in the range of MHz and the power applied is not higher than 1
35W/cm 2 (Patist and Bates, 2008). When the applied power of ultrasound is higher, the acoustic 36 waves could affect the medium generating interesting effects for industrial applications. This use
37of ultrasonic technology is known as "power ultrasound" or "high intensity ultrasound" and the 38 2 main objective is to induce changes in products or processes. In this case, the frequency is in 39 the range of 20-100 kHz (Mason and Lorimer, 2002).
41The aim of this work was to address different power ultrasound applications in order to highlight factors affecting some innovative approaches to food processing. 42
Effects of ultrasound
43The effects produced by high power ultrasound when travelling across a medium are diverse
44and their relative importance depends on the characteristics of the medium. In general,
45ultrasound produces alternating compression and decompression of the media. In liquids, when 46 ultrasonic power attains a th...
ElsevierOzuna López, C.; Puig Gómez, CA.; García Pérez, JV.; Mulet Pons, A.; Carcel Carrión, JA. (2013). Influence of high intensity ultrasound application on mass transport, microstructure and textural properties of pork meat (Longissimus dorsi) brined at different NaCl concentrations. Journal of Food Engineering. 119 (1) The aim of this work was to evaluate the effect of high intensity ultrasound and NaCl 28 concentration on the brining kinetics (5±1 ºC) of pork loin as well as its influence on the 29 textural and microstructural changes. In order to identify the effect of both factors on NaCl
30and moisture transport, kinetics were analyzed by taking the diffusion theory into account.
31The textural and microstructural analysis of raw and brined meat both with and without
The application of power ultrasound sped up the drying kinetics at every temperature tested, achieving drying time reductions of up to 77%, which was linked to the improvement in diffusion and convective mass transport. In overall terms, ultrasound application involved a greater degradation of polyphenol and flavonoid contents and a reduction of the antioxidant capacity, which was related to the cell disruption caused by the mechanical stress of acoustic waves.
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