Effect of different power ratio mode of intermittent microwave convective drying on quality attributes of Kiwi fruit slices

Effect of the power ratio (PR) of microwave on product quality during intermittent microwave convective (IMWC) drying of kiwifruit slice was investigated in a laboratory-scale microwave convective dryer. This study investigates vitamin C, total polyphenol degradation and color changes during IMWC drying of kiwifruit slices. The nutritional quality of the dried samples showed that there was a significant difference between the fresh and IMWC dried samples and lower power ratios obtained better nutrient retention. Major correlation between pulse ratio and color degradation was also observed from this study where the color degradation of the dehydrated product increased with the decrease of microwave pulse ratio. The drying condition at PR 1/4 provided the best result since highest vitamin C retention and lowest color degradation obtained while the drying time was relatively short compared to convection drying. The lower PR might greatly maintain the dried food quality, the processing time will increase significantly, and the desired outcome might not be achievable due to lengthy exposure of food to drying environment. Even though higher PR greatly reduces the drying time, the quality of the products may degrade as a result of a severe thermal treatment. Therefore, the PR should be optimized to obtain the best quality food with shorter drying time