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Effect of ultrasound on drying rate of selected produce

Kantaş, Yeşim
The objective of this study was to discover the effect of high power direct contact ultrasound on drying rates of apple, celery root, carrot and potato. For this purpose ultrasonic generator with 24 kHz frequency was used and amplitude and pulse mode values were chosen as 40%, 70%, 100%, and 0.4, 0.7, 1.0, respectively. The temperature of drying air was 30°C, 40°C and 50°C and the velocity was kept at 3.9 m/s. The samples used were 13.5 mm in diameter with 5.0 mm thickness. It is found that ultrasound assisted drying increased the drying rate for the selected produce at all the drying conditions used the degree of which depended on the structural properties of samples. Accordingly, the most suitable drying conditions were found to be amplitude 100%, pulse mode 1.0 and 30°C for celery root, amplitude 100%, pulse mode 1.0 and 30°C for apple, amplitude 70%, pulse mode 1.0 and 50°C for carrot and amplitude 70%, pulse mode 0.7 and 50°C for potato. Data obtained were treated with respect to some mathematical models that describe the drying kinetics of samples. In this respect, Page and Modified Page models were the best to represent the drying rates in all cases. Further, the results showed that the effect of ultrasound on drying rate increased in the order of apple>celery root>carrot>potato. That order can be attributed to the structure and composition where presence of air pockets has enhancing and sugar and starch have reducing effects.