Color, texture and water activity of microwave-vacuum dried cranberries were evaluated and compared with the corresponding properties of hot-air dried and store-bought cranberries. The microwave drying was done both in the pulsed and continuous modes. The microwave-vacuum dried cranberries were redder and had a softer texture than those dried by the conventional hot-air method. The storage stability of the product dried by microwave-vacuum method was comparable to that of conventionally-dried cranberries. The microwave operating conditions have an effect on the quality of the dried cranberries.

Microwave-vacuum drying was investigated as a potential method for drying cranberries. Cranberries were pretreated with either 30°B or 60°B high fructose corn syrup solution for 24 h. They were dried using a laboratory-scale microwave-vacuum oven operating either in continuous or pulsed mode until the final moisture content reached 15% (wet basis). In the continuous mode, two levels of microwave power (250, 500 W) and absolute pressure (5.33, 10.67 kPa) were applied. In the pulsed mode, microwave power of 250 W and two levels of pressure (5.33, 10.67 kPa) were used with two levels of power-on time (30, 60s) and three levels of power-off time (60, 90, 150s). Pulsed application of microwave energy was more efficient than continuous application. In both cases, drying efficiency improved when lower pressure (5.33 kPa) was applied. Shorter power-on time and longer power-off time provided more favorable drying efficiency in pulsed mode. Power-on time of 30 s and power-off time of 150 s was the most suitable setting for maximum drying efficiency.