Ultrasound osmotic dehydration

FIG. 5 Effects of varying raw material treatments during osmotic dehydration on moisture (MC) and solid (SC) content expressed on initial dry matter (idm). Apple cubes, ultrasound (U) (Simal et al., 1998) apple slices, vacuum (V) (Salvatori et al., 1998b) and bell pepper disks, high temperature (Ade-Omowaye et al., 2002b). 

Another promising technique is ultrasound application during osmotic dehydration. Used on porous fruit such as apple cubes, it affects mass... 

Simal, S., Benedito, J., Sanchez, E.S., and Rossello, C. 1998. Use of ultrasound to increase mass transport rates during osmotic dehydration. J. Food Engineer. 36, 323-336. 

In this chapter, relevant background information will be provided regarding the principles of PEF and ultrasound technology, and its impact on biological tissues. The application of PEF as a pretreatment of raw materials prior to osmotic dehydration, air- and freeze-drying, with the resultant effects on drying characteristics and product quality, will be discussed. In the case of ultrasound, concepts for... 

Although the application of ultrasound in osmotic dehydration is, technically speaking, not a contact ultrasound application, its analysis provides an interesting insight into the principles of ultrasound-assisted drying and the different approaches to minimize mass transfer barriers applying PEF and ultrasound. It is therefore briefly discussed here. 

The fact that the mechanism of action of ultrasound in tissues seems to be primarily mechanical, and perhaps partly thermal at the tissue level (Schossler et ol., 2011 Schossler et id., 2012c), may explain this limited effect on product quality. Yet, as long as the harsh conditions of cavitation can be avoided the product quahty can be maintained when the parameters of the ultrasound treatment are well chosen. Nonetheless, detailed investigations of product quahty must accompany the optimization of process parameters, especially in the case of critical applications, such as ultrasound-assisted osmotic dehydration, or apphcations involving special conditions, such as vacuum freeze-drying. 

Parameter optimization in efficient processes is much more difficult when ultrasound is transmitted using liquids, as in the case of ultrasound-assisted osmotic dehydration. The strong physical and chemical effects of cavitation can easily cause cell disruption, with an associated loss of tissue firmness, leakage, and oxidation. 

Carcel, J. A., Golds, Y., Benedito, J., Mulet, A., 2002. Influence of power ultrasound in osmotic dehydration of apple slices. Proceedings of 13th International Drying Symposium (IDS 2002), Beijing, pp. 936-942. 

Stojanovic, J., Silva, J. L., 2007. Influence of osmotic concentration, continuous high frequency ultrasound and dehydration on antioxidants, colour and chemical properties of rabbiteye blueberries. Food Chem. 101 898-906. 

Probe systems have been used to study the influence of ultrasound application on osmotic dehydration, for example the treatment of apples in sugar solutions (Carcel... 

Baths have been used to apply ultrasound during the osmotic dehydration of apples in sugar solutions (Simal et al, 1998, 2006), cheese (Sanchez et al., 1999) or meat brining (Simal et al., 2006), and also to study its effects on mass transport kinetics. Ultrasound has also been applied in liquid-solid systems as a pretreatment prior to osmotic dehydration or hot-air drying of products such as banana (Fernandes and Rodrigues, 2007), pineapple (Fernandes et al., 2008) or malay apple (Oliveira et al., 2011). 

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