1, Control the ice crystal growth during the freezing stage
Freezing stage is important, because in this stage, freezing speed influence ice crystal size, later will influence drying speed, rehydrate speed and dried products quality.
During freezing, ice crystal quantity and size influenced by nucleation rate and growth rate. At 0C, ice crystal growth rate is ideal but nucleation rate is low. So, products freezing at 0C will cause larger size ice crystal but less quantity. Products freezing below 0C will cause small size ice crystal but more quantity. Larger ice crystal is good for sublimation but dissolution rate is low.
Generally, frozen products with smaller crystal and dried, the structure is very close to original and quality is high.
2, Precise steps temperaure set.
Careful optimization of the shelf temperature and chamber pressure during the process, and maximizing the heat and mass transfer. The main constraint of this strategy lies in the maximum temperature that the product being dried cannot exceed during the process, the so-called target temperature. The target temperature is usually set 5 C below collapse temperature, and it is an intrinsic constraint of the raws.
Proper Product Loading Volume
Too much loading may cause longer drying time, less loading volume is not cost-effective. Proper adjust the loading capacity(Based on condenser capacity or supplier recommendation) is helpful.
An Experienced Operator Helps a Lot
Whether to optimize freeze drying curve, or take notice of the abnormal, do maintenance in time, prevent further damage.
By install reliable parts, freeze dry system will have excellent stability. Always smooth working and low failure rate.