# Current Applications of Ultrasound in Fruit and Vegetables Osmotic Dehydration Processes
## 4 Ultrasound-Assisted Osmotic Dehydration
### Synergic Effect of US and Other Innovative Technics/Treatments in Osmotic Dehydration  
Recently, the synergic effect of the combination of US with other technics/treatments (innovative osmotic solutions, blanching, PEF, reduced pressure and edible coatings) has gained a particular attention in the food research. Taking into consideration that high sugar products are not desirable in the human diet [3; 16; 102], there is a necessity to develop a method to improve the taste of products and make them acceptable for consumers, without affecting too much their final sugarcontent. In fact, different combinations of UOD with solutions containing sweeteners or sweetness enhancer have been proposed as an alternative to the use of sucrose. The most popular substances from these groups are xylitol, erythritol, maltitol and dihydroxyacetone (DHA) [40], steviol glycoside [3; 16; 29] and trehalose [39] applied in order to reduce sugar content in the product, and therefore decrease the calories. [PERSON] et al. [40] observed that the application of erythroid, xylitol and DHA solutions in OD process showed a similar efficiency to sucrose and good water removal properties, however the application of US during OD did not promote any advantages on mass transfer in apple tissue if compared to just OD treatment. The application of sonication by the continuous method rather than those with 30-min intervals allowed for a significant reduction in water activity in apple tissue in all four tested solutions. [PERSON] et al. [39] studied the influence of UOD treatment with sucrose (SA) (61.5%), 30% sucrose + 0.1% of steviol glycoside (SA + STV) and 40% trehalose (T) on the mass transfer parameters and on quality characteristics during storage of cranberries. They observed that the UOD significantly increased the weight loss and water loss in cranberry samples dehydrated in all tested solutions, showing the highest values for samples dehydrated in SA, followed by SA+STV, and finally for samples treated by T. Solid gain instead was influenced by the application of UOD when SA+STV was used as osmotic agent. During storage, US pretreatment led to a lower weight reduction and higher lightness in cranberry samples treated with any type of solution in comparison to those without US pretreatment. The influence of the replacement of sucrose with 0.1% STV during UOD treatment (21 kHz, 400 W) combined with blanching and PEF treatment on the quality of hot air-dried cranberries was also studied by [PERSON] et al. [16]. The samples treated with this innovative combination of the pretreatments were compared to blanched (BL) and control (cut) samples. Drying time of cranberries subjected to BL alone was reduced by 48-50% compared to the control samples, while the combined method (BL+PEF+UOD) reduced the drying time up to 55%. However, no significant differences were observed concerning the type of osmotic solution used. Both pretreatments also resulted in a higher amount of anthocyanins and flavonoids and less sucrose than in control (cut) samples. The authors suggested that, even if there was no improvement of the quality of dried fruits treated with the combined method compared to only blanched samples, the reduction of drying time could be of benefit for the incorporation of PEF and US techniques in the industries considering especially a low energy consumption of these processes. In addition, the researchers from the same working group [3] studied the influence of combined pretreatment methods (blanching, US and vacuum) on the kinetics of OD and selected quality properties of cranberries. It was observed that the application of US in combined pretreatments lowered the water loss and solid gain if compared to the cranberry samples pretreated with BL and triplicate lowering of the pressure, independently of the solution (SA or SA+STV) used for OD. Contrarily, [PERSON] et al.