Study on drying kinetics and physical properties of tomato slices Dried by refractance window in comparison with microwave, hot air and sun drying methods

In this study, the drying kinetics and physical properties of tomato slices dried using refractance window were compared with microwave, hot air and sun drying methods. According to the results obtained, the drying rate of tomato slices was the highest in the microwave and subsequently in refractance window in comparison with hot air and sun drying methods. In the drying curves of both microwave and refractance window methods no constant period of drying was observed. The lowest and highest rate of shrinkage belonged to the samples dried by refractance window and hot air methods, respectively. The highest and the lowest rehydration ratio were observed in the samples dried in refractance window and hot air method, respectively. The indexes of L*, b* and a* were significantly higher for the samples dried by refractance window and lower in the samples dried using hot air method. The results of sensory evaluation showed that the samples dried using refractance window gained the highest score for color and the samples dried by microwave method gained the lowest color score. However, the drying period of slices dried by microwave was much shorter than that of the refractance window, but the color properties score of samples dried by microwave was significantly lower than of the samples dried by refractance window. Therefore, it can be concluded that the refractance window method can be used as an alternative to hot air and microwave methods.