Abstract: in order to study the microwave drying of raspberry fruit pulp heat transfer characteristics with framberry as raw materials, using the central composite experimental design method, the influence of drying conditions on material temperature, moisture content and dielectric properties, heat and mass transfer process of the microwave drying process of foam.
Raspberry puree during the microwave drying process, the drying period, the dielectric constant and dielectric loss factor were increased, which can increase the microwave absorption of materials, pulp temperature from room temperature up to 70 DEG C, water content had no obvious change;
The drying medium, the dielectric constant and dielectric loss factor increased first and then decreased, so the microwave energy absorbed by material was first increased and then decreased, pulp water content decreased from 90% to 40%, the temperature change is not obvious; the next stage of drying, the dielectric constant and dielectric loss factor decreased, microwave absorbing materials can reduce fruit pulp, moisture slowly dropped to about 15%, the temperature continues to rise. Microwave drying equipment can effectively improve the drying rate of high viscosity pulp.
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