Abstract:

In this study, fresh-cut slices of ‘Dangshan’ pear were pretreated by means of ultrasonic-assisted osmotic
dehydration before hot-air drying for the purpose of obtaining enhanced dehydration rate. The influences of operational
parameters including ultrasonic power and osmosis concentration on weight reduction ratio, drying time and effective
moisture diffusivity were examined. The results showed that increasing the ultrasonic power and sugar concentration in the
osmotic solution significantly improved weight reduction ratio. Compared with direct hot air drying, the total dehydration
time for pear slices pretreated by osmotic dehydration without ultrasonic treatment was prolonged by 30?60 min, but
shortened by 40?120 min for those pretreated by ultrasonic-assisted osmotic dehydration, simultaneously with an increase
in effective moisture diffusivity coefficient of 11%?56%. Therefore, it is concluded that the use of ultrasonic-assisted
osmotic dehydration as a pretreatment procedure before hot air drying can significantly shorten the total process time and
subsequently improve the drying efficiency.

Key words: ultrasonic, osmotic dehydration, hot-air drying, pear