Development of optimum microwave blanching system for fruit and vegetables

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The applicability of microwaves to the drying and blanching processes of cooking tomatoes was examined. Drying treatment was performed using hot air (50℃) and microwaves at 3 radiation powers (20, 50, and 100W/g-dry sample), and the changes in drying rate and surface color of the sample were measured and compared. The drying rate in all the microwave dryings was greater than that in the hot air drying, and the constant-rate and the falling-rate drying period were observed in the case of each microwave radiation power. Microwave drying caused a greater increase in lightness than hot air drying. Blanching treatment was performed using microwaves and the boiling water method, and changes in temperature, nutrients, and surface color of the sample were measured and compared between the 2 methods. Microwave blanching required less time, resulted in higher retention of nutrients (ascorbic acid and lycopene), and caused less change in color than boiling water blanching. These findings suggest the applicability of microwaves to the drying and of blanching processes involved in cooking tomatoes.