Uneven drying partial residual moisture, raw material shrinkage and lost natural flavor are four common lyophilization defects of freeze-dried fruits, meat and herbs, caused by improper freeze dryer parameter setting or minor equipment failure.
If local food raw materials remain wet after full freeze-drying cycle completes, check vacuum pump oil quality and drying chamber sealing strips of vacuum freeze dryer; unstable vacuum leads to incomplete ice sublimation inside fruit and meat raw materials.
Severe raw material shrinkage usually arises from insufficient pre-freezing temperature of bench-top freeze dryer and industrial lyophilizer; lower pre-freezing temperature value and extend pre-freeze holding time to eliminate this defect.
Obvious loss of natural fruit aroma and meat umami mostly happens when secondary drying heating temperature of freeze drying machine is set too high; appropriately reduce heating curve temperature for flavor-sensitive food raw materials.
If upper and lower trays inside industrial lyophilizer show obvious uneven dryness of food products, clean dust accumulated on condenser surface and check circulation fan running speed of refrigeration system.
Recording food lyophilization defect types and corresponding vacuum freeze dryer adjustment plans regularly enables operators to quickly locate abnormal problems and stabilize long-term uniform freeze-dried food quality.
