Abstract:

Onion is an agricultural product widely used in daily life in fresh or dried state where microwave-drying method is one of the exploitable techniques. In such an operation, it would be important to control the effect of the output power in the device on the physicochemical quality of the food. In addition to the water content, the study of the physicochemical quality of onions concerns the color and the shrinkage rate. Monitoring and controlling these parameters is strongly recommended for microwave-dried onions. Onion slices of fixed dimensions (thickness of 10 mm and diameter of 67 mm) are microwave dried, at four different powers (90, 180, 270 and 360 W). The physicochemical quality of the samples is measured at each end of drying and all evaluations are based on minimum values. The results show that the increase of the drying power of the onions accelerates the degradation of their color and increases their shrinkage rate; nevertheless, a reduction in the drying time is quite remarkable. The browning index and shrinkage rate of onion slices are proportional to the microwave drying power. However, the drying time is inversely proportional. Finally, a drying power equal to 90 W and a thickness of the onion slices equal to 10 millimeters are recommended.

Publisher's Version