4.3. RF heating experimental and computer simulation results
Measured temperature data in four different food components
in close proximity (Fig. 2a) within a tray during RF heating is
shown in Fig. 7. The greatest temperature difference among the
beef meatballs, mozzarella cheese, noodles, and sauce within
2 cm of each other was not more than 2 C over 30 min RF heating.
The anticipated thermal runway, namely, increasingly higher heating
rate caused by higher loss factor at elevated temperatures, did
not occur in sauce. Computer simulation results for the same heating
conditions as used in the experiment are shown in Fig. 8 with a
4 C difference between sauce/cheese and the meatball at the end
of the 30 min RF heating. Both experimental and simulation results
indicate that differential heating in food components with vastly
different loss factors, in particular at elevated temperatures, did
not occur when they were in close proximity.
The computer simulation model was used to provide an insight
into why there was no apparent overheating for the food components
with high loss factors in a heterogeneous food. The simulation
was checked at two planes. The results revealed that electric
field intensity was relatively low in the sauce (between two layers
of noodles) and high in the noodles (Fig. 9). Dielectrically, the only
main difference between the two components was the much higher
relative loss factor of sauce (Tables 4 and 5). Wang et al. (2008a)
also demonstrated experimentally and using computer simulation
that the electric field intensity in mashed potato with 1.3% salt is