Method of fruit and vegetable freeze drying based on a freeze dryer equipped with a microwave radiation generator

摘要

The method of lyophilisation of fruit and vegetable juices as outlined in a diagram based on a lyophiliser equipped with a microwave radiation generator is characterised by the fact that the method of drying the juices is carried out on a multi-stage basis using a lyophiliser equipped with a microwave generator where the raw material is initially dried in: room temperature at reduced pressure, then frozen to a fixed temperature allowing rapid sublimation,at the next stage, the frozen material is sublimated under significantly reduced pressure with the simultaneous action of microwave radiation, intensifying the process, after which the material substantially deprived of water is subjected to the required humidity using vacuum-microwave drying. The microwave radiation generator is conveniently located outside the drying chamber (outside the tube),at angle 30o,isolated from the outside environment and the temperature sensor is located inside the drying chamber. Useful during the initial vacuum microwave drying, the raw material temperature i s not higher than 40oC, the vacuum chamber pressure is up to 10 kPa, at the specified frequency and time of operation of the magnetron and the drying time: 500 W-10 s work and 5 min stop, where the initial vacuum drying time depends on the level of raw material density. A useful freezing process is carried out in the freeze chamber of the lyophiliser, up to: 50oC, and the end of the freeze process is the temperature -30oC at the geometric point of the product,measured by a temperature sensor PT 100, where the minimum freezing time depends on the density of the raw material. Useful in this process for the lyophilisation of the aided pressure in the lyophilisation chamber, set to 103 Pa, and the temperature of the ice condenser to -50oC, the cycle of operation of the microwave generator with the emission power of 500 W-6 and 10-min stop, where the maximum sample temperature i s set to -10-oC and the aided lyophilisation lead to the moment the sample reaches ok. 80% dry mass. During the final vacuum microwave drying, the raw material temperature is not higher than 40oC,the vacuum chamber pressure, up to 10 kpa, at the specified frequency and time of operation of the magnetron and the drying time shall be applied: 500 W-10 s work and 5 min rest, with the final vacuum suction time leading up to the moment the sample reaches the eye. 85% dry mass.