Ultrasound as a Pretreatment Method to Improve Drying Kinetics and Sensory Properties of Dried Apple

The effect of ultrasound pretreatment on drying kinetics and physical properties as color and rehydration rate of dried apple slices was investigated. Apple samples var. Idared were submitted to ultrasonic treatment using 21 and 35kHz for 30min in an ultrasound bath securing sound intensity of 3 and 4W/cm(2), respectively. After pretreatment, the material was dried in a convective oven at 70C and at an air velocity of 2m/s. The sonication reduced drying time by 13-17% in comparison with the untreated sample. Ultrasound treatment changed the color of apples tissue by decreasing the value of a* parameter and increasing the dried material lightness, chromaticity and the value of b* coefficient. Moreover, obtained results showed that there was a significant effect of pretreatment on rehydration properties as compared with untreated apple tissue. Practical ApplicationsThe most energy-consuming processes existing in the food technologies are the processes based on heat and/or mass transfer, for instance drying. Thus, a lot of attention is paid by researchers to conserve the energy and minimally change the physicochemical properties of food, which shape its quality. Additionally, increasing growth of consumers' expectations and their nutritional knowledge stimulate to seek some new solutions even more. Aforementioned is a reason why nonthermal technologies as ultrasound seem to be the one of the most interesting propositions.