Study of Microwave Drying of Vegetables by Numerical Modeling. Influence of Dielectric Properties and Operating Conditions

Abstract

In the present work mass and energy transfer during microwave dehydration of vegetables were studied. Microwaves interact with the polar molecules of food enabling its heating and dehydration. This interaction is affected by the change of food properties due to temperature increase and water content reduction. In certain products, the dependence of dielectric properties with temperature is affected by a change in the food structure as a consequence of the chemical change of certain components and of the water loss. Lambert's law, that considers an exponential decay of incident microwave power, was applied to model these interactions. Additionally, two consecutive stages must be considered: initial heating, followed by intensive evaporation at constant temperature. The model was successfully validated for data published in literature related to slabs of microwave dehydrated potatoes and carrots, considering different processing times, power densities, pressure and sample size.

Numerical simulation of continuous microwave drying of rice grains

“…As a consequence, the microwave energy absorption is lower in the late stage of microwave drying (Sungsoontorn et al, 2011), leading to the experimental values initially surpassing the simulated values but later falling below them after the seventh position. Simultaneously, these deviations could be attributed to the emergence of hot and cold spots (Arballo et al, 2018) in the rice grains.…”

Closed flow solar dehydration with the use of silver nanoparticles: Application for the production of Pouteria lucuma flour

“…At present there are various drying and dehydration systems using conventional energies [11][12][13][14][15] and unconventional, [16][17][18][19] in addition to processes based on ultrasound drying, natural convection, forced convection, vacuum and freezing (lyophilization). The processing phase is important, because it generates changes in the sensory and nutritional properties of the food; one of the commonly practiced methodologies is to leave the product exposed to the sun for several days for prolonged drying, however, high temperatures and direct exposure to the sun cause the product to shrink and alter its organoleptic properties.…”