Table of Contents
International Journal of Microwave Science and Technology
Volume 2011, Article ID 687548, 12 pages
Research Article

Optimization of Microwave-Osmotic Pretreatment of Apples with Subsequent Air-Drying for Preparing High-Quality Dried Product

Department of Food Science and Agricultural Chemistry, McGill University, Macdonald Campus, 21,111 Lakeshore Road, Sainte-Anne-de-Bellevue, QC, Canada H9X 3V9

Received 24 March 2011; Accepted 28 March 2011

Academic Editor: M. C. E. Yagoub

Copyright © 2011 Elham Azarpazhooh and Hosahalli S. Ramaswamy. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Prepared apple (Red Gala) cylinders were subjected to microwave-osmotic dehydration treatment under continuous flow medium spray (MWODS) conditions and then air-dried to a final 20% moisture content. The dried samples were evaluated for color and textural properties, and rehydration capacity. The MWODS pretreatments were based on a central composite rotatable design and a response surface methodology using five levels of sucrose concentration, temperature, and contact time at a constant flow rate of 2800 mL/min. The air-drying was carried out at 60°C, % relative humidity, and  m/s air velocity. The results were compared to untreated air-dried (AD) (worst-case scenario) and freeze-dried (FD) (best-case scenario) apples without the MWODS treatment. Color properties were affected regardless of the type of treatment. Conventional AD apples were darker in color, whereas MWODS-treated samples were lighter with higher and values, higher Hue and Chroma values but lower value and . Further the color parameters of MWODS-treated samples were closer or equal to the FD apples. The texture properties were also affected by the osmotic variables with MWODS treatment resulting in softer and chewier products. The AD samples were hard, and FD apples were brittle.