Microwave-Convective and Microwave-Vacuum Drying of Cranberries: A Comparative Study

Abstract

Two drying methods of cranberries (microwave-vacuum and microwave-convective) are reviewed, and their advantages and disadvantages regarding the quality of dried product and the process performance are presented. Mechanically and osmotically pretreated berries were subjected to drying and quality evaluation. Quality parameters are color (in Hunter L*a*b* coordinates), textural characteristics (toughness and Young's modulus), and organoleptic properties (color, texture, taste, and overall appearance). Special emphasis was given to the energy performance of the process, monitoring of the real-time temperature profile, and the total microwave power-on time. Two microwave power densities are assessed, as well as different microwave power-on/power-off cycling periods. In almost all observed parameters, microwave-vacuum drying exhibited enhanced characteristics when compared to microwave-convective drying. Drying performance results (defined as mass of evaporated water per unit of supplied energy) showed that microwave-vacuum drying is more energy-efficient than microwave-convective. Tasting panel results exhibited slight preference in all parameters for microwave-convective dried samples.

Keywords:

• Energy efficiency
• Dehydration
• Fruit
• Hybrid drying
• Quality analysis

Acknowledgments

The authors of this research article would like to express their appreciation towards Natural Sciences and Engineering Research Council of Canada (NSERC) for their financial support and to Mr. Yvan Gariépy for his constructive recommendations during course of this work.