Microwave‐Assisted Drying of Foods – Equipment, Process and Product Quality

Abstract

Dehydration is one of the main methods used to preserve foods, keeping it in a stable and safe condition as dehydration reduces water activity and extends the shelf life of fresh fruits, vegetables and aquatic products by preventing microbial activity (Wang et al., 2011b;Mujumdar and Law, 2010;Zhang et al., 2006). Furthermore, there are some other objectives of dehydration, for example, quality enhancement, improving ease of handling, further processing, sanitation, and the development of new products (Duan et al., 2010a).Drying is the most common, but also the most energy-consuming, food preservation process (Mujumdar, 2006;Ratti, 2001). Many conventional thermal methods, such as hot-air drying, vacuum-drying and freeze-drying result in low drying rates in the falling rate period of drying and often also in the surface drying region, due to the heat sensitivity of most foodstuffs (Clary et al., 2005;Zhang et al., 2003;Zhang et al., 2005). Furthermore, extended drying times at relatively high temperatures during the falling rate period lead to the undesirable thermal degradation of the product (Mousa and Farid, 2002). In addition, convective drying seriously damages the sensory characteristics and nutritional properties of foods. Occasionally, severe shrinkage caused by convective drying can reduce the rehydration capacity of the dehydrated product.Given the large quantities of materials produced from agriculture, horticulture and other commodities that must be dried each year, and the magnitude of associated energy inputs, there is a continuing need to improve the thermal drying systems used. The main areas for improvement are in energy transfer, drying times to reduce equipment size, and attaining better uniformity of drying rates and product quality (Souraki et al., 2009).Microwave (MW) applications offer potential opportunities for enhancing the drying of food. Microwave heating/drying coupled with other drying techniques such as convective, vacuum-and freeze-drying provides various options for microwave-assisted drying techniques with their respective merits; for example, microwave vacuum-drying (MWVD), microwave freeze-drying (MWFD),

Microwave-assisted metallurgy

“…To effectively extract gold from these materials, microwave pretreatment was proposed for enhancing ore micro-cracks and oxidising sulphides/carbonaceous matters, enabling liberation of gold. 171,172…”

Optimization of Osmotic Dehydration Parameters of Banana Under Pulsed Microwave Conditions by Response Surface Methodology

“…Microwave assisted dehydration involves the transformation of electromagnetic energy into heat which is generated due to molecular excitation into the food product. Furthermore, this leads to a positive outflow of water resulting faster drying process and reduction in drying time up to 25-90% (Orsat et al, 2006;Wray and Ramaswamy, 2013;Wang et al, 2014;Abano, 2016). However, nonuniform heating of foods during microwave heating is the major drawback for its application in the food industry.…”

Design and Simulation of a Multi-Channel Biomass Hot Air Furnace with an Intelligent Temperature Control System

“…In the context of "carbon peaking and carbon neutrality", biomass pellet fuel as a drying heat source holds great potential for development [1][2][3]. Drying agricultural products is a crucial step in agricultural production and an important component of the entire mechanization process of grain production [4]. Conventional hot air drying uses coal as the heat source, but biomass fuel, as an important sustainable energy source [5], offers a viable alternative.…”