Radio frequency (RF) treatment is a burgeoning method in food processes. RF heating non-uniformity is a main obstacle for industrial implementations and influenced by the geometry of treated materials. In this study, the effect of convex-concavo shapes of the sample top surface and step shapes at the bottom of the rectangular container by adding polypropylene (PP) blocks on the heating uniformity was investigated using a 6 kW, 27.12 MHz free-running oscillator RF system. The results showed that the RF heating uniformity index values of millets decreased with increasing convex degree and decreasing concave degree of the sample top shape. Moreover, adding PP blocks at the bottom of the sample container was a better choice of improving RF heating uniformity owing to the wider adjustable range of sample sizes and better temperature distribution. This study provided a new method to improve the RF heating uniformity by simply changing the shapes of samples in either the top or bottom surface.

射频 (RF) 处理是食品加工中一种新兴的方法。RF 加热不均匀性是工业实施的主要障碍，并受处理材料的几何形状影响。在这项研究中，使用 6 kW、27.12 MHz 的自激振荡器研究了通过添加聚丙烯 (PP) 块而在矩形容器底部的样品顶面的凹凸形状和台阶形状对加热均匀性的影响射频系统。结果表明，随着样品顶部形状凸度的增加和凹度的减小，小米的射频加热均匀性指标值降低。此外，在样品容器底部添加聚丙烯块是提高射频加热均匀性的更好选择，因为样品尺寸的可调范围更广，温度分布更佳。