Analysis of RF heating of chicken meat

OLIVERA, DANIELA; GOÑI, SANDRO MAURICIO; SALVADORI, VIVIANA O.; DELLA VALLE, MARTA; MARRA, FRANCESCO

Faro

Congreso; XII CIBIA, Iberoamerican Congress of Food Engineering; 2019

Universidad do Algarve

Radiofrequency (RF) heating is a process gaining interest in the food industry thanks to its ability to achieve a more uniform heating in samples with respect to microwaves. The aim of this work was to evaluate the performances of a RF cavity (40.68 MHz, 50 Ohm, 10 cm electrodes gap, 300 W maximum power) using both experimental and virtual analysis. Minced breast chicken samples were held in 4x4x4 cm3 ABS containers and organized as different loads and configurations arranged (for instance, horizontal or vertical arrays of 2 or more bricks). Two different RF powers (225 and 300W) were tested. On each test the heating efficiency was determined by measuring the initial and final temperature on selected locations. A mathematical model of different sample configurations in the RF cavity was considered in a virtual model, implemented in COMSOL Multiphysics software. The Gauss law for electro-quasi-static conduction was solved for both the air in the cavity and the samples, while heat transfer was modeled only in food samples. For 16 bricks configuration, near 10000 finite elements were used, and simulation time was lower than 30 seconds. The model clearly showed how important was the orientation of the samples and their configurations in determination of the process efficiency. The experimental results showed that at 225W, for 2 bricks configuration, vertical array was more efficient than the horizontal one (29.6% vs. 9.6%). For 4 bricks, there are 3 configurations: 4 bricks linearly aligned in the floor, 2x2 bricks in the floor, or 2 bricks in the floor and 2 bricks above them; the last configuration was near twice efficient that the others (40.5% vs. 21.5% and 20.7%). For 8 bricks, 3 configurations were tested: 4x2 bricks in the floor, 2x2 bricks in the floor and 2x2 above them, or 4x1 bricks in the floor and 4x1 above them; the last two were more efficient, (46.5% and 43% vs. 18.4%). For 12 bricks, a single array of 3x2 bricks in the floor and 3x2 above them was used, with an efficiency of 44%. Similar trends were obtained at 300W. The model predictions agreed well with experimental trends. The gap between top electrode and samples plays a major role in the efficiency, which is also improved using higher loads. So, it is very important in the design of new ovens the ability to change the electrode position.