Extended applications of the small-scale radio frequency system for improving the heating performance of multi-component rice

With the changing lifestyles and the rapid development of the prepared food industry, there are many different multi-component rice-based foods on the market today. Further, manufacturers of multi-component foods prepare different types of rice products and provide them to markets and restaurants. In this study, the multi-component rice was heated by a self-built small 50 Ω, 13.56 MHz radio frequency (RF) heating system to explore the effective scheme for improving heating uniformity. The dielectric properties (DPs) of the single-component material (cooked rice, carrot, and sausage) were first measured and the heating rates were recorded at a selected input power level of 500 W and electrode gap of 80 mm. Based on the above results and the occurrence of edge effect, three types (I, II, and III) of the multi-component test samples were designed to compare the heating performances and the quality changes after RF treatment with three different electrode gaps (70, 80, and 90 mm). Results demonstrated that the Type-I sample arrangement resulted in a relatively shorter treatment time and a lower heating uniformity index as compared to the other two sample arrangements (Types of II and III). It also resulted in a more uniform temperature distribution and better-quality retention than that was possible with the single-component treatment. Thus, the layered scheme (Type-I) based on the DPs of the material could effectively improve the RF heating uniformity of multi-component food.