Abstract Low moisture foods, including seasoning spices, have been associated with a number of multi-state outbreaks of salmonellosis in the past decade. The long-term objective of this study was to develop an effective in-package pasteurization treatment for seasoning mixtures based on radio frequency (RF) heating. Seasoning spices obtained from grocery stores included red, white, and black pepper; cumin; curry powder; and garlic powder with moisture contents ranging from 3.1 to 12.3% (wet basis). The dielectric properties (DP) of the seasoning spices and their mixtures as influenced by frequency, moisture, temperature, mixing fraction and salt content were determined using a precision LCR meter and liquid test fixture at frequency ranging from 1 to 30 MHz. The RF heating rates of each spice and their mixtures were evaluated using a 27.12-MHz, 6-kW pilot scale RF system with 105 mm gap between electrodes. To evaluate the effect of mixing on heating uniformity, a sample (50 g) was placed into a polystyrene plastic cylindrical container and heated to 70 °C, and surface images were taken by an infrared camera. The results showed that the relationship among moisture content, temperature and DP of white pepper can be explained by a second-order model at 13.56 and 27.12 MHz. The DP and heating rates of spice mixtures ranged between the highest and lowest values of their respective individual spices. Increase in salt content resulted in a decrease in heating rate, which resulted a better heating uniformity with smaller uniformity index (UI). The RF heating rate of samples ranged from 2.97 to 23.61 (°C min−1). The highest heating rate in samples was in a correspondence to the worst heating uniformity, and highest average temperature on the sample surface. The most uniform heat distrubition on top surface was obtained for garlic powder as 0.012 (UI) at 70 °C. The information obtained from this study is important to develop an effective RF heating strategy for pathogen control in seasoning mixture.

中文翻译：

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射频加热各种调味香料及其混合物的介电特性、加热速率和加热均匀性

摘要 在过去十年中，包括调味香料在内的低水分食品与多州沙门氏菌病的爆发有关。本研究的长期目标是开发一种基于射频 (RF) 加热的调味混合物的有效包装内巴氏杀菌处理方法。从杂货店获得的调味香料包括红、白和黑胡椒；孜然；咖喱粉; 和大蒜粉，水分含量为 3.1 至 12.3%（湿基）。调味香料及其混合物的介电特性 (DP) 受频率、水分、温度、混合分数和盐含量的影响，使用精密 LCR 计和液体测试夹具在 1 至 30 MHz 的频率范围内确定。使用 27.12-MHz、6 kW 中试规模 RF 系统，电极之间的间隙为 105 mm。为了评估混合对加热均匀性的影响，将样品（50 g）放入聚苯乙烯塑料圆柱形容器中并加热至 70 °C，并通过红外相机拍摄表面图像。结果表明，白胡椒水分含量、温度和DP之间的关系可以用13.56和27.12 MHz的二阶模型来解释。香料混合物的 DP 和加热速率介于其各自香料的最高值和最低值之间。盐含量的增加导致加热速率的降低，这导致更好的加热均匀性和更小的均匀度指数（UI）。样品的射频加热速率范围为 2.97 至 23.61 (°C min-1)。样品中最高的加热速率对应于最差的加热均匀性和最高的样品表面平均温度。在 70 °C 时，大蒜粉的上表面热分布最均匀，为 0.012 (UI)。从这项研究中获得的信息对于开发一种有效的射频加热策略来控制调味混合物中的病原体很重要。