A novel method for improving radio frequency heating uniformity of wheat kernels using aluminum foil sheets

Abstract. Improving radio frequency (RF) heating uniformity is important to ensure both the good pasteurization effect and quality of food product. The objective of this study was for providing a new method to improve the RF heating uniformity by adding aluminum foil sheets around the container walls. A 27.12 MHz, 6 kW pilot-scale RF system at an electrode gap of 110 mm was used to evaluate the heating rate and temperature distribution of wheat kernels in a rectangular container with the location, size and thickness of the foil sheet. The results showed that the RF heating behavior was influenced by foil sheets added at different oriented walls of the container. A cold spot area appeared in the place closed to the foil sheet wall at the vertically oriented addition, while a cold spot in the center and hot spots in the corners and edges still existed with the horizontally oriented addition of the sheet. The heating uniformity index (λ) value decreased with increasing foil sheet size and thickness. A clearly improved RF heating uniformity can be obtained by increasing foil sheet size and thickness at the container bottom wall.