Radio frequency (RF) energy generates fast and volumetric heating as it penetrates food materials and converts electromagnetic energy to heat. With these advantages, RF heating is considered as a promising technology for tempering and thawing processes in the meat and fishery products industry. However, non-uniform heating problems hinder its further application to meat products due to their various sizes and irregular shapes. This study utilized representative frozen beef samples to investigate the parameters of varying sample thickness (40 mm; 50 mm; 60 mm), base area (small:160 × 102 × 60 mm³; medium: 220 × 140 × 60 mm³; large: 285 × 190 × 60 mm³) and shape (cuboid; trapezoidal prism; step) and their influence on tempering uniformity in a parallel-plate RF system. A computer simulation model was established, verified by experiments and then was utilized to evaluate the volumetric temperature distribution in food samples. Results show that the heating rate increases and heating uniformity decreases with increasing sample thickness and decreasing sample base area. As sample thickness increased from 4 cm, 5 cm to 6 cm, the simulated temperature uniformity index (STUI) increased from 0.093, 0.117 to 0.194. Sample base area increases from small to large decreased the STUI from 0.229 to 0.194 and 0.090. Among all three shapes, the cuboid shape has the best heating uniformity (STUI 0.194), followed by the trapezoidal prism (STUI 0.209) and the step shape (STUI 0.282). The step shape has the worst tempering uniformity because the RF energy focuses mainly on the vertical section and results in severe regional heating. Strategies to improve the step-shape frozen beef tempering uniformity by decreasing the input power to 1/3 and enlarging the electrode gap by 40 mm only reduced the hot spot temperature from 88 to 78 °C. Further research is needed in order to develop methodologies or suitable equipment for irregular shape food RF tempering in the future.

Industrial relevance

In industrial radio frequency thawing/tempering, the raw materials are usually presented in various irregular shapes and sizes. Thus, analyzing the non-uniformity severity influenced by sample size, shape and thickness to determine the capability and throughput of the equipment is necessary. Results in this study could be utilized in pre-evaluation of a protocol design and process optimization for irregular-shape food tempering.

中文翻译：

---

各种形状和大小的冷冻牛肉的射频回火均匀性研究

射频（RF）能量穿透食物材料并将电磁能转化为热量时，会产生快速而体积大的热量。凭借这些优势，RF加热被认为是肉类和渔业产品行业中用于回火和解冻过程的有前途的技术。但是，不均匀的加热问题由于其各种尺寸和不规则形状而阻碍了其在肉制品上的进一步应用。这项研究利用代表性的冷冻牛肉样品研究了不同样品厚度（40 mm; 50 mm; 60 mm），底面积（小：160×102×60 mm ³ ;中：220×140×60 mm ³ ;大）的参数。 ：285×190×60毫米³形状和形状（长方体；梯形棱镜；阶梯）及其对平行板RF系统中回火均匀性的影响。建立了计算机仿真模型，通过实验验证，然后用于评估食物样品中的体积温度分布。结果表明，随着样品厚度的增加和样品基面积的减小，加热速率增加而加热均匀性降低。随着样品厚度从4 cm，5 cm增加到6 cm，模拟的温度均匀性指数（STU I）从0.093、0.117增加到0.194。样品的基本面积从小到大增加，STU I从0.229降低到0.194和0.090。在所有三种形状中，长方体形状具有最佳的加热均匀性（STUI = 0.194），然后是梯形棱镜（STU I 0.209）和阶梯形状（STU I 0.282）。阶梯形状的回火均匀性最差，因为RF能量主要集中在垂直截面上，并导致严重的区域发热。通过将输入功率降低到1/3并将电极间隙扩大40 mm来改善阶梯形冷冻牛肉回火均匀性的策略只能将热点温度从88降低到78°C。为了将来开发用于不规则形状食品射频回火的方法或合适的设备，需要进行进一步的研究。

行业相关性

在工业射频解冻/回火中，原材料通常以各种不规则形状和尺寸存在。因此，有必要分析受样本大小，形状和厚度影响的非均匀性严重程度，以确定设备的能力和吞吐量。这项研究的结果可用于不规则形状食品调质的协议设计和工艺优化的预评估。