A systematic review on the recent advances of the energy efficiency improvements in non-conventional food drying technologies

Background: The conventional drying technologies presently used in the food industry are hot-air based systems that are normally considered as an energy intensive processes with higher green-house gas emissions accounting approximately 15% of the overall manufacturing expenses. The most common drying processes used for the preservation of the food materials are conventional thermal drying, which proved to be a high energy consuming process. With the world progressing towards the application of green technology and sustainable methods, the use of alternative energy efficient drying systems are of paramount importance. Scope and approach: This paper extensively reviewed the energy efficiency and techno-economic performances of a number of non-conventional drying technologies that are currently used in the food industry for drying of the food materials. The reviewed drying technologies include: hybrid systems, heat pumps, super - heated steam, vacuum, microwave, refractance window (R), electrotechnologies, ohmic, adsorption mediated and impingement. Key findings and conclusions: It was found that the hybrid drying systems with the solar drying input and refractance window (R) drying were among the most promising energy efficient drying methods that could be potentially used for drying of the food materials in industrial processes.