Improving tempering uniformity in frozen chicken breast during cold-air assisted intermittent radio frequency treatment

Abstract Radio frequency (RF) tempering, as a dielectric heating technology, is widely used in the tempering of frozen meat products, but non-uniformity heating is still a major obstacle to industrial applications. In this study, an RF tempering oven with a cooler and a temperature measuring program was used to investigate effects of cold air, different temperature difference thresholds (TDT), and different time-outs of RF power on the tempering uniformity for cubic- and cylindrical-shaped frozen chicken breasts. The results showed that the sample’s temperature increased with the tempering time, and the temperature at the corners and edges was higher than that at the center of sample during RF tempering. Additionally, the cold air could reduce the temperature at the corners and surfaces of the samples and improve the RF tempering uniformity. The temperature-time histories clearly showed wave shapes during intermittent RF tempering. After intermittent RF tempering, the heating uniformity index and average temperature values of the cubic sample followed the decreasing order: right surface > left surface > bottom surface > top surface. For the cylindrical sample, the top surface also had the best tempering uniformity and the lowest average temperature, and the right surface had the worst tempering uniformity and the highest average temperature. A smaller TDT and a longer time-out resulted in a lower temperature difference between the surface and the center of the samples, a lower tempering rate, and better tempering uniformity. With the optimal TDT and time-out, the best tempering uniformity was obtained after cold-air assisted intermittent RF tempering. The results of this research may provide useful information for improving the temperature distribution in the industrial RF tempering process.