Ultrasonic pre-treatment for drying of vegetables

 

 

Fabiano AN Fernandes,^1* Francisca IP Oliveira¹ and Sueli Rodrigues²

¹Universidade Federal do Ceara, Departamento de Engenharia Química, Campus do Pici, Fortaleza – CE, Brazil

²Universidade Federal do Ceara, Departamento de Tecnologia dos Alimentos, Campus do Pici, Fortaleza – CE, Brazil

 

 

 

Abstract

Purpose of review: Dried vegetables can be used as part of foodstuffs such as soup powders, seasonings, dried foods and many others. Air-drying is energy and cost intensive and pre-treatments like ultrasonic treatment, microwave treatment and osmotic dehydration are used prior to air-drying to reduce the processing cost.

Findings: Ultrasonic pre-treatment is a useful technique that may be used prior to air-drying. The application of ultrasound induces changes to the vegetable tissue structure, creating microscopic channels that increase the effective diffusivity of water during the air-drying process. Ultrasound application may reduce the overall drying time representing an economy of energy because air-drying is energy cost intensive.

Limitations: The drawback of the process is the increase in salt uptake caused by the use of ultrasound, which may enhance the mass transfer of salt to the vegetable. Depending on the tissue structure of the vegetable and the changes produced in the tissue by the ultrasonic treatment, the ultrasonic treatment may not affect the effective diffusivity of water in the vegetable, thus not reducing the air-drying time.

Directions for future research: Further research on the use of ultrasound in the drying of vegetables should investigate the effects of ultrasound on the sensory characteristics of the dried vegetable and also focus on the improvement of shelf-life.

 

Keywords: vegetables; drying; ultrasound; optimisation

 

Stewart Postharvest Review 2008, 5:6

Published online 01 October 2008

doi: 10.2212/spr.2008.5.6