Pitchai Krishnamoorthy, Birla Sohan L, Jones David, Subbiah Jeyamkondan
Department of Biological Systems Engineering, University of Nebraska-Lincoln, NE-68583, USA.
East Campus, University of Nebraska-Lincoln, 212, L.W. Chase Hall, NE-68583-0726, USA.
J Microw Power Electromagn Energy. 2012;46(4):229-40. doi: 10.1080/08327823.2012.11689839.
Due to the inherent nature of standing wave patterns of microwaves inside a domestic microwave oven cavity and varying dielectric properties of different food components, microwave heating produces non-uniform distribution of energy inside the food. Non-uniform heating is a major food safety concern in not-ready-to-eat (NRTE) microwaveable foods. In this study, we present a method for assessing heating rate and non-uniform heating in domestic microwave ovens. In this study a custom designed container was used to assess heating rate and non-uniform heating of a range of microwave ovens using a hedgehog of 30 T-type thermocouples. The mean and standard deviation of heating rate along the radial distance and sector of the container were measured and analyzed. The effect of the location of rings and sectors was analyzed using ANOVA to identify the best location for placing food on the turntable. The study suggested that the best location to place food in a microwave oven is not at the center but near the edge of the turntable assuming uniform heating is desired. The effect of rated power and cavity size on heating rate and non-uniform heating was also studied for a range of microwave ovens. As the rated power and cavity size increases, heating rate increases while non-uniform heating decreases. Sectors in the container also influenced heating rate (p < 0.0001), even though it did not have clear trend on heating rate. In general, sectors close to the magnetron tend to heat slightly faster than sectors away from the magnetron. However, the variation in heating rate among sectors was only 2 degrees C/min and considered not practically important. Overall heating performance such as mean heating rate and non-uniform heating did not significantly vary between the two replications that were performed 4 h apart. However, microwave ovens were inconsistent in producing the same heating patterns between the two replications that were performed 4 h apart.
由于家用微波炉腔内微波驻波模式的固有特性以及不同食品成分介电特性的差异，微波加热会使食品内部能量分布不均匀。对于即食（NRTE）微波食品来说，不均匀加热是一个主要的食品安全问题。在本研究中，我们提出了一种评估家用微波炉加热速率和不均匀加热情况的方法。在本研究中，使用了一个定制设计的容器，通过一个由30个T型热电偶组成的阵列来评估一系列微波炉的加热速率和不均匀加热情况。测量并分析了沿容器径向距离和扇形区域的加热速率的平均值和标准差。使用方差分析（ANOVA）分析环和扇形区域位置的影响，以确定在转盘上放置食物的最佳位置。该研究表明，假设需要均匀加热，在微波炉中放置食物的最佳位置不是在中心，而是靠近转盘边缘。还针对一系列微波炉研究了额定功率和腔体尺寸对加热速率和不均匀加热的影响。随着额定功率和腔体尺寸的增加，加热速率增加而不均匀加热程度降低。容器中的扇形区域也会影响加热速率（p < 0.0001），尽管其对加热速率没有明显的趋势。一般来说，靠近磁控管的扇形区域往往比远离磁控管的扇形区域加热得稍快一些。然而，各扇形区域之间加热速率的差异仅为2℃/分钟，在实际中被认为不太重要。总体加热性能，如平均加热速率和不均匀加热情况，在相隔4小时进行的两次重复实验之间没有显著差异。然而，相隔4小时进行的两次重复实验中，微波炉产生相同加热模式的情况并不一致。
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