Besides conventional thawing systems, electromagnetic applications (MW and RF) appear to have the potential for industrial
use to keep thawing time to a minimum with least damage to
the quality. MWs, with their limited penetration depth compared
to RF, are less satisfactory for thawing of especially the larger sized
R. Uyar et al. / Journal of Food Engineering 146 (2015) 163–171
products due to runaway heating and non-uniform temperature
distribution. RF systems might offer better process control for
these disadvantages if an optimized process might be developed.
The first condition to design and optimize an RF thawing system
is the availability of a mathematical model.
In this study, a computational model was developed to determine the electrical field distribution in a 50 X and a free running
oscillator RF system. Temperature and distribution in the frozen
lean beef and electric potential distribution inside the system were
determined, and the models were validated with experimental
data for various sized samples. Effect of sample size and power
absorption of samples on thawing time were demonstrated while
RF thawing was also compared with a conventional way of thawing
under still air. Non-uniform temperature distribution during thawing, especially high temperatures encountered along the surface
and corners of the product, is a major disadvantage of a RF thawing
system. Applications of this validated model include, but are not
limited to:
– prediction of temperature distribution in sample processes in
the analyzed RF systems, especially for thawing cases, is very
important to prevent the local heating in the product;
– design of sample’s shape and optimization of its position in the
cavity, with respect to gap between electrodes and among electrodes and sample;
– determine, in a trustable way, the distribution of the electromagnetic field in the RF cavity and in the sample itself.