An Overview of Recent Developments and Some R&D Challenges Related to Drying of Foods

Thermal dehydration is the most common and cost-effective technique for preservation of foods and for the production of traditional as well as innovative processed products such as snacks with desired functionalities. The basic intent of this article is to provide a global overview of emerging and innovative thermal drying technologies that are already commercialized or show potential of industrial exploitation upon successful R&D to sort out some limitations. New drying technologies are needed to enhance quality, reduce energy consumption, improve safety, and reduce environmental impact. Mathematical modeling can be used for cost-effective development of untested novel designs to reduce the cost and time required for innovation. As examples of emerging drying technologies we consider selected dehydration techniques with imminent commercialization potential. These include heat pump-assisted drying, microwave-assisted drying, low-pressure superheated steam drying, pulse combustion spray drying, pulsed and ultrasound-assisted osmotic dehydration, as well as novel gas-particle contactors such as impinging streams and pulsed fluidized beds. Multistage drying, intermittent drying, and the use of hybrid drying technologies-which combine advantages of different dryers without some of their limitations-will be outlined. This article also discusses various methods of energy minimization, and the potential for use of renewable energy will also be discussed briefly. Although this overview emphasizes food dehydration, the themes covered are applicable to other materials as well.