Foods microwave-assisted drying

Chapter 9 Microwave-assisted drying of foods - Equipment, process and product... 

Orsat, V., Yang, W., Changme, V., Raghavan, G. S. V., 2007. Microwave-assisted drying of biomaterials. Food Bioprod. Process. 85(C3) 255-263. 

Microwave-Assisted Drying of Foods - Equipment, Process and Product Quality... 

Figure 9.14 presents typical temperature curves of microwave-assisted drying for food. Here, the shape of the temperature curve of microwave-assisted freeze-drying can be seen to differ from that of the three other types of microwave-assisted drying, due to different drying mechanisms. Temperature changes are heavily dependent on the microwave power, microwave emission mode, type of dryer used, and the presence or absence of a temperature control unit. 

Fig. 9.14 Typical temperature curves of microwave-assisted drying for food, where 1 and 2 indicate the temperature changes in...

Table 9.2 presents the SEC and drying efficiency values for different microwave-assisted drying processes of food materials, as determined by various research groups. The minimal theoretical value of SEC for a dryer is 2.3 MJ per kg of evaporated water, based on the maximal theoretical specific moisture extraction ratio (SMER) of 1.55 kg per kWh and the latent heat of water evaporation at 100 °C (Holtz et cd., 2009). These results are expected to depend heavily on the scale and design of dryers, as well as on the method used to measure energy consumption (Durance and Wang, 2002). 

Quality Changes in Food during Microwave-Assisted Drying... 

Several groups have correlated the volume or size changes of food materials during microwave-assisted drying with the moisture content (Tab. 9.3). 

In order to accelerate sample preparation, new extraction methodologies such as accelerated solvent extraction (ASE) and MAE, based on the use of elevated temperature and pressure to heat the mixture sample-solvent, have been recently developed and applied for PAH extraction from meat [695] and vegetables [696-698]. Garda Falcon et al. [699] used microwave treatment with hexane to accelerate PAH extraction from freeze-dried foods. The fat extracted in this way underwent microwave assisted saponification with ethanolic KOH. Hernandez-Borges et al. [700] combined microwave-assisted hydrolysis and extraction to isolate organic pollutants from mussels, while... 

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