Comparison of ultrasound- and microwave-assisted drying of agricultural products – a review

 

 

 

R Vadivambal¹ and DS Jayas^2*

¹Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada

²Administration Building, University of Manitoba, Winnipeg, MB, Canada

 

 

 

Abstract

Purpose of review: The objective of this paper is to compare ultrasound- and microwave-assisted drying of agricultural products and to present the pros and cons of both methods. The paper also discusses the most recent research and development in ultrasound- and microwave-assisted drying of fruits, vegetables and other agricultural products.

Findings: Microwave drying and ultrasonic drying are aimed at reducing the drying time while protecting product quality. Ultrasonic drying seems to be better for heat-sensitive materials because there is no significant temperature rise in the product compared with microwave drying. In microwave drying, intermittent or variable microwave power is suggested to maintain product quality, otherwise, the product may be overheated due to higher temperatures attained. Compared with conventional air drying, both drying methods are energy efficient and reduce drying time while maintaining product quality in most of cases.

Directions for future research: A comparison of the research on ultrasound- and microwave-assisted drying with that on conventional hot air drying shows that ultrasound- and microwave-assisted drying are better than conventional drying in terms of drying time and product quality. Since both methods have now been shown to be commercially viable, more experimental studies should be conducted to compare microwave and ultrasound drying using similar samples, and the energy efficiency, product quality and cost should be evaluated. The effect of ultrasonic dehydration on tissue structure, and sensory characteristics such as texture and adhesiveness of fruits and vegetables need to be studied extensively.

 

Keywords: drying; microwave; ultrasound; agricultural products; quality

 

Stewart Postharvest Review 2009, 5:2

Published online 01 October 2009

doi: 10.2212/spr.2009.5.2