2.4.1. Microwave vacuum drying equipment
The drying method for convective drying or MVD of nonimpregnated
apple slices was not transferable to impregnated apple
parenchyma, capable drying conditions and drying parameters
for MVD of enriched Braeburn apples were investigated. The MVD
were performed with a lab scale MVD dryer (mWaveVac0150 1c,
Püschner, Schwanewede, Germany). The system consisted of a vacuumvesselwith
an integratedwall heater to avoid condensing vapor
in the system. The vessel wall was adjusted to 50 C during the
drying process. The dryer had a maximal microwave power of
1000Wproduced by 1.2kW/2450MHzmagnetron and amagnetron
protection system. During the drying process, the pressure was
decreased by a vacuum pump. To avoid overheating and product hot
spots, a rotary plate for product movementwas used. Tomeasure the
drying procedure the drying temperature was checked with a fiberoptical
thermometer. In addition, the reflected microwave energy,
the drying rate, the product weight and the actual vacuum conditions
were controlled via a real-time computer system.