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Notes:
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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. |
