Department of Environmental Engineering, Institute for Environmental Engineering Systems, Faculty of Mechanical Engineering, Szent István University, Gödöllő, Hungary.
PLoS One. 2013;8(1):e53720. doi: 10.1371/journal.pone.0053720. Epub 2013 Jan 16.
Extension of shelf life and preservation of products are both very important for the food industry. However, just as with other processes, speed and higher manufacturing performance are also beneficial. Although microwave heating is utilized in a number of industrial processes, there are many unanswered questions about its effects on foods. Here we analyze whether the effects of microwave heating with continuous flow are equivalent to those of traditional heat transfer methods. In our study, the effects of heating of liquid foods by conventional and continuous flow microwave heating were studied. Among other properties, we compared the stability of the liquid foods between the two heat treatments. Our goal was to determine whether the continuous flow microwave heating and the conventional heating methods have the same effects on the liquid foods, and, therefore, whether microwave heat treatment can effectively replace conventional heat treatments. We have compared the colour, separation phenomena of the samples treated by different methods. For milk, we also monitored the total viable cell count, for orange juice, vitamin C contents in addition to the taste of the product by sensory analysis. The majority of the results indicate that the circulating coil microwave method used here is equivalent to the conventional heating method based on thermal conduction and convection. However, some results in the analysis of the milk samples show clear differences between heat transfer methods. According to our results, the colour parameters (lightness, red-green and blue-yellow values) of the microwave treated samples differed not only from the untreated control, but also from the traditional heat treated samples. The differences are visually undetectable, however, they become evident through analytical measurement with spectrophotometer. This finding suggests that besides thermal effects, microwave-based food treatment can alter product properties in other ways as well.
延长产品保质期和保持产品新鲜度对食品工业来说都非常重要。然而，就像其他过程一样，提高速度和生产效率也是有益的。虽然微波加热在许多工业过程中都有应用，但关于它对食品的影响仍有许多尚未解答的问题。在这里，我们分析了连续流动微波加热的效果是否等同于传统传热方法。在我们的研究中，研究了液体食品在传统和连续流动微波加热下的加热效果。除了其他性质外，我们比较了两种热处理方式下液体食品的稳定性。我们的目的是确定连续流动微波加热和传统加热方法对液体食品是否有相同的效果，以及微波热处理是否可以有效地替代传统热处理。我们比较了不同方法处理的样品的颜色、分离现象。对于牛奶，我们还监测了总活菌数，对于橙汁，除了通过感官分析品尝产品外，还监测了维生素 C 含量。大多数结果表明，这里使用的循环线圈微波方法与基于热传导和对流的传统加热方法等效。然而，在牛奶样品分析中的一些结果显示出传热方法之间的明显差异。根据我们的结果，微波处理样品的颜色参数（亮度、红绿值和蓝黄值）不仅与未处理的对照样品不同，而且与传统热处理样品也不同。差异在视觉上无法察觉，但通过分光光度计的分析测量可以明显看出。这一发现表明，除了热效应之外，基于微波的食品处理还可以以其他方式改变产品特性。
