Abstract In radio frequency (RF) assisted heat treatment of food products, heating behavior depends on the composition and geometry of a product. In this study, the effect of salt added to a food simulant on its dielectric properties and penetration depth (dp) were determined across a temperature range from 5 to 80 °C. Three primitive geometries (cube, cylinder and sphere) of a food simulant having a standardised volume (3.98 × 10−4 m3) heated in a custom-built 50 Ω RF system to investigate the impact of sample geometry and orientation on power absorption and heating uniformity. Experimental results revealed vertical oriented cylinder samples followed by cubes showed better temperature uniformity. The temperature at the core of food simulant samples after 6 min RF heating using 500 W power was 44 ± 7.1 °C, 45.3 ± 0.9 °C and 52.9 ± 3.5 °C in cube, cylinder, and sphere sample, respectively. However, the sphere sample was characterized by having the hottest spot at the bottom section. RF power level also played a significant role in heating uniformity with lower power input resulting not only in a slower heating rate but also in less uniform temperature distribution. This study provided a potential insight on the use of food simulants for evaluating RF heating design and performances.

中文翻译：

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射频加热过程中食品的几何形状和方向对加热均匀性的影响

摘要 在食品的射频 (RF) 辅助热处理中，加热行为取决于产品的成分和几何形状。在这项研究中，在 5 到 80 °C 的温度范围内确定了添加到食品模拟物中的盐对其介电特性和渗透深度 (dp) 的影响。在定制的 50 Ω RF 系统中加热具有标准化体积 (3.98 × 10−4 m3) 的食品模拟物的三种原始几何形状（立方体、圆柱体和球体），以研究样品几何形状和方向对功率吸收和加热的影响均匀性。实验结果表明，垂直取向的圆柱体样品和立方体显示出更好的温度均匀性。使用 500 W 功率射频加热 6 分钟后，食品模拟物样品的核心温度为 44 ± 7.1 °C、45.3 ± 0.9 °C 和 52.9 ± 3.5 °C（立方体），分别为圆柱体和球体样本。然而，球体样品的特点是在底部有最热点。射频功率水平在加热均匀性方面也发挥了重要作用，较低的功率输入不仅导致加热速度变慢，而且温度分布也不太均匀。这项研究为使用食品模拟物评估射频加热设计和性能提供了潜在的见解。