Radio frequency (RF) heat treatment is one of the most promising methods for disinfestations and pasteurizations of granular foods but the combined effects of geometry and dielectric properties of granular materials on the non-uniformity of heating in RF are poorly understood. A coupled thermal-electromagnetic model for RF heating (27.12 MHz, parallel plate) of a single layer of spherical particles (1–5 cm diameter) was developed using two different formulations of the particles−$-$an approach that considers the geometry of individual particles and a simplified approach that considers the effective properties of an air-particle mixture. The spherical particles, prepared from soybean powder, represented dry granular foods. Model predictions were validated using point and spatial temperature measurements. Results show that while an effective properties approach can be sufficient for smaller (∼1 cm diameter) particles (with internal temperature range of 3 °C), consideration of the exact geometry (individual particles) would be needed for accurate prediction of heating non-uniformities (with internal temperature range of 39 °C) in larger diameters (diameter of 5 cm). Heating non-uniformities are present due to corner/edge heating, focusing effect, as well as contact heating between particles or between a particle and the tray. Results should greatly benefit computer-aided design and optimization of RF heating processes for granular products.

射频（RF）热处理是对颗粒食品进行杀菌和巴氏灭菌处理的最有前途的方法之一，但人们对颗粒材料的几何形状和介电特性对RF加热不均匀性的综合影响了解甚少。使用两种不同的粒子配方，开发了单层球形粒子（直径为1-5 cm）的射频加热（27.12 MHz，平行板）的耦合热电磁模型-$-$一种考虑单个颗粒几何形状的方法，以及一种考虑空气颗粒混合物有效特性的简化方法。由大豆粉制得的球形颗粒代表干颗粒食品。使用点和空间温度测量值验证了模型预测。结果表明，对于较小（直径约1厘米）的颗粒（内部温度范围为3°C），有效的方法可能就足够了，但需要准确的几何形状（单个颗粒）来准确预测非直径较大（直径为5厘米）时具有均匀性（内部温度范围为39°C）。由于拐角/边缘加热，聚焦效应以及颗粒之间或颗粒与托盘之间的接触加热，会导致加热不均匀。