Effect of ultrasound on drying rate of selected produce

By admin

Kantaş, Yeşim
Ph.D., Department of Food Engineering
Supervisor : Prof. Dr. Alev Bayındırlı
Co-Supervisor: Prof. Dr. Ali Esin

April 2007, 188 pages

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 30ºC, 40ºC and 50ºC 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 30ºC for celery
root, amplitude 100%, pulse mode 1.0 and 30ºC for apple, amplitude 70%, pulse
mode 1.0 and 50ºC for carrot and amplitude 70%, pulse mode 0.7 and 50ºC 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.