Microwave convective drying

Garcia H. and Bneno J.L., Improving energy efficiency in combined microwave-convective drying. Drying Technology, 1998, 76(1-2), 123-140. 

Sharma and Prasad (2006b) optimized the process parameters for the microwave-convective drying of garlic cloves using a constrained optimization technique (Tukey s multicomparison pair-wise test), in an effort to identify the best compromise between quality and drying time. The results revealed that a... 

P., 2007. Microwave convective drying of plant foods at constant and variable microwave power. Drying Technol. 25 1149-1153. 

Holtz, E., Ahrne, L Rittenauer, M., Rasmuson, A., 2010. Influence of dielectric and sorption properties on drying behaviour and energy efficiency during microwave convective drying of selected food and non-food inorganic materials. J. Food Eng. 97(2) 144-153. 

Soysal, Y, Ayhan, Z., Esturk, O., Arikan, M. F., 2009. Intermittent microwave-convective drying of red pepper Drying kinetics, physical (colour and texture) and sensory quality. Biosystems Eng. 103 455 63. 

Uprit, S., Mishra, H. N., 2003. Microwave convective drying and storage of soy-fortified paneer. Food Bioprod. Process. 81(2) 89-96. 

Microwave-assisted (0.1 or 0.2 Wg-1) convection drying was also applied to osmotically dehydrated blueberries, leading to dried berries that were comparable to freeze-dried ones in much shorter time (Venkatachalapathy and Raghavan, 1998). Frozen blueberries were also dried in a microwave and spouted bed combined dryer (MWSB) after a pretreatment using ethyl oleate and a NaOH dipping solution followed by sucrose osmotic treatment (Feng et al., 1999). Osmotic dehydration prevented the blueberries from... 

Figures 2 show a comparison of convective drying with or without microwaves [23], Whilst for convective drying there are definite eonstant rate and falling rate periods, when microwaves are added the form of the eurves ehanges [24-25],...

Sunjka, P. S., T. J. Rennie, C. Beandry, and G. S. V. Raghavan. 2004. Microwave-convective and microwave-vacnnm drying of cranberries A comparative stndy. Drying Technology 22 1217-1231. 

Kowalski, S.J. and K. Rajewska, 2009. Convective drying enhanced with microwave and infrared radiation. Drying Technology, 27(7), 878-887. 

Estiirka, O. and Y. Soysal (2010). Drying properties and quahty parameters of dill dried with intermittent and continuous microwave-convective air treatments. Arim Bilimleri Dergisi Journal of Agricultural Sciences 16 26-36. 

Osmotic pretreatment before microwave-assisted air drying increase the final overall quality of the product [187]. Fruits and vegetables treated by osmosis can be further dehydrated in a convection dryer to lower the water activity to the level of 0.65-0.90. At those water activities, water content in the material is still high and the product presents such organoleptic attributes as chewiness, softness, elasticity, and plasticity [76,188-190], The product has a natural color, well-preserved flavor, and high retention of vitamins [132], Its shrinkage is much smaller when compared with that observed in convection-dried products at the same water activity. 

At normal atmospheric pressure, the boiling point of water equals 100°C. Consequently, in order to obtain an internal overpressure, the temperature of the porous medium must be above that level during at least one part of the process. This is the aim of convective drying at high temperature (moist air or superheated steam) and a possible aim of contact drying or drying with an electromagnetic field (microwave or radio frequency). 

FIGURE 62.7 Drying curves by convective drying of kaolin clay samples enhanced with different microwave powers. 

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