Abstract:

In this work, we examined the enhancing effect of air-borne ultrasound treatment on conventional hot air drying
of pear slices. The results showed that ultrasonic energy attenuated significantly with an increase in ultrasonic radiation
distance, and a reduction in ultrasonic radiation distance was beneficial to improve both ultrasonic energy efficiency and
drying rate. The drying rate was increased and the drying time was shortened by increasing the drying temperature and
ultrasonic power. The enhancing effect of ultrasound on drying rate was obvious in the initial drying period, but declined
with decreasing moisture content in samples. The values of effective moisture diffusivity ranged from 3.21 × 10-10 to
7.43 × 10-10 m2/s, which were increased significantly by increasing either drying temperature or ultrasonic power. Therefore,
air-borne ultrasound could notably reinforce traditional hot air drying of pear slices and increase the drying rate.

Key words: ultrasound, hot-air drying, pear, drying characteristics