食品加工与技术杂志

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Impact of Microwave Drying on the Quality Attributes of Okra Fruit

Lam Van Man, Takahiro Orikasab, Yoshiki Muramatsuc and Akio Tagawaa

The impact of microwave drying on quality attributes of dried okra was investigated at three levels of power between 500 and 800 W during microwave drying and was compared with that of hot air drying at four temperatures ranging from 40 to 70°C. The drying characteristics, the decreasing rate of the ascorbic acid and the total color change of okra during microwave and hot air drying were examined. An exponential model was suitable to describe the microwave and the hot air drying characteristics of okra. The drying constant k1 ranged from 0.27 to 0.36 min-1 for microwave drying and from 0.15 to 0.49 h-1 for the hot air drying. The ascorbic acid content during microwave and hot air drying was measured and then a first-order reaction equation was used to calculate the decomposition rate of the ascorbic acid. Values of the coefficient of decomposition rate ranged from 0.40 to 0.46 min-1 for microwave drying. Using the change on standing in the total color difference during microwave and hot air drying, the extent of browning, B and the coefficient of browning rate k2 were estimated. In addition, the rehydration rate of the sample which was dried with the seven conditions in this test was highest at 800 W for the microwave drying. Therefore, it was confirmed that the microwave drying at 800 W was most suitable for okra drying within this test.