Ultrasound as pre-treatment for drying of fruits: Dehydration of banana

Dehydration of fruits is an alternative to reduce post-harvest loss of fruits and also a process to produce dried fruits, which can be directly consumed or become part of foodstuffs like cakes, pastries and many others. The effect of ultrasonic pre-treatment prior to air-drying on dehydration of bananas (Musa ssp.) was investigated. The study allowed estimating the water diffusivity in the air-drying process for bananas submitted to ultrasound. Results showed that the water diffusivity increases after application of ultrasound and that the overall drying time was reduced by 11%, which represents an economy of energy since air-drying is energy cost intensive. During the ultrasonic treatment the bananas lost sugar, so the ultrasonic pre-treatment can be an interesting process to produce dried fruits with low sugar content. The use of ultrasound as a pre-treatment prior to air-drying was compared to the use of osmotic dehydration as a pre-treatment prior to air-drying. Results showed that the use of ultrasonic pre-treatment is interesting when large amounts of water needs to be removed from the fruit, case in which the combined processing time (pre-treatment and air-drying) is shorter. (C) 2007 Elsevier Ltd. All rights reserved.